If a patient has a stroke involving the basilar artery, what clinical sign is expected?

The expected clinical sign in the case of a stroke involving the basilar artery is diplopia, which refers to double vision. The basilar artery is responsible for supplying blood to important areas of the brain that control various functions, including eye movement and coordination. When a stroke occurs in this area, it can affect cranial nerves III, IV, or VI, which are responsible for controlling eye movements. Consequently, the patient may experience diplopia due to weakness or paralysis of the muscles around the eyes.

While the other options such as loss of sensation in limbs, visual field loss, and slurred speech might occur with strokes in different arterial territories or locations, they are less specific to the involvement of the basilar artery. This artery primarily impacts brainstem function and cranial nerves, thus rendering diplopia as the most characteristic sign following a basilar artery stroke.