Medical therapy is tailored for each patient and might include various combinations of the drugs listed below. Therapy is best coordinated with the primary care physician and appropriate consultants.
The initial pharmacotherapy for Lambert-Eaton myasthenic syndrome (LEMS) is with agents that increase the transmission of acetylcholine (ACh) across the neuromuscular junction, either by increasing the release of ACh or by decreasing the action of acetylcholinesterase. Treatment of the associated cancer may also decrease the weakness and other symptoms.
If these treatments are not effective and the patient has relatively mild weakness, aggressive immunotherapy may be warranted. In such cases, plasma exchange (PEX) or high-dose intravenous immunoglobulin (IVIg) may be used initially to induce rapid, albeit transitory, improvement.
Immunosuppressants should be added for more sustained improvement. Prednisone and azathioprine, the most frequently used immunosuppressants, can be used alone or in combination. Cyclosporine may benefit patients with LEMS who are candidates for immunosuppression but cannot take or do not respond well to azathioprine.
IVIg, given in a course of 2 g/kg over 2-5 days, also induces clinically significant temporary improvement in many patients. The frequency of improvement in response to repeated courses of treatment has not been determined.
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Characteristic responses to repetitive nerve stimulation in patient with Lambert-Eaton myasthenic syndrome. (A) Responses elicited from hand muscle by stimulation of nerve at 3 Hz. Amplitude of initial response is less than normal, and response is decremental. (B) Responses as in A, immediately after voluntary activation of muscle for 10 seconds. Amplitude has increased. (C) Responses in hand muscle elicited by 20-Hz stimulation of nerve for 10 seconds. Response amplitude is less than normal initially, falls further during first few stimuli, then increases and ultimately becomes more than twice initial value.
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Compound muscle action potentials elicited from hand muscle before and immediately after maximal voluntary activation of muscle for 10 seconds. Amplitude is small initially, increasing almost 10 times after activation.
