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MEDIAN NERVE

Presented By:JITHIN MAMPATTA

•Mixed nerve (contain motor & sensory fibers).

•Root value: C 5,6,7,8 & T1

• Runs in the median plane of the forearm , so its called median nerve

•Arises in the axilla by 2 roots (lat &med):

1) lat .root : from the lat . Cord of the brachial plexus

2) med .root : from the med . Cord of the brachial plexus .

In axilla• Median nerve is formed by lateral root from lateral cord

and medial root from medial cord of brachial plexus

• Median nerve runs lateral side of axillary artery

In arm• median nerve continues to run on the lareral side of brachial

artery till the middle of arm , where it crosses infront of the artery and passes anterrior to the elbow joint into forearm

In forearm• Enters to the forearm b/w two heads of pronator teres .

• Then deep to fibrous arch of flexor digitorum superficialis , in proximal third

• In mid forearm descends b/w flexor digitorum superficialis and flexor digitorum profundus .

• About 5 cm above wrist , it comes to lie on the lateral side of the flexor digitorum superficialis , becomes superficial just above wrist

In hand

• Nerve passes deep to the flexor retinaculum and enters the palm

• Muscular braches supply muscles of thenar eminence ( abductor pollicis brevis , opponens pollicis and flexor pollicis brevis )

• Finally divides into 4 to 5 palmar digital branches supplying lateral three and half digit and their nail beds

• Also , motor braches are given to the first and second lumbrical muscles

Branches

• In arm : vascular branches to the brachial

• In the forearm : muscular branches to all superficial flexor muscles ( pronator teres , flexor carpi radialis , palmaris longus and flexor digitorum superficialis )

Anterior interosseous , which comes off the median nerve supplies lateral half of flexor digitorum profundus , flexor pollicis longus and pronator quadratus

Articular branches supply the elbow joint and proximal ulnar joint

Palmar cutaneous branch supply skin over thenar eminence and central part of palm

INJURY TO MEDIAN NERVE

• Median nerve is most commonly injured near the wrist or high up in the fore arm

• Muscles supplied by median nerve affected acc. To level of median nerve injury.

1.High median nerve palsy

2.Low median nerve palsy

Low median nerve palsy

• Injury in the distal third of the forearm

• Cuts infront of wrist or by carpal dislocation

• There will be sparing of the forearm muscles , but the muscles of the hand will be paralysed

• There will be anaesthesia over the median nerve distribution in the hand

cont• Thenar eminence is wasted and thumb abduction

and opposition are weak

• Sensation is lost over the radial three and half digits and trophic changes may seen

High median nerve palsy

• Injury proximal to the elbow

• Generally due to forearm fractures or elbow dislocation

• Stabs and gunshot wounds may damage the nerve at

any level

• This will cause paralysis of all the muscles supplied by the median nerve in the forearm and hand

•Muscles examined:• 1) flexor pollicis longus : this muscle is tested by

holding thumb at its base and patient asked to bend the terminal phalanx

• 2) flexor digitorum superficialis and & profundus (lateral half )…..Ochsner’s clasping test is : when the patient is asked to clasp the hands , the index finger of affected side fail to flex

• 3) flexor Carpi radialis : the hand deviate to ulnar side when it is flexed against resistance

• 4) muscles of thenar eminance

• abductor pollicis brevis…….pen test : the patient is asked to lay his hand flat on the table , a pen is held above the palm and the patient is asked to touch the pen with his thumb

• opponens pollicis : brings the tip of the thumb towards the tips of other fingers

Median nerve compression • Three separate syndromes are recognised

1.Carpal tunnel syndrome

2.Pronator syndrome

3.Anterior interosseous syndrome

It is compressive neuropathy of median nerve as it passes through the carpal tunnel of the wrist joint.

causes

• Ideopathic - Most common• Inflamatory - Rheumatoid Arthritis

- Wrist osteoarthritis• Post traumatic - Bone thickening • Endocrine - Myxoedema - Acromegaly

• High prevelance rates have been reported in persons who perform certain repetitive wrist motions ( frequent computer users )

• Pregnancy

• Gout

Symptoms and SignsSymptoms include

• Pain of the hand and wrist associated with tingling and numbness, classically distributed along the median nerve (the palmar side of the thumb, the index and middle fingers, and the radial half of the ring finger)

• Typically, the patient wakes at night with burning or aching pain and shakes the hand to obtain relief and restore sensation.

• Thenar atrophy and weakness of thumb opposition and abduction may develop late.

AtrophyAtrophy

Physical examination• Phalen’s maneuver

• Tinel’s sign

• Carpal compression test

Treatment

• Splinting – prevent wrist flexion

• corticosteroid/anesthetic injection – give temporary relief

• surgical decompression

Wearing a lightweight wrist splint especially at night, and taking mild analgesics

•If symptoms persist or recur or if hand weakness and thenar wasting develop, the carpal tunnel can be surgically decompressed by using an open surgical division of the transverse carpal ligament

Complications of surgery• Injury to palmar or cutaneous or recurrent motor branch

of the median nerve

• Hypertrophic scarring

• Hematoma

• Artery injury

Pronator teres syndrome

• Pronator teres syndrome is a compression neuropathy of the median nerve at the elbow between heads of pronator teres

• It is rare compared to compression at the wrist (carpal tunnel syndrome) or isolated injury of the anterior interosseous branch of the median nerve (anterior interosseous syndrome).

• Symptoms are similar to those of carpal tunnel syndrome , although night pain is unusual and forearm pain is more common

• phalen’s test obviously be negative

• Symptoms can be provoked by resisted elbow flexion with forearm supinated ( tightening of bicipital aponeurosis )

• By resisted forearm pronation with the elbow extended ( pronator tension )

• Tinel’s sign may be positive over the nerve proximally but not at carpal tunnel

Anterior interosseous syndrome

Is a medical condition in which damage to the anterior interosseous nerve, a motor branch of the median nerve, causes pain in the forearm and a characteristic weakness of the gripping movement of the thumb and index finger.( unable to make ok sign )• Most cases are due to compression of the

nerve as a result of trauma at the elbow, often associated with haemorrhage into the deep musculature.

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