13 Acute Peripheral Neurologic Disorders, part 2

Question 1

Examples of focal mononeuropathies

Answer 1

Median mononeuropathy (carpal tunnel syndrome)
Ulnar mononeuropathy (cubital tunnel syndrome and guyon’s canal syndrome)
Deep peroneal nerve entrapment
Meralgia paresthetica

Question 2

Most common systemic cause of noncompressive focal neuropathy

Answer 2

Diabetes

Question 3

most common form of any focal mononeuropathy

Answer 3

median mononeuropathy or carpal tunnel syndrome

Question 4

Provocative testing in carpal tunnel syndrome

Answer 4

Tinel’s sign
- detects irritated nerves by percussing over the nerve and eliciting tingling
Phalen’s maneuver
- positive for carpal tunnel syndrome when holding the wrists in flexion for 60 seconds evokes or worsens symptoms

Question 5

most common ulnar mononeuropathy

Answer 5

Cubital tunnel syndrome
Cubital tunnel is located behind the medial epicondyle at the elbow

Question 6

Guyon’s canal is bounded by

Answer 6

hamate and pisiform bones
Guyon’s canal syndrome is aka “handlebar palsy”

Question 7

PE in ulnar mononeuropathy

Answer 7

A positive elbow flexion sign is seen when symptoms recur within 3 minutes of the elbow being held in flexion with the wrist in extension
Froment’s sign
- an inability of the thumb to oppose or put pressure against the index finger
- to perform this test, ask the patient to hold a piece of paper between thumb and index finger.
- If you can pull the paper away or the thumb flexes at the interphaleangeal joint to compensate for weakness of the adductor pollicis brevis, the test is positive

Question 8

In the patient with suspected cubital tunnel syndrome, consider

Answer 8

C8 entrapment and thoracic outlet syndrome
C8 ENTRAPMENT
- presnece of neck pain and worsening symptoms with neck flexion
THORACIC OUTLET SYNDROME
- worsens with shoulder abduction

Question 9

the deep peroneal nerve may become entrapped at three locations

Answer 9

1. fibular head
2. anterior to the ankle joint as it passes beneath the extensor retinaculum (anterior tarsal tunnel syndrome)
3. distal to the point in #2

Question 10

Features of compression of the deep peroneal nerve

Answer 10

1. Results from proximal fibular fracture or habitual crossing of the legs
2. Patients develop foot drop or numbness of the web between the great and second toes
3. Conservative treatment is recommended initially - provide a splint or brace to maintain the foot at a right angle with the leg

Question 11

What is meralgia paresthetica?

Answer 11

Entrapment of the lateral femoral cutaneous nerve in the inguinal canal.
Entrapment causes numbness and pain of the anterolateral thigh.
On examination, the patient may complain of hyperesthesia in the area of pain, and Tinel’s sign may be evident when percussing ove the anterior superior iliac spine

Question 12

Remarks on pelvic compression test

Answer 12

Supports the diagnosis of meralgia paresthetica
Turn the patient on his or her side,
compress the pelvis,
and if the patient’s symptoms are relieved after 30 seconds of lateral compression of the pelvis, the diagnosis is confirmed

Question 13

Examples of plexopathies

Answer 13

Brachial plexopathy
Lumbosacral plexopathy
Cervical plexopathy

Question 14

Most common site of plexopathy

Answer 14

Brachial plexus, formed by C5-T1 nerve roots
1. Brachial plexopathies generally manifest as weakness first, but pain and paresthesias may also develop
2. The upper trunk is the more common site of involvement, affecting proximal arm and shoulder musculature

Question 15

Causes of brachial plexopathy include

Answer 15

Trauma (penetrating trauma, humeral neck fracture, severe traction injury, or dislocation
Shoulder reduction
Neoplasm (Pancoast tumor)
Radiation
Surgery

Question 16

Remarks on lumbosacral plexopathy

Answer 16

1. The L1-S4 nerve roots form the lumbosacral plexus
2. Causes are less likely traumatic, and **more likely to include radiation, diabetic amyotrophy, AORTIC ANEURYSM, retroperitoneal hemorrhage, or compression from AVM
3. Differentials include cauda equina and canus medullaris syndromes

Question 17

Least common plexopathy

Answer 17

Cervical plexus, formed by the C1-C4 nerve roots
Management is usually nonoperative

Question 18

Examples of neuromuscular junction disorders

Answer 18

Botulism
Tick paralysis
Inflammatory myopathies

Question 19

Remarks on Botulism

Answer 19

1. affects infants between 1 week and 11 months
2. has been implicated as a cause of sudden infant death syndrome
3. Toxins irrevesibly bind the presynaptic membrane of peripheral and cranial nerves, inhibiting the release of acetylcholine

Question 20

Classic presentation of botulism

Answer 20

1. Descending, symmetric paralysis
   The muscles first affected are the cranial nerves and bulbar muscles
2. No sensory deficit and no pain

Question 21

Important point of differentiation of botulism from myasthenia gravis

Answer 21

Botulism: Pupils are often dilated and nonreactive to light (from anticholinergic effect)
MG does not affect the pupil

Question 22

Treatment in botulism

Answer 22

Administer antitoxin as soon as the diagnosis is made

Question 23

Presentation of tick paralysis

Answer 23

Ataxia, then ascending weakness and paralysis without sensory involvement
Perform a complete body search for ticks before initiating treatment for other possible diagnoses
Tick paralysis and GBS are indistinguishable even with nerve conduciton studies.

Question 24

How to remove ticks

Answer 24

Take hold of the very head of the tick with tweezers and apply gentle steady traction.
If a tick is not found on the skin, use a fine-tooth comb to look through hair.

Question 25

Disposition for inflammatory myopathies

Answer 25

Admit patients with
- rhabdomyolysis
- respiratory distress
- profound weakness
Otherwise, patients may be discharged with neurology or rheumatology follow-up within 7 days

Question 26

Examples of subacute and acute-on-chonic peripheral nerve lesions

Answer 26

HIV-assocaited peripheral neurologic disease
CMV radiculitis
Diabetic peripheral neuropathy

Question 27

Patients in the early stages of HIV infection have greater susceptibility to

Answer 27

GBS
Presentation and treatment is similar as in non-HIV GBS

Question 28

In the latter stages of AIDS,

Answer 28

CMV may acutely infect the lumbosacral nerve roots, causing a polyradiculopathy or cauda equina syndrome
Evidence of systemic CMV infection, including retinitis, is almost always present
Treatment: IV ganciclovir for 3-6 weeks (may be initiated before definitive dignosis)

Question 29

most common cause of noncompressive focal neuropathy

Answer 29

Diabetes mellitus
emphasize strict foot care to the diabetic who has already developed neuropathy