PDF - NMJD

Question 1

What type of channels of on endplate at NMJ?

Answer 1

Nicotinic acetylcholine receptors

Question 2

What happens to ACH in the NMJ?

Answer 2

Broken down by acetylcholinesterase

Question 3

Treatment MG?

Answer 3

Can be improved by drugs that inhibit AChE, effectively increasing the amplitude and duration of the EPP

Question 4

What happens in botulism?

Answer 4

Bacterial toxin binds presynaptically at NMJ, preventing ACh release = weakness

Question 5

What is MG?

Answer 5

Autoimmune disease in which the immune system inappropriately reacts self-antigen.
- T and B-cells produce Ig blocking and destroying AChRs
faster than they can be synthesized

Question 6

Where do T cells develop?

Answer 6

Thymus?

Question 7

Common abnormalities seen in MG?

Answer 7

1. Glandular enlargement or hyperplasia of thymus

2. Thymoma = less common

Question 8

Presentation MG?

Answer 8

1. Weakness and fatigue of skeletal muscles

2. Without pain, sensory or cognitive impairment

Question 9

Most common symptoms MG?

Answer 9

1. Ptosis (eyelid drooping)
2. Diplopia (double vision from asymmetrically weak extraocular muscles)
3. Dysarthria (slurred speech)
4. Dysphagia (weakness of swallowing)
   * **Can at times be asymmetrical

Question 10

Normal Neurological signs in MG?

Answer 10

1. Muscle stretch reflexes
   2 Cognition
2. Higher cortical functions
3. Muscle atrophy develops only rarely

Question 11

What is occular MG?

Answer 11

Only have eye symptoms

Question 12

What is In neonatal myasthenia?

Answer 12

Healthy newborns of myasthenic mothers may have MG symptoms for a few days, until maternal Ig “wash out”

Question 13

What happens in myasthenic crisis?

Answer 13

Profound weakness may cause quadriplegia, with patient unable to speak, swallow or breathe.
- May be suddenly triggered by a serious infection or other systemic illness

Question 14

Type of infarction that can be similar to MG?

Answer 14

Extensive infarction of brainstem, where hyperreflexia may be noted

Question 15

GBS presentation?

Answer 15

Weakness developing over days with areflexia and sensory impairment accompanying

Question 16

How to diagnose GBS?

Answer 16

1. EMG

2. Elevated CSF protein

Question 17

Tests for MG?

Answer 17

1. Marked improvement after injection of an ACh-esterase inhibitor drug like edrophonium (Tensilon)
2. Single fiber jitter on electromyography
3. Serum AChR antibodies - Most specific

Question 18

What to look for in typical MG symptoms of Ig AChR negative?

Answer 18

Serum Ig to MuSK (muscle specific receptor tyrosine kinase), an NMJ protein important for clustering of AChRs.

Question 19

Poison with effect similar to MG?

Answer 19

Curare, an NMJ antagonis

Question 20

Rx MG? Side effect?

Answer 20

1. Pyridostigmine (Mestinon) ACh esterase inhibitor
   - Cholinergic crisis “DUMBBELLS”
2. Immunosuppressants - if refractory - prednisone
3. Thymectomy
4. Some will simply go into remission

Question 21

Rx Mg crisis?

Answer 21

1. IVIG
2. Plasmapheresis - gamma globulin component of plasma,
   containing all circulating antibodies as well as anti-AChR, is physically removed

Question 22

What muscles does LEMS impact?

Answer 22

Proximal muscles of shoulders and hips as well as trunk, mimicking weakness seen in a myopathy

Question 23

Other symptoms in LEMS?

Answer 23

1. • Muscle stretch reflexes may be decreased but reappear along w/ improved strength after a brief isometric exercise
     Autonomic symptoms:
2. Dry mouth
3. Orthostatic hypotension
4. Erectile dysfunction
   * Sensory deficits, cognitive symptoms, and pain not usually found

Question 24

What usually causes LEMS?

Answer 24

Small cell carcinoma of lung

Question 25

Dx LEMS?

Answer 25

1. Presynaptic NMJ abnormalities on electromyography

2. Serum Ig to voltage-gated Ca channel

Question 26

Rx LEMS?

Answer 26

1. Treat cancer

2. Guanidine or 3,4-diaminopyridine - increase ACH