Postural Sway Predicts Growth in Untreated Vestibular Schwannoma: A Retrospective Volumetric Study.

Background: One in three vestibular schwannomas (VS) will grow within 3 years after diagnosis, but no reliable baseline parameter has been found to predict such growth.

Objective: To determine if postural sway is associated with growth of untreated VS.

Methods: Patients with newly diagnosed sporadic VS assigned to a wait-and-scan protocol were identified from a prospectively maintained database. Postural sway was measured by posturography at baseline and patients were classified as steady or unsteady. Observer-blinded volumetric tumor measurements were performed on the diagnostic MRI and a 3-year control MRI. Tumor growth quantified as relative growth (%) and volume-doubling time (VDT and VDT-1) were investigated as dependent variables against baseline parameters.

Results: Out of 204 VS patients, 53 (26%) were classified as unsteady on the platform at baseline. Median tumor volume was 0.32 cm3 (range 0.02-4.79), and 51% demonstrated significant growth within 3 years. Unsteady patients had significantly faster-growing tumors, with a mean relative growth of 172.5% compared to 79.5% in steady patients (p < 0.006). Seventy-seven percent of unsteady patients had >20% volume increase, compared to 42% in steady patients (p < 0.001). Mean VDT-1 was 0.65 doublings per year for unsteady patients, and 0.22 for steady patients (p < 0.001). Multivariate regression analysis including demographic and clinical parameters showed an OR of 5.6 (95% CI 2.6, 11.8) for growth in unsteady patients.

Conclusions: This is the first demonstrated association between a measurable parameter and future growth in untreated VS. Our findings may help clinicians identify patients with a higher risk for tumor growth and provide closer monitoring or early treatment.