**Core Concept**
Cranial irradiation is a therapeutic modality used to treat various conditions affecting the central nervous system (CNS). It involves the delivery of ionizing radiation to the brain to ablate or reduce the growth of malignant cells, alleviate symptoms, or prevent the progression of disease.

**Why the Correct Answer is Right**
Cranial irradiation is employed in the management of primary brain tumors, such as glioblastoma, meningioma, and acoustic neuroma. It is also used in the treatment of secondary brain tumors, which originate from metastasis of primary cancers, such as lung, breast, and melanoma. Radiation therapy can be delivered using various techniques, including fractionated external beam radiation therapy, stereotactic radiosurgery, or brachytherapy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as cranial irradiation is not typically used for the treatment of infections, such as meningitis.
**Option B:** This option is incorrect as cranial irradiation is not a primary treatment modality for stroke or cerebral vasculitis.
**Option C:** This option is incorrect as cranial irradiation is not used for the treatment of demyelinating disorders, such as multiple sclerosis.

**Clinical Pearl / High-Yield Fact**
Cranial irradiation can cause long-term side effects, including cognitive decline, radiation necrosis, and secondary malignancies. It is essential to weigh the benefits of radiation therapy against the potential risks and to use the lowest effective dose to minimize adverse effects.

**Correct Answer:** C.