Reversible electrophysiological abnormalities in hypokalemic periodic paralysis.

Compound muscle action potential (CMAP) amplitude declines during a paralytic attack in patients with hypokalemic periodic paralysis (HPP). However, serial motor nerve conduction studies in HPP have not been commonly reported. We report a 9 year old girl with HPP, who had severely reduced CMAPs in all motor nerves at presentation during the episode of quadriparesis. However, the amplitude of CMAPs increased and reached normal levels as the serum potassium concentration and motor power returned to normal state.