Ask the Experts - Could Jaw Fatigue Be a Presenting Symptom of...
I have a patient who presented with a complaint only of jaw fatigue when eating -- no pain or other muscle symptoms. Acetylcholine receptor antibody is elevated, but the electromyograph is negative for myasthenia. Chest CT is negative. Is this a variant of myasthenia gravis, and if so, what is the patient's prognosis?
This patient almost certainly has myasthenia gravis, which is currently localized to the muscles of mastication. The clinical findings fit this diagnosis. Although it is not particularly uncommon for conventional electrodiagnostic tests (repetitive stimulation) and chest CT scans (looking for thymic hyperplasia or thymoma) to be negative or normal in patients with myasthenia gravis, false-positive acetylcholine receptor antibody tests are extremely rare. Some large series of myasthenic patients find that it is unlikely for patients to develop new patterns of weakness more than 3 years after symptom onset. Therefore, the longer this patient experiences only this localized weakness, the less likely that other muscles will become involved.
I have a patient who presented with a complaint only of jaw fatigue when eating -- no pain or other muscle symptoms. Acetylcholine receptor antibody is elevated, but the electromyograph is negative for myasthenia. Chest CT is negative. Is this a variant of myasthenia gravis, and if so, what is the patient's prognosis?
This patient almost certainly has myasthenia gravis, which is currently localized to the muscles of mastication. The clinical findings fit this diagnosis. Although it is not particularly uncommon for conventional electrodiagnostic tests (repetitive stimulation) and chest CT scans (looking for thymic hyperplasia or thymoma) to be negative or normal in patients with myasthenia gravis, false-positive acetylcholine receptor antibody tests are extremely rare. Some large series of myasthenic patients find that it is unlikely for patients to develop new patterns of weakness more than 3 years after symptom onset. Therefore, the longer this patient experiences only this localized weakness, the less likely that other muscles will become involved.
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