(A) Ipsilateral XII # CN XII Hypoglossal Nerve:> Origin: Medulla> Innervation: Muscles of the tongue except Palatoglossus> Function: Movement of the tongue> Dysfunction: Unilateral lesions can cause paresis, atrophy, furrowing, fibrillation and fasciculation on the affected half.> On protrusion tongue deviates towards the affected side due to unopposed action of the Contralateral Genioglossus> Flaccid Paralysis: Dysphagia Dysarthria Dyspnea Difficulty chewing food# XII Cranial nerve controls all tongue movements.> Nuclear or intranuclear lesions produce paralysis, atrophy, and fasciculations of the tongue on involved side.> Supranuclear lesions produce mild to moderate contralateral weakness that may be transient.> Bilateral supranuclear lesions, seen in pseudobulbar palsy, produce moderate to severe inability of the tongue to function> The transient nature is usually the clue> Nuclear lesions produce atrophy, weakness, or paralysis and fasciculations. Amyotrophic lateral sclerosis and polio are two causes.> Syringobulbia, infarction, and intraspinal tumors are other etiologies.> Nuclear lesions are often bilateral because of the closeness of the two nuclei in the medulla.> Hypoglossal nerve involvement after the individual fibers exit from the medulla is seen with many of the lesions that affect the spinal accessory nerve.> Tumors can compress the nerve in the hypoglossal canal and in the jugular foramen.> Basilar meningitis, due to granulomatous infection or carcinoma, can produce hypoglossal lesions.> Unilateral twelfth nerve palsy has been reported as one of the more common cranial mononeuropathies due to metastases