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.

This paper reports data on the spontaneous course of hearing in 156 patients with purely intracanalicular vestibular schwannomas. The mean pure tone average (PTA) was 51 dB HL and the mean speech discrimination score (SDS) 60% at diagnosis. The risk of a significant subsequent hearing loss (≧10 dB PTA or ≧10% SDS) was 54% during 4.6 years of observation. Patients with normal speech discrimination at diagnosis had a significantly smaller risk of loosing hearing. The hearing loss at diagnosis and during observation was not related to age, gender, diagnostic tumor size, tumor- induced expansion of the internal auditory canal or tumor sublocalization (fundus, central or porus). However, the loss of PTA was smaller in shrinking tumors and the PTA deterioration rate correlated with the volumetric tumor growth rate. After 4.6 years observation, the PTA had increased by 14 dB to 65 dB HL, and the SDS reduced by 17% to 43%. The proportion of patients eligible for hearing preservation treatment as determined by word recognition score class I (70–100% SDS) was reduced to 28% (a 44% reduction), and by AAO-HNS class A to 9% (a 53% reduction).

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