Objective: To determine if inhibitory transcranial alternating current stimulation (tACS) applied to the sensorimotor cortex can modulate regional and global neural activity in patients with blepharospasm (BSP).

Background: BSP is characterized by involuntary contractions of eyelid muscles and is thought to stem from reduced inhibitory control within sensorimotor networks. Botulinum toxin can lessen BSP symptoms but involves repeated often painful injections that can cause adverse events. Noninvasive tACS may provide a safe, viable approach to augment this therapy or offer a therapeutic alternative. Prior studies have shown 15 Hz tACS can induce temporary changes in cortical excitability that may have long-ranging effects. Whether tACS can modulate abnormal network function in patients with BSP is not known.

Method: Eight-minute resting state functional MRI (rsfMRI) scans were obtained before and during a 20-minute session of 15 Hz tACS of the sensorimotor cortex. RsfMRI data were evaluated using regional homogeneity (ReHo) analysis to measure the degree of local synchronization of neural activity and degree centrality (DC) to assess for global change in connectivity in 7 BSP patients (6 female, 1 male, mean age of 64.3 +/- 7.8 years) and 10 age and gender-matched healthy controls (HC) (7 female, 3 male, mean age of 65 +/- 8.1 years). Imaging analysis was performed using SPM12 and FWE corrected for multiple comparisons to an alpha=0.05.

Results: Within-subject paired t-tests in BSP patients showed areas of reduced ReHo in the right sensorimotor cortex and left cerebellum during stimulation compared to pre-stimulation while HC showed reduced ReHo in left cerebellum, right cuneus and right inferior/middle occipital gyrus and reduced DC in the right inferior frontal gyrus during stimulation. Two-sample t-tests before stimulation showed that compared to HC, BSP patients had reduced ReHo in the left cerebellum and left calcarine gyrus, and reduced DC in the left cerebellum. During stimulation, BSP patients showed no significant differences in ReHo or DC compared to HC.

Conclusion: Inhibitory tACS to the sensorimotor cortex can modulate regional and global connectivity, and in BSP patients this may help normalize abnormal neural activity within the motor network. Noninvasive brain modulation with inhibitory tACS may have therapeutic potential in BSP.

References: 1. Ruffini G, Fox MD, Ripolles O, Miranda PC, Pascual-Leone A. Optimization of multifocal transcranial current stimulation for weighted cortical pattern targeting from realistic modeling of electric fields. Neuroimage. 2014;89:216-225. 5.
2. Fusca M, Ruhnau P, Neuling T, Weisz N. Local Network-Level Integration Mediates Effects of Transcranial Alternating Current Stimulation. Brain Connect. 2018;8(4):212-219.
3. Wei S, Lu C, Chen X, Yang L, Wei J, Jiang W, Liu Y, Li HH, Qin Y, Lei Y, Qin C. Abnormal regional homogeneity and its relationship with symptom severity in cervical dystonia: a rest state fMRI study. BMC neurology. 2021 Dec;21(1):1-8.

« Back to 2022 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/transcranial-alternating-current-stimulation-modulates-motor-network-connectivity-in-patients-with-blepharospasm/