1) Assess whether hearing loss in patients with sporadic vestibular schwannomas(VS) is cochlear or neural in origin using otoacoustic emissions (OAE). 2) Identify factors which influence degree of cochlear hearing loss.
Methods
From April 2008 to January 2009, a cross-sectional study of 89 patients undergoing a watch, wait, and rescan protocol as management of sporadic VS was performed (36 females, 53 males). There were 50 right-sided tumors and 39 left. Mean age 58.9 years. Distortion product OAEs (DPOAE) were recorded bilaterally on patients. DPOAE amplitudes at different frequencies in tumor and non-tumor ears were compared. DPOAEs and pure tone audiograms were compared. 38 patients were excluded (4 middle ear disease; 34 bilaterally absent OAEs secondary to presumed bilateral cochlear pathology, e.g., presbycusis). The remaining 51 patients were analyzed.
Results
Mean pure tone average (PTA) in the tumor and non-tumor ear was 57.2dB(SD 25.5) and 22.9dB(SD 15.3) respectively. 43 patients had absent OAEs in the tumor ear and normal OAEs in the non-tumor ear suggesting a cochlear or mixed hearing loss. Three patients had OAEs better than expected from the audiogram suggesting a neural hearing loss. Three patients had a high frequency cochlear loss and a low frequency neural loss. Two patients had symmetrical PTAs and OAEs. Detailed frequency specific data will be presented. Mean tumor size 9.9mm(SD3.8). OAE amplitude did not correlate with tumor size.
Conclusions
DPOAEs are absent in the majority of patients with vestibular schwannomas suggesting that a significant proportion of hearing loss is cochlear in origin. This may reflect compromise of cochlear blood flow.
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