Optic Nerve Sheath Meningiomas: A Retrospective Cohort Study Comparing Outcomes in Treated Versus Observed Patients.

Background: The rarity of optic nerve sheath meningiomas (ONSMs) complicates the guidelines surrounding optimal treatment strategies and prognostic factors. There are limited data on the visual outcomes of those treated with radiotherapy versus those observed without treatment. This study aimed to characterize the clinical and radiographic presentations of patients diagnosed with ONSMs and to identify factors predicting improvement in visual function after treatment.

Methods: This is a retrospective case series of 26 patients who presented to 2 tertiary neuro-ophthalmology practices for 10 years with the presumptive diagnosis of ONSM. Demographic, clinical, investigative, radiologic, treatment, and outcome data were collected. Visual improvement was defined as improvement in visual acuity (VA) by ≥2 Snellen lines or visual field (VF) mean deviation (MD) improvement by ≥2 dB. Statistical analyses were performed to compare patients who experienced improvement in visual function with those who did not poststereotactic radiotherapy to identify pretreatment predictors of visual recovery.

Results: Seventeen patients underwent radiotherapy (16 received 54 Gy in 30 fractions and 1 received 50 Gy in 25 fractions) and 4 elected observation. Five were lost to follow-up. Visual function improvement was seen in 10 patients who underwent radiotherapy. Pretreatment VA (logMAR 0.492 vs 1.42, P = 0.025), tumor size (8.50 vs 18.3 mm, P = 0.028), and a decrease in tumor size postradiotherapy (P = 0.009 for VA and 0.035 for VF MD improvement) were significantly associated with objective visual improvement.

Conclusions: Pretreatment VA and tumor size may predict improvement in visual function in patients with ONSMs treated with radiotherapy. Future larger scale studies that include these data may be able to draw more definite conclusions.