An alternative mechanism of crossed vertical gaze palsy in unilateral mesodiencephalic infarction.

Crossed vertical gaze palsy refers to a rare combination of elevation paresis in one eye and depression palsy in the fellow eye. It was once reported in a patient with unilateral infarction involving the mesodiencephalic junction, and was ascribed to selective disruption of the fibers projecting from the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) to the oculomotor nuclear complex. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare cause of ophthalmoplegia and crossed vertical gaze palsy has not been described in this disorder. Our patient with a circumscribed acute infarction involving the left mesodiencephalic junction due to CADASIL showed both upward and downward gaze palsy in both eyes, but more marked depression paresis in the ipsilesional eye and more conspicuous elevation deficit in the contralesional eye, which was consistent with crossed vertical gaze palsy. We provide alternate explanation for this rare phenotype of vertical gaze palsy. Selective disruption of riMLF fibers may cause crossed vertical gaze palsy in unilateral mesodiencephalic lesion.