Closed-loop optimization of transcranial magnetic stimulation parameters with electroencephalography feedback

Abstract BACKGROUND Although gross total resection (GTR) with chemoradiation is the standard of care for treating glioblastoma (GBM), tumor infiltration and treatment sequelae can impair activity of eloquent regions. Transcranial magnetic stimulation (TMS) has been explored as an adjunct therapy to rehabilitation for post-stroke motor deficits. TMS could be effective for postoperative rehabilitation in GBM, but its effect on GBM cells has not been evaluated. While TMS utilizes magnetic fields to induce electrical currents at low frequencies to cause neuronal excitation or inhibition, tumor-treating fields (TTF) utilize electrical currents with intermediate frequency to exert anti-mitotic effects, demonstrating promise as an adjunctive therapy in recurrent GBM. Although similarities exist between electrical and magnetic fields, the effects of magnetically induced electrical currents at low frequencies via TMS must be studied systematically in vitro on GBM cell lines. METHODS We studied the effect of theta burst stimulation (TBS), a form of patterned TMS, on in vitro G55 cell viability using colony forming assays. We compared TMS-treated cells to controls using a combination of parameters: continuous versus intermittent TBS (cTBS and iTBS), 300 versus 600 pulses, stimulation intensity of 32% versus 60%, and no pre-TMS chemotherapy versus 100 nM or 100 µM temozolomide (TMZ). Viability measurements between controls and TMS were analyzed using analysis of variance (ANOVA). Independent t-tests were used to analyze effects of stimulation parameters on viability percent difference within each TMZ condition. RESULTS There was no statistically significant increase in viability between control and TMS conditions for any of the stimulation parameters (+/- TMZ) while some showed decreased viability of GBM cells. CONCLUSIONS TMS did not significantly increase GBM viability compared to controls. Future studies include validation in other cell lines and characterization of the effects of stimulation parameters in conjunction with TMZ and dexamethasone, (often administered concurrently with GBM treatment).

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Reliability of single and paired pulse transcranial magnetic stimulation parameters across eight testing sessions

Brain Stimulation ◽

10.1016/j.brs.2018.08.008 ◽

2018 ◽

Vol 11 (6) ◽

pp. 1393-1394 ◽

Cited By ~ 4

Author(s):

Katherine Dyke ◽

Soyoung Kim ◽

Georgina M. Jackson ◽

Stephen R. Jackson

Keyword(s):

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Paired Pulse ◽

Stimulation Parameters

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Transcranial Magnetic Stimulation as an Intervention Tool to Recover from Language, Swallowing and Attentional Deficits after Stroke: A Systematic Review

Cerebrovascular Diseases ◽

10.1159/000494213 ◽

2018 ◽

Vol 46 (3-4) ◽

pp. 176-183 ◽

Cited By ~ 7

Author(s):

Ana Dionísio ◽

Isabel Catarina Duarte ◽

Miguel Patrício ◽

Miguel Castelo-Branco

Keyword(s):

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Future Research ◽

Stroke Event ◽

Eligibility Criteria ◽

Attentional Deficits ◽

Post Stroke ◽

Stimulation Parameters ◽

Effective Interventions

Background: Following a stroke event, patients often are severely affected by disabilities that hinder their quality-of-life. There are currently several rehabilitative options and strategies, and it is crucial to find the most effective interventions. The applicability of transcranial magnetic stimulation (TMS) to the recovery of nonmotor functions such as communication skills, swallowing ability and spatial attention after stroke remains important clinical questions. Summary: We searched PubMed and ISI Web of Science for articles that used repetitive TMS protocols to rehabilitate post-stroke deficits. We analysed qualitatively 38 articles that met the eligibility criteria; of these, 21 dealt with aphasia, 8 with dysphagia, 8 with neglect and 1 with visual extinction. The efficacy of TMS as an intervention for post-stroke rehabilitation of these nonmotor deficits was studied as well as the current limitations were assessed. Key Messages: Most part of the included studies reported statistically significant functional improvements, supporting the use of TMS for the rehabilitation of aphasia, dysphagia and neglect. Future research, with larger sample sizes, is mandatory to confirm its efficacy, determine the optimal stimulation parameters and investigate inter-subject variability.

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