The case of a patient with paralysis of the lateral gaze to the left, paresis of both eyes when he tried to look upwards and a disfunction of the cerebellum to the left, is reported. During the evolution the paresia of both eyes when the patient looked upwards and the disfunction of the cerebellum disappeared, but the paralysis of the lateral gaze to the left, remained. Later on the patient went a little confuse, did not understanding what other persons spoke to him, and speak badly. The necropsy showed one old infarct in the medial longitudinal fasciculus in the left, the same type of lesion in the ventral part of the upper pons which was also to the left and desmielinizition of the motor lemniscus of the same side. It was also seen a more recent infarct in the transverse girus of the left cerebral hemisphere and also the white matter below it. The study of the medial longitudinal fasciculus by means of the secundary degeneration showed that it was crossed above the 6° nuclei, but was straight to the contrary of what is said about it. The authors also observe that the cells of the intersticial nucleus of Cajal were in chromatollisis. These findings justificy the syndrome and the absense of the internuclear anterior ophtalmoplegy to the right.