Our objective was to review retrospectively patients with a unilateral acoustic neuroma managed by observation. One hundred patients with tumours (<24 mm) were followed a median 25.5 months. Thirty-six acoustic neuromas grew with four growth patterns. No factors were associated with growth. Eighty percent of growing tumours grew in the first year. Eleven patients proceeded to surgery. Twenty-two patients were eligible for hearing preservation surgery; five of the 15 available for analysis subsequently lost eligibility.

In conclusion, selected patients can be safely observed with serial imaging and follow up. Size increase in the first year may predict future growth. Delaying surgery until required by symptoms or tumour growth does not result in more morbidity for the patient. Some may lose the opportunity for hearing preservation surgery but operating on all would result in more sustaining a loss of hearing in the first few years after diagnosis.