PERIPHERAL NERVE INJURIES

Anatomy:Macroscopic

Mixed spinal nerve – sensory and motor root; sympathetic rami; posterior and anterior rami.

Microscopic:Axon, Schwann cells, Myelin – endoneurium; Group of axons – fasicle –perineureum, nerve sheath or epineureum

Classification:Seddon:

a. Neuropraxia: Physiological interruption of nerve impulse- degeneration of myelin only, complete motor but some sensory lossa. Axonotmesis: Incomplete division – only axon divided,

endoneural tube intact – closed fractures, dislocations, pressure etc.b. Neurotmesis: Complete division – open fractures, GSW, traction etc.

Sunderland: I-V : Myelin, axon, endoneurium, peri neural, entire nerve

PathologyNerve injury – clot – Wallerian degeneration, Axonal sprouts, regeneration at the

rate of 1 mm per day – end or side neuroma / recovery.Other structures – muscles, end plates, joints, brain

Etiology of nerve injuryFractures, dislocations, pressure, wounds, GSW etc.

SymptomsMotor – Loss of motor power – depending on the level and closest muscle groupSensory – According to the zone of supplySympathetic – AnhydrosisCausalgia – (Incomplete injury) Hyperhidrosis, warmth, redness

SignsInspection:

Attitude e.g. claw hand –Ulnar N.Scar of injuryAnesthetic skin looks smooth & shiny, fingers thin and tapering, nail fissuredTrophic changesMuscle wasting

Palpation:Skin feels cool, smooth and dryAnesthetic skinNeuromaTinnel sign

Movement:Lack of active movements

X-rays: Osteoporosis

InvestigationsIs there a nerve lesion? Level? Type? Recovery?1. Tinnel sign2. EMG3. NCS2. Sweat test, Skin pressure test

TreatmentConservative

Neuropraxia & some axontomesisCare of paralysed part: a. Protection of skin

b. Movement of joints & musclesc. Splintsd. Electric stimulation

OperativeNeurontemesis & some axontomesisTiming: Clean wound – primary repair

Contaminated wound – tagging & late repairVery early repair difficult; late repair impossible; Must be done before 18 months of injury

Nerve surgery – Nerve repair – Neurorrahaphy Method of bridging the gap: Mobilization of nerve. Position of the limb, transposition of nerve, nerve grafting, cable grafting, shortening of bone.

Secondary surgeryTendon transfersArthrodesisAmputation

PrognosisType of lesionLevel of lesionType of nerveSize of gapAge, Time and associated lesions

MEDIAN NERVE INJURIES

High lesion - At or above the elbowLow lesion – In the forearm or wristEtiology:

GSW, fracture dislocation at the elbow, wrist cut, dislocation of lunate, colles fracture, CTS

Clinical featuresLow lesion – wasted thenar muscle, Opponens pollicis, Loss of sensationHigh lesion – wasted forearm muscle, Benediction attitude, thumb, index and middle finger and wrist flexors, pronators , Ochsner’s clasping test (FDP index), Pen touch test (APB);Trophic changes, Ape like thumb

Treatment:Primary or secondary repairOpponens plastyWrist arthrodesis