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When a patient is asked to stick out the tongue, the tongue deviates to the right. That means that the patients probably has a lesion on:
a. The right cranial nerve of XII
b. The left cranial nerve of XII
c. The medulla bilaterally
d. The pons bilaterally
What is a. right cranial nerve of XII
The cranial nerve responsible for motor innervation of the tongue is the hypoglossal nerve (XII). With a R cranial nerve XII lesion, the action of the ipsilateral genioglossus muscle is compromised; thus, during tongue protrusion, only the left genioglossus muscle pushes the tongue out, causing it to deviate towards the right (weak) side.