Nerve and Muscle

Question 1

Two tests for Myasthenia gravis:

Answer 1

Tensilon test: edrophonium, a readily reversible ACh esterase inhibitor, or the ice pack test, that can temporarily reverse ptosis.

Question 2

Myasthenia gravis shows what on EMG?

Answer 2

Decremental response to repetitive stimulation.

Question 3

What type of antibodies are found in MG?

Answer 3

Anti-ACh receptor, in about 80-90% of patients.

Question 4

What is MG?

Answer 4

A neuromuscular junction disorder where antibodies block and distort the acetylcholine receptor.

Question 5

Treatment for myasthenic crisis:

Answer 5

IVIG, plasmapharesis immediately to reduce antibody load in blood, however proactive intubation in an emergency.

Question 6

What is Lambert-Eaton myasthenic syndrome?

Answer 6

a paraneoplastic disorder. It is characterized by slowly progressive weakness that, in contrast to myasthenia gravis, usually spares eye muscles, and there is a brief improvement in strength with exercise. This is seen on EMG as an incremental response to repetitive stimulation. The mechanism is by the production of antibodies against presynaptic calcium channels.

Question 7

The tumor most likely to cause Lambert-Eaton myasthenic syndrome is:

Answer 7

Lungs (often small-cell).

Question 8

Treatment for MG:

Answer 8

Maintenance with pyridostigmine (Mestinon), a reversible cholinesterase inhibitor, steroids (azathioprine) are also standard of care.

Question 9

What is myasthenic crisis?

Answer 9

Patients will have respiratory insufficiency that is out of proportion to the rest of their muscle weakness or increased generalized weakness of their bulbar muscles necessitating intubation. This is a medical emergency. Patients must be admitted to the ICU and have their respiratory muscle strength monitored with serial FVC measurements.

Question 10

LP results in GBS:

Answer 10

WBC normal, RBC normal, protein high: this pattern is referred to as albuminocytologic dissociation.

Question 11

Which infectious agent commonly precedes GBS?

Answer 11

Campylobacter jejuni

Question 12

Treatment for GBS:

Answer 12

IVIG (easier and less SE), plasmapharesis

Question 13

Decreased conduction velocity and conduction block indicate a _____.

Answer 13

demyelinating process

Question 14

What is GBS?

Answer 14

An autoimmune disorder, often following a GI illness, where patients developing ascending weakness with minimal sensory symptoms.
Symptoms develop over hours to days and patients may also have significant back pain due to inflammation of nerve roots.
Loss of reflexes is a key to clinical diagnosis.

Question 15

Where to look for ulnar nerve symptoms or “claw hand.”

Answer 15

The course of the ulnar nerve around the posterior aspect of the medial epicondyle makes it susceptible to traumatic injury when patients strike the medial epicondyle of the humerus posteriorly, or inferiorly with the elbow flexed, compressing the nerve against the bone.

Question 16

Drop wrist and numbness on the back of the hand is due to injury of which nerve?

Answer 16

Radial nerve

Question 17

Injury of femoral nerve presents how?

Answer 17

Weakness of knee extension and hip flexion.

Question 18

What is lateral femoral cutaneous nerve syndrome?

Answer 18

Meralgia paresthetica: compression of the nerve as it exits the inguinal ligament, presents with sensory symptoms on the lateral thigh and can be treated with weight loss and wearing looser clothes.

Question 19

Which nerve, when injured, leads to foot drop?

Answer 19

The common peroneal nerve divides into the deep and superficial branches. The deep branch is responsible for foot drop. There is also numbness of the lateral calf and foot.

Question 20

The tibial nerve is responsible for what?

Answer 20

Foot plantar flexion

Question 21

The sciatic nerve does what in the leg?

Answer 21

hamstring muscles/knee flexion

Question 22

C5 and C6 nerve roots mediate which reflexes?

Answer 22

Biceps and brachioradialis

Question 23

C6 and C7 (mostly C7) mediate which reflex?

Answer 23

Triceps reflex

Question 24

L3 and L4 (mostly L4) mediates which relfex?

Answer 24

Knee jerk

Question 25

S1 nerve root mediates which reflex?

Answer 25

Ankle jerk

Question 26

Periumbilical area is innervated by which dermatome?

Answer 26

T10

Question 27

Nipple area is innervated by which dermatome?

Answer 27

T4

Question 28

What causes descending paralysis?

Answer 28

Botulism

Question 29

What is pseudohypertophy of muscle and when is it seen?

Answer 29

Infiltration with fatty tissue and the muscles are actually breaking down. Duchenne Muscular Dystrophy.

Question 30

Which gene is mutated in DMD?

Answer 30

dystrophin

Question 31

What is the mechanism of inheritance of DMD?

Answer 31

X-linked recessive

Question 32

CK levels in DMD:

Answer 32

Could be 100x normal

Question 33

DMD treatment:

Answer 33

avoid exercise (injures muscles), weekly steroid treatments, death occurs in the mid 20s.

Question 34

What is Becker’s MD?

Answer 34

Similar to DMD but milder, patients can often walk into early adulthood.

Question 35

Ragged red muscle fibers are seen in what?

Answer 35

Mitochondrial myopathies. Abnormal accumulations of mitochondria. Serum or CSF lactate and pyruvate are often increased as well.

Question 36

What is inclusion body myositis?

Answer 36

> 50 years old, distal muscles of hands/feet, asymmetrical, CK is normal or moderately elevated, thought of as neurodegenerative disease of muscle without effective treatment.

Question 37

What is polymyositis?

Answer 37

> 18 years old, subacute inflammatory myopathy that is progressive in a “lim-girdle” distribution, often cardiac involvement, CK up to 50x normal, treatment with steroids.

Question 38

What is dermatomyositis?

Answer 38

Adults and children, heliotrope rash, scaly (mechanic’s) hands, Anti-Jo-1 antibodies, higher likelihood of temporal arteritis, measure ESR, treat with prednisone.

Question 39

What is hyperkalemic periodic paralysis?

Answer 39

An autosomal dominant disease of sodium channels. Serum and urinary K are high during attacks. Presents before age 10 with acute onset proximal muscle weakness provoked by cold, resting after exercises, potassium rich foods. Treat with acetazolamide.

Question 40

What is hypokalemic periodic paralysis?

Answer 40

An autosomal dominant disease of calcium channels, early childhood presentation with soreness in back/thighs/limbs, episodes last several hours but start/end abruptly. Provoked by resting after exercise and carb consumption, treat with oral K supplementation.

Question 41

What is paramyotonia congenita?

Answer 41

Caused by mutation in Na channel, severe stiffness caused by cold exposure, rest, or low K.

Question 42

What is myotonia congenita?

Answer 42

Caused by a mutation in the chloride channel, presents with muscle stiffness that worsens with rest, improved with exercise.