Abstract
IntroductionWriter’s cramp (WC) as a focal hand dystonia is characterized by abnormal postures of the hand during writing. Impaired inhibition and maladaptive plasticity in circuits linking the basal ganglia and sensorimotor cortices have been described. In particular, a dysfunction of lateral premotor cortices has been associated with impaired motor control in WC. We applied diffusion tensor imaging to identify changes in white matter connectivity between premotor regions and important cortical and subcortical structures.MethodsWhole brain white matter tracts were reconstructed in 18 right‐handed WC patients and 18 matched controls, using probabilistic fiber tracking. We restricted our analyses to left‐hemispheric fibers between the middle frontal gyrus (MFG) and basal ganglia, thalamus, primary motor, and sensory cortex. Diffusion parameters (fractional anisotropy and linear anisotropy) were compared between both groups.ResultsA significant reduction in fractional anisotropy values was shown for patients (mean ± SD: 0.37 ± 0.02) vs. controls (0.39 ± 0.03) regarding fibers between the left‐sided MFG and the putamen (p < 0.05). The same applied for linear anisotropy values in this connection (p < 0.05).ConclusionsOur results suggest an impaired structural connectivity between the left‐hemispheric MFG and putamen with a loss of equally aligned fibers in WC patients. This could reflect a structural basis for functional findings interpreted as altered inhibition and plasticity, both within the premotor cortex and the basal ganglia, that at last lead to the clinical symptoms of WC.
Highlights
| INTRODUCTIONWriter’s cramp (WC) is an isolated idiopathic task‐specific focal hand dystonia (Albanese et al, 2013; Epidemiological Study of Dystonia in Europe Collaborative, 2000), leading to involuntary hyperactive contractions and dystonic postures of hand and arm muscles during writing only (simple WC) or during other hand motor tasks (dys‐ tonic WC; Schenk, Bauer, Steidle, & Marquardt, 2004)
Writer’s cramp (WC) as a focal hand dystonia is characterized by abnor‐ mal postures of the hand during writing
Patients with WC showed an alteration of diffusivity within the fibers connecting left‐hemispheric cortical structures harboring the premotor cortex (PMC) to the basal ganglia
Summary
Writer’s cramp (WC) is an isolated idiopathic task‐specific focal hand dystonia (Albanese et al, 2013; Epidemiological Study of Dystonia in Europe Collaborative, 2000), leading to involuntary hyperactive contractions and dystonic postures of hand and arm muscles during writing only (simple WC) or during other hand motor tasks (dys‐ tonic WC; Schenk, Bauer, Steidle, & Marquardt, 2004). The advanced technique of probabilistic tractography offers the advantage to estimate the distribution of possible pathways be‐ tween complex regions of high uncertainty such as crossing fibers. This has rarely been applied in dystonia, not yet in pa‐ tients with WC, so far (Argyelan et al, 2009; Blood et al, 2012; Bonilha et al, 2009; Rozanski et al, 2014). We focused on left‐hemispheric connections in right‐ handed subjects
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