Bell Palsy involves which cranial nerve?

Bell Palsy involves which cranial nerve?

• A. CN VII
• B. CN IX
• C. CN VIII
• D. CN X

Answer: (A)

Bell palsy is a peripheral, lower motor neuron palsy of the facial nerve, the seventh cranial nerve. This nerve directly innervates the muscles of facial expression on the same side, so when it is inflamed or injured you get sudden unilateral facial weakness that affects the forehead, the eye (inability to close it), and the smile. This pattern—facial weakness that involves the entire half of the face on one side—points to a lesion of cranial nerve VII rather than a higher brain lesion, which would spare the forehead. Other cranial nerves have different roles (for example, glossopharyngeal for taste/swallowing, vestibulocochlear for hearing/balance, and vagus for voice and autonomic functions), so they don’t produce this classic facial-palsy presentation.

Bell palsy is a peripheral, lower motor neuron palsy of the facial nerve, the seventh cranial nerve. This nerve directly innervates the muscles of facial expression on the same side, so when it is inflamed or injured you get sudden unilateral facial weakness that affects the forehead, the eye (inability to close it), and the smile. This pattern—facial weakness that involves the entire half of the face on one side—points to a lesion of cranial nerve VII rather than a higher brain lesion, which would spare the forehead. Other cranial nerves have different roles (for example, glossopharyngeal for taste/swallowing, vestibulocochlear for hearing/balance, and vagus for voice and autonomic functions), so they don’t produce this classic facial-palsy presentation.