**Core Concept**
Calcium channel blockers are a class of medications that inhibit the influx of calcium ions into smooth muscle cells, thereby reducing muscle contraction. In the context of increased intracranial tension (ICT), certain calcium channel blockers can be used to reduce cerebral blood flow and subsequently lower ICT.

**Why the Correct Answer is Right**
Nicardipine, a dihydropyridine calcium channel blocker, is specifically used in cases of increased intracranial tension due to its potent cerebral vasodilatory effects. It rapidly reduces cerebral blood flow and intracranial pressure by dilating cerebral arterioles. This is particularly useful in the management of acute subarachnoid hemorrhage, cerebral edema, and other conditions associated with increased ICT.

**Why Each Wrong Option is Incorrect**
* **Option A:** Nimodipine is primarily used to treat cerebral vasospasm following subarachnoid hemorrhage, but it is not the first-line agent for increased intracranial tension.
* **Option B:** Verapamil is a non-dihydropyridine calcium channel blocker that can cause cerebral vasodilation, but it is not typically used in the management of increased ICT.
* **Option D:** Diltiazem is another non-dihydropyridine calcium channel blocker that can cause vasodilation, but it is not commonly used in the treatment of increased intracranial tension.

**Clinical Pearl / High-Yield Fact**
When treating increased intracranial tension, it's essential to choose a calcium channel blocker that rapidly and effectively reduces cerebral blood flow. Nicardipine's potent cerebral vasodilatory effects make it an ideal choice in these situations.

**Correct Answer: C. Nicardipine**