Review paper: The Lambert-Eaton myasthenic syndrome

LEMS in SCLC patients is caused by an immune response against SCLC antigens, which crossreacts with similar antigens on the motor nerve terminal, impeding neuromuscular transmission and presenting with truncal and leg weakness. The diagnosis may be suggested by the presence of dry mouth; and strongly supported by the finding of diminished tendon reflexes which reappear following a sustained muscular contraction. Appropriate neurophysiological tests can confirm the diagnosis more reliably than immunological studies, although there is rapid development in this field. A new diagnosis of LEMS should prompt a careful and ongoing search for underlying SCLC, with serial thoracic CT scans. In patients with established SCLC/LEMS, neuromuscular symptoms usually improve following successful anticancer treatment, or immunosuppression. While awaiting the benefits of these strategies, and for patients in whom they are inappropriate, DAP provides useful palliation of weakness and sometimes of autonomic dysfunction. It is available at a small cost, from specialist centres, on a named patient basis. LEMS is not widely recognized, and is commonly mistaken for myopathy or neuropathy. It appears that many physicians are not surprised to find that SCLC patients are weak, and therefore do not pursue a neurological diagnosis. Those providing palliative care may be the first to consider LEMS in SCLC patients complaining of weakness, and can offer useful therapy once the diagnosis has been established.