AUDIOVESTIBULAR FINDINGS IN MENINGIOMA OF THE CEREBELLOPONTINE ANGLE - A RETROSPECTIVE REVIEW

The aim of this study was the determination of the incidence of sympto ms of audio-vestibular dysfunction and of abnormalities on audio-vesti bular testing in patients found to have a unilateral meningioma of the cerebello-pontine angle (CPA). The case notes of 25 patients diagnose d with unilateral, sporadic and histologically proven CPA meningioma w ere retrospectively reviewed. The age range of this series was 31-71 y ears, with a mean age of 50 years. Two patients were male (eight per c ent) and 23 were female (92 per cent). The mean length of history was 44.7 months. The distribution of tumour size was skewed toward larger tumours, with 15 cases (60 per cent) having tumours with a maximum dia meter greater than 3.5 cm on imaging. Pure tone audiometry was normal in five cases (20 per cent), and no patients exhibited the high freque ncy sensorineural hearing loss that is characteristic of vestibular sc hwannoma. Speech audiometry was normal in 50 per cent of cases. Calori c testing was abnormal in 77 per cent of the 18 cases tested, whilst a uditory brainstem responses (ABR) were abnormal in 100 per cent of the 18 cases who had sufficient hearing for this test to be possible. The presence of normal audiometry in patients with a proven CPA lesion in dicates that, if in a protocol for investigation, asymmetry of hearing is mandatory then some pathology will be missed. Any suspicion of a C PA lesion warrants investigation even in the absence of hearing loss. The investigation of choice for the identification of CPA lesions has become magnetic resonance imaging (MRI). If this technique is not avai lable then this study indicates that ABR is a suitable and sensitive i nvestigation. It should be borne in mind however that the data in this study has been derived from a series of predominantly large tumours, and the sensitivity of ABR to smaller CPA meningiomata may fall, as is the case for vestibular schwannoma.