Delayed-onset cavernous sinus dural arteriovenous fistula after nasoseptal flap reconstruction: illustrative case

BACKGROUND: Pedicled nasoseptal flap (NSF) is the gold-standard skull base reconstruction method in endoscopic endonasal surgery (EES). Although vascular complications, such as internal carotid artery injury or carotid-cavernous fistula (CCF), are well documented, dural arteriovenous fistula (dAVF) originating from the vascular network of an NSF is exceedingly rare. Herein, the authors report the first case of a cavernous sinus (CS) dAVF supplied by an NSF. OBSERVATIONS: A 50-year-old woman underwent EES with NSF reconstruction for tuberculum sellae meningioma. She experienced delayed hemorrhage from the sphenoid sinus on postoperative day 21, requiring bipolar coagulation and packing. Five months later, she developed right-sided pulsatile tinnitus. MRI and digital subtraction angiography revealed a CS dAVF (Borden type I). The primary feeder was the sphenopalatine artery (SPA), which supplies the CS through the vascular network of the transposed NSF. The patient is currently under conservative management, with stable symptoms. LESSONS: Pathophysiology likely involved postoperative inflammation and angiogenesis triggered by delayed hemorrhage and subsequent healing. The proximity of the NSF to the medial CS wall may have facilitated abnormal shunting between the SPA-supplied flap and venous sinus. Despite the efficacy of NSF, clinicians must recognize its potential as a vascular source of dAVF. https://thejns.org/doi/10.3171/CASE26300.