Clinical relevance of electrophysiological tests in the assessment of patients with Huntington's disease.

Assessment programs recently designed to follow-up patients with Huntington's disease (HD) in therapeutic trials have not included electrophysiological testing in the list of mandatory examinations. This omission is likely due to the current lack of data establishing a clear correlation between the electrophysiological results and those of clinical assessment. We address this issue in a cohort of 36 patients at relatively early stages of the disease (I and II). Electrophysiological studies comprised the recording of palmar sympathetic skin responses (SSRs), blink reflexes (BRs), thenar long latency reflexes (LLRs), cortical somatosensory evoked potentials (SEPs), and electromyographic silent periods evoked by transcranial magnetic stimulation (SPs). Results were analyzed with reference to disease duration and staging and to specific cognitive, psychiatric, and motor alteration. SEPs were the most and very sensitive markers, because they were abnormal in 94% of patients. Except for LLRs, alteration of electrophysiological results increased in parallel to the evolution of the disease. Except for LLRs and SSR latency, electrophysiological results correlated with those of specific clinical examinations. In particular, an increased BR latency or a reduced amplitude of the N20 component of SEPs correlated with the extent of bradykinesia, whereas a reduced amplitude of SSRs or of the N30 component of SEPs correlated with hyperkinesia. Overall, electrophysiological tests, in particular SEPs and BRs, appeared sensitive and interesting in the follow-up of HD patients and correlated with various clinical parameters, suggesting that these easy to perform and noninvasive repeatable examinations could be added fruitfully to the assessment programs for HD.