Quantitative analysis of vestibular response in cerebello-pontine angle tumors.

The results obtained by vestibular examination are reported for 20 patients with cerebellopontine angle tumours. Eye pursuits, spontaneous, positional and caloric induced nystagmus (lateral and directional preponderance for duration, frequency and speed of slow phase) were evaluated in order to identify the most sensitive parameter. Half cases showed abnormalities in eye tracking test, one third a spontaneous nystagmus, 5% only a positional nystagmus. A lateral preponderance of the healthy side was found in 95% of the cases when calculated on the slow phase velocity of the caloric nystagmus, while lower rates were obtained with duration (79%) and frequency (74%). These results suggest that an asymmetry in the speed of slow phase of the caloric nystagmus is the most relevant sign to proceed to X-ray examination, especially if found in cases where the residual hearing does not allow reliable audiometric results.