Which diagnostic test is used for myasthenia gravis?

• A. Thyroid function tests
• B. Nerve stimulation tests
• C. Tension test
• D. Spinal tap

Answer: (C)

The main idea is that myasthenia gravis is diagnosed with a test that temporarily boosts transmission at the neuromuscular junction. The Tensilon test uses edrophonium, an acetylcholinesterase inhibitor, to briefly raise acetylcholine levels. If MG is present, muscles that are fatigued with use—especially eye and facial muscles—show a rapid, noticeable improvement in strength within minutes after the dose. This transient improvement supports the diagnosis because it directly demonstrates that the weakness is due to impaired neuromuscular transmission.

Safety is important, so this test is performed in a setting where heart rate and other cholinergic effects can be monitored. Other options may play roles in evaluating MG or related disorders, but they do not provide the same rapid, direct confirmation as this pharmacologic test.