Neuromyotonia is a disorder of peripheral nerve hyperexcitability characterized by myokymia, muscle cramps and stiffness, delayed muscle relaxation after contraction (pseudomyotonia), and hyperhidrosis, associated with well described spontaneous electromyographic features. Ocular NMT is a rare clinical entity, which is characterized by spontaneous spasm of ocular muscles resulting in paroxysmal diplopia and strabismus. Inappropriate discharges from ocular motor neurons or axons with unstable cell membranes may cause the sustained contraction of their respective ocular muscles. An auto-immune mechanism has been suggested in at least a subset of patients. Various therapies have been tried with different outcome. A patient with NMT responding well to high-dose immunoglobulin treatment is presented. Anticonvulsants, including phenytoin and carbamazepine, usually provide significant relief from the stiffness, muscle spasms, and pain associated with NMT. Serum anti-voltage-gated potassium channel antibodies were positive. Electromyography showed generalized NMT and myokymic discharges.
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