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Myasthenia Gravis (Examination (Eyes (Bilateral ptosis: worse on sustained…
Myasthenia Gravis
Examination
Inspect
Thymectomy scar
Eyes
Bilateral ptosis: worse on sustained upward gaze
Complex ophthalmoplegia
Facial Movements
Myasthenic snarl on smiling
Voice
Nasal
Deterioration: ask pt. to count to 50
Limbs
Fatiguability: repeatedly flap arm
Completion
Assess respiratory muscle function: spirometry (FVC)
Viva
Ix
Abs:
Anti-AChR, Anti-MuSK
EMG:
↓ response to titanic train of impulses
Tensilon test:
improvement w/ edrophonium
(anticholinesterase)
TFTs:
Graves in 5%
CT mediastinum:
thymoma in 10%
Mx
Acute
Plasmapheresis or IVIg
Monitor FVC: consider ventilation
Chronic
Pyridostigmine
Immunosuppression: steroids and azathioprine
Thymectomy: benefit even if no thymoma
Associations
<50, female
AI disease: DM, RA, Graves, SLE
Over 50, male
Thymoma
Bilateral Ptosis
MG
Myotonic dystrophy
Congenital
Senile
Bilateral Horner’s (rare)
LEMS
Abs vs. VGCC
Often paraneoplastic: e.g. SCLC
Lower limb girdle weakness
Weakness improves on repetitive testing