The Effect of Botulinum Toxin on Network Connectivity in Cervical Dystonia: Lessons from Magnetoencephalography

Abstract

Background: Pharmacological management of cervical dystonia (CD) is considered to be symptomatic in effect, rather than targeting the underlying pathophysiology of the disease. Magnetoencephalography (MEG), a direct measure of neuronal activity, while accepted as a modality for pre-surgical mapping in epilepsy, has never been used to explore the effect of pharmacotherapy in movement disorders. Methods: Resting state MEG data were collected from patients with CD, pre-and post-botulinum toxin injections. All of these patients exhibited good clinical benefit with botulinum toxin. Resting state MEG data from four age-and gender-matched healthy controls with no neurological disorders were also collected. Results: Our exploratory study reveals a difference in coherence between controls and patients in the following regions: fronto-striatal, occipito-striatal, parietostriatal, and striato-temporal networks. In these regions there is an increase after botulinum toxin. Specifically, increased coherence in the left putamen and right superior parietal gyrus was noticeable. Both intrahemispheric and interhemispheric networks were affected. Discussion: This is the first attempt to directly assess changes in functional connectivity with pharmacotherapy using MEG. Botulinum toxin might affect sensorimotor integration, leading to clinical benefit. The presence of increased interhemispheric coherence and intrahemispheric coherence points to the importance of global and local networks in the pathophysiology of dystonia.

Cervical Dystonia and Executive Function: A Pilot Magnetoencephalography Study

“…Our previous study assessing changes in coherence using resting state had shown that compared to controls, CD patients showed a state of lower amplitude and frequency of synchronicity, and a lower frequency of synchronicity of oscillating neurons, or coherence [ 9 ]. With task specific testing, controls showed increased coherence in one pathway involving the cingulate gyrus, associated with decision-making.…”

“…Our study is also the first to assess the effect of botulinum toxin treatment on network connectivity while performing a task assessing executive function using MEG-CSI. Previously, we showed that efficacious botulinum toxin use is associated with a change in coherence in specific pathways in the resting state, suggesting a role of sensorimotor integration in clinical benefit [ 9 ]. Our current study shows a statistically significant change in coherence, albeit small, during the visual CPT in CD patients with botulinum injection.…”

“…A detailed description of the MEG based methodology used in this study has been previously published by our lab in a resting state MEG study of CD patients [ 9 ].…”

“…Magnetoencephalography coherence source imaging (MEG-CSI) has also been used to investigate CD [ 9 , 10 ]. Our previous MEG-CSI study demonstrated difference in resting-state coherence between controls and CD patients in the fronto-striatal region, but not in occipito-striatal, parieto-striatal and striato-temporal networks [ 9 ].…”

Sensorimotor Integration and GABA-ergic Activity in Embouchure Dystonia: An Assessment with Magnetoencephalography

“…9 Our lab has also previously published work on cervical dystonia using MEG-CSI. 10,11 In the present study, we characterized the functional connectivity in a patient with ED where touch is used to evoke dystonic movements.…”