Which diagnostic test is used to confirm MG by showing improvement after administration of an acetylcholinesterase inhibitor?

• A. CT/MRI
• B. Blood glucose
• C. Urinalysis
• D. Edrophonium chloride test showing improvement

Answer: (D)

In myasthenia gravis, weakness comes from impaired transmission at the neuromuscular junction due to fewer functional acetylcholine receptors. A short-acting acetylcholinesterase inhibitor increases acetylcholine levels at the junction, temporarily boosting neurotransmission. If MG is present, this extra acetylcholine produces a noticeable, temporary improvement in muscle strength, which is what the edrophonium chloride (Tensilon) test demonstrates. That immediate, reversible improvement after a cholinesterase inhibitor is the hallmark used to confirm MG in testing.

Imaging like CT or MRI looks for structural causes (such as thymic abnormalities or brain lesions) and isn’t a test of NMJ transmission. Blood glucose or urinalysis assess metabolic or renal status, not neuromuscular transmission, so they don’t diagnose MG.