**Core Concept**
The question is testing the knowledge of a specific type of mitochondrial degeneration called "Lafora bodies," which are characteristic of a rare genetic disorder called Lafora disease. Lafora bodies are abnormal, rounded inclusions composed of polysaccharide material that accumulate within the cytoplasm of neurons.

**Why the Correct Answer is Right**
Lafora bodies are typically found in the neurons of the brain and the cells of the peripheral nervous system. They are not commonly seen in other cell types or organs, such as muscles or the liver. The accumulation of Lafora bodies leads to the breakdown of neurons and the disruption of normal neuronal function, resulting in progressive neurological deterioration.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Lafora bodies are indeed found in the neurons of the brain, which is an organ composed of all types of cells, including neurons.
**Option B:** This option is incorrect because Lafora bodies are not typically found in the liver, which is an organ composed of various cell types, including hepatocytes and sinusoidal cells.
**Option C:** This option is incorrect because Lafora bodies are not commonly seen in muscles, which are composed of muscle fibers and other cell types.

**Clinical Pearl / High-Yield Fact**
Lafora disease is a rare genetic disorder characterized by the accumulation of Lafora bodies in neurons, leading to progressive neurological deterioration. It is caused by mutations in one of two genes, EPM2A or NHLRC1, which are involved in the regulation of glycogen metabolism.

**Correct Answer: D. Muscles.