Dr. Arun MoreOrthopedics Lecturer

MTH Pokhara

PERIPHERAL NERVE INJURIES

Peripheral nerve injuries

Anatomy Mechanism Assessment Management Discussion

Peripheral nerve structure and function

Composed of Nerve fibres Blood vessels Connective tissue

Outer most Epineural sheath encloses fascicles with surrounding alveolar tissue called Epineurium

Fascicles are nerve bundles covered with connective tissue called Perineurim

Vary in diameter of 2-25 micrometer

Biological response to nerve injury

Nerve degeneration

Part of neuron distal to the point of injury undergoes secondary or wallerian degeneration

Proximal part undergoes primary or retrograde degeneration for a single node

Biological response to nerve injury

Nerve regeneration Axonal stump from proximal segment begins to

grow distally If endoneureal tube with its contained schwann

cell is intact the axonal sprouting occurs Rate of recovery 1mm/day Muscles nearest to the site of injury recovers

first Followed by others as the nerve reinnervates

muscles from proximal to distal so called motor march

If the endoneurial tube is interrupted, the sprouts may migrate aimlessly throught the damaged area to form a neuroma

Classification

Neuropraxia

the mildest form, reversible conduction

block loss of function, which persists for

hours

or days direct mechanical compression,

ischemia,

mild burn trauma or stretch

Axontmetic

axon continuity is disrupted fascicular integrity is maintained Wallerian degeneration occurs

Neurotmesis

laceration from sharp or blunt forces

the only important consideration is

the timing of repair acute repair or more bluntly

lacerated

nerves are repaired 3-4 weeks

Etiology

Mechanical injury Saturday-night paralysis ,Tourniquet paralysis

Crush and percussion injury fractures, hematomas, compartment syndrome

Laceration injury – blunt, penetrating injury

Stretch injury - brachial plexus High-velocity trauma - RTA , gunshot wounds Iatrogenic injury

Fibrillation potentials andpositive sharp waves

Acute Denervation

Long duration, small amplitude polyphasic motor unit potentials

Regeneration

Clinical Signs Motor function

Tinel’s sign

positive-sensory function

negative(after 4-6weeks)-total interruption

Sweating-sympathetic fiber

Sensory function

Diagnosis

Chronic Injuries of Peripheral Nerves by Entrapment

Pain Paresthesia Loss of function

Clinical diagnosis of nerve injuries: Highet Scale: 0 – total paralysis. 1- muscle flicker. 2-muscle contraction. 3- muscle contraction against gravity. 4- muscle contraction against gravity and

resistance. 5-normal muscle contraction .

Tinel sign :A positive Tinel sign is presumptive

evidence that regenerating axonal sprouts that have not obtained complete myelinization are progressing along the endoneurial tube.

@- neuropraxia(sunderland1) -------negative Tinel sign.

@- axonotmesis (sunderland2,3) -------positive Tinel sign.

(sunderland4-------- negative Tinel sign )

@- neurotmesis (sunderland 5) ------- negative Tinel sign.

Other diagnostic test:Sweat test.,skin resistance test, electrical

stimulation

Electrophysiological Tests

EMG SNAP SSEP Intraoperative NAP

Diagnosis

EMG SNAP

SSEP

Intraoperative NAP

Diagram of EMG tracing depicting normal insertion activity, which also may be present immediately after denervation.

A, Diagram of EMG tracing demonstrating positive sharp wave consistent with denervation 10 to 14 days after injury. Rhythm is regular, amplitude is 100 to 400 uV, duration is 5 to 150 msec, and rate is 2 to 40 Hz.

B, Diagram of EMG tracing demonstrating spontaneous denervation fibrillation potentials present within 14 to 18 days after injury. Rhythm is regular, amplitude is 50 to 1000 uV, duration is 0.5 to 2 msec, and rate is 2 to 30 Hz. 

GENERAL CONSIDERATIONS OF TREATMENT.

FACTORS THAT INFLUENCE REGENERATION AFTER NEURORRHAPHY :

1-Age2-Gap Between Nerve Ends3-Delay Between Time of Injury and Repair4-Level of Injury

5-Condition of Nerve Ends

Conservative Tx Indications

not long history

mild-moderate, intermittent

reversible cause

pregnancy, oral contraceptive, endocrine abnormalities(DM…), type writer

Method

nonsteroidal anti-inflammatory drugs

splint

Treatment

Surgical Indications

Failed conservative tx Typical clinical finding

with electrodiagnostic data

Severe

sensory loss

muscle atrophy

motor weakness

Treatment

TECHNIQUE OF NERVE REPAIR:

Endoneurolysis (Internal Neurolysis

Partial NeurorrhaphyNeurorrhaphy and Nerve Grafting

Methods of Closing Gaps Between Nerve Ends:

Mobilization

Positioning of Extremity

Transposition

Bone Resection

Nerve Stretching and Bulb Suture

Nerve Grafting

Techniques of Neurorrhaphy:

Epineurial Neurorrhaphy

Perineurial (Fascicular) Neurorrhaphy

Interfascicular Nerve Grafting

Injured Peripheral Nerve

Evaluation of Closed Injury

Conclusions1. Immediate primary repair in sharp injuries with

suspected transsection of nerve

Immediate repair is especially important for brachial plexus and sciatic nerve transsections because delay leads not only to retraction but also to severe scaring

Bluntly transsected nerve best repaired after a delay of several weeks.

2. A focally injured nerve should be explored if no functional return within 8-10 weeks

3. Decision - making as to whether neurolysis or resection & repair in a lesion in gross continuity based on intraoperative electrophysiological evaluation

4. Split repair with usually graft - lesion in continuity 가 partial function or undergoing partial regeneration

5. Careful patient selection for operation

- plexus involved

6. Nerve anastomosis failure

① inadequate resectin of scarred nerve ends

② nerve suture distration

7. A good end result requiring rehabilitation from onset of treatment. Prevention of disuse, relief of pain, predicting probable end results of operative procedures.

Conclusions

Entrapment of Thoracic Outlet

• Etio - Cervial rib or anomalous transverse

process of C7

- Fibromuscular bands or scalene muscle abnomality

• Inv.- X-ray

- NCV & EMG

- Angiography – vascular anomaly

• Tx : Supraclavicular approach

- Best op. management

scalene anterior and medius M.

Carpal Tunnel Syndrome

thenal atrophy

Entrapment of Radial Nerve

Entrapment of Ulnar Nerve- Cubital tunnel - Guyon’s canal

Motor Deficit of Ulnar Nerve

• Bediction posture : clawing of ring

& small finger

• Froment’s sign : weakness of adductor pollicis, there will

be flexion of the interphalangeal joint of the thumb because of substitution

of the median innervated flexior pollicus longus for a weak adductor pollicis

Meralgia Paresthesia

Lateral femoral

cutaneous nerve

injury (L1-2)

Tarsal Tunnel Syndrome

Etiology of peripheral nerve injuries: - Metabolic or collagen diseases - Malignancies -Endogenous or exogenous toxins -Thermal -Chemical -Mechanical trauma

Diagnostic tests:Electrodiagnostic studies provide the clinician with a

base of knowledge as follows:: 1-Documentation of injury Location of insult 2 -3-Severity of injury 4-Recovery pattern 5-Prognosis 6-Objective data for impairment documentation 7-Pathology 8-Selection of optimal muscles for tendon transfer 9-

procedures

Operations Neurolysis : internal/external Nerve repair

end-to-end repair : epineural/fascicular

autologous graft : sural N. Neurotization

intercostal N./accessory N./cervical plexus

within 1 year Muscle and tendon transfer

Operations Neurolysis : internal/external Nerve repair

end-to-end repair : epineural/fascicular

autologous graft : sural N. Neurotization

intercostal N./accessory N./cervical plexus

within 1 year Muscle and tendon transfer

Epineural Repair

Nerve Graft

# leading cause of failure of nerve graft • Inadequate resection • Distraction of repair site

Pathophysiology of Entrapment Direct compression

segmental demyelination

wallerian degeneration(distal) Ischemia

swelling of nerve

microcompartment SD