ABSTRACT
We report a patient with unilateral midbrain hemorrhage which caused ipsilateral complete oculomotor nerve palsy with pupillary involvement, contralateral upgaze paresis, contralateral limb ataxia and Parinaud’s syndrome. CT scan and MRI brain demonstrated a hemorrhage in the left paramedian midbrain probably involving the oculomotor fascicles; extension of the hemorrhage to the most rostral midbrain may have involved the pupillary fi bers. It was previously thought that a lesion in the superior colliculus, surrounding nuclei (Darkschewitsch and Cajal nuclei), and the posterior commissure (i.e. dorsal midbrain) were responsible for clinical fi ndings similar to those found in our patient, but our patient showed a hemorrhagic lesion in the left ventral midbrain which did not extend to dorsal midbrain. We propose that the responsible lesion in our patient might involve the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF).