Slow saccades and quick phases of nystagmus after pontine lesions.

A patient was referred to the university hospital to test eye movements after she had suffered cerebellar hemorrhage one month previously. Examination showed a selective deficit of saccades and quick phases of nystagmus toward the lesion site in the horizontal plane, which was later confirmed pathologically, and which corresponded precisely to the paramedian pontine reticular formation (PPRF). This may suggest that velocities in the quick phase of nystagmus, whether visual or vestibular, and saccades show the same result in PPRF lesion and they share the same neural circuitry in cells located in the PPRF. In the present study, the non-linear saccade velocity-amplitude equation was best-fitted to this patient. Quantitative evaluation of the quick phase may provide a simple and quick reference in saccade slowing.