Stereotactic Radiosurgery for Cystic Vestibular Schwannomas

Background/Objective: The optimum treatment for cystic vestibular schwannomas (VS) is controversial. Anecdotally, many treating physicians feel they do not respond to stereotactic radiosurgery (SRS) as well as noncystic VS. However, in the current literature there is little evidence to support or discredit this treatment bias. The primary objective of the current study is to examine treatment response of cystic VS to SRS. Design: The study is a retrospective chart review. Setting: This study was performed at a single tertiary academic referral center. Participants: Patients diagnosed with cystic VS who were treated with SRS between 2007 and 2014 using the Leksell Perfexion Gamma Knife system. All patients were screened for cystic components using pretreatment T1- and T2-weighted MRI sequences. Main Outcome Measures: The main outcomes were tumor control and treatment-associated complications. Results: A total of 20 patients (10 females; median age 68 years; range, 20–82 years) met inclusion criteria. Overall, 17 tumors were sporadic whereas3 were associated with NF2. Three patients previously underwent microsurgical resection and received SRS for growing residual tumor. Eight patients (40%) had a serviceable pretreatment hearing. Two patients (10%) had pretreatment House-Brackmann grade 3 facial palsy after receiving prior surgery, and two patients (10%) had trigeminal neuropathy. The median tumor volume was 2,240 mm 3 (range, 366–12,040 mm 3 ); median cyst volume was 300 mm 3 (range, 7–1,880 mm 3 ); and median percent of tumor volume that was cystic was 11% (range, 1.7–38%). The median marginal dose was 13 Gy and the median maximum dose was 26 Gy. Nine patients (45%) had audiologic follow-up at a median of 12 months (range, 7–60 months) post SRS. One patient experienced a decline in AAO-HNS hearing class, from class B to D. At a median clinical follow-up of 17 months (range, 1–60 months), three patients (27%) experienced a change in trigeminal symptoms (one improved numbness, one new numbness, and one new pain) and one patient (9%) experienced temporary facial paresis with full recovery. Sixteen patients (80%) had radiologic follow-up at a median of 24 months (range, 7–60 months) following treatment. Overall, 3 (19%) tumors remained stable, 12 (75%) VS decreased in size, while 1 (6%) grew by 2.5 mm at last follow-up. No patient has required additional treatment to date. Conclusion: Our data demonstrate that early treatment associated morbidity is low and tumor control is on par with noncystic VS series. Longer follow-up is required to study the durability of tumor control. In addition, studies including VS with larger cystic components are needed.