investigations
Last reviewed 06/2021
There is an established series of tests for diagnosing myasthenia gravis:
- diagnosis can be confirmed by observing an improvement in strength after administering a short-acting anticholinesterase drug, for example, edrophonium chloride.
- electromyography may reveal that repetitive supramaximal nerve stimulation at low frequencies (3Hz) causes an abnormal decrement of the compound muscle potential due to blocking of transmission to individual muscle fibres
- in approximately 75% of patients with ocular symptoms, acetylcholine receptor antibodies are present. These are present in approximately 90% of patients with generalised disease
- a mediastinal computerise tomographic or magnetic resonance scan is required to detect a thymoma
N.B. anti-striated muscle antibody is associated with an increased risk of thymoma.
anti-acetylcholine receptor (AChR) antibody test