Functional Neural Networks in Writer's Cramp as Determined by Graph-Theoretical Analysis

Abstract

Dystonia, a debilitating neurological movement disorder, is characterized by involuntary muscle contractions and develops from a complex pathophysiology. Graph theoretical analysis approaches have been employed to investigate functional network changes in patients with different forms of dystonia. In this study, we aimed to characterize the abnormal brain connectivity underlying writer's cramp, a focal hand dystonia. To this end, we examined functional magnetic resonance scans of 20 writer's cramp patients (11 females/nine males) and 26 healthy controls (10 females/16 males) performing a sequential finger tapping task with their non-dominant (and for patients non-dystonic) hand. Functional connectivity matrices were used to determine group averaged brain networks. Our data suggest that in their neuronal network writer's cramp patients recruited fewer regions that were functionally more segregated. However, this did not impair the network's efficiency for information transfer. A hub analysis revealed alterations in communication patterns of the primary motor cortex, the thalamus and the cerebellum. As we did not observe any differences in motor outcome between groups, we assume that these network changes constitute compensatory rerouting within the patient network. In a secondary analysis, we compared patients with simple writer's cramp (only affecting the hand while writing) and those with complex writer's cramp (affecting the hand also during other fine motor tasks). We found abnormal cerebellar connectivity in the simple writer's cramp group, which was less prominent in complex writer's cramp. Our preliminary findings suggest that longitudinal research concerning cerebellar connectivity during WC progression could provide insight on early compensatory mechanisms in WC.

Network localization of pediatric lesion-induced dystonia

“…Although rarely seen in childhood, studies of focal dystonia in adults have demonstrated alterations in connectivity to the motor cortex in spasmodic dysphonia, 38 cervical dystonia, 39 and writer’s cramp. 40, 41 EEG connectivity studies have found abnormalities in the cortical electrophysiological patterns in patients with dystonia, 42 including patients with dystonic cerebral palsy. 43 Our study highlights the importance of the cortico-basal ganglia-cerebellar network in lesion-induced dystonia, through both functional and structural network involvement of these regions.…”

Physiological Recordings of the Cerebellum in Movement Disorders

“…Writer's cramp is a common form of idiopathic, focal dystonia, which involves involuntary muscle contractions causing difficulty in writing. Neuroimaging studies in dystonia have shown evidence of cerebellar involvement [33].…”