Median nerve

MEDIAN NERVE

Root value: C5,6,7,8,T1. Beginning: by 2 roots, Lat root from lat cord & med root from med cord of brachial plexus. Course and relations: - Descends lat to axillary & brachial A. - At the middle of the arm it crosses the brachial A & passes med to it to enter the cubital fossa. - Leaves cubital fossa by passing between 2 heads of pronator teres. - Descends between flexor digitorum superficialis (superficial) & flexor digitorum profundus (deep). - Passes deep to flexor retinaculum to the hand then divides into terminal branches

Injury of median nerve: (Ape like hand) A] Injury above cubital fossa: Motor: • Paralysis of pronator teres & quadrates loss of pronation. • Paralysis of wrist flexors except flexor carpi ulnar is weak flexion accompanied by adduction. • Paralysis of flexor pollicis longus & brevis → loss of thumb flexion. • Paralysis of opponens pollicis → loss of opposition (Ape like).

Sensory: loss of sensation of ant side of lat 2/3 of hand & lat 3½ fingers. B] Injury at wrist: Cause: carpal tunnel syndrome due to compression by inflammation, bone dislocation or overstretch by extended hands (e.g.: typewriters). Motor: loss of opposition (Ape like hand). Sensory: loss of sensation of ant side of lat 3½ fingers.

ULNAR NERVE

Root value: C7,8,T1. Beginning: from med cord of brachial plexus. N.B.: med cord of brachial plexus does not contain C7, it reaches the ulnar nerve through lat root of median nerve. Course and relations: - Descends med to axillary & brachial A. - At mid arm it passes to post compartment. - Passes post to med epicondyle. - Passes between 2 heads of flexor carpi ulnaris to forearm. - Descends between flexor carpi ulnaris (superficial) & flexor digitorum profundus (deep). - Passes superficial to flexor retinaculum to the hand.

Injury of ulnar nerve: (partial claw hand) A] Injury above the elbow: Motor: • Paralysis of flexor carpi ulnaris  weak flexion of wrist accompanied by abduction. • Paralysis of med 2 lumbricals  clawing of ring & little fingers (partial claw hand). • Paralysis of interossei  loss of adduction and abduction of med 4 fingers. • Paralysis of adductor pollicis  loss of adduction of thumb.

Sensory: loss of sensation of med 1/3 of hand & med 1½ fingers (ant & post). B] Injury at wrist: differs in: Motor: • Claw hand is more severe due to further flexion by flexor digitorum profundus (ulnar paradox). • No affection of wrist flexion Sensory: loss of sensation of med 1½ fingers.