Objective: To investigate the relationship between white matter changes in the motor network and kinematic writing measures in WC and healthy volunteers (HV).

Background: Writer’s cramp (WC) dystonia is a disabling movement disorder characterized by abnormal and painful postures in the fingers, hand, and arm during writing. Existing therapies show limited clinical benefit. To develop more effective therapies, there is an urgent need for neuroimaging studies to identify pathological brain regions that associate with behavioral abnormalities and can serve as targets for clinical interventions.

Method: 20 HV and 15 WC participants completed a behavioral writing assay, which consisted of copying a single sentence ten times in a digital writing software that generated 25 kinematic writing measures. Participants completed structural MRI (DTI, T1W). BrainSuite software was used to generate fractional anisotropy (FA). Mean FA for 86 brain masks in Yeo’s motor network was extracted from all participants using a publicly available brain atlas. These FA values were correlated within participant with the kinematic writing measures using Pearson (R) correlation. FA-writing correlations that showed a minimum |R| > 0.6 in HV or WC were selected for analysis. Group differences were calculated using generalized linear regression and data adjusted for multiple comparisons using Benjamini Hochberg method.

Results: 42 FA-behavior correlations were identified in WC that were different from HV. WC demonstrated increasing correlation between FA in primary somatosensory cortex and writing dysfluency behavior (WC: R=0.61 p=0.02; HV vs. WC: 8799 counts, p=0.007) and increasing FA in premotor cortex to pen pressure (WC: R=0.72, p=0.003; HV vs. WC 4869 N, p=0.002). WC also showed inverse correlation between increasing right cerebellum-lobule VI FA and decreasing writing velocity (WC: R=-0.83, p = 0.0001; HV vs. WC: -716cm/s, p=0.01) and decreasing writing size (WC: R=-0.79, p= 0.0004; HV vs. WC: -92cm, p= 0.01).

Conclusion: This study provides valuable insights into the neural mechanism of WC dystonia by identifying distinct white matter changes in Yeo’s motor network that correlate with kinematic writing behavior. These findings confirm a key role of primary somatosensory cortex, premotor cortex, and right cerebellum lobule VI in WC pathophysiology, suggesting these brain regions as promising neuromodulation targets.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/white-matter-alterations-in-yeos-motor-network-correlate-with-kinematic-writing-behavior-in-writers-cramp-dystonia/