Vestibular Schwannoma Growth Rates in Neurofibromatosis Type 2 Natural History Consortium Subjects

Abstract

Objective: To determine the amount of growth in vestibular schwannomas in Neurofibromatosis type 2 (NF2) patients from diagnosis through short-term (up to 2 yr) and long-term (up to 4 yr) follow-up. Study Design: Retrospective magnetic resonance imaging (MRI) films were obtained on subjects enrolled in the NF2 Natural History study and examined for changes in vestibular schwannoma size over time. Setting: Data were collected from nine foreign and domestic NF2 centers, including hospital-based, academic, and tertiary care centers. Subjects: NF2 patients with MRI data and at least one follow-up examination within 9 months to 2 years of diagnosis were included; n = 56 patients with 84 lesions for evaluation of growth. Intervention: Routine, clinically obtained, magnetic resonance images were digitized and measured using image management software. Short-term follow-up was defined as up to 2 years (n = 84 lesions), and long-term follow-up was defined as 3 to 4 years (n = 29 lesions). Outcome Measures: Vestibular schwannoma size was assessed using anterior–posterior, medial–lateral, and greatest diameter linear measurements. Results: Vestibular schwannomas increased in size (at least 5 mm) in 8% of the vestibular schwannomas across short-term follow-up. At long-term follow-up, 13% of the tumors had increased in size. On average, schwannomas increased in greatest diameter 1.3 mm per year across short-term follow-up. Conclusion: Slightly greater than 1 in 10 diagnosed NF2-related vestibular schwannomas increased in size by at least 5 mm by 4 years of follow-up, if still untreated at that time.