Ask an Expert: Myasthenia Gravis vs. Lambert-Eaton Syndrome

Myasthenia Gravis

Myasthenia Gravis vs. Lambert-Eaton Syndrome
08/30/2000

Question:

What is the difference between Myasthenia Gravis and Lambert-Eaton syndrome? How do doctors differentiate between the two in diagnosis? Is the treatment similar?

Answer:

Myasthenia gravis causes muscle weakness that patients usually appreciate becoming significantly worse with activity. Double vision, swallowing and speaking abnormalities, and difficulty walking and using the arms are common symptoms. Lambert-Eaton may produce similar symptoms, but double vision is less common. Muscle aches are more common and patients often have dry mouth. Patients may also have impotence, constipation, impaired sweating, and blurred vision.
Myasthenia gravis is caused by antibodies against acetylcholine receptor and compromise the muscle side of the nerve-muscle communication point. Lambert-Eaton syndrome appears to be caused most often by antibodies to calcium channels of the nerve. Lambert-Eaton is often triggered by the development of a lung cancer.
An EMG test can differentiate between myasthenia gravis and Lambert-Eaton. Also, blood tests for antibodies may also help with their differentiation.
Many of the treatments for the disorders are similar, although patients with Lambert-Eaton often do not respond as well. Thymectomy is not used to treat Lambert-Eaton.

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Response by:

Henry J Kaminski, MD
Formerly, Professor of Neurology
Department of Neurology
School of Medicine
Case Western Reserve University