Application of exercise test in patients with paroxysmal kinesigenic dyskinesia

Objective To explore the application of the exercise test (ET) in paroxysmal kinesigenic dyskinesia (PKD). Methods We conducted the ET in 33 controls and 45 PKD patients following standardized protocols, and the decrement in the amplitude and in the area of compound muscle action potentials (CMAP) after long ET and other seven parameters were calculated and compared in both groups, and the normal range of parameters was defined as the mean±two standard deviation of the control values. Results According to the control group, the normal range of the change in the amplitude of CMAP immediately after short ET was -13%-27% and the normal range of decrement in the amplitude of CMAP after long ET was less than 33%. And the ET was abnormal in 16 of the 45 PKD patients (36%). Comparing the nine parameters between two groups, we found that both the decreases of the amplitude(25.5%±13.4% vs 16.2%±8.6%, t=-3.72, P=0.00) and the area(31.8%±16.3% vs 19.0%±16.8%, t=-2.39, P=0.02) of CMAP after long ET in PKD patients were larger than those in controls. No statistically significant difference was found between 19 non-ion channel disease patients and 14 normal controls. No statistically significant difference was found between the nine parameters in 27 PKD patients before and after medication, though all the patients had obvious clinical improvement. Conclusion We found that abnormal ET may appear in PKD patients, and this finding hinted that abnormal muscle membrane excitability might be an underlying mechanism responsible for PKD. Key words: Movement disorders; Episodic kinesigenic dyskinesia; Exercise test; Electromyography