Neuromuscular Junction Disorders Flashcards
MG
- ai d/o pf post-synpatic NMJ (AChR are degraded or blocked)
- also get abnormalities of thymus (glandular enlargement or hyperplasia)
LEMS
pre-NMJ voltage gated calcium channel
what are the most common initial symptoms of MG
- ptosis (eye lid drooping)
- diplopia (dbl vision from asymmetrically weal extraocular muscles)
- dysarthria (slurred speech)
- dysphagia (weakness of swallowing)
more on MG
- asymmetrical weakness is common
- some ppl improve with rest
ocular myasthenia
10-20% of ppl who ONLY have visual s/s after 2-3yrs
-restricted form of MG
generalized MG
majority: 80-90%
neonatal myasthenia
healthy newborns of myasthenic moms may have MG s/s for a few days until mom’s Ab wash out of their system
myasthenic crisis
- profound weakness may cause quadriplegia
- pt unable to speak, swallow, breathe
- may be triggered by a serious infection or other systemic illness
- tx with IVIG or plasmapheresis
diagnosis of MG
*clinical history
most specific diagnostic test for MG
presence of serum AChR Ab
treatment of ai MG
- anticholinesterase drugs: Pyridostigmine (monitor dose for r/o cholinergic crisis)
- thymectomy
- corticosteroids (*prednisone) and some other immunosuppressants
LEMS muscle fatigue and weakness
- affect proximal muscles of shoulder, hip, trun
- autonomic s/s: dry mouth, orthostatic hypotension, ED
- ai dysfunction is related to an underlying cancer (small cell carcinoma of the lung)
LEMS tx
- tx underlying ca
- enhance ACh release: guanidine or 3,4-diaminopyridine
depending on distribution of clinical findings muscle weakness can be caused by disorders of:
- UMN
- LMN
- peripheral nerve
- NMJ
- muscle fibers
LMN/anterior horn cells
- spinal muscular atrophy
- ALS
- paraneoplastic syndromes
- poliomyelitis
