## **Core Concept**
The genioglossus muscle is one of the extrinsic muscles of the tongue, primarily responsible for protruding the tongue. It is innervated by the **hypoglossal nerve (CN XII)**, which is a motor nerve. The genioglossus muscle plays a crucial role in maintaining the tongue's position within the oral cavity and aiding in speech and swallowing.

## **Why the Correct Answer is Right**
Palsy of the right genioglossus muscle, which is caused by damage to the right hypoglossal nerve (CN XII), leads to weakness of the muscle on the affected side. When the genioglossus muscle is weakened on one side, the tongue deviates to the side of the lesion upon protrusion. This is because the intact genioglossus muscle on the opposite side pushes the tongue towards the weakened side. Therefore, when a patient with right genioglossus palsy protrudes their tongue, it deviates to the **right**.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because deviation to the opposite side (left) does not accurately reflect the effect of genioglossus palsy on the same side as the lesion.
- **Option B:** This option might seem plausible but does not accurately describe the deviation caused by genioglossus palsy.
- **Option D:** This option does not accurately describe the clinical manifestation of genioglossus palsy.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that when testing for hypoglossal nerve (CN XII) function, asking the patient to protrude their tongue can help identify a lesion. If the tongue deviates to one side upon protrusion, it indicates weakness of the genioglossus muscle on the side to which the tongue deviates.

## **Correct Answer:** . **Right**