Acuteness of preoperative factors to predict hearing preservation in acoustic neuroma surgery.

OBJECTIVES: To determine in patients with acoustic neuromas the predictive factors of hearing preservation according to clinical, radiological, and electrophysiological parameters and to evaluate, for each of these predictive factors, the percentage of patients with preserved hearing. STUDY DESIGN: The study involved 107 candidates for hearing preservation attempt. Mean age was 49.7 +/- 11.4 years. Quantitative and qualitative parameters were prospectively studied. Quantitative parameters were age, duration of functional complaints, hearing loss assessed by pure tone and speech audiometry, and auditory brainstem responses (ABRs). Qualitative parameters (expressed in percentage of presence) were sex, functional complaints, vestibular deficit revealed by vestibular testings, well-shaped ABRs, wave I, III, or V of ABRs, and transient evoked otoacoustic emissions (TEOAEs). METHODS: Patients were divided into two groups according to whether their hearing was preserved (52.3%) or not preserved (47.7%). First, quantitative and qualitative factors were compared between both groups to identify predictive factors. Second, all patients were considered together and the percentage of hearing preservation was determined according to the presence of each predictive factor. RESULTS: The results confirmed the predictive value of classic parameters such as preoperative hearing level, radiological data, and trace of ABRs. They also emphasized the predictive role of other parameters such as short duration of hearing loss, presence of wave III in ABRs, and presence of TEOAEs. CONCLUSIONS: The size of the tumor and the preoperative hearing levels are longstanding predictive factors of hearing preservation in acoustic neuroma surgery, and candidates for hearing preservation are therefore now selected according to these factors. This study added more recent predictive factors and, among the 10 factors identified as predictive, the most relevant to hearing preservation were the presence of TEOAEs (69.7%), short duration of hearing loss (66.7%), and presence of wave III in ABRs (66.7%).

Is the presence of transient evoked otoacoustic emmissions in ears with acoustic neuroma significant?

One hundred sixty-eight patients admitted for acoustic neuroma removal were involved in this study. In all cases, the size of the tumor and the presence or absence of tinnitus and vertigo or dizziness were evaluated. Investigated functional procedures included bilateral measures of pure-tone audiometry (PTA), auditory brainstem response (ABR), electronystagmography (ENG), and transient evoked otoacoustic emissions (TEOAEs). Thirty-five patients (21%) had normal preoperative TEOAEs in the affected ear, whereas 133 patients (79%) failed to show reproducible responses. The aims of this study were 1. to evaluate what distinguishes patients with preoperative TEOAEs in the pathological ear (group A) from those who had no TEOAE (group B); and 2. to determine in cases of attempted hearing preservation whether preoperative TEOAE presence in the neuroma ear (group C) was predictive of postoperative hearing preservation compared with the group of patients without TEOAEs (group D). The presence of vertigo or dizziness was significantly less frequent, the age was lower, and preoperative mean PTA loss in both ears was lower in group A compared with group B. Frequency of the other studied parameters and ABR threshold were similar in both groups. When hearing preservation was attempted, the mean preoperative PTA loss of group C patients was lower in both ears compared with group D. However, postoperative mean PTA loss did not significantly differ in the two groups. In group C, the percentage of hearing preservation (66.6%) was significantly higher than the percentage of deafness (33.4%), whereas in group D the percentage of postoperative preserved audition and deafness did not significantly differ (respectively 44.4% and 55.6%). The findings suggest that 1. TEOAEs in ears with acoustic neuromas are found in younger patients with a lower preoperative mean PTA loss and are accompanied by fewer functional complaints, perhaps because preserved TEOAEs indicate a better preservation of inner ear vasculature; and, 2. along with radiological and electrophysiological investigations, TEOAE presence in the pathological ear could provide an additional criterion or predictive factor for the successful outcome of attempted hearing-conservation surgery in ears with acoustic neuromas.