## Core Concept
The hypoglossal nerve (cranial nerve XII) is responsible for controlling the intrinsic and extrinsic muscles of the tongue, except for palatoglossus. Unilateral injury to the hypoglossal nerve affects the motor function of the tongue on the same side.

## Why the Correct Answer is Right
A unilateral injury to the hypoglossal nerve leads to weakness of the ipsilateral tongue muscles. This results in difficulty protruding the tongue, deviation of the tongue to the side of the lesion upon protrusion, and impaired tongue movements on the affected side. However, it does not cause significant difficulties in swallowing (dysphagia) or speech articulation (dysarthria) initially, as these functions are primarily coordinated by other cranial nerves and the brain.

## Why Each Wrong Option is Incorrect
- **Option A:** Tongue deviation to the side of lesion on protrusion. This is correct because when the tongue is protruded, the weakened muscles on the side of the lesion cannot counterbalance the push from the unaffected side, causing deviation towards the side of the lesion.
- **Option B:** Difficulty in protrusion of tongue. This is a direct consequence of hypoglossal nerve injury, as the nerve supplies the muscles responsible for tongue protrusion (genioglossus).
- **Option D:** Impaired tongue movements. This is accurate since the hypoglossal nerve injury affects the muscles responsible for various tongue movements.

## Why Option C is Correct (and thus the correct answer to "all except")
- **Option C:** Significant dysphagia. While some difficulty in managing food in the mouth and initial phases of swallowing might occur due to impaired tongue movements, significant dysphagia (swallowing difficulty) is not typically a primary symptom of isolated hypoglossal nerve injury. The primary functions of swallowing are coordinated by multiple cranial nerves (including but not limited to the hypoglossal nerve), and initial unilateral weakness might not lead to pronounced dysphagia.

## Clinical Pearl / High-Yield Fact
A key clinical feature to remember in hypoglossal nerve injury is the deviation of the tongue towards the side of the lesion upon protrusion. This is a quick bedside test that can help identify unilateral hypoglossal nerve palsy.

## Correct Answer: C. Significant dysphagia