MSK: Nerve Injuries

Question 1

Effects of ulnar n. injury at the wrist? At the elbow?

Answer 1

Injury at wrist:

• paralysis of medial 2 lumbricals… loss of MCP joint flexion and weakened IP joint extension… ULNAR CLAW
• paralysis of interossei… loss of finger abduction and adduction (can’t grip paper)
• sensory loss over palmar side of medial 1 and 1/2 fingers (palmar and superficial brs)

Injury at elbow:

• same as above +
• paralysis of flexor carpi ulnaris… wrist flexion accompanied by abduction
• paralysis of medial 1/2 of FDP… less severe ulnar claw due to inability to flex distal IP joints
• sensory loss over dorsal and palmar medial 1 and 1.2 fingers (dorsal, palmar and superficial brs)

Question 2

Effects of radial n. injury at the axilla?

Answer 2

Motor functions:

• paralysis of triceps brachii… loss of elbow extension
• paralysis of brachioradialis and other posterior forearm muscles… loss of wrist and finger extension… WRIST DROP

Sensory functions:
- affects all 4 cutaneous branches of radial n. … loss of sensation over lateral and posterior upper arm, posterior forearm and dorsal surface of lateral 3 fingers

Question 3

Effects of median n. injury at the wrist? at the elbow?

Answer 3

Wrist:

• paralysis of thenar muscles… loss of thumb opposition and wasting of thenar eminence
• paralysis of lateral 2 lumbricals… loss of index and middle finger MCP joint flexion… HAND OF BENEDICTION
• anaesthesia in lateral 3 and 1/2 fingers and central palm

Elbow:

• as above +
• paralysis of flexors and pronators of forearm (exc. flexor carpi ulnaris and medial 1/2 of FDP)… forearm suppinated and weak flexion
• paralysis of flexor pollicis longus and brevis… loss of thumb flexion

Question 4

Effects of axillary n. injury.

Answer 4

Motor:

• paralysis of deltoid and teres minor… loss of shoulder abduction >15 degrees and deltoid atrophy
• loss of upper lateral cutaneous n. of arm… loss of sensation over regimental badge area

Question 5

Effects of superior brachial plexus injury

Answer 5

ERB-DUCHENNE PALSY:

• affects nerves derived from C5 or C6 roots - musculocutaneous, axillary, suprascapular and n. to subclavius
• muscles paralysed: biceps brachii, brachialis and coracobrachialis, deltoid and teres minor, supraspinatus, infraspinatus and subclavius
• loss of motor functions: shoulder abduction, flexion and lateral rotation, forearm supination
• anaesthesia of lateral aspect of upper limb (C5 and C6 dermatomes)

‘WAITER’S TIP’ position: adducted shoulder, medially rotated arm, extended elbow and pronated forearm

Question 6

Effects of inferior brachial plexus injury

Answer 6

KLUMPKE PALSY

• affects nerves derived from C8 or T1 roots - ulnar and median
• muscles paralysed: intrinsic hand muscles, flexor carpi ulnaris and ulnar 1/2 of FDP
• loss of motor functions: MCP joint flexion and IP joint extension
• paraesthesia of ulnar 1/2 of hand and forearm (C8 and T1 dermatomes)

CLAW HAND: paralysis of intrinsic hand muscles… MCP joint hyperextension and IP joint flexion