Evoked potentials in Huntington's disease

Visual (VEPs), brainstem (BAEPs), median and tibial somatosensory (SEPs) evoked potentials, motor evoked potentials (MEPs) elicited by transcranial(TMS) and spinal magnetic stimulation and transient period of inhibition (silent period, SP) in the EMG activity followed TMS were recorded in 10 patients with Huntington's disease (HD) and in a control group. BAEPs were normal almost in all patients. Only one patient had low amplitudes of II-V waves. The common abnormality of VEPs and SEPs was significant reduction in amplitude of the main analyzed cortical components (P100, cortical median N20 and tibial P40). Latencies were mostly in a normal range or slightly prolonged. In all patients SEPs n. tibialis were abnormal, VEPs were altered in 7 subjects and SEPs n. medianus in 4 subjects. Latencies of MEPs after TMS and central conduction time (CCT) were slightly prolonged in 6 subjects. Decrease in amplitude of MEP after TMS was present in 4 patients. Abnormal SP duration was found in all 7 examined subjects. Reduction in VEP and SEP amplitude of evoked response and mild latency delay could reflect diminished sensory inflow to cortex in HD patients. Abnormalities of MEPs after TMS could indicate an impairment of the corticospinal pathway. Changes of the central inhibitory mechanisms in HD patients are also discussed.