Professional and Linguistic Assessments Board (PLAB) Practice Exam

In which artery would you expect to find occlusion leading to contralateral lower limb sensory loss?

1. Middle cerebral artery

2. Posterior cerebral artery

3. Anterior cerebral artery

4. Basilar artery

The correct answer is: Anterior cerebral artery

The anterior cerebral artery is responsible for supplying blood to the medial portions of the frontal lobes and the superior medial parietal lobes. Occlusion of this artery typically affects areas of the brain that control the lower limb. Since the motor and sensory functions of the lower limbs are represented in the medial section of the motor and sensory cortices, an occlusion can lead to sensory loss in the contralateral lower limb. This sensory loss occurs because the primary sensory pathways cross over in the central nervous system. Thus, if there is an occlusion in the anterior cerebral artery on one side of the brain, the processing of sensory information from the opposite lower limb may be compromised, resulting in the described sensory loss. The other arteries mentioned serve different territories: the middle cerebral artery primarily affects the lateral aspects of the hemispheres, which are more associated with the upper limbs and facial regions. The posterior cerebral artery supplies the occipital lobe and inferior parts of the temporal lobe, affecting vision and memory functions instead. The basilar artery supplies the brainstem and cerebellum, playing a lesser role in the sensory pathways of the lower limbs.