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Question

There are two tests that you can perform at bedside in patients with suspected myasthenia gravis. One is an easy adjunct to the neurologic exam and the other is only included for historical purposes. Name these tests.

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Answer

The most reliable way to diagnose myasthenia gravis is through serologic laboratory studies assessing acetylcholine receptor and muscle-specific tyrosine kinase antibodies. But……………there are two bedside tests that can help prior to expensive labs.

• Ice Pack Test
  • Used as part of the neurologic examination, it is based on the physiologic principle that neuromuscular transmission improves at lower muscle temperature. In patients with myasthenia gravis, placing an ice pack over a closed eyelid for 2 minutes can improve ptosis in 80% of patients.

• Edrophonium Test
  • Taught more for historical purposes, edrophonium is an acetylcholinesterase inhibitor with a rapid onset and short duration of action. The main effect is prolonging acetylcholine in the neuromuscular junction to improve muscular strength.
  • It is not available in the US, nor used in the diagnosis