Clinical outcome of Gamma Knife radiosurgery (GKRS) for indirect carotid-cavernous fistulas (CCFs)

Gamma Knife radiosurgery (GKRS) has shown promising results in the treatment of carotid-cavernous fistulas (CCFs); however, it remains widely regarded as an adjuvant modality. This study aims to evaluate the efficacy of GKRS as a standalone treatment for indirect CCFs and to compare our results with those reported in the literature. A retrospective chart review was conducted on 20 patients with indirect CCFs who underwent GKRS between December 2017 and December 2023. The mean follow-up duration was 47.4 months. GKRS was performed using a marginal dose of 16 to 18 Gy at the 50% to 60% isodose line. Clinical symptoms and imaging findings were evaluated at 3, 6, and 12 months after treatment using magnetic resonance imaging and magnetic resonance angiography. Of the 20 patients, 6 were classified as Barrow type B, 10 as type C, and 4 as type D. The mean target volume was 0.53 cm³ (range, 0.13–1.64 cm³). One patient with bilateral symptoms underwent bilateral GKRS. Four patients with contralateral symptoms were treated at the primary fistula site in 2 patients and the symptom site in 2 patients. Pretreatment symptoms included eyelid edema in 19, elevated intraocular pressure (IOP) in 16 patients (mean IOP, 27.7 mm Hg; range, 19–42 mm Hg), chemosis in 10, exophthalmos in 9, ocular pain in 9, headache in 8, and diplopia in 7 patients. Most symptoms resolved within 3 months (mean 1.3 months), except for elevated IOP, which normalized after about 6 months. The mean time to complete radiologic obliteration was 5.3 months (range, 1–12 months). The overall obliteration rate was 100%, and there was no complication or recurrence. GKRS achieved complete occlusion of indirect CCFs with excellent symptom resolution and no adverse events. These findings support the consideration of GKRS as a definitive, noninvasive treatment option for selected patients with indirect CCFs.