Diagnosing Myasthenia Gravis with an Ice Pack
Wendy W. Liu, M.D., Ph.D.Adam Chen, M.D.
A 68-year-old man presented with unilateral ptosis and no other symptoms. The neurologic examination revealed ptosis of the left eye after a sustained upward gaze (Panel A). The movements of the extraocular muscles were normal. Myasthenia gravis was suspected, and the ice-pack test was performed with the placement of an instant cold pack over the left eye (Panel B). After 2 minutes, the ptosis was substantially diminished (>5 mm), indicating a positive test (Panel C). The diagnosis was further supported by the presence of serum anti–acetylcholine receptor antibodies and by electrodiagnostic testing, which showed a decremental response to repetitive nerve stimulation. The ice-pack test can be a useful bedside test to distinguish myasthenia gravis from other causes of ptosis or ophthalmoparesis. The inhibition of acetylcholinesterase activity at a reduced muscle temperature is thought to underlie the observed clinical improvement. The patient was treated symptomatically with pyridostigmine, and the ptosis was diminished.
Wendy W. Liu, M.D., Ph.D.
Harvard Medical School, Boston, MA
Adam Chen, M.D.
Brigham and Women’s Hospital, Boston, MA