Clinical Application of Exercise Test in Patients with Periodic Paralysis

J Korean Assoc EMG Electrodiagn Med 2003;5(2):59-68.
Published online May 10, 2003.

Abstract

Objectives: It is difficult to diagnose periodic paralysis when the patient visited hospital after recovery of paralysis. The purpose of this study is to investigate the value of exercise test as an electrophysiologic method of evaluating the patients with periodic paralysis in symptom-free period. Methods: Exercise test was performed in 16 patients with periodic paralysis at interictal period and 20 normal healthy persons. Incremental and decremental percentage were calculated by using the measured compound muscle action potential (CMAP) amplitude of ulnar nerve. The values more than mean+2 standard deviation (SD) of controls were regarded as abnormal and the results of the two groups were compared. Results: The incremental and decremental percentage of the exercise test in patients with periodic paralysis(23.9 15.7% and 36.7 20.5%, respectively) were greater than controls with statistical significance(p<0.01). Regarding the incremental and decremental percentage of more than 24.0% and 32.4% as abnormal results, the specificity and sensitivity of the exercise test in diagnosing periodic paralysis were 95% and 44%, respectively. Conclusion: The exercise test can be used not only as a confirmative test for diagnosis of the periodic paralysis with high specificity predicting the existence of abnormal excitability of the muscle membrane, but also as an useful electrophysiologic method for monitoring disease status.

Key Words: Exercise test, Periodic paralysis, Muscle membrane excitability