Interictal conduction slowing in muscle fibers in hypokalemic periodic paralysis.

Conduction velocity in muscle fibers of the short head of biceps brachii was reduced between attacks in all the affected members of a family suffering from hypokalemic periodic paralysis. This finding represents a further evidence of a primary alteration of sarcolemmal function in this disease. Interictal conduction slowing in muscle fibers is consistent with the prevailing pathophysiologic hypothesis, which considers an increased membrane permeability to sodium ions as the fundamental defect underlying all forms of familial periodic paralysis.