Confusion and controversies in diagnosis and treatment of myasthenia

Myasthenia gravis is an afferent ocular motor mimic. The disease may appear with any pattern of pupil-sparing, painless ocular misalignment with or without ptosis; accordingly, common mistaken diagnoses included CN3 palsy or internuclear ophthalmoplegia. Variability adds to diagnostic confusion, as patients may be asymptomatic and have a normal exam at certain stages in the disease. Clinical context remains the first diagnostic key, however, lab and electrophysiology are very helpful. Acetylcholine receptor antibodies are present in approximately 50% of ocular MG, but are highly specific. Single fiber EMG is perhaps the most sensitive test, being abnormal in approximately 90% of cases. Treatment is symptom dependent; pyridostigmine is often used as initial therapy and quite effective for ptosis and dysphagia, while additional immunosuppressives are often required for diplopia. We often initiate therapy with low dose every other day prednisone, and have a low threshold to add mycophenolate mofetil.