Abstract
Gamma Knife stereotactic radiosurgery (GK-SRS) is an effective treatment of meningioma in the definitive and adjuvant setting. While SRS is generally safe, some patients develop significant post-treatment edema leading to seizures and neurological deficits requiring medical intervention. This study identifies risk factors associated with the development of significant edema after SRS. Between 2014 and 2020, 126 patients with 182 WHO grade I-III meningiomas were treated with GK-SRS at our institution. We retrospectively identified a subset of patients with clinically significant post-treatment edema on MRI and documented steroid use. Clinical and treatment parameters such as treatment intent, dose, tumor location, and tumor volume were collected. The median follow-up was 34 months. A total of 6 patients (4 females and 2 males, median age 60.5) developed symptomatic edema, including 4 of 71 patients treated in the definitive setting, 1 of 16 patient in the postoperative adjuvant setting, and 1 of 39 patient in the salvage setting. 2 patients had convexity meningioma, 3 patients had parasagittal meningioma, and 2 patients had skull base meningioma. The median onset of symptomatic edema after SRS was 5 months (range: 2-5months); the median duration of steroid use was 1.5 months (range: 0.5-3months). Mild headache and vision changes were reported in 2 patients. 4 patients developed seizures and required hospital admission. 1 patient died of cardiac arrest during admission. The remainder of patients were symptom-free following discontinuation of steroids and required no surgical intervention. The median tumor volume was 3.625cc (range: 2.74-12.15cc). All patients received single-fraction SRS with a median dose of 16Gy (range: 16-20Gy). 2 patients had received prior fractionated cranial radiation. A subset of meningioma patients treated with SRS can develop significant post-treatment edema requiring intervention. This small series showed that the risk of symptomatic edema with SRS is low, and most symptoms are transient.