Purpose To evaluate the efficacy and safety of multisession gamma knife radiosurgery (GKRS) for orbital apex venous cavernous malformation causing optic neuropathy.

Methods Retrospective cohort study in a single tertiary institution from January 2007 to December 2016 on patients who underwent multisession GKRS for orbital apex venous cavernous malformations causing optic neuropathy.

Results There were 12 patients included in our study. The mean age was 40.2±14.5 years, and men comprised 66.7% (n=8). Decrease in visual acuity (83.3%) was the most common symptom at presentation. The mean clinical follow-up was 28.5 months. Ten (83.3%) of the 12 patients had improvement in best corrected visual acuity. Of the 10 patients with pre-existing relative afferent pupillary defect (RAPD), 6 (60%) had complete resolution of RAPD. Of the 12 patients with visual field defect, 7 (58.3%) had complete resolution, 3 (25%) had partial improvement, while 2 (16.7%) remained unchanged due to optic atrophy from long-standing compressive optic neuropathy. Mean proptosis reduced from 2.3±1.7 mm pre-GKRS to 0.5±1.3 mm post-GKRS (p=0.005). Tumour shrinkage was observed in all patients. The mean tumour volume at the time of GKRS was 3104 mm³ (range 221–8500 mm³), which reduced to 658 mm³ (range 120–3350 mm³) at last follow-up. None of the patients experienced GKRS-related ocular morbidity during the follow-up period.

Conclusion Multisession GKRS has shown to be an effective and safe option for the treatment of orbital apex venous cavernous malformations causing optic neuropathy, with significant improvement in ophthalmic outcomes and reduction in tumour volume.