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Mobilisation of the NervousSystem

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David S. Butler B. Phc:Jr>c:Jc:Jc:Jc:Jc:Jc:JC=.CHURCHIIL UVINGSTONE"'ffi!..BOURNEMADRID EDINBURGH LONDON TOKYO AND NEW YORK 1991

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1~"'"CHURCHILL LIVINGSTONEMedical Division. of Longman Group UK Limited

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Dislributcd in Australia by Longman Cheshire PtyLimited, Longman House, Kings Gardens, 95 CovcnU)'StreCI', South Melbourne 3205, and by associatedc:ompanies throughout the world.

.' , Longman Group UK Limited 1991

National Library of AustraliaCataloguing in Publication dataButler. David S. (David Sheridan), 1956-

Mobilisation of the nevous system.

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ISBN 0-443-04400-7

All righlS reserved. No pan of this publication may be:reproduced, stored in a rcuicval system, or trnnsmiuc:d inany (orm or by any.means, clecrronic, mechanical,photocopying, recording or otherwise, without the priorpermission of the: publishers (Churchill Li\1ngslonc,Raben Stevenson House, 1-3 Baxtcr's Place, Leith \'o;Ialk,Edinburgh EHI 3AF), or a licence pc:nnining restrictedcopying in the United Kingdom issued by me CopyrightLicensing Agency Ll.d, 90 Touenham Coun Road,London, WIP 9HE.

First published 1991Reprinted 1992 (twice), 1993, 1994 (twice)

Includes index.ISBN 0 443 04.400 7'.

1. Nevous syslem, 1. Jones, Mark A.612.8

Library of Congt'eSs CaUloging-in-Publicauon Dala

Butler, David S. (David Sheridan), 1956-Mobilisation of the nervous systemIDavid S. Butler;

with a contribution by Mark A. Joncs; artWork byRichard Gore.

p. em.Includes bibliographical references and index.ISBN 0-443-

Contents

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Introduction - to\vards a multifactorialapproach xiii 4. The clinical consequences of injury to the

nervous system 75

108109

115122

lower limbs andtesting - the127

Where can the pain come from? 75Signs and symptoms following neural

injury 79Area of symptoms 80Kinds of symptom 82History 83 .Postural and movement pancms 84

Imroduction 91The clinical reasoning process 92Ch:uacteristics of cxpcnise 95Analysing Structures and contributing

ftlcton; 96Inquiry strategies 98Structural differentiation 102Precautions tlnd comraindications 104

Gencml points 107Subie

xii CONTCNTS ---------~The concept of base tension testsPassive Neck Flexion 128Straight Leg Raise 130Prone Knee Bend 136The Slump T~t 139

127 Some useful techniquesPOsture 209Prophyb.x..is 210

205

13. Adverse neural tension disorders basedon the spinal canal 231

PART IVSeleeted disorders and case studies

Introduction 213The extremities 213The foot and ankle 214The hand and wriSt 218Thocacie outfe{ syndrome 222Menlgia paraesthetira 222The nerve lesion in lower limb muscle

tcars 223Peripheral 'nerve surgery 224Repetition strain injury (RSO 226

'":~:Tension testing - the upper limbs 147 -W~" _ '1.

Upper ""Limb Tension Test I 141Upper Limb Tension TeSt' 2 153Upper Limb Tension Test 3 156Other uppcr limb tcnsion [CStS 159

9. Application, analysis and funhertesting 161

Essentials of testing 161The relevance of examination findings Hi!Essenti:tl features of tension tCSt analysis 163Establishing sit~ of adverse tension 165Taking tension testing funhe.. 167Recording 171Palpation of the nervous system 172Classifications of nerve injury 175

PART III

12. Adverse neuralin the limbs

tension disorders centred213

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251

258

238

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247An unusual and vague foot pain 247An example of extraneural pathologyThc 'pain evcrywhere' kind - where to

St(lrt? 253A typical tennis elbow? 255A passing mention of fingerup pain

14. Selected case studies193

198199

11. Self Treatment 203

Nerve root injuries 231Treatment and treatment potential (!o r"(f-c:. H Loss of spinal extension

Whiplash 236.tt::.eT 1'

Introduction - towards a multifactorial approach

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Joint-specific thinking is dominant in the systemsof manual therapy in usc in the world today.There ace, however, other schools of thoughtwhich favour treatment via muscle or fascia. Theobvious implications are that the ~S( approachwill be 'structure selective', I believe that opti-mum open-mindedness in manual therapy mustlead to a questioning of a onc-structure approachin the treatment of so-called 'musculoskeletal'disorders.

In any ncuro-onhopa(:dic disorder, it is impos-sible [0 have JUSt one structure involved. For

cxample~ in the kind of pure nerve injury thatmight happen from a misplaced injection, therewill probably be manifestations in non-neuralsuuc{ures'related via impulse conduction andaxoplasmic transport. The patient who [Urns andlocks his or hcr neck is likely to have reflex spasmin associated neck musculature. The longer theneck stays locked. thc greater the likelihood ofthere being changes in the associated muscles, inother structures and in affective responses. Still,at a cenain stage of a disorder it is likely mat aproblem could be cured with trearment directedat one StruCture. However. in terms of speed ofrecovery and preventive management, it is doubt-ful that a one-SU'\Icture approach will be optimal.

With a model using joint strUcture as the focus,acknowledgement of the role of the nervous sys-tem and its control of symptom presentation canbe diminished, even bclitued. The nervous sys-tem is cenainly involved, direcuy or indirectly, inall patient prnhlems. It could be injured and bea source of symptoms. Even if uninjured, it stillcarries the afferent impulses frc~.. r.:m-nel,O;alstructures and efferent signals for responses suchas u.uscle spasm. Symptoms are an expressioq. of

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the status of the tissues involved (e.g. ioint, mus-cle. fascia, dura mater etc.). as conductedthrough the nervous system and modified by theenvironment. The}' provide the physiotherapistwith invaluable clues to understand the patient'sproblem and discover the most effective managememo Thus. attention to all potential factorsinfluencing a patient'S symptoms is essential andrequires a model which is not dominated by anysingle structure, but rather, where all struCturesand contributing factors (e.g., environment andculture) are taken into account. Classic struCNralor direct approaches in manual therapy focus onone S(roctu.re such as joint (e.g., Cyriax, McKcnzic, Kahcnborn. early l\1aidand, chiropracticsand osteopathy). or muscle (e.g.. Janda andLewit). Their survival is testimony to n:aeasuresof success. However, other approaches without aslnlctural focus which might be called'facilitative' or 'indirect' (e.g., ProprioceptiveNeuromuscular Faciliation, Feldenkrais, Alexan~der. psychological), are also successful in their ~results. These approaches could be said to attendmore to the quality of mO\'emenr rather than tospecific strUctures or biomechanics. The point of-this discussion~is to encourage the usc of a mul-tifactorial approach to patient examination andmanagement.

\Xlhi]e one cannot hope to achieve expertise inall appco3ches, awareness and understanding ofwhat is available will facilitate utilisation and con~sultation for the benefit of the patient and thephysi9thcrapist. It is tempting to suggest the ner-vous system is the central system linking both the;,LnIcturaUdirecl and facilitati\e/indircc[ ap~proaches as they both must communicate theireffects via the nervou's system. However, this

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XlV llITRODUCTION

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could inhibit open.,.minded thinking, as it wouldif any other structure or system were considered

PART I

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The basis for adverse neural tension

L Functional anatomy and physiology of thenervous system

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INTRODUCTION

To imcrpret the signs and symptoms of injury tothe nervous system accurately. a physiotherapistrequites an understanding of its stark and dy-namic anatomy; and this understanding is alsofundamental to safe and effective mobilisation.

This chapter is a study of the anatomy andphysiology associ'l.(ed with movement of thenervous system. In the context. the study ofmovement of the nervous system is no ditrcremfrom that of joint or muscle. The nervoussystem is built primarily for impulse conduc-tion. The main aim of the chapter ~s (0 showthat the impulse conducting function is sup.paned by anatomy that allows conductionwhile accomodaling body movements.

Because this chapter has a bias toward lhcfunctional an3[Qmy of the nervous system relatedto the function of its own movement, the all jm~portant function of impulse conduction mayseem neglected. There are many wonhwhile textson this subjecr. Recent and recommended ones,among others, are Walton (1982), Mathers(1985) and Bowsher (1988).

The concept of the continuous tissue tract

The peripheral and central nervous systems needto be considered as one since they fonn a con-tinuous tissue tracr. For the majority of functions,any division into peripheral and central compo-nents can only be artificial.

The sYStem is a Continuum in three ways.Firstly, the connective tissues are cOnlinuous, al-though in differeD( (oor-ats, such as epineuriumand dura mater. A single axon can be associated

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with a number of these connective tissues. Sec-ondly, neurones arc interconnected electrically sothat, for example, an impulse generated at thefOOt may be received at the brain. Lastly, the ner-vous system may be regarded as continuouschemically. The same neurotransmitters exist pe-ripherally as centrally and there is a flow ofcYtoplasm inside axons.

Arguably, there is no other structure in thebody with such connectedness. Sll'esses imposedupon the peripheral nervous system during move-ment are transmitted. to me central nervoussYStem. Conversely, tension 'can be conveyedfrom the central nervous System to the peripheralnervous system.

[f the nervous system were to be considered asan organ rather ilian the multisegmemed sU'Uc-lure it is commonly thought to be, it would leadto a far bener understanding of the" system andof the pathomechanical and pathophysiologicalconsequences of altering its mechanics. One ofthe greatest implications of 'organ thinking' isthat, if there is some change in part of me system,then it will have repercussions for the whole sys-tem. The continuous tissue tract makes thisinevitable.

The need for specialised anatomy

There is one outstanding difference between themechanical features of the nervous system andthe mechanical features of other body structures.That is, the nervous system carries impulses toand. from those other Structures. This featureunderlines the imponance of the normal mech:m-ics of ncur:d tissue and its associated connectivetissues.

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4 MOBIUS....TION OF THE 'NERVOUS SYSTEM

Humans 'are, capable of highly skilled move-ments wilh Ihe nervous system stretched or slack,stationary or mobile. Observation of dancers, orsponsmen and women, for example, makes thisobvio\Is. The nervous system not only has to con-duct impulses .during a remarkable range andvariety of movements. it has to adapt mechani-cally during Ihe movements. Some biomechanicalfacts help to emphasise this. The spinal canal isfrom 5 em to 9 cm longer in flexion than extcn-sion (Inman & Saunders 1942, Breig 1978, Louis1981). It may be even longer in hypennobile in-dividuals. This rather remarkable variation in thelength of the spinal canal and its repcrcussionson the tissues contained within is of great clinicalimponance.

Because of the continuous tissue tract, anylimb movement must have mechanical conse-quences for nerve trunks and the neuraxis.(Neuraxis is a tenn used when the CNS is con-sidered along its length irrespectivc of its bends

. and folds (Bowsher 1988 ..Consider also whathappens at the elbow and hip. Here, major nelVesare on oppo~ite sides of the axes of movement.So, in elbow flexion, while the ulnar nerve

. srretc'he's, its counterpartS', the median and radialnerves, must adaptively shonen. The same tis-sl,les. while still conducting impulses. undergovery different mechanical defonnations. The re-verse will obviously happen during elbowextension.

Peripheral nerves have to adapt to markedchanges in the length of the nerve bed. For ex-ample. Millesi (1986) calculated that. from wristand elbow flexion to wrist and elbow extension,the bed of the median nerve is approximately20% longer. Somehow, the median nerve has toadapt to this and conduct impulses at the sametime. Nerve trunks also need a protective mech-anism from compressive forces. This is especiallyso where the trunks lie close to the exterior. suchas cutaneous nerves, or where nerves ron overbone, such as the common peroneal nerve at thehead of the fibula.

It appears that nervous system mechanics gofurther than adapting to movement and protec-tion from compression. The contbuous :;ssuetract also has the ability to limit cenain combi-'-3.tions of movement. A review of the anatomy

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Fig.1.1 In the Slump position the r.tnge of mO\'cment ofknee extension will be dictated by the head position. \X'iththe nee\:: extended, the subject c:an extend her knee: furthcr

and biomechanics in following chapters will showthat it has a functional anatomy easily capable ofsuch a purpose. A combination of movements,such as the Slump Test position (Fig. 1.1), is anexample. This test is discussed in detail in Chap-ter 7.

Thus, to cater for this dual role of impulse con-duction and a variety of related movements,complex anatomical adaptations which prmectneurones and allow conduction in any desiredposture or movement are inbuilt in thc svstem.Such varying roles for a structure demands acomplex functional anatomy. '

Gross shape and features

There are tWO main kinds of tissue making upthe nervous systcm: those associated with impulseconduction and those associated with SUppOrTand protection of the impulse conducting tissues.Examples of the fanner :tre axons. myelin andSchwann cells, examples of the latter are tile con-nective tissues such as neuroglia, the meninges

~nd perineurium. These two kinds of tissues h2\'can intimate relationship to allow for uninter-rupted impulse conduction while the bodymoves.

Some gross feature.s of neuroanatomy arc rd-evant f.:lr a study of its mechanics. Theperipheral nervous system requires more ada~tive mechanisms than the ceI::ttral nervous system.

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FUNCTIONAL ANATOMY A."D PHYSIOLOGy 5

THE PERIPHERAL NERVOUS SYSTEM

Structures: firm and unyielding; such as the radialnerve in me spiral groove of the humerus, or soft,such as me tibial nerve surrounded by posteriorthigh muscles. The system also Courses throughtunnels mat may be osse.ous, fibro-osseus orsolely soft tissue. With injuD." the naNre of thesurrounding structure will be consequential forthe type and exeent of injury.

In this section, for convenience's sake, the ner-vous system is discussed under the U'aditionalheadings of the peripheral and central nervoussystems. The peripheral nervous system is tradi-tionally defined in anatomical tenns as the cranialnerves (except the optic nerve), the spinal nerveswith their roots and rami, the peripheral nervesand the peripheral components of the autonomicnervous system (Gardner & Bunge 198-1). Theperipheral nervous system is associat~d \\ithSchwann cells; these arc replaced by glial srruc.cures in the ~entral nervous system,

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The neurone

A neurone comprises a cell body (perikaryon),some de~rites and usually one axon. A.'Xons arceither myelinated or unmyelinated', and aregrouped together inco bundles, or fascicles.Axons are usually referred to as 'nerve fibres'.The cytoplasm of the neurone, known as axo-plasm, is contained, and flows \\ithin and arounda syseem of microtubulcs and neurofilamenrs,within the axon. Each axon is surrounded bySchwann cells, which, in the case of the myeliwnated fibres, produce myelin and ensheath theaxon. In non-myelinated fibres, one Schwann cellis associated with a number ofaxons whereas, inthe myelinated fibres, the ratio is one Schwanncell per axon, Nodes of Ranvier interrupt the con-tinuiey o:f the sheath (refer to Fig. 1.3). Thisdiscontinuity in the myelin sheath allows rapidimpulse conduction as thc action potemial leapsfrom one node [0 the next. An individual axoncan extend L'1C length of a limb, for example,from the cell body in a lumbar dorsal root gan-glion to a synaptic tcnni~al in the foot. Yet, c\en

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Much of the neuraxis and the meninges is pro-tected by the cranium and. to a lesser degree, thespinal column. A nOled problem area is whereperipheral nerves join on to the less mobile neu-raxis. Most peripheral nerves and trunks run deepand are on the flexor aspect 0" limbs. This keepsthem close to th~ axes of movement as well asaffording protection. The ulnar nerve at meelbow is a notable example of a nerve on theextensor ~spect and is consequenrly vulnerable toinjury.

Overall, and rather simply, the entire nervoussystem fonns an 'H' on its side. Being a contin-uous tissue U'act, this means that any tensionplaced at any part of the 'H' can be dissipatedin two directions. Such thinking will be helpfulin the examination of the mechanics of areas thatcontribute to adverse tension.

The peripheral nervous system forms manysubdivisions and plexuses, both internal and ex-ternal. The main purpose of this is to assemblethe necessary sensory, motor and autonomiccomponents to a nerve trunk. However, with alittle 'mechanical thinking', the gross shape of thesubdivisions and, plexuses could also be seen asa convenient force distributor. Take the intercon-nections of the brachial plexus for example (Fig.1.2). During movement, the mesh of nervous sys:'tern keeps excessive forces away from a singlebranch. An even more complex branching ofnerve fibres occurs inside the nerve trunks. Thisis discussed and iIlusU'ated later in this chapter.

In its course through the body, the nervoussystem comes in contact with many different

Fig. l.Z The brachial plexus as a forte distributor,Tension on one trunk will be distributcd throughout thewhole plexus

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6 ~OBIUSAT10N Of TI-lE NERVOUS SVST'EM

Fib'. 1.3 Dia1:nmm~tic m}"Clin:Hed md unm)"Clil\

also consider movement at this microscopic level.Given that minor demyelination is a possiblesource of ectopic impulse generation (Calvin cral 1982), abnonnal biomechanics of the myelinsheath may also contribute.

Three kinds of nerve fibres arc carried in pe-ripheral nerve - motor, sensory and autonomicfibres. Motor fibres originate from cell bodies inthe ventral hom of the spinal cord and tcnninatcat the neuromuscular junction. Cell bodies ofpresynaptic sympathetic nerve fibres also lie inthe ventral hom from cord segments Tl to L3.Postganglionic fibres arise from the sympathetictrUnk. Sensory fibres originate from cell bodiesin the dorsal root ganglia and terminate at recep-tors such as Meissner's corpuscles, Paciniancorpuscles or as free nerve endings. The pro-portion of fibres in each nerve depends on thefunction of the nerve. The median nerve andsciatic nerve) both destined primarily for theextremities, have the greatest proportion of auto-nomic fibres. Some nerves, such as the lateralfemoral cutaneous nerve, are purely sensory,whereas there are no pure motor nerves. Allnerves carry at least a few afferent fibres, perhapsfrom joint S[I'Uctures if not from muscle.

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Fig. I.S The eonnective tissue sheam of a mulc:ifasdcularsegment of peripheral nerve. A axon, BV blood vessel, Eendoneurium, EE external epineurium, IE internalepineurium, M mesoncurium, P perineurium

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RJNCTlONAL ANATOMY A."D PHYSIOLOGY 7..

Endoneurium

Surrounding the basement membrane is the en-doneurial tube: a distensible, elastic structuremade up of a matrix of closely packed collage-nous tissue (see Fig. 1.3). Note the endo-neurium and the two outer connective tissue lay-ers in Figure 1.5. The matrix containsfibroblasts) capillaries) Mast cells and Schwanncells. There is no evidence of any lymphatic chan-nels (Sunderland 1978, Lundborg 1988).

Endoneurium plays an important role in themaintenance of the endoneurial space and fluidpressure, hence a constant nerve fibre environ-ment. A slightly positive pressure is maintainedin the space. Without lymphatics, any alterationin th,e pressure, as may occur with oedema (Ch.3); could intCTfere with conduction and move-ment of the axoplasm (axoplasmic flow).According to some resc"Ld.~rs (Granit &Skoglund 1945, Sunderland 1978), if the tubes

u~come severely damaged, neural disorganisa

tion, including neuroma formation and artificialsynapses between neighbouring fibres, is possible.

The collagen fibril orient,ation in the endoneur-ium is essentially longitudinal - evidence thatthe endoneurium has a role in protecting theaxons from tensile force. The three connectivetissue sheaths, the endoneurium, perineurium andepineurium, all have collagen fibres arranged lon;-gitudinally, although with some cross fibresforming a lattice. Cutaneous nerves have agreater percentage of eridoneurium, probably dueto the extra cushioning a nerve requires when itis close to the surface (Gamble & Eames 1964).

Perineurium

Each fascicle is surrounded by a thin lamellatedsheath known as the perineurium (see Fig. 1.5).Up to 15 layers may be present in mammaliannelVe trunKs (Thomas & Olsson 1984). There isno basal lamina between perineurial cells, and thecells overlap. Thus they form 'tight junc'tions'

8 MOBIUSATION OF TIfE 'NERVOUS SYSTEM

(Thomas & Olsson (1984). Lundborg (1988)outlines the roles of the perineurium as:-

Protecting the contents or the endoneurialtubes

Acting 3S a mechanical barrier to e:m:malforces

Serving as a diffusion barrier. kee=:pingcertain subnances out of the intrafascicularenvironment.

With lamellae composed of collagen and asmall amoum of e=:.lastin. the perineurium isthought to be the structure most resistant to ten~site force (Sunderland 1978). Much of thecollagen fibres run parallel to the direction of thenerve fibre, aJthough the=:re=: ace=: circular andoblique=: bundles which may protect lhe nervefrom kinking whe=:n it has to go around an acuteangle. as does the ulnar nerve at the elbow(Thomas 1963). The pe=:rineurium is the last pe=:-riphera1 nerve connective tissue sheath torupture in tensile testing (Sunderland 1978). Al-though, re=:cently, Kwan e=:t al (1988) found that

"the perineurium of rabbit tibial nerve rupturedfirst under tensile testing while leaving the: nervegrossly intact. Intrafascicular pressure has to beraised to approximatdy 300-750 mmHg beforethe perineurium will rupture=: (Selande=:r &Sjostrand 1978). It is a tough, strong tissue. Itsimportant role as a diffusion barrier is discussedlater in this chapter.

Epineurium.

This outectnost connective tissue investment sur-rounds. protects and cushions the fascicles,Collagen bundles are arranged primarily in theI

FUNCTIONAL A."':'ATOMY A.'-o PHi'SIOl..OCY 9

Fil:. 1.7 Compression of the fucide$. Where a peripheralnerve is multifucicular, a Cfe3ler pressure will be requiredto affect nerve fibres than whne there is a small numberof f3sciclc5

crease the nerve is composed of approximatelyeight fascicles, yCt a few centimeU'~s further dis-tally. at the head of the fibula, approximately 16fascicles are present (Sunderland & Bradley 1949).At the head of the fibula the common peron~alnerve is subject to compressive forces; for exam-ple. it is rachel' inconveni~otly placed at bumperbar height. Also, che nerve is attached quite finnlyto the head of the fibula, making it difficult toslip away from an~' external forces. There is alsoa greater amount of connective tissue in the com-mon peroneal nervc at the head of th~ fibula(68%), compared to 51 % in the popliteal fossa(Sunderland & ~radley (I 949). In general, atleast half of a peripheral nenoe is connective tis-sue. The range is from 210./" to 81 %, with grealerpercentages present where a ne['\'e is located neara joint (Sunderland 1978). .

The significance of the fascicular arrangementis obvious for ne('\'c surgery - sonie knowledgewill be vital to get the best fascicular match dur-ing nerve suture. The significance is less so forphysiotherapists. If the ne('\ous system is pal-pated (Ch. 9) it will be easier to gel a neuralresponse in areas where there are few fascicles(sec Fig. 1.7). In segments where there ar~ agreater number of fascicles, it will require firmerpalpation and the connecli\'e tissue may be symp-

Toil:. 1.6 The fueto.dar branehing in themusculoeu:aneOU$ neNe. From: Sunderland S 1978Ne.rves and nerve injuric$, 2nd edn. Chun:;hill Livingstone,&hnbur,ho With kind pcnnis$ion from the publishers and"'uthor

(1988) referred to this as a 'loose conjunctiva likeconnective tissue'. Nerve movement wjIJ not al-ways be the sliding type. As Sunderland (1989)painted Out, those familiar with injection tech-niques know the cord-like nerve can slip sidewaysaway from the poine of pressure. The mesoneur-ium is an important slnIc(Urc if the nervoussystem is thought of in mechanical lenns. Its roleis not yet completely understood. While the nerveprobably slides through the mesoneuriurn tosome degree. there are likely to be attachmentsboth inside the mesaneurium and frommesoneurium to adjacent structures.

Fascicular arrangement in the epineurium

. Nerves are nO[ uniform structures. Fascicles runin a wavy course throughout the nerve trunk andConn constantly changing plexuses' within thetrunk, Figure 1.6 shows this in a segment ofmusculocutaneous nerve. The position within thetrunk differs as does the number and size of fas-cicles. Art inverse relation el'ists between thenumber and size of the fascicles (Sunderland1978). It does appear, however, that the fascic-ular mesh as described by Sunderland (1978) ismore complex in the proximal portion of thenerve trunk and less so distally (Jabalay et al1980). Together with assembling the required af-ferent and efferent constituents of a nerve' branch,

th~ constantly changing position within the trunkoffers protection from compression and tensileforces, more so than if the fascicles ran in astraight line.

When a greater number of fascicles are present,a nerve is better protected from compressiveforces (Fig. 1.7). The common peroneal nerve atthe knee provides a nice example. At the knee

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THE CENTRAL NERVOUS SYSTEM

Ncrve roots

Nerve roots are ~onsidered to be more a part ofthe central than the periphe.ral nervous system.They involve the meninges, lack Schwann cellsand receive at least half of their nutrition fromthe cercbrospinal fluid.

The connective tissues of nerve trUnks are verydifferent to those in the nerve roots, even thoughthe same axon may be present as in the ventralroOts. Many authors have drawn attention to thefact that the connective tissue eO\'erings in nerveroOts are much weaker, or not present at all.Thus, the suggestion arises, also based on clinicalfindings, that nerve roots arc more susceptible toinjury (Murphy 1977). Morphologicall)' and

preganglionic fibres, one on either side of the ver-tebral column. extending from the base of theskull to the coccyx. Some 21-25 ganglia are con-tained in the chain. A number of postganglionicfibres (rami communicantes) eme~ge from theganglia and connect to the corresponding spinalnerve or to other fibres in the chain (Gardner &Bunge 1984). '

The sympathetic ganglia are capsulated. thecapsules being a Continuation of the epineuriumof attached branches. In the cervical spine, thechain is anterior [Q the transverse processes ofthe cervical vertebrae. In the thorax, it is anteriorand attached to the head of the ribs. close to thecostovertebral joints. Finally, in the abdomen,it is anterolateral [Q the bodies of the vertebrae.The chains are anterior to the sacrum and jointogether anterior to the coccyx (Williams & \'('ar-wick 1980). The location of the chain to axes ofmovement and its connection with adjacentstructures will bc important in body movement.These issues arc discussed. and illustrated in thesection on biomechanics of the autonomic ner-vous system in Chapter 2.

The preganglionic fibres foc the head and neckarise from segmcnts C8 to TS. Those for theupper limb arise from T2 to TIO and those forthe lower limb from TIO to L2. However, withthe continuum of the chain. mechanical influ-cnces may be from further afield.

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".10 MOBIUSATION OF TIl NERVOUS SY$TE.\t

The auConOnllc nervous system

The autonomic nervous system (ANS) is oftenthe forgotten nervous synero. Its di\'ision fromthe somatic nervous syStem must be regarded asartiliciaL It consists of [Wo succeeding neurones.The axons of the firs( are known as 'pre-ganglionic' fibres. They originate in the brain orspinal cord, lie in the lateral grey columns of thespinal cord and exit over some cranial nerves andventral roots, synapsing in autonomic ganglia.The axons of cell bodies originating in the auto-

- nomic ganglia are referred to as

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physiol~gicalty. the connective tissues afe differ-ent and no purpose is served by comparison.Nerve roots lack the connective tissues that arcso much a pan of a periphcral nerve. Gamble(1964) conductcd an electron microscopy studyand found that connective tissues of the nerveroOts were more like the leptomeninges(arachnoid and pia mater) than that of theperipheral nerve trunk. In agreement, Park &Watanabe (1985), using a scanning elecltonmicroscope. observed that each rootlet. as itemerged. was ensheathed by a pial layer. theoutermost of which fonned a covering aroundindividual fascicles. When examined under themicroscope this resembled a 'wispy sheet ofgauze'. Park & Watanabe (1985) ha\'c call1=:dthese layers the 'radicular pia' and noted. undermicroscopy. that the open meshed nature of thesheath allowed free percolation of the cert=hro-spinal fluid (CSF).

This decrease in coment and strength of theconnective tissue structures does not rnt=an thatfibces in' the necve roOts ace left without protec-tion. Othenvise it would seem that nerve' rootavulsion from the cord and severe injury to thencrve roots would bc commonplace. For the mostpan. this does not happen. 'Injuries to neI\'e roOts

- arc commonly not from traction. but rathcr, in-directly from the neighbouring strUctures such asdiscs and zygapophyscal joints. It is extremely dif-ficult to avulse nt=rve roOts from the cord byapplying tension Onto nerve trUnks and plexuses(Barnes 1949. Frykolm 1951). Obscrvations ofbinh paralysis. where the injurit=s are in the bra-chia' plexus and .not at nerve root level. point toconsiderable safety mechanisms at root level.

. Tension and movement, which can be easily ab-sorbed in peripheral nerve. is rransmined elsewhere at nerve roOt level. There arc a number offeatures at nerve root level allowing this trans-mission.

). The fourth, fifm and sixth cervical spinalnerves have' a suong altachment to the gunerof their respective transverse process.Sunderland (1974) examined cadaver materialfrom the lower cervical spinc and found that,'the nc-ural structures and their coverings werenot attached [0 the foramen'. The: "'enebral

artery presses the spinal nerves back onto meguners. Sunderland (1974). in his study of thecervical and upper thoracic spine, noted thatsuch auachmcnts were not evident elsc:where.

Extrathccal attachments of lumbosacralnerve roots have been weU"described (SpencerCl al 1983. Tencer c{ at 1985) and arereviewed below. No comparison has beenmade between thesc: attachments in thevarious regions of me body.

Although the nerve tOOt complex is allowedmovement in the intervertebral foramen. thereare orner areas of auachmcnt. such as themidline dural attachmems to the spinal canal(sec page 17).

2. At segmental levels. dural and epiduraltissues form a connective tissue sheath. Theepidural tissues must include the epiduralsheath described by Dommisse (1975) andHasue et al (1983). Beyond tht= dorsal cOOtganglion, this sheath. fonns the epineuriumand perint=urium. The thcee peripheral necveconnec(ive tissue sheaths do not join upexacrly with the uuee meninges as is oftentaught. Functionally this arrangement wouldnot be the best. The strong perineurium hasno mechanical equlvalent in the nerve roots,and if therc were some means of tensiontransmission. it would be far tOO strong focthe delicate ara.chnoid. The epidural tissuesand thc dura combine to form the epineuriumand the outer layers of the perineurium. Theepdoneurium is a Continuation of the pia'(Shantavt=erappa & Bourne. 1963; Sunderland.1974). Halter et oJ (1971) noted the 'openendedness' of the perineurium in that its outerlayers arc continuous with the dura/arachnoidand the inner layers form the pial sheath (Fig.1.8). This arrangement is bese for forcedistribution together with prcsen'ing a constantenvironment around the nerve fibre. Theperineurium can continue its diffusion batTiermechanisms with the dura and its containedCSF, and the blood nerve barrier of theendoneurial vessels is continued in some waywith tht= pia mater. This junctional area isofu"o misu~derstood. Most descriptions of thearea are of animals. especially rats.

3. The dural slcc\'e forms a plugging

--1'----------- -----.._.._-.....

,

~ "

12 MOBIUSATION OF THE NERVOUS SYSTEM

Fig. 1.8 The junctional zone between peripheral andcenual nervous systems. A arachnoid. D dura. EDepidural tissue, P perineurium, E epineurium. Not toscale. From: Sunderland S 1978 Nerves Bnd nerveinjuries, 2nd eOO. Churchill Livingstone, Edinburgh. Withkind pennission [rom lhe publishers and aumor

mechanism. This not only stops the nerveroots being pulled out of the intervertebralforamen, it is also a convenient forcedistributor (Fig. 1.9). Plugging of the foramenoccurs as the dural sleeve is pulled into theintervertebral foramen (Sunderland, 1974).Sunderland (1974) also noted that tractionwas finally tr~nsmitted to the cord via thedenticulate ligaments and this partially easedthe tension on the nerve rootS.

4. Nerve roots also have their own inbuilt"mechanisms in that they lie in undulations andare able to unfold. Cerebrospinal fluid (CSF)supplies approximately half of the nerve root'Smetabolic needs (park & Watanabe, 1985).CSF also cushions and protects the roots(Louis. 1981; Rydevik et al. 1984). Individualfascicles within the nerve root have the abilityto slide on each other as they do in peripheral

nerv~. The kinking and 'pig-tailing' in theblood vessels supplying the fascicles, furtherexpanded upon and illustrated later in thischapter. provides plenty of evidence (Parke &Wat,anabe, 1985).;Some forces will ultimately be uansmitted cen~ually. It is important to realise that both the

connectiv~ tissues and- the neural tissues will ab~sorb the force.

It seems ~l..::.t r:.erve r'::lots d-:: not always haUl:,"a straightforward exit from the spinal canal in thelower cervical and upper thoracic regions. There

Fig. 1.9 Plugging of me inlervenebral fommen. C cord,D dura mater, NR nelVe root, DRG dorsal toOt ganglion.From: Sunderland S 1978 Nerves and nelVe injuries, 2ndedn. Churchill Livingstone, Edinburgh. With kindpermission from the publishers and 3UmOr

are persistent reports in the literature of an-gulated nerve roots between C3 and T9(Baldwin, 1908; Frykolm. 1951; Reid. 1958,1960; Nathan & Feuerstein, 1970). Angulated or'ascending' nerve roots mean the roots descendin the dural theca and then ascend to emergefrom their respective intervertebral foramina (Fig.1.10). Reid (1960) d-issected 80 cadavers, 5 yearsold and over, and found that 71% had nerveroots running in an 'anomalous' direction. ~athan & Feuerstein (1970) reported an incidenceof angulated nelVe rootS in 38 out of SO cases.Reid (1960) noticed also that. by changing theflexion/extension position of the head. the rootscould be- made to run rostrally or caudally. Thiswas more evident in younger cada\'ers. His resultswere derived from po~itioning the head in a rep-resentation of 'nonnal erect posture'. Extensionincreased the number of ascending rootS. Thisoccurrence is likely to place the rootS and duralsleeves at risk during movement. An obser..ationof Figure 1.10 shows that these angulated nen'eroots will be at risk from movement in all direc-tions. Angulated nelVe roots may be, at least inpart. a result from some pathology such as de-generative shrinkage of the spinal column or thedura being tethered below with the rest of me

",,'>'Il--- sc

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FiC". 1.10 AnguJ:lted c:ourse or ncl'\'C roots. D dura, OSdur.1l sleeve:, P pc:dic:Jc, DRG dorsal roOt ganglion, SCspinal cord. Adap[c:d from Nathan & Feuc:rs[c:in (1970)

,

meninges and neuraxis adapting by aogulating.In both studies. such changes were rarely notedin cadavers, under the age of 25 years. It shouldbe noted that Dommisee (1986) debated theirexistence.

The neuraxis

The neuraxis (spinal cord) is a continuation ofthe medulla oblongata. At approximately lhe L2vertebral segment, it tapers to a point. formingthe conus medullaris (Fig. 1.11). Roughly.. theneuraxis occupies half of the space in each direc-tion in the spinal canal (Hollinshead & Jenkins1981). The ascending tracts arc located in theperiphery of the cord. This not only makesthem more susceptible to compressive forcesfrom herniated disc material or blood, for exam-ple, but also means they will have to contend

RJNC1l0NAL ANATOMY AND PHYSIOLOGY 13

Fig. I.ll The neurnxis and dura. CE cervicalenlargement, CEq cauda equina, D dura, CUt andreflected, FT' filum tenninale, P pons, SN spinal nerve LElumbar enlargement, Adapted from Mathers (1985)

with greater amounts of movement. In spinalflexion, the posterior columns will need to movemore than tracts on the anterior side of the neu-raxis (Breig 1978), the axis of flexion/extensionbeing well forward of the neuraxis. It seems likelythat the opposite will happen-during spinal ex-tension. In spinal lateral flexion mo\ements,tracts on the convex side will be stretched morethan those on the concave side (Fig. 1.12).

Axons in the centra! nervous system are wellprotected by a variety of connective tissue struc-tures, but, like peripheral nerve, the nen'e fibresare not without their own intrinsic protection, Innormal physiological movements the fibres have

,....-----------_._~..

Fig. 1.13 Thl: eUm of elongation on a. segtnent ofhuman spina.l cord taken from the area of the anteriormedian fissure and the 'nferior while commissure (x 525)" The effect of elongation ::IS in spinal fieldon. B Thedfect of shoncnmg. NOle sepan.tion of nerve fibres, insome a.reas inaeased thickness and because or the roldingof the:: tibm. they annOI be:: followed duoughou[ theirlength, From: Breil A. 1978 Adverse mechanical tension inthe central nervous syslem. AJmqvist & Wiksdl,Stockholm, with pennission

14 MOBIUSATION OF THE NERVOUS SYSTE.v.

DC

--=71-r-r-GM""'~~~sc

"-':::: ST

A B

Ii!

!l!

!

II

Fig. 1.12 TraclS of the cord - with the Ilppro~im:ltelocation or lhe axis of flexion and txlemion. The dorulcolumns will need to mo~ further ahan the other In.etsduring flexion and extension... approximate centre. orrotation, B body, C5 I;onieospinal ll";Ict. DC dorsalc;olumn~ GM gray m:llller. SC spinocerebellar lr.ICI, 51'spinous process, ST spinoth:llamic traCt, DL denticuuteligament

no problem keeping up with the body movementsthey control via conduction. Axons are notstraight> as countless textbooks would have it) butare.arranged in folds and spirals which suaightenas the spinal cord elongates (Fig'. 1.13). The pos-terior columns are more folded and twisted thanthe anterior columns since they are funher awayfrom the instantaneous axis of rotation than theother U'aC(S (White & Paniabi, 1978).

Breig (1978) nates twO methods of neuraxialadaptation to stcctch:

Unfolding and untwisting as axons straighten Movement in relation [0 neighbouring

venebral segments.

The CUt end of frcsh spinal cord win ac[ually flowlike a mucoid gel if devoid of connecth'e tissueattachments (Breig 1978). Transfeldt & Simmons(1982) reported similar movement adaptivemechanisms present in the spinal cords of cats.

The meningesThree connective tissue membranes, known asmeninges, surround the spinal cord. The innertwo. the arachnoid and pia mater. are knO\\ll asthe leptomeninges. The much thicker outer layeris the dura mater (Figs. 1.14) 1.15).

Pia marer and araamoid materThese are very delicate membrones. far more sothan the dura mater. A mesh> or lattice) of col-lagen fibres make up the pia and arachnoidmatees. This allows stretch and some compres-sion without kinking (Breig 1978) (Fig. 1.16). Itthus offcrs protection to the neural elementswhile) at the same time) allowing a mov~mentmechanism. This latticing is also present in theneuroglia of both grey and white maner as weU asin lymph ductS within the neuraxis (Ereig 1978).Pia mater is a continuous tissue) separating theCSF of the subarachnoid space from the spinalextracellular fluid spaces. Arachnoid trabeculaecross from pia to the arachnoid. Nicholas & \\'eller(1988) documented the existence of an inter-mediate leptomeningeal layer bet\....een arachnoidand pia (see Fig. 1.14). They suggested that

T'UNCTIONAL ANATOMY .... ND PHYSIOLOGy 15

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asee

asee

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Fig. 1.14 Scanning electron micrograph of the lumbarspinal cord of a 15 month old child. L denticulatcligaments, D dura (note: the layers) A arachnoid, S dorsalseptum, IL intermediate: leptomeningeal layer. From:Nicholas D S, Wdler R 0 1988 The fine an3lomy of mehuman spinal meninges. Journal of Neurosurgery 69:276-282, with kind permission from the publishers andauthors

this layer, along with the arachnoid trabeculae,may serve to dampen pressure waves in the CSFduring body movements, The arachnoid mustcontain the CSF and it appears well adapted todo- this. consisting of multiple layers with someof the membranes fused (\Vaggener & Beggs1967).

D

--A

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~::!i;\-- SAS

t'C----"- N'!i~""':,,--sc

Fig. 1.15 Diogramm:ltic cutaway section of the 5pinalcanal. meninges and 5pinal cord. A arachnoid, 0 disc, DL

d~nticulolc ligament, DM dura maler, NR nerve root, Ppedicle (cuI). SAS subarachnoid 5pace, SC spinal cord,SN spinal nerve

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Fig. 1.16 The collagen arr.mgement of the araclmoid andpia aUow5 some streIch and compression

,.--.- ..eSF, subarach1loid alld subdural spacesThe subarachnoid space (see Fig. 1.14, 1.15)contains CSF. CSF has a primarily nutritive role.but also assists with cord biomechanics. It isthought to act as a hydraulic cushion, surround-ing the cord and nerve roots with fluid and thusoffering protection during body movement (Louis1981). The significance of the mechanical role isevident by the complications that may followdural puncture or durotomy, either accidental orintentional. The CSF cushion is lost with CSFleakage through the resulting dural defect. Theconsequent tr

..,'

-.

16

sponse to changes in intracranial. intra-abdominal and intrathoracic pressure (Maninset al 1972). This indicates that CSF has con-siderable dynamics in response to movement.Due to the relatively incompressible shape of thespinal canal, the shape of the dural theca mustchange as me pressure in the epidural venousplexus does. The inclusion of pathology insidethe spinal canal could easily interfere with thesemechanisms.

The subdural space (see Fig. 1.14) is a poten-[ial space, containing a little serous fluid, whichprobably allows sliding of the arachnoid on thedura.

Dura macer

Durn mater is the Qutennost meningea:11ayer andby far the toughest and strongest (see Figs 1.14& l.15). It consists primarily of collagen fibresand some elastin fibres aligned in the longitudinalaxis and in layers (Tunturi 1977). This gives thedurnl theca great aKial strength. although it isconsiderably weaker in the ttansvc=rsc direction(Haupt & Stoffi 1978). Surgeons have oftcn com~mented that, if the dura tears. it tcars in an axialdirection. Dura mater is a remarkable tissue. itdoe~ n.ot .deteriorate with age and is sui[ablc asa material for heart valve-replace-':lent (van Noortet al 1981). This sugge'sts a toughness, combinedwith good vascularisation and i'nnervation. Duralinnervation and its consc=quences are discussedlater in this chapter and in Chapter 4.

The spinal dural theca is a continuous enclosedtube running from the foramen magnum [0 thefilum terminale at the coccyx. At segmental levelsthere arc prolongations - the nerve root sleeves.Spinal dura mater is continuous with the cranialduni. .

Other spinal CQJ'lol contenuThe epidural space contains the internal vertebralvenous plexus, discussed in more detail later inthis chapter. There are also fat deposits. Fat de-posits are localised in' the intervertebral foraminaand in the Dosterior recess between the ligamentaflava (Parkin & H:mison 1985). The fat appearsto be regulated by the space available. In spinal

stenosis the amount of fat in the spinal canal di-minishes.

NERVOUS SYSTEM RELATIONS -SPACES AND ATIACHMENTS

A relationship between component pans exists inany moving structure. In the nervous system, thisis defined by the space around the componentpans and the connections between componentparts. Adequate space is needed around the neu-ral and connective tissue and there must beenough space at rest and during physiologicalmovements of the spine. Within the spinal canal,lhe CSF-fitted subarachnoid space. me potentialsubdural space and the epidural space arc themain considerations. The integrity of these spacesis essential for movement.

The nervous system is anached to surroundingtissues and structures. These attachments differin different areas of the body, but are repe:uableanatomical features and arc essential for normalrange of movement of the n~rvous system. Thisis an imponant concept for physiotherapists. JUStas the knee. for example, has collateral and cru-ciate ligaments to guide and limit the movementof the knee. a similar role is played by the canneetions of the nervous system. Alterations in thestructure and nature of the spaces and attach-ments' are likely to be of clinical significance inadverse tension syndromes. Attachments needconsideration in tenns of those anaching neuraltissue ontO connective tissue, such as the dentic-ulate ligaments. and those attaching connectivetissue (and thus the neural tissue) ontO otherstructures. such as the dural ligaments.

Hasuc et al (1983) have shown that the spacearound neural tissue. both in the spinal canal andthe intervertebral foramen, is less in males thanin females. These authors also point out that de-velopmental and degenerative stenosis is morecommon in the male.

The e",..ternal connections of the dura

Inside the cranium, the dura mater is loosely ad-hered to lhe central portions of the cranial bonesand tightly adhered at the suture levels (Murzin& Goriunov 1979). The spinal dura mater is con-

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FUNCTIONAL ANATOMY AND PHYSIOLOGY 17

Fig. 1.17 Diagrammatic lransversc seclion of the spinal canal ;md the auachmems of the neuraxis and meninges. Aarachnoid, B body, D dur.l, DuL dural ligament, DeL denticulale ligament, DMS dorsomedian septum, DR dorsal roO!,SAS subar.lchnoid space, SAT subarachnoid trabeculae, SN spinal nerve, SP spinous process, VR ventral roOI.

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.,

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ligaments around lA: were stronger and more nu-merous than elsewhere - so strong that theycould not be displaced with a probe. Thoracicdural ligaments tend to be filmier and longer, andin the ccrvical spine, they are shorter and thickcr(Romanes 1981). The Studies' of Tencer et al(1985) have revealed that, in the lumbar spine,dural ligaments, ,nerve roots and trunks are ofequal importance in the distribution of forces.Yet. Tencer et al (1985) also found that theseligaments provided minimal restraint to duralmovemcnt in the .longitudinal axis. Nevertheless,the peripheral nervous system provides theneuraxis and its membranes with a very strongphysical acraclunent to the rest of the body.

Dorsally, a plica or septum (dorsomedian sep-tum) has been shown to be a consistent featurein the posterior aspect of the spinal canal betweenthc f1avalligament and the posterior dura mater.(Parkin & Harrison 1985, Blomberg 1986,Savolaine et al 1988) (see Fig. 1.17). These at-tachments are longer than the anterior

~>,----"

tinuous with the cranial dura mater. There is afirm a'uachment at the foramen magnum and, atlhe caudal end, to the coccyx by the externalfilum tcrminale. This is a thin elastic tube, moreclastic than the spinal cord, and a likely bufferto cord overstretch (Tani et al 1987). It is a reg-ular occurrence for physiotherapists investigatingcoccydynia (Ch. 13) [Q find that patients withthis common disorder present with altered ner-vous system mechanics.

A network of dural ligaments (Hoffman liga-ments) attaches the anterior theca to the anteriorand anterolateral aspect of the spinal canal (Figs1.17 & 1.18). Early anatomists were well awareof these tethering ligaments. A revival of intcresthas spurred a resurgence of study into these Iig_aments as a part of neuraxial and meningealbiomechanics (Spencer Ct al 1983, Tencer Ct al1986). In the lumbar spine, the ligaments areparticularly well devcloped and not only do theytether the dura centrally, they also tether it in thelateral recess. Blikna (1969) noted that the dural.

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._----==-=-=-- ;=-'.- ...18 MOBIUSA1l0N OF 1'1iE NERVOUS SYSTEM.

Fie. 1.18 Dunllipme.au. A thor.lcic, B lurnbu. 'I"M dun! lho:a. is held back with probe. From: Tc.nccr A F, Allen B L.Ferguson R L 1985 A biome:dumical study of choncolumbar spine fnetuee:S with bone:. in ihe:. canal. Put III. MecbaniC1lproperties of the:. dur.l and its tethering ligaments. Spine 10: 741-747, ",;!.h kind pennission trom the: publishers and authors

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anachm~ts (Parkin & Hamson 1985). They areanatomically complex. strong. and it SttI1lS ioev.irable that they win be. involved in the bio-,mechanics of neuromeningeal tissues. particularlyin. the considerable antero-poSlerior movementsnoted by Penning & Wilmink (1981). This pos-terior dural anachment could also be a reasonwhy some epidural injections may not have thedesired effect. If the plica is a continuous tissue,all the dura may nOt be bathed in the injectionmaterial.

Internal dural attachments

Inside the dural sac !.here are 21 pairs of dentic-ulate ligaments (see Figs 1.14, 1.15 & 1.17).These run from me pia mater (0 the dura andarc orientated to keep the cord central in thedural theca. With the cord 'slung' in the theca,any rension or movemcnt is far greater in thctheca than in the cord (Epstein 1966. White &

Panjabi 1978) (Fig. 1.19). Tarn et al (1987) haveshown that the denticulate ligaments, as \\ell as

. the filum tenninale. prevent excessive elongationof the cord during flexion. Thickened denticulateligaments associated with cervical spondylosishave been implicated in cord degeneration (Bed-ford et al 1952).

The subarachnoid trabeculae run from thearachnoid to the pia. They form large channelsfor the CSF, and probably dampen pressurewaves in the CSF (Nicholas & Weller 1988).

Attachm.ents of the peripheral nervoussystem.

The peripheral nel"\'es are also attached to sur-rounding tissue. However. they arc allowedmovement in their nerve beds. less in some areasthan in others. such as where blood vessels enter01'" where nerves branch. This is an understudiedarea. probably mirroring the importance glven to

jlII

'. FUNcnONAL. ....NATOMy ...:-':D PHYSIOLOG' 19

understanding of symptom reproduction relatedto the ncryous system:

The supply of blood 10 the nervous system The axonal transpon systems The innervation of the connccti\'c tissues of

the nervous system.

All of these processes will be influenced br me-chanical deformation.

CIRCUlATION

,B L,edJthors

have In as II,tionJlate ilosis3ed-

the ,

.nels ~Isu"").

$ur-wedteasntet:liedn to

DC

tJ ~.,,,. ",.It ( ..... -... '}

\... , ..'......_.-....

Fig. 1.19 The demieul3le Jig:3menfs sling (he cord in thedUr31 thCOl. These ligamcnfS st:lbilise the cord eentrally inthe dUr31 meca :md provide stability against axial ::lIldtr.Jfl5VCfSC forces. 0 dura. DL denlicuble lisamems, SCSpilUl cord. at 2Xi~J ICTlsion. It lMI11S\'crse lensioll. Ad2plcdfrom Whilc & Panjabi (1978)

nerve biomechanics Oil present. The mesoneurial(issues, the ner'\'c itself and the stnlc(ure to whichit anaches, dearly possess quite complex anatomyfor movement purposes. \\1hat is unmistakable isthat, along: the course oC a peripheral nerve, thereare some areas where me nerve is more attachedthan others. for example, the common peronealnerve at the head of the fibula, and the radialnerve to me head of the radius. Yet in oilierareas, a remarkable amount of movement of over1.5 em occurs (McLellan & Swash 1976). In anearlier section I discussed the mesoneurium.Where a peripheral nerve is attached to an adja-cent sttuclure i( must attach in some way throughthe mesoncurium. if the mcsoneurium is a con-tinuous sU'Ucture. This connecrion ne~dshistological an~lysis.

THE BASIS OF SYMPTOMSKnowledge of rjvo:c pro,:csses :': important EO ':',',

The nervous system consumes 20% of the avail-able oxygen in the circulating blood yet consistsof 2% of body mass (Dommisse 1986). Amongcells, ncutones arc especially sensitive to alter-ations in blood now. An unimeInlpred \'ascularsupply is imperative for the metabolic demandsof normal neural ftJOction. The blood supply tothe nervous system (vasa nervorum) is wellequipped to ensure that blood flow to neuronesis unimpeded in all dynamic and static postures.Blood supplies the neccssary energy for impulseconduction and also for me intracellular'move-mCnt of the cytoplasm of me neurone.

A general pattern of blood supply to ncuronesexists. There are extrinsic vessels supplying feederaneries to thc nerve. Once inside the neryous sys-tem. iliere is a .well developed intrinsic system(Fig. 1.20). In rn3!1Y pans of the body, bloodsupply is SO assured that if some feeder vesselsarc compromised, the intrinsic system can pro-vide enough blood for nonnal neural function.\Vith such an assured supply, it may seem thatthe nervous system can be relatively independentof its blood supply. Stripping of feeder vessels,3S occurs in peripheral nerve surgef)', may notgive rise to a defect. However, if after suipping,

EN -,.. .'

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'N nFig:. 1.2.0 The extr.ancural and inl,~(l(uf3J design Qf thecirCUlatOry S)'Slem. EN c:ur.mcural vessel, I>: imranellolvessel, FV feeder vcssel, N ncr'\'ous system

.' .'. ."-~1l:'.- ~. . .

20 MOBIUSATION OF THE NERVOUS SYSTEM

Vasculature of the spinal canal andneuraxis

a vital feeder artery is blocked. the nerve will faitrapidly (Porter & Wharton 1949).

There are usually around eight medullary feedc=rarteries (Lazorthes et 031 1971, Dommissee 19(4),These arteries are more common in the lumbarand cervical spines. although gecat variation be-tween cadavers has been noted (Dommissc1986), Some: cadavers have been noted with onlytwo anterior medullary feeders, while others mayhave up to 17 (Dommisse 1986). It is clear thatthe person with only two such arterics is more atrisk and may present different signs and symp-toms &om the samc injury than a patient withmany medullary feeder arteries. Most of the ar-teries enter the cord in the low cervical spine andthe lumbar spine, This is a sensible design, for,not only are there neurones of the brachial andlumbosacral plexuses to supply, but during spina!movc=rnents tilese plexus areas have limited mm-e-ment in relation to the spinal canal (Louis 1981)(Fig, 1.21). These issues of cord and spinal canalmovements are taken up in the nC:l.:t chap(er.

-,----~: -.~-~-----.-:-:=--=- - -.==:----

These structures have a multiple supply. The ver-tebral artery, the deep cervical, the posteriorintercostal and the lumbar arteries supply the ver-tebral column. They also supply, via segmentalsubdivisions, the spinal canal and contems. Atcertain vertebral levels, mc=dullary feederbranches arise and join the longitudinally runninganterior and two small posterior spinal arteries.At every level. the segmental spinal arteries giverise to radicular arteries which supply the distall1alf of the nerve roots. The anterior spinal arterysupplies about 75/" of the cord. It is more a lon-gitudinal system of functionally independentvascular entities with a related feeder vessel.

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Fig, 1.21 Photograph of an inj~CI(d and deared cervicothoraciesection of I neonatal spinal rord_ This shows the a"~rial medullaryvasculari~tion It the C5-11e:vel oCtile cervial spinaJ canal. At thislevel of the spiruJl canal me lumen. is It its narro.....est. From:P:ldtc WW 1988 Corttblive an.llomy of cenial spondyloricmyclopathy. Spin~ 13: 831--837, with kind pennissi

Vasculature of the nerve roots

Blood is supplied to each root from two distinctafferent vessels. In the proximal radicular anery,blood arises from a longitudinal spinal artery andflows distally. The distal radicular anery ari~ssegmentally and blood flow is proximal. (parkeer al 1981) (Fig. 1.23). At chI! meeting of the(wo systems there is an area of relativehypovascularity. Within the rOOt itself. me in.uaneural supply is very complex. Parke &Watanabe (1985) produced a detailed study ex-amining the compensatory adaptations that thevascular supply of the nerve roots have for move.mem. In Figure 1.24, the full range ofadaptations [0 movement are evident in order toallow the fascicles to slide on each other duringmovement. These fearures are more evident inthe lumbar nerve roots than cervical (Parke &Watanabe 1985). Parke & \\"'atanabe (1985) referro the adaptations as 'coils) T-Bars and pig tails'.The coils and pig tails allow scretch while theTBar branches allow rapid shunting of blood if

F'UNCI10NAL ANATOMY ......";0 PHYSIOl..OGY 21

coughing and strainIng. Together with the CSFpressure) via the alterations in the venous system,a balance of intraspinal canal preSSure is main-tained. The ,,:,enous pl~xuses take up much of theremaining non-neural Space in the spinal canal.This also offers the cord some protection. Theseveins consequently have a function as 'pressurestabilisers') according (0 Penning and Wilmink(1981).

A critical vascular zone exists from the T4 toT9 ven-ebral levels. The spinal canal is at its nar-rOweSt and the blood supply is less rich in thisarea (Dommisse 1974). This rna}' be relevant insyndromes such as the 'T4 syndrome' (Ch. J3).

t

Clefts in me cord allow blood vessel access toncurones. These perivascular spaces arc alsolymph dvcts draining me cord. A similar lanicedcollagen arrangement to the leptomeninges existsin these elefts or ducts whereby the lattice of col-lagen fibres protects the blood vessels in stretchand compression (Breig 1978). With this mech-anism) plus a multiple segmental supply to allareas of the system) blood supply is normally as-sured. Also. the system of segmental feeder.vesselS running transversely) together with in-traneural vessels running longitudinally, willassist. When the cord is elongated the vesselsrunning longitudinally are scretched while thoserunning transversely arc folded. The opposite ef.feet occurs on shortening of the cord (Fig. 1.22).Another protective mechanism may come fromthe strong pulse in the cord continually'bumping' it away from possible impinging struc-tures Uockich et al 1984).

A multiuse venous system exists in me spinalcanal. Intramedullary veins drain into a series oflongitudinal veins in the epidurnl space - thevenebral venous plexus. These veins in the spinalcanal are valveless and under linle pressure (Pen-ning & Wilmink 1981). This allows now rever-sibility) and an accommodating mechanism tosudden in-rushes of blood, as may occur rrom

np-\ilh.,-

andfor,andinal)\"c-81)mal

:der; 4)..barbe-issemlynay:hateat

FiC. 1.22 The blood suppl}' during s(rO:lo:h 2ndCOtnpression. or the spinal cord. A

Fi\:. 1.24 Tho: intrinsic blood supply to Ii nerve root. A anenalt, FP fasicular pia, RP radic:ular pia. V \enule. Adapl~d(rom Parke & W"alalUbt (1988)

I,i,,

!iI

fa bra.,l)cl). is, blQcked. WaranaJbe & Parke (1986)nored that, in a cadaver with spinal stenosis, the'pig tails' were accentuated to the=: sides of theconstriction but absent under the constriction.The overall arrangement permits lateral and axialmovement betwee=:n fascicles. These are necessaryadaptations for movement given the 'piston-Iike'movement of the nerve roots that occurs in theforamina during spinal movements (Sunderland1978).

The radicular veins are few in number, and tosome e=:xtent mimic the arterial supply, althoughobviously with a reversed flow of blood (Parke &Watanabe 1985).

Vasculature of the peripheral nervo~system

The peripheral nervous system has a vascularsupply as good as, if not better than, the central

nerv~us syStem (Fig. 1.25). Perhaps this.vascula-'ture has developed duc to lhe greatcr ranges ofmovements required of the=: peripheral nervoussystem. The vulnerability ofaxons of the periph-eral nervous syslCm to vascular changes is wellknown (Sunderland 1976, Rydevik et al 1981Gclhetman et al 1983, Powell & Myers 1986).The v3scular arrangement is, once again, de-signed for uninterrupted flow, regardless of theposition of the nervc in relarion to the sUn'ound-ing tissue. The extrinsic supply of the peripheralnerves is such that it allows leeway for movement;

that is, there is slaek in the feeder vessels so that:l nerve can glide without alteration in the bloodsupply. Note in Figure 1.26, where a net\'c hasbem, how the adaptations of the circulatory sys-tem have ensured adequate blood supply. Ingeneral. major feeder vessels entet: nerves at areaswhere there is minimal or no nerve movemenr inrelation to surrounding tissue. Examples of thisare at the elbow for the median and radial nCITes.These issucs are discussed in detail in the next

. chapter. However, if part of the extrinsic supplyis occluded) the intrinsic supply is also sufficientfor the needs of the=: nerve fibreii (Lundborg 1970,1975).

The intrinsic vascular system is extensi\'c) link-ing endoneurium, perineurium and e=:pineurium.Only capillaries cross the perineurium and musinto the endoneurial environment. These vesselsrun in an oblique direction across the perineur-

)um and this may allow a valve mechanism,squeezing the vcssels closed if thc intrafascicular-pic=:ssure rises. Note me insct in Figure 1.25(Lundboq: 1988).

Under normal conditions) only part of the in-. traneural vascular system is used. Howe\'er, iftraumatised) many mOre vessels come inca usc(Lundborg 1970). Intraneural blood no\\' is re-versible and collateral systems exist. Kate thearterial loops in Figure 1.25. Such anatomy em-phasises me need for uninterrupted blood supph'to nelVe fibres and me importance of maintaininga constant endoneurial environment. (Lundborg

FUNCll0NAL ANATOMY .-\.';"D PHYSIOLOGY 23

'NV

"\

."!"-:""', ..

Fig. 1.25 The blood supply of a multifascicuJar scgmcrn of p..-riphcr.l1 nervc. EN endoneurium, E~'V e:'l.UaI1cur.1l \'essel,EP epineurium. FV feeder "esse!. P perineurium. The Inset shows the oblique direction of a blood I'csse] entering mefascicle. Adap[(~d from Lundborg (1988)

AA

,

'"--HI"\' I

=~.

1975, Bell & Weddell 1984). Intraneural bloodvessels arc sympathetically inner\"3red (Hromada1963, Lundborg 1970, Appenzeller ct a1 1984).According to Appenzeller ct al (I984), the nervesupply to ::t particular blood vessel arises from thenerve trunk that the blood vessel supplies. Thisprobably allows an adjusrable blood supply forfunctional demands on the nerve.

Stretch and compression will surely alter thecirculation, although. the mechanisms are notfully understood. Stretch will lessen the diameterof the longitudinally running \'cssels, plus raiseintrafa.scicular pressure and perhaps result insqueezing closed the vessels crossing the peri-neurium. Arrest of blood flow will begin atapproximately 8% elongation (rabbit sciatic tract)and complete arrest will occur at approximately15% elongation (Lundborg & Rydevik 1973,Ogata & Naito 1986). The clinical consequencesof this arc discussed in Chapter 3,

Fi:::. !.U Diagr::mmalic ::Iuslralion of the ~';~p[a[ions infeeder "csscls [0 allow inlr.lfascicul:lr rnm'cmcnl. F fascicle,BV blood vc:ssel

The blood nerve-barriers

A slightly positive pressure exists in the in-

iIIIiI

III

iJ

24 MOBIUSATlON OF THE NERVOUS SYS1cM

uafascicular environment. This tissue pressure isreferred to as the endoneurial Ouid pressure(EFP) and is probably maintained by the elastic-ity of the perineurium. Lundborg (1988) hasshown how me endoneurial contents will'mushroom' through dle perineurium. if CUt. Al-terations in the ionic composition or pressureswithin mis environment may inrcrfcre with bloodflow and, consequently, conduction and the flowof axoplasm. There are twO barriers which main-tain the endoneurial environment theperineurial diffusion barrier and the blood-nervebarrier at endoneurial micro\'cssels. The peri-neurium is the more resistant barrier (Lundborg1981). Perineurial lamellae arc pan of the diffu-sion barrier mechanism. The junctions form'right cells' and, b}' control ofsubSlancc flow, canregulate the intrafascicular em"ironment (Lund-borg 1988). Onl}' small capillaries and venulespass through the lamellae and these travel in anoblique direction (Myers et al 1986) (see Fig.1.25). The b:urier funcrion is bi-dircctional. Aswell as protection from the exrerior, this mecha-nism means th~{ if we intrafascicular pressureincreases, such as from an oedematous reaction(Lundborg & Rydcvik 1973), the barrier mayclose. A good example of me protective functionof the diffusion bamer is where periphcrnl nervestravel through infected areas without nerve con-duction being altered. The perineurial barrier isresistant to trauma. and. cven after surgery toepineurium, the resultant epineurial ocdema willnot breach the perineurium (Rydevik et al1976). Nor will an ischaemic induced epineurialoedema affect the bamer, at least initially(Lundborg et al 1973, Lundborg 1988). InChapter 3. the consequences of a prolongedoedcmatous reaction in and around the nervoussystem are discussed.

The endoneurial capillary bed can be consid-ered a peripheral example of the blood~brainbarrier. known as the 'blood-nerve' barrier'

(W~ksman 1961). Substances such as radioactivetracers and dyed proteins will cross throughepineurial blood vessels but not through the tightendothelial cells of the endoneuria I microvessels(Oisson &. Reese 1971.0:;;500 et a\ ~971). Onenotable exception to this> and relevant to diabe-tes. is that simple sugars can cross the barrier

. i!!I" "~-~1- ':fa.

(Mackinnon & Dellon 1988). Both these barrierswill break down after acute or chronic compres-sion (Rydcvik & Lundborg 1977, McKinnon et.1 1984).

The perineurial barrier funclion is illustratedin Figure 1.27. Simply, a reaction outside theperineurium win not gain access to the endoneur-ial environmem. Yet. a reaction such as ischaemicdamage to microvessels. leading to oedema, wiltincrease the endoneurial fluid pressure fromwithin and consequently close the barrier (Sun-derland 1976, Lundborg 198B> Mackinnon &Dellon 1988). The perineurium of the peripheralganglia has a barrier function similar to that of

A

c

Fig. 1.21 The perineurial diffusion b3rrier. Eendoneurium, Ep epineurium, P perineurium.A NQnn~! segment of pcripher~l nerve. B If a rea~lioJ\ i~inlfodu,ed around !.he nelVe and inlo !.he epineurium, thepcrineurut! dilrusion baTTier, via subst:lnec: ,ontrol protectsIhe imnfascit'Ular envicolUTlenl. C If :I re:lC1ion hct;insinside the p.:rineurium (e.g., virus, oedema) ~ndintrafasdcu!ar pressure incrc:ases, the b~rrier closcs ::md thereaction is kepi within the perincurium. DcstN'lion ofneural tissue may folio.....

"

\

I1

.;;

rrierspres-,n et

rated, the Incur- Ilemic f

will .I, ,from ,:Sun !:m & ,,hcral Ilat of !

I,

,

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I

peripherol nerve. McKinnon & Dellon (1988)h.we postulated lhat breakdown of the bloodnerve barrier may mean a breakdown of an im-munological barrier, similar to the blood-brninbarrier. which can be broken with inflammationor injury.

Physiotherapists need knowledge of the prop-erties of the perineurium and the diffusionbarriers. Many answers in disorder interpretationand prognosis lie within its stnlcrurc. Techniquesof mobilisation and prognosis will differ depend-ing on whether a pathology is inside thcperineurium or outside of it. In Chapter 3 thepathological processes that follow impairment ofthe function of the diffusion barriers arc dis-cussed.

AXONAL TRANSPORT SYSTEMS

Within the cytoplasm of all cells. there is move-ment of materials and substances. The cy[Qplasmof the neurone (a.."

26 MOBIUSA"ON OF THE NERVOUS SYSTEM

mately 400 mm per day and the substancescarried. such as neurotransmitters and transmit-ter vesicles, are for use in transmission ofimpulses at the synapse (Droz et al 1975). ThistransPOrt depends on an uninterrupted supply ofenergy from the blood. Various toxic substancesand deprivation of blood will slow or block thetransport (Ochs 1974).

In the slow amegrade transpon (1-6 mm perday), cyloskeletal material such as microtubulesand neurofilaments are carried (Levine & Willard1980, McLean Ct 31 1983) Essentially, the slowtransport exists for maimenance of the structureof the axon.

The exact mechanisms of transport are un-known. Various hypotheses, including forcegenerating enzymes and transport filaments, havebeen summarised by Lundborg (1988).

... Retrograde transport

Rerrograde lr3nspOrt from target tissues to thecell body moves rapidly (approx 200 mm perday). The system carries recycled transmitter ves-icles and cxtracdlular materials such as neuritegrowth promoting factors from the nerve tennin:J.1or from damaged segments of nerve.

It also seems very likdy that the rettognde flowcarries 'ttophic messages' about the Staws of theaxon, the synapse and the general environmentaround the synapse, including the target tissues(Kristensson & Olsson 1977, Varon & Adler1980, Bisby 1982). If the retrograde flow is al-tered by physical constriction or Crom loss ofblood flow, nerve ceIl body reactions are induced(Ochs 1984, Dahlin & McLean 1986, Dahlin etal 1987). Viruses. such as herpes simplex, can betrampc:>rted via the retrograde transport: to the celtoody (Kristensson 1982). In Chapter 3, the cir-cumstances leading to, and the effects of,depletion of the axoplasmic flow are discussed inmore detail.

An understanding of the concepts of axonaltnlnspon is imponant for physiotherapists em-ploying mobilisation of the nervous system as atreatment. As KOrT has suggested for some years(1978, 1985) many of the disorders we treat andthe rtsponses from treatment may be related tothe axonal transPOrt systems. In this regard, KarT

- . ;1!:."?~'-'''t' .. ".'~ .

is refemng to lrCatment via joint soucrures. Theeffects of mobilising the nervous system as \'-"ellas joint structures 'NiIllogicalIy have a greater ef-fect on the flow of axoplasm. Knowledge of thesesyStems is also imponant in order to understandthe development of symptoms along the nenoussyStem (ie, double crush, multiple crush syn-dromes) and the need to treat often more thanthe local area for optimum results.

INNERVATION OF THE NERVOUSSYSTEMThe title of this section is somewhat paradoxical.However, the connective tissues of the nenoussystem are innervated. They are, thus, able to bea source of symptoms. Already in this chapter,the design of the nervous system for a mo\-ementfunction has been outlined. By the innervation ofthe supporting stnlCCUres, some protection to theprimal')' neurones is given. This innervation alsomeans that the connective tissues of the nenoussystem can contribute to altered sensory input inthe same way that muscle, joint and other tissuescan.

Documentation about the innervation of thenervous syStem is far from complete, and the clin-ical consequences not fully understood. )'1anymajor textbooks on the subjects of neurology andorthopaedics neglect it. Of importance also \\;th'mechanical thinking' are the connections of menervous system to other tissues. These artach-ments and the strUccures they attach to are likdy(0 be innervated.

The meningesDura mater is innervated by segmental, bilateral,sinuvertebral nerves, first described by Luschka(1850). These are tiny nerves, hardly, if at all.visible to the unaided eye. Each sinuvertebralnerve emerges distal to the dorsal rom ganglion,from the union of a somatic rOOl arising from thevenual rami and an autonomic rOot from th.: greyrami communicantes or a sympathetic ganglion(Fig. 1.29). The nerve is sometimes known asthe recurrent meningeal nerve. Each sinuverubralnerve pursues a perivascular course back into thespinal canal through the intervertebral Coram.:n.

It

i

tI

Fig. 1.29 Di~gramm:lti, rcprc:scnt:nion or Ihe sinuvcrtcbr.!! ncrye innervating the dura maler, from the I"cntral aspect. aV'blood \'Cs.~d. D dur.!. DRG dorsal root g::Inglion, GRC gr~y rami communicanles, PLL posterior longin>"::::lal lig:lment. SNs,;nu\'crtcbr.ll nc~,:. ST symp:lthClic m,mk.. NOle (hal the dur.l is innervated directly by the sinu\cncbr.ll :-:Cl'\'C and thaIsome fibres Cn \';:1 Ihe pllMcrior lonci(udin;ll Jil:~mcnl. Nerve libres from blood ,"cuds abo 5uppl)' the C~:...

t"_.

DRG,

'I---D

FUN(.TJONAL ANATOMY ASD PHYSIOLOG\" 27

of the nerve endings in the dura mater (nocicep-tive pain). Branches of the sinu\"enebral nervespread to the opposite side and up and down anumber of segments. Edgar & ~undy (1966)measured the extent of axial spread of innervationas a toral of four segments. while Groen et al(1988) measured a maximum of eight segments,four rostral and four caudal.

The sinuvertebral nerves may go directly to thedura or go via the posterior longirudinalligamenr.Groen ct al (1988) noted (WO' previously unre-corded features of the sinuverrebral nerve. Firstly,the nerve travelled as u, ,.t: ;',

~TI- '~~;, ,~",an .'"

"\'.';~

- ---- ---- ---.....-

-'"0--- - ._-

28 MOBIUSAT10N OF THE: NERVOUS SYSTEM

i'.

I,

rI ~\.

A B C

FI,. 1.30 The multiscgmc:mal mC'Shwo~ of dl,lQI innerv:lIion.. A Dorul \'iew of vo:mral durn m:HC':" (f2-T5). The pl.:l\,-U~is prim:llily lonGiTudinally amangcd and in 1Ile: 'mle:l'Stee:ve:' pan~ 1Ile: nCl""CS run do~lly. 8 Tracing of the: pholO&f'1lph.Note the CUI and curled segm~n[5 of nerve5. C Dt'3wing of m:r.jor dUr:11 nerve :md the cxtent of 5cmeneal innel"\'a\ionFrom: Grocn G J, Baljce B, Drokkcr J 1988 The inncrvatiOll of the spinal dura m;l[cr: Anatomy ;]nd elinical implkations.Acta Neurochirurgic:a 92: 42, wilh kind pc:.rmission from the publisher and the aUlhors

supply than the thoracic roar sleeves (Cuatico etal 1988).

AU recent authors on the subject agree that theventral aspect of the dura matcr has a far denserinnervation than the dorsal aspecL Cyriax (1982)uses .p~inless needle entry from lumbar pUJJcturcinto the posterior dura as an example of this dor-sal insensitivity. Towards the midline, the dorsaldura mar be completely insensitive (Groen et al1988).

Branches of the sinuvertebral nerve also supplythe dura mate. and blood vessels of the posteriorcra.nial fossa (Kimmel 1961). The greater pro-portion of the rest of the cranial dura is supplied::'y the :..;geminal nerve ~ogduk 1989}. The likelihood of some headaches originating from cranialdura has been long suggested (Penfield & McN-

aughton 1940). These headaches are discussedin Chapter 13.

An inferior branch of the sinu\'ertebral nervespasses through the dural ligaments (Parke &Watanabe 1990) and probably innervates them.Dural ligaments span two highly innervated tissues, the posterior longitudinal ligament and theventr.ll dura matcr and may well be a bridge forbranches of the sinuvcncbral nerve. This 'crypiausible suggestion was made by Groen et al(1988) who also thought that some anatomistsmay have confuscd sinuvertebral nerves for duralligaments. In the absence of literature, Sunder-land (pers. carom. 1989) feels thcy are likdy tobe innervated. Certainly, the scar formation in-volved in pathological tethcring will have a nervesupply and it may also cntrap the nervc itself.

'~"'"- "'::""1

d , ,

"&,.

;-

30 MOBIUSATION OF lliE NERVOUS SY~

Sunderland (1978) considers the pain from localpressure on a nerve to be due to the nervinervorum but also acknowledges (1979) thatthere is a lack of information regarding the statusof the nervi nervorum in pain states. It seemslogical that stretch. radu::r than compression. ofa segment of peripheral nerve would involve morenociceptive endings. Perhaps there is some spe-cial relationship between the nervi nervorum andthe primary neurones. Perhaps nociception fromthe connectivc tissues could 'close down' whenectopic impulses of a particular narure arc gen-erated along me primary neurones.

More study on the physiology of me nervinervorum and ils role in pain States is necessary.The most recent reference to this innervation isHromada in 1963. Newcr staining and examina-tion techniques may reveal more infonnationabout the nerve endings of the nervi nervorum.We can still only presume that me nerve endingsare nociceptive. The blood vessels of the peri-neurium and epineurium are sympatheticallyinnervated (Hromada 1963. Lundborg 1970.Appenzeller et al 1984 Thomas & Olssen 1985).This no doubt helps to maintain a constant in-trafascicular environment.

Hromada (1963) also noced mat the con-nective tissues of the dorsal roOt and sympacheticganglia receive innervation from fibres whosecell bodies are located in the ganglia themselves.A second source of innervation arises fromfibres entering me ganglion from associated peri-vascular plexuses.

The innerva.tion of the nervous system cannotbe neglected - it seems very likely that it plays

REFERENCES

Appenv:ller O. Dithal K K, Cowan T , Bum~lock. G 1984The nerves 10 blood ve~l~ ~upplyinl blood nCIVCS: theinnuv:uion of vasa ne['\orum. Bnin Rescafcb 31)4,:38}-386

Baldwin W M 1908 The IOpognphy of spinal nave roo[~,Anatomical Record 2: 155-156

B:imcs R 1949 TraCtion injurie~ or the: bl"'.1ehial plexus inadullS. journal of Bone and joint Surgery 31B: 10-16

Bedford P D, Bosanqu

)s in-:cti\'eptomcon-

from

)f thepulse:t bebody; sys-) sc: .....:uions on'the .:onneai"o: tissues or a pcriphe~1nco'C ~nd a spinal net\'e rOOt in the f;it, Journal of.An:Jtomy 98: 17-2')

Ga:rdncr E. Bunge R J> 198,1 Gross ~n:llomy of theperipheral nervous sS'Hcm, In; Old;. P J, Thomas P K.1..:Imben E H. Gungc R (cds) I'eriphel"lll neuropathy.2nd cdn, S:nlnden. Phibdclphi:, Vol I

Gclberman R H, Sz~bo R /\1, W'i11ianlSOll R V 1983 Tissuepreuure threshold for periphcr~1 neo'c I'i~bili[)', Clinic~lUl1hQlnCOlcs:Jtld Related Research 118: 28>-291

Glee! P 1943 Ob$

32 MODlUSA1l0N OF THE NERVOUS SYSTEM

Levine J, Willard M 1980 The CQmpesition andorganisation of a.,;omlly lransported proteins in theretin:ll ganglion 0::115 of the guinea pig. Brain R=rch194: 137-154

Louis R 1981 Venebror.ldieular and ~n.:bromc,odullardynamics. Anatomica Cliniea ): I-II

Lundborg G 1970 Isehaemie nerve injul'}'; experimentalstudies on intr.meur.ll microvascular pathoph)'siolog)' andnerve funeLion in a limb, subjected to temporarycircul:ltory Irresr. Scandinavian Journal of Plastic andReeon!OtnJctive Surgery (SupP() 6: 1-113

Lundborg G 1975 StruC1U~ :tIId function ofthe lnlr.lncural miclUYcS!icls as rcl;lIc,od 10 tr.IUma,edema formation and nc:n't function, Joum~ of Doneand Joint Sutiery 57A: 938-948

Lundborg G 1981 Mechanical" elTcc:ts on circulation andnerve function. In: Gono A, Millesi H, Mingero S(eds.) POSt-traumatic netVe regeneration. Ibvcn Press,New York .

Lundbor: G 1988 Nerve injury and repair. ChurchillLivingstone, Edinburgh

Lundborg G, Rydevik B 197) Effects of suetching thetibial nerve of the r.lbbit: a preliminal'}' study of theinuaneuta! eirculation and the barrier function of theperineurium, Journal of Bone :and Joint Surgery 55B:390--401

Uulrthes G, Gauazc A, Zadeh J 0 1971 A..-tcrialvascularis.:ttion of the s.pinal cord. Journal ofNeurosurgery 35: 253-261

L.uschlta H von 1850 Die nen'en des mcnsrnlicheneirbelbnales. Tubingcn, Laupp

MacKinnon S E, Ddlon A L 19S8 SurgC!1-' or ttl.:periphccal ner....c. Thicme, Ncw York

M::tnins 1\ M, Wiley J K, Mycrs P W 1972 Orn~mics ofthe cerebrospinal nuid and the spin:ll dura nlater.Journal of Neurology, Neurosur~cl'}' and Ps)'chiauy 35:468-47)

Malben L H 1985 The peripherul nervous syStcm.BU11eJwonhs, BoslOn .

MaeKinnon S E, Dellon A 1., Hudson 1\ R el ~11984 Chronic nerve compreuion - an espc:rimemalmodel in the cat. Annals of Pl:omic S~ry13: 112-120

McLellan 0 C. Swash M 1976 l.,Qngirudinal sliding of themedian nCl'Ve during movcmcms or the upper limb.Journal of Neurology, NeU!'01urgcl'}' and Psrchi~tr)' 39:566-570

Mmesi H 1986 Thc ncrve gap: theol'}' and cliniC

,,

f

I[,'.

S ...o'lline E R. P:lndj3 J B. G,rcenblau E H ct ~I 1.988Anatomy of the Jumb:lr epldunll.5p:lce: new insIghts

sing CI'-cpidurograph}'. Ancslhiology 68: 2175 711ndcr D. Sjostnnd J 1978 L..ongitudilUll spread of

CjRuancurally injeclC'd 10(';l1 anesthetics. Ada,a.naesthologica Se:mdin:l\'iC::1 22: 622-634

stanthavecrappOl T R, Doumc G H 1963 The pcrinCUr;l1epithelium: nacure and signifiClncc. Nature 199: 571-579Sin~cM. Byroml S V 1969 M.ovements in the m)'l:lin

schw;ann sheath or the \'ertcbr.ttc axon. N:ltuR: 221:1148-1150

Smith J \'if 1966 F:lc{o~ innurncing nerve rqJ:.Ur I. Bloodsuppl)' of periphcf:ll ncn'es. Archh'Cs of SurgetY 93:335-341

Spielman F J 1982 POst Jumb1r puncture h"::ldachc:.. HC2dachc 22: 280-283

SpcrtCCr 0 J. Irwin G S. Miller J A A 1983 M:llomy ~dsignificance of function of the Jumbouoal nerve rootSin sciatica. Spine 8: 672-679

Sunderland S, Bradlt:y K C 1949 The cross 5Cl.ion~1 :I~aof peripheral nCf\'e tnlnks devoted 10 nerve fibrC$. Brain72: 428-439

Sunderland S 1974 Meninge:lJ-neuraJ relations in theintelVcrteb:"al fOl1lmcn. journal of N~urosufgc:lY40:756-76)

Sundcrland S 1976 Thc ncrve lesion in eztpal tunnelsyndrome. journal of Neurology, Neurosur;ery andPsychiauy 39: 615-616

Sunderland S 1978 Nerves and nel'\'e injuries, 2nd edn.Churdiill Livingsione. Edinburgh

Sunderland S 1979 The p~inf\ll nelVe lesion: a prologt.le.In: Bonica J J 1:1 al (eds) Adl/~ns in P~in Rnearch a."IdTher.lp),. Raven Press, New Yoril. 3: 36--37

Sunderland S 1989 FC~I\lrcs of nClVes Ihat protect themduring normal daily aCli,ilies. In: Jones H M, Jones MA, Mildc M R (cds) Sixlh Biennul Confe~nc:cProc'eedings, Manipulati\"l~ TherapiS1s Association ofAustralia. Adelaide

Tani S, Yamada S. Knighton RS 1987 Extensibility ofthe lumbar and sacral cord: palhoph)'$ioIO&)' of thetethered spin~' cord in C~IS. Journal of Neurosur;ery 66:116-123

Tencer A F, Allen B 1... Ferguson R L 1985 Abiomechanieal study of Ihoracol\lmb~rspine: fraClun:s....,lh bonc in lhe canal. Part 3 M~anical properties oflhe dura m:uer and iu t~th~ring ligalRCOls. Spine 10:741-747

.....

E..,~..-"1

'L'. .Iil .

FVNCTIONAL ANATO.\W A.'"D PHYSIOLOGY 33

Thomas P K 1963 Th~ connecti\'e: tissue: of peripheralnerve: an eleclron microscope srud~. Joum:ll ofAn:Uomy 97: 35-44

Thomas P K 1982 Pain in peripheral neuro;lath)' : clinicaland morphological aspectS. In: Culp \t' J, Ochoa J (cds.)Abnonnal nerves lind muscles as impulse gcner:llOf5.Oxford, N~w York

Thom;u P K, Olsson Y 1984 lI.l..kroseopic analomy andfunction of the conntive tissue components ofperipheral neeve. In: Dyek'P J, ThomOl.s P K, 1..:Imben EH, Bunge R (eds) Peripheral 'Keufop"thy, 2nd edn..Saunden, Philadelphia

Transfc:ldt E E, Simmol1$ E H 198::! Functional andpathologiC:l[ biomec:h:Lni~ of lhe spin:ll cord: an in-vivostudy. International society (or me srud}' of the lumbarspine, Toromo.

Tunturi A R 1977 FJastic:ity of the spinal cord dura inlhe dog. joumozl of Neurosur&er)' 47: 391-396

Van Beek A, Klcinert H E 197i Prac:ti,"almicroncurorraphy. Orthopa~dic: Clinics of ~onhAmc:ric:a 8: 377-386

V;m Noort R, Black M M, Martin T R P, .\leanley S1981 A study of the uniaxial mechatlinl propcrties ofhuman dura m:uer p~sc:rved in gl~'cerol, Biomatenals 2:41-45

Varon S, Adler R 1980 Nerve grol\ID faclOr and controlof nerve growth. Currcnt Topics in DevelopmentalHiolog)" 16: 207-252

Waggener J D, Beggs J 1967 The membr:tnous eOI/c:rin(:5of neural tissues: an electron mic:rosc:o;lY srud}'. Joumalof Neurop:llhology =d Experim~ntal ~curology 26:412-416

WaksmOl.ll DH 1961 Experimental sNdy of diphmeriepolyneuritis in the rabbit and guinea rig, III Theblood-nerve barrier in the r.lbbil. Jou:':!"1 or Neuropathyand Expcrimenlal NcurOloa;y 21: 35-77

Walton J 1982 Essc:ntials of n~rology, S~ e

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36 MOBIUSATION OF THE NERVOUS SYSTEM

NS

Fig. 2.1 Diagt'3mmatic reprcsentation of the mechanicalinterface, MI mechanical imerface NS nervous system

Fig. 2.2 The posterior inlerosseus nerve passing into aconstricted arcade of Frohse (alTOw) in the supinatormuscle, From: Dawson 0 M. Hallett M. Millender L H1983 Enlrapmem neuropathies. little, Brown. Boston,with permission

mater. Zygapophyseal joints are yet another im-portant interface. A known sources of pain them-selves (Mooney & Robertson 1976), they alsohave a close topographical relationship with nerveroms and vascular strllcrores which may have lessprotection from chemical and mechanical de(or-mation than elsewhere in the body. Although thepure mechanical interface may be "a fascial sheetor a blood vessel, a more relevant interface suchas muscle or ligament may be adjacent to it. In-terfaces of a pathological nature certainly exist.Examples of possible pamological interfaces areosteophytes, ligamentous swelling or fascial scar-ring, A tight plaster or bandage could beconsidered as a fur:ther example. The introduc-tion of a fluid such as oedema or blood aroundme nervous system could also engender a patho-logical interface. For the purposes of me conceptspresented in this book, interfacing tissues may be

regarded as extraneural or extradural strucrores,that is, 'outside' me nervous system.

In this chapter. the biomechanics of the clini-cally important and central mechanical interface,e spinal canal. are discussed, Some peripheralinterfaces, such as the intcrfacing strucroresinvolved in the carpal tunnel. are discussedin Chapter 12 under individual syndromes. Priorto a discussion of the spinal canal, a re\iewof how the nervous system adapts