Myasthenia gravis

1. What is the etiology of MG?
2. What is the presentation of MG?
3. How is it diagnosed?
4. What are the findings on standard EMG for MG?
5. What is the treatment of MG?

Answers:
1. Autoimmune response to the ACh receptors on the post-synaptic membrane. Often associated with thymic disorder.
2. Proximal fatigue and weakness, exacerbated by exercise, heat, or later in the day, improved with rest. Normal MSR. Ptosis, diplopia, dysphagia, dysarthria.
3. Tensilon test: 2mg of edrophonium followed by 8mg dose, improvement in 1 min. Muscle bx shows loss of postsyn junction folds and receptors. Blood shows anti-ACh receptor ab.
4. SNAP and CMAP are normal. EMG shows unstable MUAP.
5. Thymectomy, anticholinesterase drugs, corticosteroids, immunosuppressive agents, plasmapheresis. 1/3 improve spontaneously.