Safety, Feasibility, and Efficacy of Non-invasive Vagus Nerve Stimulation (nVNS) in the Treatment of Aneurysmal Subarachnoid Hemorrhage

This is a single-site, single-arm, open-label pilot study assessing the safety, feasibility, and efficacy of non-invasive vagus nerve stimulation (nVNS), gammaCore, for the acute treatment of aneurysmal subarachnoid hemorrhage (SAH). The hypothesis is that two 2-minute non-invasive stimulations of the cervical branch of the vagus nerve with nVNS, 3 times daily (TID), is a safe, practical, and potentially effective treatment after SAH in the neurocritical care setting. After diagnosis and surgical repair of the SAH, patients admitted to the Neuroscience Intensive Care Unit (NeuroICU) at Massachusetts General Hospital (MGH) will be screened for eligibility. Upon providing informed consent, eligible patients will be enrolled, begin the treatment protocol, and will be monitored. Data collection will be completed using automated systems, electronic reports, and manual collection before, during, and after nVNS. The primary objective is to examine the safety, feasibility, and possible efficacy of nVNS as a treatment after aneurysmal subarachnoid hemorrhage (SAH). Safety will be assessed by the incidence of severe adverse device events (SADEs) following nVNS. Feasibility of the nVNS implementation will be evaluated by the ability to deliver \>85% of doses per protocol, report of minimal interference with current standard of care treatments and procedures in in the NeuroICU, and beginning of treatment within 72 hours of presumed aneurysm rupture. Efficacy of nVNS will be explored using the following assessments: * subject disability measured using mRS at 10 days (or discharge) and 90 days after SAH * effects on EEG, TCD, and ICP before, during, and after nVNS * DCI/ischemic stroke detected by CT scans and/or angiography * HR (heart rate), HR variability, and BP before, during, and after nVNS The study period starts within 72 hours of presumed aneurysm rupture and ends at 10 days or discharge, if sooner. The PI and co-investigators will conduct safety monitoring of this small, single-site, low-risk pilot study on a continuous basis, ensuring adherence to the Mass General Brigham (MGB) Institutional Review Board (IRB) guidelines accordingly.