The most sensitive test for the diagnosis of myasthenia gravis is: (AIPG 2009)
|A||Elevated serum ACh-receptor binding antibodies.|
|B||Repetitive nerve stimulation test.|
|C||Positive edrophonium test.|
|D||Measurement of jitter by single fibre electromyography.|
Measurement of jitter by single fibre electromyography.
1. Administration of intravenous edrophonium (a short-acting cholinesterase inhibitor) usually produces a transient improvement in strength in patients suffering from myasthenia gravis.
Extra edge: (Ref. Hari- 18th ed., pg- 3481)
The edrophonium test is now reserved for patients with clinical findings that are suggestive of MG but who have negative antibody and electrodiagnostic test results. False-positive tests occur in occasional patients with other neurologic disorders, such as amyotrophic lateral sclerosis, and in placebo-reactors.
2). Repetitive nerve stimulation studies can demonstrate a decremental response of the compound muscle action potential.
a. Acetylcholine receptor antibodies can be detected in the blood of 80%-90% of patients.
b. A thoracic CT or MRI scan shows a thymoma, if present.
c. EMG is the most sensitive & most specific test.