[Parinaud's syndrome and tonic vertical gaze deviation. 3 anatomo-clinical observations].

Two anatomo-clinical cases of downward gaze palsy and one case of upward gaze palsy are reported. A tonic and intermittent downward gaze deviation is described. The supranuclear palsies of the downward gaze were related to paramedian lesions of the rostral mesencephalon; the lesions involved the rostral interstitial nucleus of the medial longitudinal fasciculus, the nucleus interstitial of Cajal, and/or their afferent and/or efferent pathways. The supranuclear palsy of the upward gaze was related to lesions of the posterior commissure. Tonic and intermittent downward deviation of gaze and ocular bobbing have opposed features. The former could be related to disinhibited reticular mesencephalic neurones activated by vestibular inputs. Tonic upward deviation of gaze is also related to a vestibulo-ocular reflex. In this case, partial or total damage of the nucleus of Cajal, and/or its input and/or its output fibers appears to have a critical role.