**Core Concept**
Alexander disease, Canavan disease, and adrenoleukodystrophy are all neurodegenerative disorders primarily affecting the white matter of the brain. White matter consists of myelinated nerve fibers responsible for transmitting signals between different brain regions. These disorders typically involve demyelination, axonal loss, or other pathologies affecting the myelinated fibers of the white matter.

**Why the Correct Answer is Right**
Neuronal ceroid lipofuscinosis (NCL) is a group of inherited disorders characterized by the accumulation of lipofuscin in the lysosomes of neurons. This leads to neuronal dysfunction and death, primarily affecting the gray matter of the brain. The primary pathology in NCL involves the accumulation of abnormal proteins and lipids within neurons, causing cellular dysfunction and death, rather than direct damage to the myelinated fibers of the white matter.

**Why Each Wrong Option is Incorrect**
**Option A:** Alexander disease is a rare degenerative disease of the central nervous system, characterized by the accumulation of Rosenthal fibers in the white matter.
**Option B:** Canavan disease is a genetic disorder that affects the myelin sheath, leading to demyelination and axonal loss in the white matter.
**Option D:** Adrenoleukodystrophy is a genetic disorder that affects the metabolism of fatty acids, leading to the accumulation of very-long-chain fatty acids in the white matter of the brain, causing demyelination and axonal loss.

**Clinical Pearl / High-Yield Fact**
When diagnosing white matter disorders, it's essential to consider the clinical presentation, family history, and imaging findings. Alexander disease, Canavan disease, and adrenoleukodystrophy often present with distinct clinical features, such as seizures, developmental delay, and visual impairment.

**✓ Correct Answer: C. Neuronal ceroid lipofuscinosis**