Changes in resting-state brain networks in writer's cramp

Area of Science:

• Neuroscience
• Motor Control Disorders

Background:

• Writer's cramp (WC) involves excessive muscle cocontractions during writing.
• Functional MRI (fMRI) activation changes in WC can be ambiguous, reflecting either pathology or adaptation.
• Examining brain activity during rest can clarify the primary pathophysiological mechanisms in WC.

Purpose of the Study:

• To investigate differences in resting-state functional brain networks between individuals with writer's cramp and healthy controls.
• To identify specific brain regions and networks affected by writer's cramp using independent component analysis (ICA).
• To explore whether observed network changes are reversed after botulinum toxin treatment.

Main Methods:

• Independent component analysis (ICA) was applied to resting-state fMRI blood oxygen level-dependent (BOLD) time series.
• 16 patients with writer's cramp and 16 healthy controls were included in the study.
• Analysis utilized FMRIB's Software Library for processing and evaluation.

Main Results:

• Two distinct functional networks, the sensorimotor network and the default-mode network, exhibited significant between-group differences.
• Writer's cramp patients showed reduced connectivity in the left postcentral area and increased connectivity in the basal ganglia compared to controls.
• These observed connectivity alterations in WC patients were not ameliorated by botulinum toxin treatment.

Conclusions:

• The study confirms a dysfunction in cortico-subcortical circuits in writer's cramp.
• Affected areas include the somatosensory cortex, sensorimotor interfacing regions, and the putamen contralateral to the symptomatic hand.
• These findings highlight persistent network abnormalities in WC, independent of task-related activity or botulinum toxin intervention.