A patient presents with difficulty chewing and numbness over the right side of the face. Examination reveals weakness in the muscles of mastication and impaired sensation to touch and pain in the distribution of the trigeminal nerve. Which cranial nerve is most likely affected?

The correct answer to the question "A patient presents with difficulty chewing and numbness over the right side of the face. Examination reveals weakness in the muscles of mastication and impaired sensation to touch and pain in the distribution of the trigeminal nerve. Which cranial nerve is most likely affected?" is Option C: Trigeminal nerve (V).

The other options — A) Facial nerve (VII), B) Glossopharyngeal nerve (IX), D) Hypoglossal nerve (XII) — are incorrect for this USMLE Exam Prep question. As explained above: The trigeminal nerve (CN V) provides motor innervation to the muscles of mastication (masseter, temporalis, pterygoids) and sensory innervation to the face, including touch and pain. Its dysfunction …