Compression neuropathy – pathophysiology &treatment

Ian GrantConsultant Plastic Surgeon - Cambridge

17/10/2014

Compression neuropathy:

Chronic Nerve Compression: acquired neuro-degenerative condition – demyelination

Axon loss – only in later stages of the disease

Pathophysiology – Schwann cellGeneticsHistory of surgical intervention Diagnosis / tests – decision making

chronic nerve compression

Central nervous system

- not subject to compression or stretch

Peripheral nervous system- vulnerable to compression or stretch

• Chronic nerve compression

SyndromesCarpal tunnel syndromeCubital tunnel syndromeSupraspinatus syndromeAnterior interosseous syndromePosterior interosseous syndromeThoracic outlet syndromeMeralgia parasetheticaTarsal Tunnel syndromePeroneal syndrome

Peripheral entrapment neuropathy

Symptoms - Tingling, numbness, pain, weakness

Pathophysiology - Reduced conductionAbnormal excitability

RELEASE OF CONSTRICTION – RELIEVES SYMPTOMS

Photo supplied by: CHOJNOWSKI ADRIAN

OBVIOUS MACROSCOPIC CHANGES IN MEDIAN NERVE AT CONSTRICTION

THENAR MUSCLE WASTING

Chronicnerve

compression

proximal compressio

n

systemic conditions

genetic predispositi

onHNLPP

Diabetes, AmyloidHypothyroid, Pregnancy , Obesity

1.5 megabase deletion , 17p11.2 – PMP22

AGE1039 pt’s neurophysiological carpal tunnel syndrome.Nora et al 2004 Mean Age 48

PREVALENCECTS European Prevalence: estimate 2.7-5.8 %

AGE & PREVALENCE OF CARPAL TUNNEL SYNDROME

>53000 operations for CTS England 2011

NERVE ANATOMY – THE NERVE CELL

With thanks to Caitlin Monney: illustrator

Compression neuropathy – crucial event is dymelination - crucial cell – the Swann Cell

Sh3tc2 tuj1

Sh3tc2 tuj1

sh3tc2sh3tc2

sh3tc2sh3tc2

Caspr

MPZ MPZ

Caspr

ANATOMY – NERVE FIBRES

With thanks to Caitlin Monney: illustrator

Denny-Brown, and Bremmer 1944 – rodent sciatic nerve compression

Investigation of compression neuropathy

Oedema – is evident within 4 hours of constriction

4 hours: 80mmHg

Oedema

Cannulation of the compressed peripheral nerve: confirms increased fluid pressure

Histologic studies confirm that with prolonged compression (> 4 hours) demeylination occurs

Demyelination

In vitro studies of Schwann cells, compression results in:

c-Jun, Knox-20

Neurosci Lett 2009

In vitro immunoflouresence of Schwann cells distraction results in:Characteristic changes in morphology – bands appear

Compression / stretching

Vascular compromise

oedema

Schwann cell activation

Demyelination / remyelinationThin myelin

Axon loss, Intraneural fibrosis / degeneration

Axoplasmic transport interrupted

Intraneural fibosis: reduced extensibility

increased ion channels along axon:Abnormal Impulse Generating Sites

Matrix-metalloproteinases (MMPs) 2 and 9

hypoxia-inducible factor 1α (HIF1α), catalase, superoxide dismutase (SOD)

Summary of sequence of changes -

With thanks to Caitlin Monney: illustrator

The double crush in nerve entrapment syndromesAdrian Upton, Alan McComas, Lancet 1973

• 115 patients with entrapment

• 70% had cervical lesion

A sick nerve or proximal compression:predisposes to entrapment neuropathy at a peripheral site

This is explained through interruption of axoplasmic transport

Nerve pain: mechanically sensitive as consequence of compression or entrapment

• Ectopic electrogenesis • Nervi-nervorum on outside of nerve –

increased sensitivity to stretch

STRAIN Connective tissue thickening

Restricted neural mobility

Dilley and Bove 2008

Failure of axoplasmic transport results in accumulation of mechanosensitive components proximal to the blockage

Oedema Demyelination / remyelination

Diffuse Demyelination, structural irreversible changes / established

pain and weakness

Duration and magnitude of compression

symptoms Irretrievable Loss of function

Window of treatment

Treatment : non surgical

Ramsay Hunt: The thenar and hypothenar types of neural atrophy of theHand American Journal of Medical Sciences 1911

Gessler:Die motorische Endplatte und ihre Bedeutung für die peripherische Lähmung,Habitations Schrift, München, 1885

Treatment: Surgery for CTS

Marie and Foix 1913: Atrophie isolé de l’éminence thénar d’origine néevritique.

Rôle du ligament annulaire antérieur du carpe dans la patholgénie de la lésion. Rev Neurol., 26: 647-649, 1913

Severe bilateral atrophy of the thenar muscles, at autopsy a neuroma of the median nerve,just proximal to the transverse carpal ligament

Lancet 1946: Spontaneous compression of both median nerve in the carpal tunnel

Russell Brian DM Oxfd, FRCP A Dickson Wright MS Lond., FRCSMarcia Wilkinson BM Oxfd, MRCP

6 cases – middle aged or elderly women

Treated by surgical division of the carpal ligament at the wrist

Marcia Wilkinson DM Oxfd FRCP 4th February 2013

Arthur Dickson-Wright MS Lond FRCS

Father to the chef:Clarissa Dickson-Wright

Phalen 1950: Neuropathy of the median nerve due to compressionbeneath the transverse carpal ligament

4 cases = three of which were treated by surgical division of the transverse carpal Ligament, with excellent results

Linked disease to occupation ?

Ulnar nerve compression – cubital tunnel syndrome

Panas, J 1878: Sur une cause peu connue de pralysie du nerf cubitalArchivee Générales de Médecine, 2 (VII Serie)

Repeated trauma – hyperaemia – oedema, - infiltration of fibrous tissue

Geoffrey Osbourne 1957: “tardy ulnar neuritis” – band of fibrous tissue bridging the two heads of flexor carpi ulnaris –

Sir W.R Gowers 1866 – Manual of diseases of the nervous system

Alan Apley remarked : that he had “difficulty accepting this analogy, -pain was a prominent factor in carpal tunnel syndrome”

The patient has severe neurological symptoms at presentation for example altered sensation, muscle wasting or weakness of thenar abduction.

OR

The patient has moderate symptoms has not responded to a minimum of 3 months of conservative management, including local corticosteroid injections and a compliant trial of nocturnal neutral wrist splints.

Surgery funded if :

• Mild – intermittent paraesthesia

• Moderate – paraesthesia that interferes with ADL – constant waking

• Severe – constant numbness, wasting, weakness of thumb muscles

Clinical tests – questionable value

CTS• Tinel’s• Phalen’s• Reverse Phalen’s• Carpal compression

Cubital tunnel syndrome• Elbow flexion• Froment’s

Catch me if you can 2002

Sensibility testing LIGHT MOVING TOUCHTen-test1 – compare two sides(1.Strauch et al 1997 PRS)

Reliable in unilateral / early disease

2-point discrimination – late disease

Neurophysiological tests

Images: Dr Andrew Michell, Consultant Neurophysiologist

• Scored questionnaire• 80-85% sensitivity, 90%

positive predictive value

• Nerve Conduction studies• 92-96% sensitive, 92-94%

positive predictive value

• Scar

• Grip

4 weeks 4 months

Ian GrantConsultant in plastic & reconstructive surgeryCambridge

Addenbrooke’s HospitalThe Spire Lea Hospital

Hand surgery: including children’s hands & peripheral nerve surgery

With thanks to Caitlin Monney, Dr Rhys Russel, Mr Adrain Choznowski, Mr Harry Belcher, Dr Andrew Michell