Peripheral Nerve Disorders

Question 1

Wallerian degeneration occurs (proximal/distal) to the site of injury.

Answer 1

distal

Question 2

What are the Bands of Bungner?

Answer 2

proliferation of Schwann cells under the old basal lamina of a nerve with axons growing inside

Question 3

What is segmental demyelination?

Answer 3

Scattered demyelination with replacement by thinner myelin and shorter variable internodes (normally the nodes of Ranvier have a set internodal length)

relative axonal sparing

Question 4

What kind of demyelination is seen with diptheria?

Answer 4

segmental

Question 5

Porphyria causes what type of neuropathy?

Answer 5

Rapid, severe, symmetric, motor > sensory loss, bilateral brachial weakness

Question 6

Uremia causes what type of neuropathy?

Answer 6

painless, symmetric, sensorimotor, lower > upper limbs

Question 7

In GBS, pathologic examination reveals _____.

Answer 7

perivascular mononuclear infiltrates and segmental demyelination

Question 8

When is the protein peak seen in GBS on CSF?

Answer 8

5 weeks

Question 9

What do nerve conduction studies show in GBS?

Answer 9

decreased velocity and amplitude

Question 10

What percent of GBS patients have severe/permanent weakness?

Answer 10

10%

Question 11

Experimental allergic neuritis is caused by _____.

Answer 11

T cell mediated attack of P2 protein

Question 12

What is the inheritance of Dejerine Sottas? What type of disease is it?

Answer 12

AR

hereditary/hypertrophic (onion bulb) neuropathy

Question 13

What is the inheritance of Refsum’s disease?

Answer 13

AR

Question 14

What is Refsum’s disease?

Answer 14

a type of hereditary/hypertrophic (onion bulb) neuropathy

deficiency in phytanic acid oxidase

Question 15

What is neuropraxia?

Answer 15

functional but no structural damage (nerve concussion) with temporary loss of function that may last 6–8 weeks

Question 16

What is axonotemesis?

Answer 16

interruption of axons and myelin with intact perineurium and epineurium

spontaneous regeneration may occur at 1–2 mm/day

Question 17

What is neurotemesis?

Answer 17

transection of the nerve and nerve sheath

axonal regeneration may lead to neuroma formation

Question 18

Acute ophthalmoplegia can be seen in what metabolic disease? What is the mechanism?

Answer 18

diabetes

ischemia of the vaso nervosum

Question 19

What is a Morton neuroma?

Answer 19

traumatic neuroma that forms on the digital nerve between the toes

Question 20

What is Brachial Plexitis?

Answer 20

Idiopathic onset of upper limb pain and weakness that usually resolves in 6 to 12 weeks; there is no fever, leukocytosis, or elevated ESR

Question 21

In carpal tunnel syndrome, what causes the compression?

Answer 21

transverse carpal ligament

Question 22

What causes cubital tunnel syndrome?

Answer 22

caused by compression of the ulnar nerve under the two heads of the flexor carpi ulnaris

Question 23

What is posterior interosseous syndrome?

Answer 23

Causes weakness of the radial-innervated forearm and hand muscles (supinator, extensor digitorum, extensor carpi ulnaris, and abductor pollicis longus). No sensory loss. It causes a finger drop without a wrist drop because of sparing of the extensor carpi radialis longus

Question 24

What is anterior interosseous syndrome?

Answer 24

Pure weakness without sensory loss caused by compression of the anterior interosseous branch of the median nerve in the deep forearm. It involves the pronator quadratus, flexor pollicis longus, and flexor digitorum profundus 2 and 3 (FDP 4 and 5 are innervated by the ulnar nerve). Patients are unable to form the “okay” sign and demonstrate the “pinched” sign

Question 25

What is meralgia paresthetica?

Answer 25

Compression of the lateral femoral cutaneous nerve (L2, 3) under the inguinal ligament. It causes anterolateral thigh numbness and dysesthesia. It is associated with obesity, pregnancy, and diabetes.

Question 26

What is tarsal tunnel syndrome?

Answer 26

Compression of the tibial nerve with paresthesias of the sole of the foot without motor changes

Question 27

Patients with b/l CN VII nerve palsies are suspicious for ______.

Answer 27

GBS and Lyme disease