Chapter

Peripheral Nerve Hyperexcitability Syndromes

Srikanth Muppidi and Steven Vernino

in Myasthenia Gravis and Myasthenic Disorders

Second edition

Published on behalf of © 2012 by Mayo Foundation for Medical Education and Research

Published in print March 2012 | ISBN: 9780199738670
Published online April 2013 | e-ISBN: 9780199322848 | DOI: http://dx.doi.org/10.1093/med/9780199738670.003.0010

Series: Contemporary Neurology Series

Peripheral Nerve Hyperexcitability Syndromes

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Neuromyotonia is a rare, but dramatic, disorder resulting from high-frequency spontaneous repetitive discharges arising at or near the motor nerve terminal. Peripheral nerve hyperexcitability (PNH) consists of a spectrum of disorders ranging from the dramatic presentation of Isaacs syndrome or Morvan syndrome to more benign variants such as cramp-fasciculation syndrome. PNH can result from genetic causes, especially mutations in voltage-gated potassium channels such as episodic ataxia type 1. Evidence points to an autoimmune etiology for most cases of acquired generalized PNH. Antibodies against voltage-gated potassium channel complex proteins are found in many patients and appear to alter VGKC function directly. Neuromyotonia may occur in association with other autoimmune disorders or with cancer (especially thymoma or small cell lung carcinoma). Seizures or changes in behavior sometimes are seen even in PNH, and probably reflect the action of autoantibodies in the CNS. Focal nerve injury or demyelination or toxins that alter nerve excitability can also produce PNH. If the symptoms are not disabling, symptomatic therapy with membrane-stabilizing drugs is usually sufficient. Immunomodulatory agents and plasma exchange are reserved for the severely disabled patients.

Chapter.  7895 words.  Illustrated.

Subjects: Neurology

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