Temporal discrimination of somesthetic stimuli is impaired in dystonic patients.

Clinical and experimental evidence documents abnormal somatosensory functions in dystonia. Despite the fact that somatosensory processing is inherently temporal, mainly spatial aspects of somatosensory functions have so far been assessed in dystonic patients. Seven patients with idiopathic dystonia and nine healthy controls were given pairs of non-noxious electrical stimuli separated by different time intervals and asked to report if they perceived single or double stimuli. Somesthetic temporal discrimination thresholds (STDT) were obtained by computing the shortest time interval at which stimuli, applied to the left or the right hand, were perceived as separate. STDT were significantly higher in dystonic than in controls thus showing for the first time that temporal and not only spatial somatosensory processing is altered in dystonia.