A patient’s tongue deviates to the left when protruded. This finding indicates a:

When a patient's tongue deviates to the left upon protrusion, it suggests a dysfunction in the cranial nerve that controls the muscles of the tongue. The hypoglossal nerve (Cranial XII) is responsible for motor control of the tongue muscles. When there is a lesion affecting this nerve on one side, the muscle on that side will weaken, causing the tongue to deviate towards the weaker side.

In this case, since the tongue deviates to the left, it indicates that the left side of the tongue is affected. This is typical of a left-sided hypoglossal nerve lesion. The unaffected side (in this case, the right side) can push the tongue towards the weak side, which is why the deviation occurs. This neurological assessment provides insight into potential underlying issues such as an injury or illness affecting the hypoglossal nerve.

Understanding this concept highlights the importance of cranial nerve assessments in clinical practice and underlines the specific functions of the different cranial nerves. The other choices relate to different cranial nerves or conditions that do not produce this specific pattern of tongue deviation, hence indicating why they would not be the correct answer.