Transient cardiac arrest due to trigeminocardiac reflex during aneurysm clipping: illustrative case.

backgroundTrigeminocardiac reflex (TCR) is a well-known phenomenon that causes bradycardia, hypotension, and cardiac arrest through mechanical stimulation of the trigeminal nerve distribution. Although TCR has been reported during posterior fossa surgeries, cardiac arrest during supratentorial aneurysm clipping is exceptionally rare. OBSERVATIONS: An 88-year-old woman with a ruptured internal carotid-posterior communicating artery aneurysm underwent craniotomy via a pterional approach. During clip application using a slightly curved Sugita no. 65 clip inserted along the sphenoid ridge dura, an 8-second cardiac arrest occurred before clip closure. Immediate clip withdrawal resulted in spontaneous recovery of rhythm. Subsequently, a straight Sugita no. 15 clip was applied horizontally toward the suprasellar cistern to avoid dural contact, and successful clipping was achieved without cardiac arrest. Intraoperative monitoring confirmed a complete electrocardiogram and arterial pressure loss during the initial episode. LESSONS: This case demonstrates that TCR can occur during supratentorial aneurysm clipping through stimulation of trigeminal nerve-innervated dural structures. Complications were prevented by changing the clip geometry from a curved to a straight configuration and modifying the surgical approach to avoid dural contact. Appropriate clip selection considering the spatial anatomy, trajectory control, and surrounding anatomical structures is crucial for preventing this potentially serious complication during aneurysm surgery. https://thejns.org/doi/10.3171/CASE25591.