peripheral nerve injuries

PERIPHERAL NERVE INJURIES

PATHOLOGY

Nerves can be injured by ischaemia ,compression, traction, laceration or burning.

Aetiology:-Direct trauma

- Systemic causes-DM,leprosy,lead poisoning

- Entrapment neuropathies

e.g.,carpal tunnel,cubital tunnel,supinator syndromes

Nerve injuries types-Seddon’s

Neurapraxia

Axonotmesis Neurotmesis

NeurapraxiaA reversible physiological nerve conduction block followed by spontaneous recovery after

a few weeks .It is due to mechanical pressure causing segmental demyelination and is seen typically in crutch palsy, Saturday night

palsy,tourniquet palsy .

Axonotmesis There is loss of conduction but the nerve is in

continuity and the neural tubes are intact. The denervated target organs (motor end-plates

and sensory receptors) gradually atrophy, and if they are not re- in nervated within 2 years they

will never recover .

NeurotmesisIn Seddon's original classification, neurotmesis meant division of the nerve trunk

BRACHIAL PLEXUS

MEDIAN NERVE INJURY

FindingMuscle NervePlexusRoot

Thumb Abd APBMedian Lower trunkC8T1

Medial cord

Thumb oppOPMedianLower trunkC8T1

Medial cord

Sensory lossMedian------Median claw hand-loss of lat 2 lumbricals

Oschners clasp test(pointing index) Ape thumb deformity Pen test

Median Nerve

FindingMusclePNPlexus*RootWr dropECR, ECURadialPOST C C5,6,7,8

Fing dropEDC,EIRadial POST C C7, C8

Elb flxBRRadialPOST C C5,C6

Th ExtEPL, EPBRadialPost CC7,8

Sens ----Radial------

RADIAL NERVE INJURY

Triceps, long head

Triceps, lateral headTriceps, med hd

Brachioradialis

ECRL

ECRBSuperficial

SupinatorRadial sens

Ext Digit

Abd Pol LongusPost Interosseous

Ext Pol Longus

Ext Pol Br

Ext Indicies

ULNAR NERVE INJURY

FindingMusclePNPlexusRoot

Fing AddPalm IntUlnarMCc8,T1

Fing AbdDors IntUlnarMCC8T1

Ulnar claw hand-due to loss of intrinsic function

Card test-Finger adduction

Froments book test-Adductor pollicis

Ulnar nerveElbow

Flexor carpi ulnaris

Flex Dig Prof III/IV

Dorsal uln cut

Wrist

Adductor PollicusAbductor

Flex Pollicus BrOpponens Digiti MinimiFlexor

Dorsal/palmar

Interosseous

3rd/4th lumbricals

THE DEGREE OF INJURY

Tinel's sign -peripheral tingling or dysaesthesia' provoked by percussing

the nerve . In a neurapraxia, Tinel's sign is

negative. In axonotmesis, it is positive at the site

of injury because of sensitivity of the regenerating axon sprouts.After a delay of a few days or weeks, the Tinel sign will then advance at a

rate of about 1mm each day .

THE DEGREE OF INJURYElectromyogram (EMG)&Nerve conduction study(NCS)

Studies can be helpful (Campion, 1996). If a muscle loses its nerve supply, the EMG will show denervation potentials at the third

week .This excludes neurapraxia but it does not distinguish between axonotmesis and

neurotmesis;

PRINCIPLES OF TREATMENT

Treating underlying cause Oral corticosteroids-to reduce

inflammation & edema

Active and passive physiotherapy to muscles

Galvanic stimulation Dynamic splints –To prevent

contracture of the affected muscle

PRINCIPLES OF TREATMENT

Nerve exploration

. Exploration is indicated:

(1) if the nerve was seen divided and needs to be repaired;

(2) type of injury (e.g. a knife wound or a high energy injury) suggests that the nerve has been divided or severely damaged;

(3) if recovery is inappropriately delayed and the diagnosis is in doubt.

Epineurial neurorrhaphy

Perineurial (fascicular) neurorrhaphy

Nerve grafting Free autogenous nerve grafts can be used

to bridge gaps too large for direct suture. The sural nerve is most commonly used

Neurotization

Care of paralysed parts

While recovery is awaited the skin must be protected from friction damage and bums.

The joints should be moved through their full range twice daily to prevent stiffness and minimize the work required of muscles when they recover.

'Dynamic' splints may be helpful.

Tendon transfers

Motor recovery may not occur if the axons, regenerating at about 1mm per day, do not reach the muscle within 18-24 months of injury. The principles can be summarized as follows:

Tendon transfers

The donor muscle should be expendable Have adequate power Be an agonist or synergist The recipient site should be stable Have mobile joints and supple tissues The transferred tendon shouldbe routed

subcutaneously Have a straight line of pull Be capable of firm fixation

Radial nerve –tendon transfer

Robert jones transferBoyds transfer

CLAW HAND-ULNAR&MEDIAN

Boyds transferRiordan transferFowlers technique

Common peroneal nerve palsy

Trauma at fibular neck DM,leprosy,injectionpalsy,compression neuropathy(lithotomy)

- causes foot drop & toe drop & sensaory impairment over dorsum of foot

- Foot drop preventive splint

- transtibial & transosseous transfer