What's special about task in dystonia? A voxel‐based morphometry and diffusion weighted imaging study

Abstract

Background Numerous brain imaging studies have demonstrated structural changes in the basal ganglia, thalamus, sensorimotor cortex and cerebellum across different forms of primary dystonia. However, our understanding of brain abnormalities contributing to the clinically well-described phenomenon of task-specificity in dystonia remained limited. Methods We used high-resolution MRI with voxel-based morphometry and diffusion tensor imaging with tract-based spatial statistics of fractional anisotropy to examine gray and white matter organization in two task-specific dystonia forms, writer’s cramp and laryngeal dystonia, and two non-task-specific dystonia forms, cervical dystonia and blepharospasm. Results A direct comparison between the both dystonia forms revealed that characteristic gray matter volumetric changes in task-specific dystonia involve the brain regions responsible for sensorimotor control during writing and speaking, such as primary somatosensory cortex, middle frontal gyrus, superior/inferior temporal gyrus, middle/posterior cingulate cortex, occipital cortex as well as the striatum and cerebellum (lobules VI-VIIa). These gray matter changes were accompanied by white matter abnormalities in the premotor cortex, middle/inferior frontal gyrus, genu of the corpus callosum, anterior limb/genu of the internal capsule, and putamen. Conversely, gray matter volumetric changes in non-task-specific group were limited to the left cerebellum (lobule VIIa) only, while white matter alterations were found to underlie the primary sensorimotor cortex, inferior parietal lobule and middle cingulate gyrus. Conclusion Distinct microstructural patterns in task-specific and non-task-specific dystonias may represent neuroimaging markers and provide evidence that these two dystonia subclasses likely follow divergent pathophysiological mechanisms precipitated by different triggers.

Current Opinions and Areas of Consensus on the Role of the Cerebellum in Dystonia

“…Using structural neuroimaging techniques, such as VBM and diffusion tensor imaging, grey matter increase or decrease and white matter changes were observed in primary dystonias in the sensorimotor, premotor, and parietal cortex, the basal ganglia, the thalamus, and the cerebellum. Cerebellar changes were reported in sporadic forms including non-task specific cervical dystonia and blepharospasm [116–118], task-specific laryngeal dystonia, and writer’s cramp [118], as well as inherited forms [99, 119]. Using diffusion imaging, white matter changes were also observed in the cerebellum of sporadic dystonia [118]and the cerebello-thalamo-cortical fiber tract in DYT1-6 dystonia [99, 113].…”

“…Cerebellar changes were reported in sporadic forms including non-task specific cervical dystonia and blepharospasm [116–118], task-specific laryngeal dystonia, and writer’s cramp [118], as well as inherited forms [99, 119]. Using diffusion imaging, white matter changes were also observed in the cerebellum of sporadic dystonia [118]and the cerebello-thalamo-cortical fiber tract in DYT1-6 dystonia [99, 113]. Changes varied between studies and types of dystonia, and so far, it is not precisely known whether these variations are due to the type of dystonia or to technical differences between studies.…”

Impairment of a parieto‐premotor network specialized for handwriting in writer's cramp

“…Patients with task-specific dystonia have local structural abnormalities in the lateral premotor area, the striatum and the cerebellum [Ramdhani et al, 2014; Delmaire et al, 2009]. Structural brain abnormalities in the striatum were found also in patients with cervical dystonia who do not have task-specific symptoms [Pantano et al, 2011].…”

Robert Schumanns høyre hånd

“…Ved overlappende felt i cortex kan denne fine balansen forrykkes (25). Med nyere MRmetoder har man sett at det er økt volum av grå substans (i hovedsak cortex) og samtidig endringer i nervebanene gjennom den hvite substansen ved oppgavespesifikk dystoni, mens endring i grå substans ved generaliserte dystoniformer hovedsakelig var begrenset til cerebellum (26). Slike tilstander forverres betydelig under påvirk-ning av stresshormoner og følelser og kommer ofte til sterkest til uttrykk da.…”