**Core Concept**
Increased intracranial pressure (ICP) follows a predictable clinical sequence after head injury, with early signs reflecting brainstem compression and disruption of consciousness due to impaired cerebral perfusion.

**Why the Correct Answer is Right**
Altered mental status is the earliest and most common manifestation of rising ICP. As pressure builds, cerebral blood flow decreases, leading to reduced neuronal function and impaired consciousness. This occurs before any pupillary changes or motor deficits, which appear later as the condition progresses. The brainstem, which governs consciousness, is particularly vulnerable to pressure, making mental status changes the first detectable sign.

**Why Each Wrong Option is Incorrect**
Option A: Ipsilateral pupillary dilatation occurs in the **late** stages of increased ICP due to midbrain compression, not early.
Option B: Contralateral pupillary dilatation is not a typical finding and may indicate other pathologies like stroke or brain herniation, not early ICP rise.
Option D: Hemiparesis results from focal brain injury or herniation and appears **after** significant ICP elevation, not in the initial phase.

**Clinical Pearl / High-Yield Fact**
Remember the "Cushing triad" (bradycardia, hypertension, irregular respiration) occurs in **late** stages of severe ICP, while **altered mental status** is the first clue. Early recognition of mental status changes is critical for timely intervention.

✓ Correct Answer: C. Altered mental status