[Measurement of the latencies of voluntary and corrective ocular saccades. Value in otoneurology].

The delay between the stimulus and the voluntary eye saccade is the only parameter of the saccadic system which can be measured by using standard apparatus. Taking manually the measurements made on records obtained by using minicomputer; the authors show that such manual measurement of latencies is easy and yet sufficiently accurate to be of great clinical value. The latencies of voluntary saccades are normal in peripheral pathology (less than 250 milliseconds). Latencies of voluntary saccades are significantly increased in extrinsic brain stem lesions: tumours (in particular ponto cerebellar tumours), meningitis, head injury; but the velocity of the saccade is normal. This effect goes in parallel with impairement of the smooth pursuit. In intrinsic brain stem lesions (multiple sclerosis, acute brain stem stroke, oculomotor paralysis) latencies are increased bilaterally and above all, there is a significant slowing of the saccade. The role of fatigue increased latencies in some patients of this series. Two populations can be discerned in vestibular neuritis: one normal and one with abnormal smooth pursuit and increased saccadic latencies.