Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which symptom is typical of a contralateral hemiparesis due to dysfunction of corticospinal fibers?

1. Loss of vision

2. Contralateral paralysis

3. Facial droop

4. Difficulty swallowing

The correct answer is: Contralateral paralysis

The typical symptom of contralateral hemiparesis due to dysfunction of corticospinal fibers is contralateral paralysis. This condition arises from damage to the motor pathways that cross over in the brain, particularly in the medullary pyramids, leading to weakness or paralysis on the side of the body opposite to where the brain injury or dysfunction has occurred. Corticospinal fibers are responsible for voluntary motor control, and when these fibers are compromised, the result is weakness or paralysis affecting the arm, leg, and trunk on the opposite side of the body. This is a hallmark of upper motor neuron lesions, which can occur with various neurological conditions such as stroke or multiple sclerosis. The other symptoms listed, while they can occur in neurological conditions, are not specifically indicative of corticospinal fiber dysfunction. Loss of vision is typically associated with optic nerve damage or visual pathway issues. Facial droop may suggest involvement of the facial nerve or lower motor neurons. Difficulty swallowing is related to dysfunction in areas controlling the cranial nerves responsible for swallowing rather than direct corticospinal tract involvement. Thus, contralateral paralysis is the most specific and direct symptom associated with the dysfunction you're examining.