Myasthenia Gravis Quick overview
Signs and Symptoms
● Fatigable muscle weakness – most common
1) ptosis and diplopia 80%.
● 2) Bulbar muscles ( dysarthria and dysphagia)
● 3) Limb weakness usually proximal and symmetric
● Worse at end of day
- Resp muscle weakness = myasthenic crisis
● Bedside Icepack test
● Edrophonium test (historically)
● Anti- AChR/MuSK antibody titer – high in
- Repetitive nerve stim shows decreasing response
● Anti-AChE (-stigmines)
● Plasmapheresis and IV-Ig
○ Yes if thymoma present
○ Otherwise uncertain if recommended
– An autoimmune disease targeting post-synaptic acetylcholine receptors
– 7 – 23 new cases/million people/year; 70 – 320/million people live with MG
– Bimodal age distribution: peaks in 2nd and 3rd decades (female predominance) and 6th to 8th decades (male predominance)
– Diplopia, ptosis, dysphagia which is worsened with muscle use (fatigability), and improved with rest
– Often asymmetric symptoms at presentation
– Proximal muscles sometimes involved
– Myasthenic crisis: respiratory muscle weakness leading to respiratory insufficiency and
pending respiratory failure = emergency!
– Ice pack test (bedside), acetylcholine receptor antibodies (80% sens, 100% spec), MuSK antibodies (38% sens, unknown spec), repetitive nerve stimulation with EMG, CT chest
– Thyroid ophthalmopathy, brainstem or cranial nerve lesion, myotonic dystrophy and oculopharyngeal dystrophy, general fatigue, Lambert-Eaton, ALS, botulism
– First line – pyridostigmine
– Thymectomy if thymoma present on chest CT
– If weakness affects eating/breathing, give IVIG or plasmapheresis
- Refractory MG treated with prednisone or azathioprine
Shawn J Bird, MD. Diagnosis of myasthenia gravis. 2018.
Shawn J Bird, MD. Clinical manifestations of myasthenia gravis. 2018.
Summarized by Dr. Kazmi, Medical student : Dr. Joey Gerondale
This is the basic information. Needs improvement. Read up-to-date.