Mononeuropathies

Question 1

Carpal tunnel syndrome vs more proximal median nerve lesion

Answer 1

Anterior interosseous nerve is branch of median nerve that enters hand superficial to the carpal tunnel (between the flexor retinaculum and carpal bones). This innervates opponents brevis which keeps thumb opposing index finger (get patient to make an ‘o’ with finer and thumb and try to break the contact). Median nerve LOAF muscles (2 lateral lumbricals, opponens brevis, abductor pollicus brevis (median nerve in 99%), flexor pollicus brevis

Question 2

Ulnar nerve

Answer 2

Supplies all other muscles of hand except LOAF muscles (median nerve). Doesn’t supply sensation proximal to hand. Signs of palsy include wasting of dorsal interssoei and hypothenar eminence and ulnar claw (hyper extension MCP 4th and 5th digit, flexiom or IP joints

Question 3

Distinguishing median, ulnar and T1 palsy

Answer 3

APB weak, FDIO normal = median nerve
APB normal, FDIO Weak = ulnar nerve
APB weak and FDIO weak = T1

Question 4

Radial nerve

Answer 4

• Wrist extensors (c7) C8
• Finger extensors (posterior interosseous branch)
  triceps (c7), brachioradialis and Supinator (C6)

Intact tricep reflex suggests lesion below spiral groove of humerus

Question 5

Common perineal nerve (L4 L5)

Answer 5

High stepping gait (foot drop)
Wasting of muscles of later aspect of foot
Sometime reduced sensation of lateral aspect
Intact ankle reflex (S1)
Weakness of ankle dorsiflexion and foot eversion
In L5 radiculopathy foot inversion and eversion is also affected - this distinguishes the two. Common peroneal injury allows foot inversion but L5 injury doesn’t