Acoustic neuromas (diagnostic value of testing the function of the trigeminal nerve, the cerebellum and optokinetic nystagmus).

The involvement of the trigeminal nerve, cerebellum, and optokinetic nystagmus in patients with acoustic neuromas, as well as the methods of investigation, are described. The corneal and/or facial sensibility was found to be reduced in 29 per cent of the whole series and in 53 per cent of tumors larger than 40 mm. There was a significant correlation between reduced corneal and/or facial sensibility and the findings of pressure at the trigeminal root at operation. Only three patients had a persistent reduction of trigeminal function post-operatively. Cerebellar dysfunction was found in 32 per cent, but significantly more frequently (58 per cent) in patients with tumors larger than 40 mm. Post-operatively, six patients had cerebellar symptoms in the form of gait disturbances; five of these patients had a supplementary suboccipital removal performed, after the initial translabyrinthine approach. A defective optokinetic nystagmus was found pre-operatively in 10 patients, nine of whom had tumors larger than 40 mm in diameter. All patients with a defective optokinetic nystagmus had a large anatomic impression in the pons at operation. In patients suspected of having an acoustic neuroma, symptoms from the trigeminal nerve, the cerebellum and the optokinetic nystagmus predict the presence of a large tumor and subsequent difficulties at operation. The symptoms were completely reversible in the vast majority of cases and post-operative symptoms persisted only in patients in whom tumor removal was difficult and the tumor very large. Testing of the trigeminal nerve, the cerebellum and the optokinetic nystagmus still deserves its place in the diagnostic work-up of patients with unilateral acoustic or vestibular symptoms, especially in cases with severe hearing impairment, which necessitate the use of tests that are independent of acoustic function.