History is very important that the patient has fluctuating muscle weakness that causes the symptoms cited above. With the neurological examination, the neurologist can see that there really is muscle fatigue (can be seen, for example, that the eyelids fall to look up one time, or that the patient gets tired to hold up arms). To confirm the diagnosis, we must perform a series of tests:
Blood test
The blood test to detect blood will anti-acetylcholine receptor. These antibodies can be found in 85% of patients with generalized myasthenia and in 50% of patients with pure ocular myasthenia.Electromyogram
It consists of applying an electrical stimulus to the muscle and recording the muscle response. In patients with myasthenia, the record shows characteristic changes (decreased amplitude of contraction after repeated stimulation, which improves with rest).
Edrophonium test (Tensilon)
Edrophonium is a drug which, when injected intravenously, produces rapid improvement of symptoms, but short-lived.
CT (scan) of the chest
It is a CT scanner to see if patients have thymoma.
What diseases can be mistaken for myasthenia?
The most important difference to other disease myasthenia gravis is muscle weakness that worsens with repeated movements (fatigue), and the symptoms fluctuate.
There are diseases affecting the muscle itself (mitochondrial myopathy, inflammatory myopathies, muscular dystrophies, etc..), Which can produce symptoms similar to myasthenia. In these cases, are not detectable acetylcholine receptor antibodies, the edrophonium test is not an improvement so clear and the electromyogram shows another type of alterations.
Thyroid disease can affect the eye muscles and produce symptoms similar to ocular myasthenia.
credit to: Dra. María del Mar Carreño Martínez, Dra. Camilla Buckley, Dr. John Newsom-Davis
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