Neuromyotonia

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Classification according to ICD-10
G71.1 Myotonic Syndromes
ICD-10 online (WHO version 2019)

The neuromyotonia is a neurological syndrome , which is characterized by an increased excitability of the skeletal muscle and as autoimmune disease or paraneoplastic syndrome in small cell bronchial carcinomas , lymphomas and thymomas described. The cause is a disturbed function of the neuromuscular synapse ( motor end plate ), which is caused in the vast majority of cases by the formation of autoantibodies against voltage-activated potassium channels (VGKC antibodies) ( Isaacs syndrome or Isaacs-Mertens syndrome ). When neuromyotonia is associated with symptoms of limbic encephalitis , the term Morvan's syndrome is used. In addition to the acquired forms, there are also inherited forms. Neuromyotonia was described in the 1960s by the South African physiologist and clinical neurophysiologist Hyam Isaacs and the German neurologist Hans-Georg Mertens.

clinic

Neuromyotonia occurs sporadically and at any age and is considered very rare. Clinically involuntary tonic muscle spasms, fasciculations and, as a particularly characteristic feature, permanent, wave-like muscle tension, which are clearly visible in slim people ( myokymia ), dominate. Often the muscles cannot be relaxed properly and appear stiff (pseudomyotonia). Sometimes excessive sweating ( hyperhidrosis ) can also be observed. Electromyographically , muscle action potentials can be demonstrated during relaxation, as well as signs that correspond to denervation ( fasciculations and fibrillations ). Antibodies against voltage-activated potassium channels can be detected in the serum in around 40% of patients, and many people also have other autoantibodies, for example against acetylcholine receptors such as the one Myasthenia gravis .

Treatment is purely symptomatic, with anti-epileptic drugs ( e.g. phenytoin , carbamazepine , valproic acid , lamotrigine ), immunosuppression or plasmapheresis . Removal of the tumor, if any, often does not improve symptoms much.

literature

  • Hyam Isaacs: A syndrome of continuous muscle-fiber activity. In: Journal of Neurology, Neurosurgery and Psychiatry. London 1961, 24, pp. 319-325.
  • Hans-Georg Mertens, S. Zschocke: Neuromyotonia. In: Clinical weekly. Berlin 1965, 43, pp. 917-925.

Individual evidence

  1. ↑ Isaac Syndrome. Retrieved May 25, 2019 .
  2. ↑ INSERM US14-- ALL RIGHTS RESERVED: Orphanet: Isaacs Syndrome. Retrieved May 25, 2019 .