Objective: To investigate the effects of continuous theta burst stimulation (cTBS) in cervical dystonia targeted to the brain network identified based on causal brain lesions.

Background: The neurobiological mechanisms of dystonia are not yet fully understood. Although DBS is highly effective in treatment of dystonia, efficacious noninvasive brain stimulation treatments are lacking. Previous studies have used multiple different targets with heterogenous results and without conclusion of the most promising target [1]. A recent study identified a brain network based on lesions causing cervical dystonia (CD) [2]. This network included subcortical regions positively connected and sensory cortex (S1) negatively connected to lesions causing CD. Connectivity from the main hubs of this network in the cerebellum and S1 were abnormal in primary CD, and connectivity from the stimulation site to these hubs were associated with treatment response in patients with GPi-DBS, suggesting relevance for treatment in primary CD. Here we test the brain metabolic effects of cTBS to the CD network cortical hub in S1.

Method: Twelve patients with CD and 14 healthy controls were included in the analyses. Each subject received single sessions of cTBS and sham targeted to the cortical peak of the cervical dystonia network in the right S1 on separate study visits. Brain ¹⁸FDG-PET imaging was performed immediately after each stimulation session. The effects of the stimulation were investigated by comparing cTBS vs. sham in the stimulation target and voxel-wise in the subcortical regions.

Results: CD patients showed increased glucose metabolism locally at the stimulation site following cTBS (P=0.02 compared to controls). In addition, in the CD group only, stimulation increased regional glucose metabolism in the brain stem (P_FDR=0.04).

Conclusion: Our findings show that S1 cTBS induces 1) an abnormal local response and 2) remote effects in brain glucose metabolism in patients with CD. These results provide further proof of abnormal sensory system function in CD and show that a single session of S1 cTBS is sufficient to induce brain metabolic changes. Further studies are needed to investigate the therapeutic potential of S1 stimulation in cervical dystonia.

References: 1. Morrison-Ham J, Clark GM, Ellis EG, et al. Effects of non-invasive brain stimulation in dystonia: a systematic review and meta-analysis. Ther Adv Neurol Disord 2022;15:17562864221138144.
2. Corp DT, Joutsa J, Darby RR, et al. Network localization of cervical dystonia based on causal brain lesions. Brain 2019;142(6):1660-1674.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/brain-metabolic-response-of-primary-sensory-cortex-transcranial-magnetic-stimulation-in-cervical-dystonia/