If these treatments are not effective and the patient has relatively mild weakness, determine if aggressive immunotherapy is justified. When such therapy is warranted, plasma exchange (PEX) or high-dose IVIg may be used initially to induce rapid, albeit transitory, improvement. Immunosuppressants should be added for more sustained improvement, although a theoretical concern exists that immunologic suppression of tumor growth may thereby be reduced in paraneoplastic LEMS.
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. Improvement may be seen within 1-2 month after initiation of cyclosporine, with the maximum response usually observed in 3-4 months.
PEX produces improvement in many patients with LEMS. Improvement is temporary unless the patient is also receiving immunosuppression. Response to PEX is often more gradual in patients with LEMS than in those with MG. Maximal response may take several weeks. Repeated courses of PEX may be necessary to maintain improvement. PEX may be performed 4-6 times over 7-10 days, as described in standard protocols. Potential complications include autonomic instability, hypercalcemia, and bleeding due to depletion of clotting factors.
IVIg, given in a course of 2 g/kg over 2-5 days, also induces clinically significant temporary improvement in many patients. [13] 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.
