Neuromuscular Junction Disorders Flashcards
Myasthenia Gravis
Autoimmune disorder of the postsynaptic NMJ
- T cells with help of B cells destroy AchR
- normal architecture and folding of post synaptic junction is lost
Occurs at any age
What factor plays an important role in the etiology of MG?
THYMUS gland
-most often glandular enlargement or hyperplasia less often tumor or thymoma
Symptoms of MG?
weakness and fatigue of skeletal muscles
when doing non strenuous activity
- ptosis
- diplopia
- dysarthria
- dysphagia
- asymmetric weakness is common
- muscle reflex, sensation, higher cortical function normal
ocular myasthenia
only visual symptoms
10-20% of patients
generalized myasthenia
more than just occular
neonatal myasthenia
healthy newborns of myasthenic mothers may have MG symptoms for a few days until mothers antibodies are out
myasthenic crisis
profound weakness may cause quadriplegia with the patient unable to speak swallow or breathe
Triggered by serious infection
What is the most specific test for MG?
serum AChR antibodies
Treatment of autoimmune MG
- oral anticholinesterase drugs-pyridostigmine
- too high a dose will result in cholinergic crisis-weakness, sweatiness, salivation, diarrhea, excessive urination - immunosuppressants-corticosteriods(prednisone)
- maybe thymectomy?
Crisis
- IV immunoglobulin
- plasmapheresis
Lambert-Eaton Myasthenic Syndrome
voltage gated calcium channels at the presynaptic membrane
-muscle fatigue and weakness but tend to disrupt proximal muscles of shoulders and hips and trunk
(symptoms do not usually involve the eyes, swallowing or speech)
-muscle stretch reflex may appear decreased but improved with isometric exercise
autonomic symptoms: dry, mouth, orthostatic hypotension, erectile dysfunction
Autoimmune related to SMALL CELL CARCINOMA OF THE LUNG
Treatment: drugs that enhance release of Ach-guanidine
-immunosuppressants and plasmapheresis
treatment not as effective as in MS
