Neurophysiology in Huntington's disease: an update.

Huntington's disease (HD) is a hereditary movement disorder with dementia and behavioral difficulties caused by a mutation in the HTT gene. Age-at-onset, clinical phenotype and disease evolution vary and are not explained by the mutation alone. Electrophysiological techniques, like transcranial magnetic stimulation and electroencephalography, have advanced our understanding of the pathophysiology but have not revealed any consistent abnormalities suitable as biomarkers. The most promising candidate may be somatosensory or visual evoked potentials, which repeatedly had reduced amplitudes in manifest HD. To test their potential, large cohorts of clinically homogeneous patients need to be studied with electrophysiological in conjunction with neuroimaging techniques to delineate neural network function in relation to micro- and macro-structural brain changes.