Oculomotor abnormalities in patients with lesions involving the tectal region.

An analysis of ocular movements was performed in four patients with retraction nystagmus and paralysis of the upward gaze. The clinical and radiological data indicate that the lesion were relatively limited to the most rostral and dorsal portion of the mesencephalon. The electrooculographic examination disclosed not otherwise obvious abnormalities of horizontal ocular movements. The most prominent defect was a tendency to perform hypometric saccades followed by multiple corrective movements. This tendency was particularly evident in saccadic movements toward a light spot unexpectedly displaced in the visual field of the subject. It is suggested that lesions responsible for retraction nystagmus can also affect the visuomotor integration mechanisms; the foveation of the target is then obtained through a typical modification of the motor strategy.