Answer :
Final answer:
A unilateral corticobulbar tract stroke typically results in palsy of the lower facial muscles on the opposite side of the lesion due to the contralateral innervation of these muscles. The upper facial muscles are often spared due to bilateral innervation. The correct answer is option D.
Explanation:
The question delves into the ramifications of a unilateral corticobulbar tract stroke on facial muscle control. The corticobulbar tract acts as the conduit for motor commands to cranial nerves responsible for facial muscle coordination. While this pathway exhibits ipsilateral projections initially, extending from the cortex to the motor nucleus on the same side, it subsequently innervates cranial nerve neurons bilaterally. Nonetheless, the muscles of the lower face predominantly receive contralateral cortical innervation. Consequently, the aftermath of a unilateral corticobulbar tract lesion typically manifests as palsy of the lower facial muscles contralateral to the affected side.
To encapsulate, the precise response to the query regarding a patient displaying symptoms of a unilateral corticobulbar tract stroke, particularly pertaining to facial palsy, is unequivocally "d. lower facial muscles contralaterally." This assertion stems from the fact that the upper facial muscles benefit from dual innervation originating from both hemispheres of the brain, often shielding them from paralysis post a unilateral cortical lesion. Conversely, the lower facial muscles are more prone to impairment due to their primary contralateral innervation, thereby elucidating the observed clinical manifestation.
