**Core Concept**
The Kernohan's notch phenomenon is a clinical observation where a lesion in the contralateral cerebral hemisphere, particularly in the frontal lobe, causes ipsilateral hemiparesis. This occurs due to the compression of the corticospinal tract against the tentorium cerebelli.

**Why the Correct Answer is Right**
The correct answer involves the concept of the "uncal herniation" and its effects on the brainstem. In cases of increased intracranial pressure, the uncus of the temporal lobe can herniate through the tentorial notch, compressing the cerebral peduncle and causing ipsilateral hemiparesis. This is known as Kernohan's notch phenomenon.

**Option A:** **Option A:** is incorrect because it does not relate to the Kernohan's notch phenomenon.
**Option B:** **Option B:** is incorrect because it is more related to the **Cushing's reflex**, which is a different phenomenon.
**Option C:** **Option C:** is incorrect because it is related to the **Duret's hemorrhage**, which occurs due to downward transtentorial herniation, not Kernohan's notch.

**Clinical Pearl / High-Yield Fact**
Kernohan's notch phenomenon is a classic example of how a lesion in one part of the brain can cause symptoms in another part, due to the compression of the corticospinal tract.

**Correct Answer:** C. Transtentorial herniation.