Myasthenia gravis is caused by antibodies that bind to postsynaptic acetylcholine receptors of the neuromuscular junction of skeletal muscle. The majority of patients with myasthenia gravis present to the emergency department (ED) with an exacerbation of the disease or complications of their medications. Brainstem stroke can present with altered mental status, ptosis, diplopia, and pupillary abnormalities. MRI with diffusion-weighted imaging can reliably distinguish acute brainstem stroke from myasthenia gravis. One reliable diagnostic tool for myasthenia gravis is the edrophonium (Tensilon) test, which may help to differentiate a cholinergic crisis (that is, overmedication of cholinesterase inhibitors) from a myasthenic crisis, and guide subsequent therapy. Careful attention to airway support is of primary importance in the myasthenic patient. Immunosuppressive agents are useful for long-term suppression of the disease. All patients with airway compromise require intensive case unit (ICU) admission.