Impaired interhemispheric processing in early Huntington's Disease: A transcranial magnetic stimulation study

Changes in interhemispheric connectivity in Huntington's Disease (HD) have been only recently investigated and little is known about their temporal relation with clinical features or grey matter atrophy: callosal disruption could contribute both to cognitive dysfunction and impairment of associative functions (Rosas et al., 2010) and likely occurs many years before clinical onset, along a posterior-to-anterior direction (Phillips et al., 2013). In early HD, interhemispheric disruption may have important implications for the impaired sensorimotor integration, in addition to the supposed defective gating of peripheral afferent input. To date, little is known about the impairment of interhemispheric processing as assessed by electrophysiological methods. Transcranial magnetic stimulation (TMS) provides a unique opportunity to evaluate functional relationships between neural targets and clinical phenotype. Here, we evaluated changes in ipsilateral silent period (iSP: onset latency, iSPOL, and duration, iSPD) and transcallosal conduction time (TCT) in HD patients and correlated electrophysiological findings with mutational load and motor score.