Abstract
OBJECTIVE: Inflammation contributes to morbidity following subarachnoid hemorrhage (SAH). The authors of this study evaluate how applying noninvasive transauricular vagus nerve stimulation (taVNS) can target this deleterious inflammatory response following SAH and reduce the rate of radiographic vasospasm. METHODS: In this prospective, triple-blinded, randomized controlled trial, 27 patients were randomized to taVNS or sham stimulation. Serial blood and CSF samples were collected every 3 days to quantify inflammatory markers. Radiographic cerebral vasospasm severity and functional outcomes (modified Rankin Scale scores) were analyzed. RESULTS: No adverse events occurred. Radiographic vasospasm was significantly reduced (p = 0.018), with serial vessel caliber measurements demonstrating a more rapid return to normal than in the sham-treated group (p < 0.001). In the taVNS group, tumor necrosis factor-α was significantly reduced in both plasma (days 7 and 10) and CSF (day 13); interleukin-6 was also significantly reduced in plasma (day 4) and CSF (day 13) (p < 0.05). Patients receiving taVNS had higher rates of favorable outcomes at discharge (38.4% vs 21.4%) and first follow-up (76.9% vs 57.1%). Patients treated with taVNS had significant improvement in modified Rankin Scale scores from admission to first follow-up (p = 0.014), unlike patients in the sham-treated group (p = 0.18). The taVNS group had a significantly lower rate of discharge to a skilled nursing facility or hospice (p = 0.04). CONCLUSIONS: taVNS is a noninvasive method of neuro- and systemic immunomodulation. This trial supports the finding that taVNS following SAH can mitigate the inflammatory response, reduce radiographic vasospasm, and potentially improve functional and neurological outcomes.