Neuromyotonia

Neuromyotonia, abbreviated NMT, is a form of peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potentials originating in the peripheral nervous system. It is considered one of the most severe conditions within the broader spectrum of peripheral nerve hyperexcitability disorders, a spectrum that also includes the related and more severe Morvan's syndrome, as well as milder variants such as cramp fasciculation syndrome and benign fasciculation syndrome. Neuromyotonia occurs in both inherited and acquired forms, though its overall prevalence in the population has not been well documented. People with the condition experience muscle cramps, stiffness, a myotonia-like slowness in muscle relaxation, difficulty walking, excessive sweating, muscle quivering and twitching, fatigue, poor exercise tolerance, and myoclonic jerks, with symptoms ranging from a mere inconvenience to fully debilitating; at least one third of patients also experience sensory symptoms. About 80 percent of cases are acquired and are suspected to involve an autoimmune mechanism in which antibodies target the neuromuscular junction, while the remaining cases are paraneoplastic or hereditary in origin. Symptoms are most prominent in the calves, legs, and trunk.