9. Myasthenia gravis . The edrophonium (Tensilon) test can be used to confirm the diagnosis. Facial weakness is provoked by repeated facial movements (left of slide). Edrophonium chloride, a short-acting anticholinesterase, is then injected intravenously – initially, 2 mg as a test dose, followed after one minute by a further 8 mg if there are no adverse effects. In myasthenia gravis the facial weakness is rapidly relieved by this test (right of slide). Objective testing of muscular power elsewhere in the body will reveal similar responses.
10. Thymoma (arrow) in a patient with myasthenia gravis . A lateral film confirmed that this mass was in the anterior mediastinum. The differential diagnosis of this appearance includes lymphadenopathy, retrosternal thyroid tissue or a dermoid tumor; but in the presence of myasthenia gravis, thymoma is the most likely diagnosis. Thymectomy may result in cure or great improvement in the myasthenia.