Background: Vestibular schwannoma (VS) are the most common tumour of the CPA with an annual incidence of 17.4/1 million. They typically demonstrate slow growth over time and as such, observation is a reasonable approach to management. A portion of these tumour remain static and approximately 5-10% of these tumours will demonstrate spontaneous regression while under observation, including those associated with neurofibromatosis type-2.

Previous case series (N= 13-14) have attempted to identify predictive factors for tumour growth and regression, but few have reached significance or demonstrated reproducible findings. Methods: Using a clinical database of VS treated by one team at our institution, we identified 40 patients who have demonstrated significant spontaneous regression or complete resolution of their VS. All patients received a survey by mail and telephone. Results: Radiographic descriptions were collected on 40 patients. Surveys were completed by 18 participants and an additional 18 control patients who demonstrated growth and underwent surgical resection. Conclusions: This is the largest case series we know of to date describing radiographic and clinical presentations of patients shrinking vestibular schwannoma. It is also the only study known to date to consider patient factors by survey in an attempt to identify protective factors.