The role of sensory information in the pathophysiology of focal dystonias.

Over the past few decades, abnormalities in sensory functions, such as tactile, proprioceptive and nociceptive processing, have been increasingly recognized in patients with focal dystonias. In this Review, we ask whether sensory system abnormalities are specific to particular types of dystonia, whether a causal link exists between sensory alterations and dystonic motor activity and how mechanisms underlying the sensory abnormalities fit in with the proposed 'network model' of dystonia. We suggest that alterations in the various sensory modalities participate at three different levels in the pathophysiological cascade that leads to dystonia: a background level that predisposes individuals to dystonia, a disease-related level that is evident only when dystonia becomes manifest and a causative level that triggers dystonia. We conclude that it is crucial to study sensory as well as motor pathophysiology to fully understand focal dystonias.