[Comparative values of unilateral and bilateral caloric bithermal vestibular tests in the diagnosis of acoustic neurinoma (author's transl)].

Acoustic neurinomas must be diagnosed as early as possible for the tumour to be removed while it is still small and the facial and, sometimes, auditory functions to be preserved. Since 89% of neurinomas lie on the vestibular nerve, enhancing the sensitivity of test exploring this nerve is important. Bilateral bithermal caloric stimulation is more sensitive (85%) than unilateral stimulation (71%) in detecting functional impairment. By comparing the two examinations in a series of 28 patients the authors have demonstrated that the test is more sensitive and reliable when bilateral and unilateral stimulation are practised successively. A study of correlations between these tests and the volume of the neurinoma showed that while functional impairment generally increases with the size of the tumour, it may vary from nil to 100% in small neurinomas. However, the sensitivity of the caloric test remains inferior to that of more sophisticated audiometric techniques, such as BERA-recording of stapedial reflex.