Which test is used to differentiate between myasthenia gravis and cholinergic crisis?

The Tensilon test, also known as the edrophonium test, is a crucial diagnostic tool used in distinguishing between myasthenia gravis and a cholinergic crisis. In myasthenia gravis, the administration of edrophonium chloride temporarily improves muscle strength due to its action as a short-acting acetylcholinesterase inhibitor, which increases the availability of acetylcholine at the neuromuscular junction. Conversely, in a cholinergic crisis, which occurs due to excessive cholinesterase inhibition, the administration of edrophonium can lead to a worsening of symptoms. This distinct response to edrophonium is what allows clinicians to differentiate between these two conditions effectively.

Other tests listed, such as EMG and CT scans, do provide valuable information regarding neuromuscular function and could identify thymoma or other associated factors but are not specifically designed to differentiate between myasthenia gravis and cholinergic crisis. A blood glucose test, while useful in evaluating other conditions such as metabolic derangements, does not have relevance in distinguishing these neuromuscular disorders. Thus, the Tensilon test stands out as the most appropriate and specific choice for this clinical scenario.