Abduction range: A potential parameter for the long exercise test in hypokalemic periodic paralysis during inter-attack periods.

BACKGROUND

The abduction range of the little finger in the long exercise test (ET) has rarely been reported in patients with hypokalemic periodic paralysis (HypoPP) during inter-attack periods, and the diagnostic value requires clarification.

METHODS

The long ET was performed in 43 HypoPP patients during inter-attack periods and in 20 healthy controls (HCs). The compound muscle action potential (CMAP) and the abduction range of the little finger were recorded concurrently.

RESULTS

There were significant differences in the percent changes of the CMAP amplitudes and the abduction ranges after exercise between HypoPP patients and the HCs. The curve of percent changes in abduction ranges overlapped substantially with that of the CMAP amplitudes, and the sensitivity, specificity, and cutoff values were 0.860, 0.900, and 22.6%, respectively.

CONCLUSIONS

The abduction range of the little finger can serve as a novel parameter in the long ET for the diagnosis of HypoPP during inter-attack periods.