BACKGROUND: Reports on the natural history of tumor growth and hearing in patients with a vestibular schwannoma (VS) are almost exclusively short-term data. Long-term data are needed for comparison with results of surgery and radiotherapy. 

OBJECTIVE: To report the long-term occurrence of tumor growth and hearing loss in 156 patients diagnosed with an intracanalicular VS and managed conservatively. 

METHODS: In this longitudinal cohort study, diagnostic and follow-up magnetic resonance imaging and audiometry were compared. 

RESULTS: After a follow-up of 9.5 years, tumor growth had occurred in 37% and growth into the cerebellopontine angle had occurred in 23% of patients. Conservative treatment failed in 15%. The pure tone average had increased from 51- to 72-dB hearing level, and the speech discrimination score (SDS) had decreased from 60% to 34%. The number of patients with good hearing (SDS > 70%) was reduced from 52% to 22%, and the number of patients with American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) class A hearing was reduced from 19% to 3%. Hearing was preserved better in patients with 100% SDS at diagnosis than in patients with even a small loss of SDS. Serviceable hearing was preserved in 34% according to AAO-HNS (class A-B) and in 58% according to the word recognition score (class I-II). Rate of hearing loss was higher in patients with growing tumors. 

CONCLUSION: Tumor growth occurred in only a minority of patients diagnosed with an intracanalicular VS during 10 years of observation. The risk of hearing loss is small in patients with normal discrimination at diagnosis. Serviceable hearing is preserved spontaneously in 34% according to AAO-HNS and in 58% according to the word recognition score.