The neurotologic evaluation of vestibular schwannomas. Results of audiological and vestibular testing in 100 consecutive cases

OBJECTIVES: To determine the results and sensitivity of a comprehensive audiological and vestibular work-up in patients presenting with vestibular schwannoma (VS). MATERIAL AND METHODS: One hundred consecutive cases of VS diagnosed from January 2004 to May 2005 were prospectively studied. The tumour size was classified according to Koos classification and hearing was assessed according to the five-stage classification from the Tokyo consensus. A comprehensive work-up was conducted in all patients, including pure tone and speech audiometry, Brainstem Evoked Audiologic Potentials (BEAP) assessment, Vestibular Evoked Myogenic Potentials (VEMP) examination and bithermal caloric testing using videonystagmography, on both sides. BEAP responses were considered as normal or endocochlear when interwave intervals were normal, absent because of poor hearing or retrocochlear when wave 1 to 5 interval > 4.3 ms and/or when this interval was greater than > 0.25 ms between sides, or when no response was recorded when hearing was preserved. VEMP were considered as normal absent or diminished (amplitude < 50%, as compared with contralateral). Caloric responses were considered normal, reduced (reduced by > or = 30%) absent (reduced by > 80%). RESULTS: Fifty-six women and 44 men were examined (mean age 57.8 years). Left and right side were equally affected. Vertigo, tinnitus and hearing loss were the main presenting symptom in 21%, 32% and 68% of the cases, respectively. Eighty-two per cent were operated, 17% simply monitored and 1% irradiated. The tumours were Stage 1, 2, 3 and 4 in 14%, 28%, 21% and 37%, respectively. Hearing was class A in 9%, Class B in 34%, Class C in 14% and Class E-D in 43% of the cases. Globally, BEAP showed a retrocochlear pattern in 64% of the cases and no response in 30%. Abnormal responses of VEMP were observed in 94% of the cases. Caloric testing was abnormal in 61% and normal in 11%. Responses could not be analyzed in 28% of patients. Only one patient showed normal responses to the whole work-up (99% sensitivity). This patient had a small intrameatal tumour and actually complained of contralateral symptoms. CONCLUSION: The results suggest that a full audiovestibular assessment can help diagnose VS of all sizes. But false-negative results remain possible in small intrameatal tumours (1%). In addition it can give useful postoperative prognostic information.