The advanced practice registered nurse (APRN) is assessing a patient with Bell palsy and finds paralysis of the entire right side of the face. The APRN knows that Bell palsy is caused by a peripheral lesion of which cranial nerve?

A. CN VII - Facial is correct because Bell palsy results from a peripheral lesion of the facial nerve (cranial nerve VII). This nerve controls the muscles of facial expression, including forehead movement, eyelid closure, and mouth movement. A peripheral lesion causes paralysis of the entire side of the face, unlike a central lesion, which typically spares the forehead due to bilateral cortical innervation. B. CN IX - Glossopharyngeal is incorrect because this nerve primarily innervates the posterior third of the tongue, pharynx, and parotid gland, affecting swallowing and taste, not facial movement. Lesions of CN IX would not cause hemifacial paralysis. C. CN X - Vagus is incorrect because the vagus nerve controls laryngeal and pharyngeal muscles, autonomic function of the thorax and abdomen, and some palatal muscles. A lesion would cause hoarseness, dysphagia, or impaired gag reflex, not facial paralysis. D. CN V - Trigeminal is incorrect because it primarily provides sensory innervation to the face and motor function for mastication. A lesion of CN V may cause facial numbness or difficulty chewing, but it does not cause paralysis of facial expression.