After a tongue biopsy, the patient's tongue deviates to the right on protrusion. Which nerve is responsible for this deviation?

The hypoglossal nerve (CN XII) supplies tongue musculature; with a lower motor neuron lesion, the tongue deviates toward the affected (weak) side, so right deviation indicates right hypoglossal injury.Other options: The left hypoglossal lesion would deviate the tongue left; the vagus nerves do not control tongue protrusion.Key exam takeaway: Tongue deviates toward the side of a hypoglossal (CN XII) lesion.