Professional and Linguistic Assessments Board (PLAB) Practice Exam

What condition is indicated by a lesion in the PICA?

1. Contralateral vision impairment

2. Ipsi- and contralateral sensory loss

3. Quadriplegia

4. Locked-in syndrome

The correct answer is: Ipsi- and contralateral sensory loss

A lesion in the posterior inferior cerebellar artery (PICA) is commonly associated with lateral medullary syndrome, also known as Wallenberg's syndrome. This condition results from occlusion of the PICA, leading to specific clinical manifestations. When a lesion occurs in the territory supplied by the PICA, it affects several neural pathways in the brainstem. The area is responsible for processing sensory information, and involving both the sensory pathways leads to ipsilateral loss of pain and temperature sensation due to damage to the spinothalamic tract and the nucleus of the trigeminal nerve. Additionally, there may also be contralateral loss of pain and temperature sensation because of the crossing fibers in the spinothalamic tract. Consequently, the presence of almost simultaneous side effects—both on the same side (ipsilateral) and the opposite side (contralateral)—is indicative of a PICA lesion. This dual sensory loss is a hallmark indicator and thus confirms the validity of the selected answer. The other conditions mentioned, such as contralateral vision impairment, quadriplegia, and locked-in syndrome, do not directly relate to the effects of a lesion in the PICA territory. They represent different neurological deficits resulting from lesions in other