Sensory functions in dystonia: Insights from behavioral studies

Abstract

The pathophysiology of primary dystonia is thought to involve dysfunction of the basal ganglia cortico-striatal-thalamo-cortical motor circuits. In the past, emphasis was placed on the role of the basal ganglia in controlling movements; in more recent times, however, it has also become clear that they play an important part in sensory as well as cognitive functions. Here, we review evidence for dysfunction of sensory processing in patients with dystonia, and speculate that this may lead to abnormalities in a crucial role of the basal ganglia that links sensory information to appropriate motor output. Sensory function, particularly in the somatosensory domain, has been shown to be compromised in patients with primary dystonia, both in adult onset focal dystonia and in genetically characterized DYT1 dystonia. Given that nonaffected DYT1 gene carriers may show similar abnormalities to clinically affected individuals, sensory deficits could constitute a subclinical endophenotypic trait of disease that precedes overt clinical manifestations. Whether they can trigger primary dystonia or are an epiphenomenon is an issue warranting further study, but the fact that a number of different neurorehabilitative approaches explicitly manipulate somatosensory inputs to improve motor function suggests there may be a causal link between them. We believe that in future, randomized, blind and controlled studies in large patient populations should address this issue, providing efficient strategies to aid functional recovery, particularly in focal hand dystonia, where the available medical treatments offer little benefit.

Sensorimotor network in cervical dystonia and the effect of botulinum toxin treatment: A functional MRI study

“…Converging data from both functional imaging and electrophysiological experiments in dystonic patients also suggest functional abnormalities in premotor and primary sensorimotor cortical areas together with aberrant sensorimotor integration, which is considered to be a crucial factor for the development of focal dystonia [3][4][5]. However, the published studies differ in terms of observed hypo-and hyperactivation in these cortical areas.…”

“…This evidence together indicates that primary dystonia is associated with sensorimotor dysfunction in the basal ganglia and cortico-striatalthalamo-cortical motor circuits [2,3] and several studies suggested that these abnormalities extend beyond the sensorimotor circuits controlling manifestly affected body parts [7][8][9].…”

“…Recently, it has become clear that the role of the basal ganglia extends beyond motor control into cognitive and sensory functions as well as in sensorimotor integration [3].…”

Imaging insights into basal ganglia function, Parkinson's disease, and dystonia

“…These networks might interact anatomically at the level of the motor cortex or the striatum, as evidenced by histological tract tracing in animals, 85 animal models of dystonia, 84 and functionally in healthy human volunteers, in whom cortical excitability can be modulated after cerebellar interventions [86][87][88] or after cerebellar degeneration or infarction (S46). The cerebellum might contribute to the deficit in sensorimotor integration recorded in dystonia 89 because it processes proprioceptive information, alters somatosensory thresholds in the cortex, and has a key role in both temporal and spatial discrimination (S47).…”

Cervical sensorimotor control in idiopathic cervical dystonia: A cross‐sectional study

“…The cause of CD remains unknown but in addition to motor symptoms CD is associated with nonmotor symptoms such as sensory deficits, sleep disorders, and pain (Avanzino et al., 2010; Antelmi et al., 2016; Tinazzi, Fiorio, Fiaschi, Rothwell, & Bhatia, 2009; Patel, Jankovic, & Hallett, 2014). Impaired sensorimotor integration has been described as part of the pathophysiology of CD (Tinazzi, Rosso, & Fiaschi, 2003; Fiorio et al., 2007; Konczak & Abbruzzese, 2013).…”