A Study Using Brain Stimulation and Behavioral Therapy to Increase Extent of Resection in Low-Grade Gliomas

Study Protocol: Participants will undergo a standard-of-care craniotomy for resection of low-grade glioma. If part of the lesion cannot be removed due to involvement of functional cortex, RNS (Responsive Neurostimulation System \[RNS; NeuroPace, Inc.\]) electrodes will be implanted over the tumor-invaded area(s) in five participants. Stimulation will then be optimized for each individual to disrupt the function of the invaded cortical node (e.g., hand motor area -\> hand dysfunction) (Aim 1). Over the next two months, outpatient physiotherapy will work to overcome the stim-induced deficits through gradual increases in stimulation amplitude as other, non-stimulated brain regions begin to assume its function (Aim 2). Once complete, participants will return to the OR for device explantation, repeated intraoperative mapping, and extended resection (if safe) (Aim 3).

Aim 1: Optimize stimulation to maximize stim-induced deficits and minimize side effects Rationale: To induce plasticity, stimulation parameters must be individually tuned to maximize effect and minimize side effects. Approach: After device implantation and prior to hospital discharge, stimulus settings (frequency, pulse-width, and amplitude) will be optimized to the relevant clinical response while minimizing adverse effects (e.g., focal tonus, myoclonus, or seizures) while still in the safe, inpatient setting. Outcomes: Primary Endpoints: 1) stim-induced focal clinical deficit as measured on the relevant clinical scale (e.g., manual motor score \[0-5\], picture naming \[x/10\]), repetition \[x/3\]); 2) stim-induced side effects (e.g., seizures).

Aim 2: Evaluate extent of remapping and safety of outpatient stimulation-physiotherapy protocol. Rationale: The ability to deliver chronic, outpatient stimulation is vital for practical clinical translation, yet neither its safety nor efficacy has been demonstrated. Approach: After Aim 1, a physiotherapist will assign a personalized, outpatient therapy regimen aimed at overcoming stim-induced deficits. Participants will have daily virtual sessions and return to clinic 2x/week for amplitude increases to re-induce deficits that therapy has overcome. This will continue until stimulation no longer can induce a deficit, suggesting successful functional remapping and enabling a return to the OR for further resection. Outcomes: Primary Endpoints: 1) absence of stim-related ER visits, readmissions, or serious adverse events (safety), 2) changes in intraop stimulation maps from surgery 1 to surgery 2 (induced remapping).

Aim 3: Evaluate ability to extend surgical resections and associated neurological outcomes. Rationale: Any change in functional boundaries will only be useful if it results in a safe, extended resection. Approach: Each surgery will proceed with standard-of-care intraoperative functional mapping techniques and decision making. Neurological examinations will be performed preoperatively, daily while inpatient, then again at 2-weeks and 3-months postoperatively. Extent of resection will be evaluated as 3D residual tumor volume on postoperative MRI. Outcomes: Primary Endpoint: 1) Change in residual tumor volume after second versus first resection, 2) new neurological deficits 3-months after second resection compared to before second resection. Secondary Endpoint: 1) New, temporary neurological deficits after the second surgery