Familial hypokalemic periodic paralysis. Local recovery after nerve stimulation
Exercise is known to abort attacks of familial hypokalemic periodic paralysis (FHoPP) and to improve muscle strength during attacks. Various explanations have been offered for this beneficial effect of muscle activity, none of them satisfactory. In the present studies, repetitive nerve stimulations were performed during attacks of FHoPP. Prolonged repetitive stimulation resulted in complete recovery of evoked potential amplitude, muscle potential wave form, and clinical stength. The recovery was strikingly confined to the stimulated muscles while nonstimulated, adjacent muscles remained completely paralyzed. To determine the effect of exercise during established attacks, muscle contraction was produced by electrical stimulation of the ulnar nerve during attacks of weakness in 2 sisters with FHoPP. Repeated trains of stimulation produced normal strength and evoked potential amplitude in stimulated muscles without changing the strength or evoked potential of adjacent, nonstimulated muscles. It is suggested that the beneficial influence of muscle activity during attacks of FHoPP is a local membrane event resulting in recruitment of muscle fibers.
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