The lambert-eaton myasthenic syndrome
The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease of the neuromuscular junction. The main symptom in LEMS is proximal muscle weakness in the legs, which is the presenting symptom in most patients. Autonomic dysfunction is also part of the clinical spectrum. Neurological examination generally reveals low or absent tendon reflexes. The muscle weakness and autonomic dysfunction are caused by pathogenic autoantibodies directed against voltage-gated calcium channels (VGCC) present on the presynaptic nerve terminal, causing a decreased release of acetylcholine from nerve terminals. Half of the patients have an associated tumour, usually a small cell lung carcinoma, which expresses VGCC on its surface. If the diagnosis of LEMS is suspected from the distinctive clinical features, confirmation of the diagnosis depends on detection of VGCC autoantibodies or characteristic electrodiagnostic findings. Treatment of LEMS is based on drugs which act at the neuromuscular synapse by increasing either the release or the concentration of acetylcholine, drugs which suppress the immune response or treatment of the underlying tumour.