Vertical “Half-and-Half” Syndrome with Ipsilateral Pseudoabducens Palsy due to Rostral Midbrain Lacunar Infarction

Abstract

Vertical "half-and-half" syndrome, characterized by contralateral upward and ipsilateral downward gaze palsy, is a rare variant of vertical eye movement disturbance. Similarly, pseudoabducens palsy, manifesting as abductive palsy despite no lesion to the pons, constitutes another rare type of eye movement disturbance. Both conditions have been associated with lesions in the thalamo-mesencephalic junction. We present a rare case report detailing a patient exhibiting vertical "half-and-half" syndrome with ipsilateral pseudoabducens palsy following a left lacunar infarction of the thalamo-mesencephalic junction. Additionally, we discuss the potential underlying mechanisms contributing to this rare combination of eye movement disorders.