The nurse asks for the patient to stick out their tongue. The tongue protrudes midline. What does this finding indicate?

Tongue movement is primarily controlled by cranial nerve XII (hypoglossal nerve), which innervates intrinsic and extrinsic tongue muscles responsible for articulation, swallowing, and midline protrusion. Proper function reflects intact motor innervation without unilateral weakness or deviation. Rationale: A. Loss of CN XII function results in tongue deviation toward the affected side due to unopposed action of the contralateral genioglossus muscle. Atrophy, fasciculations, and impaired articulation may also be present. A midline protrusion would not be expected in dysfunction. B. Intact CN XII is indicated by a tongue that protrudes straight midline without deviation. This reflects normal hypoglossal nerve motor function and balanced muscular activity of both sides of the tongue during voluntary movement. C. CN IX (glossopharyngeal nerve) is primarily responsible for taste sensation in the posterior one-third of the tongue and swallowing reflexes. It does not control tongue protrusion, so its dysfunction would not affect midline movement. D. Intact CN IX relates to normal gag reflex and posterior tongue sensation but does not influence tongue motor control. Midline protrusion is not dependent on glossopharyngeal nerve integrity, making this option incorrect.