Abstract
We describe two patients in whom a unilateral lesion of the midbrain produced vertical gaze palsy, and discuss the mechanism of vertical gaze palsy in relation to the rostral interstitial nuclei of the medial longitudinal fasciculus (riMLF). Case 1 displayed left oculomotor nerve nucleus syndrome, contralateral vertical gaze palsy, and right coordination disturbance. MRI revealed a paramedian dorsal infarction including nuclear involvement of the oculomotor nerve on the left side of the middle mesencephalic tegmentum. Case 2 displayed isolated upward and downward gaze palsy. MRI revealed a small hematoma extending from the anterior part of the supperior colliculus on the right side into the pretectum past the posterior commissure. In case 1, ipsilateral superior and inferior rectus palsy and contralateral superior rectus palsy were produced by the nuclear involvement of the oculomotor nerve. Upward gaze palsy in case 2 was also produced by damage to the supranuclear tracts which was caused by a unilateral lesion of the right posterior commissure. It was possible that contralateral inferior rectus palsy in case 1 and downward gase palsy in case 2 could have been produced by damage to the supranuclear tracts mediating downgaze. Based on experimental data and clinicopathological studies, it is considered that isolated paralysis of downward gaze may be caused by bilateral lesions in the riMLF. However, downward gaze palsy in our cases could have been produced by supranuclear palsy from the unilateral lesion of the riMLF.
