Drooling in Bell's palsy is caused by weakness of which branch of the facial nerve supplying the affected muscle?

Correct answer: B. Buccal branch

• A. Incorrect. The marginal mandibular branch supplies the depressor anguli oris and mentalis — weakness causes drooping of the corner of the mouth.
• B. Correct. The BUCCAL BRANCH of the facial nerve supplies the buccinator muscle (among others). In Bell's palsy, buccal branch weakness causes inability to control lip and cheek muscles properly, resulting in DROOLING (inability to retain saliva in the mouth). The buccinator is critical for holding food and liquid in the oral cavity.
• C. Incorrect. The zygomatic branch supplies the lower eyelid and cheek muscles — weakness here causes difficulty closing the eye.
• D. Incorrect. The temporal branch supplies the frontalis and orbicularis oculi — weakness causes inability to raise the eyebrow or close the eye.