Cranial Nerve XII
- If the hypoglossal nerve is paralyzed, the tongue will not protrude out straight but rather will deviate to one side.
- Damage to an upper motor neuron may result in fasciculation of the tongue muscle without atrophy; in this case, the tongue will deviate to the side opposite the lesion.
- Damage to a lower motor neuron results in flaccid paralysis and atrophy of the tongue muscles on the affected side; in this case, the tongue deviates to the same side of the lesion.
- Tongue weakness occurs primarily from metastatic tumors or cerebral infarction.
- Fasciculation and/or atrophy may indicate a peripheral nerve dysfunction.
Section: Cranial Nerve XII
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