[Cramp-fasciculation syndrome]

The cramp-fasciculation syndrome is a rare clinical entity in comparison with the frequency of cramps and isolated fasciculations in the general population. It is recognized as a benign syndrome without weakness and atrophy, however a few reports suggest that it may precede the occurrence of a motor neuron disease. Most often, the cramp-fasciculation syndrome is idiopathic and may be a component of a hyperexcitable peripheral nerve syndrome including other activities such as myokymia and neuromyotonia where antibodies to voltage-gated potassium channels (VGKCs) appear to be one of the effector mechanisms. The most complete form of this hyperexcitable peripheral nerve syndrome is Isaacs' syndrome. The central nervous system is also concerned with anti-VGKC antibodies found in Morvan's disease and limbic encephalitis which is often a paraneoplastic condition. These findings extend the spectrum of the anti-VGKC syndrome that may be associated with other auto-immune diseases, chiefly myasthenia gravis with thymoma. Carbamazepine and phenytoin cause reduction of the clinical and electrophysiological signs of the nerve hyperexcitability, and plasmapheresis and (or) immunosuppressors are useful when an auto-immune origin is considered.