SELECTIVE VERTICAL SACCADIC PALSY FROM UNILATERAL MEDIAL THALAMIC INFARCTION - CLINICAL, NEUROPHYSIOLOGIC AND MRI CORRELATES

Background - Impairment of vertical gaze has been attributed to lesion s involving the neural structures at the mesodiencephalic revel. Objec tive - Eye movements were studied in a patient with a unilateral param edian thalamic infarction documented by MRI. Case description - A 63-y ear-old mall presented 3 days after sudden onset vertical diplopia and hypersomnia. Eye movements were studied with electro-oculography and revealed impairment of vertical saccades with sparing of the vertical vestibulo-ocular reflex, vertical pursuit, Bell's phenomenon and verti cal optokinetic nystagmus. MRI scan revealed a circular zone of altere d signal intensity. suggesting infarction, In the paramedian ventral p art of the right thalamus. Conclusions - This case demonstrates that a unilateral lesion mainly affecting the dorsomedial nucleus of the tha lamus can result in selective impairment of vertical saccades and sugg ests that the corticofugal fibers mediating vertical saccades traverse in the medial thalamus en route to the rostral midbrain.