A Subset of Intracanalicular Vestibular Schwannomas Demonstrates Minimal Growth Over a 10-Year Period

Objective: Vestibular schwannomas (VS) commonly undergo magnetic resonance imaging (MRI) surveillance, but long-term data to support the ideal frequency is limited. Herein, we aim to investigate intracanalicular VS growth predictors and long-term growth rates (GR). Study Design: Retrospective chart review. Setting: Two tertiary care centers. Patients: Sporadic intracanalicular VS with initial conservative management and at least two sequential MRIs. Intervention: Serial MRI. Main Outcome Measure(s): VS were categorized by baseline internal auditory canal tertile sublocalization (fundus, midpoint, porus) and size (<= 100, 100-200, >200 mm(3)). Throughout follow-up, volumetric GR (mm(3)/yr) were determined (baseline-3 yrs, 3-5 yrs, 5-10 yrs) and treatment rates were assessed. Results: Ninety-nine intracanalicular VS were identified (mean follow-up of 6.1 +/- 4.5 yrs). Mean GR before 5-year follow-up were comparable for baseline tertile involvement and size. After 5-year follow-up, mean GR of VS involving the fundus at baseline were lower than those involving the midpoint and fundus (6.17 +/- 21.16 and 119.74 +/- 117.57 mm(3)/yr, respectively; p = 0.034). Mean GR of VS with less than or equal to 100 mm(3) at baseline (-7.29 +/- 25.44 mm(3)/yr) were lower than those with 100 to 200 mm(3) (86.55 +/- 103.99 mm(3)/yr; p = 0.011) and more than 200 mm(3) (45.70 +/- 35.71 mm(3)/yr; p = 0.031). Vestibular schwannomas involving the midpoint and fundus had greater treatment rates compared with VS involving only the fundus (p < 0.001). Conclusions: Baseline tertile involvement and size may predict long-term intracanalicular VS growth where fundal tumors or those less than or equal to 100 mm(3) exhibit little long-term growth. Extending surveillance after 5-year follow-up may be reasonable for fundal VS.