Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which condition is characterized by an ipsilateral oculomotor nerve palsy and contralateral hemiparesis?

1. Wallenberg syndrome

2. Webers syndrome

3. lacunar stroke

4. Basilar artery stroke

The correct answer is: Webers syndrome

The condition characterized by an ipsilateral oculomotor nerve palsy and contralateral hemiparesis is identified as Weber's syndrome. This syndrome results from a lesion in the midbrain, typically due to occlusion of the posterior cerebral artery or the basilar artery. The key features of Weber's syndrome arise from involvement of two critical systems in the midbrain: the oculomotor nerve (affecting eye movement and pupil reaction) and the corticospinal tract (responsible for voluntary motor control). The ipsilateral oculomotor nerve palsy occurs because the nerve supplies the muscles that move the eye and control the pupil on the same side. In contrast, contralateral hemiparesis occurs as a result of damage to the descending pathways that cross over to control movement on the opposite side of the body. This combination of symptoms—specific eye movement issues along with weakness on the opposite side—is distinctive for Weber's syndrome, differentiating it from other conditions affecting similar regions or presenting with overlapping symptoms.