This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cranial Nerve Disorders, Subject name: Medicine
[{'content': 'Right 12th nerve damage leads to? \nSelect and explain. \nA. Tongue deviation to left on protrusion, B. Tongue deviation to right on protrusion, C. Nasal twang to voice, D. Scanning speech defects', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Tongue deviation to right on protrusionRef: Harrison 19th ed. / Ch 367Following a lesion of the hypoglossal nucleus or nerve* ATROPHY of the muscles of the IPSILATERAL one-half of the tongue occurs.* FASCICULATIONS (tiny, spontaneous contractions) can be seen.* Upon protrusion, the tongue will deviate TOWARD the side of the lesion (i.e.} same side). This is due to the unopposed action of the genioglossus muscle on the normally innervated side of the tongue (the genioglossus pulls the tongue forward).The corticobulbar input to the hypoglossal nucleus arises from motor cortex and is predominantly CROSSED. Thus, a lesion in motor cortex will result in deviation of the tongue toward the opposite side or CONTRALATERAL to the lesion. In contrast to the atrophy and fasciculations seen in lesions of the hypoglossal nucleus and nerve (lower motor neuron), NO such signs are present after lesions of the corticobulbar tract.', 'role': 'assistant'}]