Prolonged trigeminocardiac reflex following transvenous coil embolization for cavernous sinus dural arteriovenous fistula with brainstem edema: illustrative case.

BACKGROUND: The trigeminocardiac reflex (TCR) is a transient intraoperative phenomenon caused by chemical irritation during Onyx embolization of cavernous sinus dural arteriovenous fistulas (CS-dAVFs). Prolonged postoperative TCR after coil-only embolization is exceedingly rare. OBSERVATIONS: A 79-year-old woman with a right CS-dAVF presented with progressive ocular symptoms and brainstem edema caused by posterior venous drainage. Despite spontaneous improvement of ocular findings, brainstem edema on MRI worsened, prompting transvenous coil embolization. Although dangerous venous reflux to the brainstem was eliminated, a residual shunt from the contralateral cavernous sinus persisted through the intercavernous sinus. Immediately after extubation, she developed severe bradycardia requiring temporary pacing. Unlike typical TCR, bradycardia recurred intermittently for several days. Delayed abducens nerve palsy developed on postoperative day 3, suggesting progressive intracavernous inflammation. Bradycardia resolved spontaneously. At the 2-year follow-up, MRI demonstrated sustained resolution of the brainstem edema without recurrent abnormal flow. LESSONS: Coil packing within the cavernous sinus can induce prolonged postoperative TCR when persistent hemodynamic stress and secondary inflammation are present. Preexisting venous congestion-related brainstem edema may lower the TCR threshold through central sensitization. Careful postoperative monitoring is essential for high-risk patients with CS-dAVF. https://thejns.org/doi/10.3171/CASE26654.