NMJ

Question 1

Disorders of NMJ

Answer 1

• presynaptic
• synaptic
• postsynaptic

Question 2

Presynaptic disorders

Answer 2

• Lambert-Eaton myasthenic syndrome
• Botulism
• Magnesium

Question 3

Synaptic disorders

Answer 3

-N agents

Question 4

Postsynaptic disorders

Answer 4

• MG

- curare

Question 5

Myasthenia Gravis- etiology

Answer 5

• ab’s to nACHR
• sporadic (but high freq of B8 and DR3)
• seen w other autoimmune diseases (thyroid)
• younger women, older men

Question 6

MG- clinical sx’s- 3 general characteristics

Answer 6

• Fluctuating weakness- excessive fatigability
• Ocular m’s affected first- ptosis and diplopia
• clinical response to cholinergic drugs

Question 7

MG- diagnosis

Answer 7

• anti-ACHR Ab’s (55% of ocular MG and 80% of generalized MG)
• MUSK ab’s (M specific tyrosine kinase)
• EMG- decremental response on repetitive stim (U-shaped)
• Tensilon (edrophonium test)- SE’s of bradycardia, ventricular arrhythmias

Question 8

MG- tx

Answer 8

• ACHase inhibitors (Mestinon)
• prednisone
• plasma exchange/ IVIG
• thymectomy

Question 9

MG- drugs that can exacerbate or unmask

Answer 9

• neuromuscular blockers
• excessive ACHase medication
• BOTOX
• Aminoglycosides!!!!!

Question 10

Lambert-Eaton Myasthenic Syndrome

Answer 10

• ab’s against voltage-gated Ca channels on presynaptic n terminal
• presynaptic abnormality of ACH release- weakness
• assoc with SCCL!!

Question 11

Lambert-Eaton Myasthenic Syndrome- clinical presentation

Answer 11

• proximal weakness, loss of DTRs (vs MG), myalgias, dry mouth, impotence
• oropharyngeal and ocular m’s (but not as affected as in MG)
• strength improves after exercise

Question 12

Lambert-Eaton Myasthenic Syndrome- lab data

Answer 12

• voltage-gated Ca channel ab’s
• low amplitude motor responses that facilitate (increase) after a brief period of exercise
• incremental response on fast repetitive stimulation

Question 13

Lambert-Eaton Myasthenic Syndrome- tx

Answer 13

• first look for and treat malignancy!!
• ACHase inhibitors
• immunosuppression
• IVIG

Question 14

Botulism

Answer 14

• toxin blocks presynaptic mech’s for release of ACH
• dry, sore mouth and throat, blurred vision, diplopia, N/V (sx’s begin from top down)
• tx- ICU monitoring

Question 15

Nerve gases- clinical features

Answer 15

(Sarin and VX- organophosphate compounds)

• inhibit ACHase at NMJ to cause cholinergic crisis
• sx’s- miosis, inc secretions, bronchospasm, abd cramps, diarrhea, seizures
• death- resp failure

Question 16

Cholinergic crisis (n gases) vs MG flareup

Answer 16

-fasciculations, inc secretions, cramps, diarrhea–> cholinergic crisis!!!

Question 17

Nerve gas- tx

Answer 17

• decontamination
• resp support
• atropine
• 2-pralidoxime chloride