High incidence of transient perifocal edema following upfront radiosurgery for intraventricular meningiomas.

Intraventricular trigonal meningiomas (ITM) seem to have a tendency for extensive perifocal edema formation following radiosurgery (RS). To further investigate this hypothesis, we undertook the following study.We retrospectively reviewed records of patients who underwent RS for intraventricular meningiomas at our institution.From 1999 until 2019, 5 patients underwent single-session RS as primary treatment for ITM. Patients were treated either with a Gamma Knife or a CyberKnife. The mean prescription dose (PD) was 13.0 Gy ± 0.9, the mean tumor volume was 5.8 cc ± 3.1, and the mean follow-up (FU) was 8.9 years ± 5.6. Perifocal edema developed in 4/5 patients after a mean interval of 6.4 months ± 1.2. It was symptomatic in 2/5 patients. The edema regressed spontaneously in 4/5 patients. One of the patients underwent RS for the same ITM twice. One patient's edema was treated medically with steroids, and none of the patients underwent surgery following RS.Even though the number of patients is low, there seems to be a comparably high risk for the formation of a perifocal edema following RS for ITM. Single-session RS as primary treatment for ITM seems to be safe and effective even though a perifocal edema is likely to develop. The perifocal edema and the ensuing neurological deficits were transient and could be managed conservatively in all of our 5 cases.