Cerebellar motor and non-motor contributions to dystonia pathophysiology and treatment.

Dystonia is “a movement disorder characterized by sustained or intermittent abnormal movements, postures, or both [].” However, this narrow diagnostic perspective does not account for the significance of non-motor symptoms that many individuals with dystonia experience [, ]. Sleep disturbances such as insomnia, fragmented sleep, and restless nights are common yet underexplored, despite their profound impact on quality of life [, ]. These unknowns highlight areas of opportunity to better understand the critical links between sleep, cognition, and motor function, underscoring the complex and interconnected nature of dystonia that extends its pathophysiological basis beyond being a purely motor condition. Compounding dystonia’s complexity is the role of the cerebellum, which has been traditionally regarded as a motor structure having an important role in motor coordination and motor learning. However, emerging research has revealed cerebellar contributions to a broad range of non-motor functions, including sleep regulation, cognition, and sensory, emotional, and social processing [, –]. Conditions involving cerebellar dysfunction, including dystonia, Parkinson’s disease, autism spectrum disorder, and Cerebellar Cognitive Affective Syndrome (CCAS), among many others, exemplify the intricate interplay between cerebellar dysfunction and both motor and non-motor symptoms [–]. The overlapping challenges in these conditions suggest a broader, systems-level interaction between motor deficits and non-motor symptoms, with the cerebellum as a central hub. This mini review explores this complexity in the context of dystonia, highlighting a pressing need to better understand sleep, cognitive dysfunctions, and aberrant plasticity for the purpose of creating more comprehensive therapeutic strategies that will improve the overall outcomes for those affected. Dystonic motor symptoms can occur in various forms. Focal dystonia affects isolated body parts, like the neck in cervical dystonia or the hand with writer’s cramp, to segmental dystonia affecting contiguous muscles, to generalized dystonia involving larger muscle groups distributed across the body [, ]. The severity of these symptoms often fluctuates, influenced by factors such as stress, fatigue, and voluntary movement []. The pathophysiology of these motor symptoms is complex and multifactorial, involving a broad “dystonia network” dysfunction rippling across the basal ganglia, thalamus, cortex, and cerebellum [–]. Although much of the literature has historically focused on task-specific focal dystonia, substantial evidence now demonstrates that network-level abnormalities also characterize non–task-specific focal dystonia and generalized dystonia, including widespread cortical dysfunction, impaired inhibition, and abnormal connectivity across basal ganglia-thalamo-cortical and cerebello-thalamo-cortical loops [, , ]. Reduced functional connectivity within the sensorimotor and inferior parietal cortices contributes to the polygenic risk of dystonia []. Functional and structural abnormalities across prefrontal–parietal, caudate, and thalamic regions likely reflect the underlying vulnerability to dystonia penetrance, whereas additional abnormalities in the premotorparietal-temporal and cerebellar regions are linked to dystonia manifestation with adaptive, compensatory and secondary changes []. Interestingly, both task-specific and non-task focal dystonia involve disruptions in the basal ganglia and cerebellum, yet their underlying mechanisms also diverge []. Compared to non-task dystonia, which involves more isolated dysfunction in the somatosensory cortex, task-specific focal dystonia engages cortical network dysfunction, with broader interactions among functional cortical domains whose involvement depends on the task []. For example, laryngeal dystonia is associated with the parietal cortex, inferior frontal gyrus, and anterior insula, while musician’s dystonia involves the primary and secondary sensorimotor cortex and middle frontal gyrus, reflecting the task specificity of different focal dystonias []. Importantly, dystonia is not restricted to primary motor circuits, and multimodal cortical regions that integrate motor, sensory, cognitive, and affective information are also implicated across dystonia subtypes, underscoring that dystonia reflects disturbances within a distributed network rather than isolated motor circuits.