Clarifying variability of corticomotoneuronal function in kennedy disease.

INTRODUCTION

Although Kennedy disease (KD) is regarded as a pure lower motor neuron disorder, recent transcranial magnetic stimulation (TMS) studies have reported subclinical corticomotoneuronal dysfunction in KD. To clarify these findings, this study applied novel triple stimulation (TST) and threshold tracking TMS techniques to gain further insights into corticomotoneuronal function in KD.

METHODS

TMS studies were undertaken in 12 KD patients and 38 age-matched controls. Motor evoked potentials were recorded over the abductor pollicis brevis (threshold tracking TMS) and abductor digiti minimi (TST).

RESULTS

The mean TSTtest:TSTcontrol amplitude (99 ± 0.7%, normal >93%) and area (98.4 ± 1.6%, normal >92%) ratios were normal in Kennedy disease. In addition, short-interval intracortical inhibition (SICI) was similar in KD and controls (KD: 8.1 ± 1.3%; controls: 10.1 ± 0.7%; P = 0.11), as were the motor evoked potential amplitude, resting motor threshold, intracortical facilitation, and cortical silent period duration.

CONCLUSIONS

Triple stimulation and threshold tracking TMS techniques have reiterated normal corticomotoneuronal function in KD.