Oculocardiac Reflex during Electrode Placement in Trigeminal Schwannoma Surgery via Cavernous Sinus Approach

The oculocardiac reflex (OCR) is well known in ophthalmic surgery, but its occurrence during neurosurgical procedures is rare and often unexpected. Mechanical stimulation of trigeminal pathways at the skull base can cause significant hemodynamic changes; however reflex activation during preparatory steps rather than tumor manipulation is rarely described. We report an intraoperative event in a 22-year-old male undergoing resection of a cystic trigeminal schwannoma via a subtemporal transcavernous approach under general anesthesia, during which periorbital needle electrodes were placed for cranial nerves III, IV, and VI monitoring. During electrode insertion, the patient developed sudden bradycardia from 72 to 34 beats per minute with a brief hypertensive response, followed by persistent bradycardia and eventual decrease in blood pressure. Immediate removal of the stimulus led to rapid recovery of hemodynamic stability without the need for anticholinergic therapy, and the surgery proceeded without further issues. This case shows that even minor periocular manipulation during neurosurgical preparation can trigger OCR. Early detection of unusual triggers, awareness of the characteristic biphasic cardiovascular response, and good communication between surgical and anesthesia teams are essential to prevent hemodynamic instability. Further documentation of similar cases may help identify contributing factors and improve preventive strategies.