**Core Concept**
Cranial irradiation is a treatment modality that involves the delivery of ionizing radiation to the brain to target and destroy rapidly dividing cells, such as cancer cells. This technique is often used in conjunction with surgery and chemotherapy to treat various types of brain tumors.

**Why the Correct Answer is Right**
The correct answer is related to the treatment of certain types of brain tumors, particularly those that are sensitive to radiation. Cranial irradiation works by inducing DNA damage in cancer cells, leading to cell death. This is especially effective in tumors with a high proliferation rate, such as glioblastoma multiforme. The radiation can be delivered using external beam radiation therapy (EBRT) or stereotactic radiosurgery (SRS).

**Why Each Wrong Option is Incorrect**

**Option A:** This option is incorrect because cranial irradiation is not typically used to treat infections, such as meningitis or encephalitis.

**Option B:** This option is incorrect because cranial irradiation is not primarily used for the treatment of vascular malformations, such as arteriovenous malformations (AVMs).

**Option C:** This option is incorrect because cranial irradiation is not the standard treatment for degenerative conditions, such as Alzheimer's disease or Parkinson's disease.

**Clinical Pearl / High-Yield Fact**
One important consideration when using cranial irradiation is the risk of long-term side effects, such as radiation-induced cognitive decline, which can manifest as memory impairment, attention deficits, or decreased processing speed.

**Correct Answer:** D.