What medical condition is characterized by an accumulation of cerebrospinal fluid in the brain?

Hydrocephalus is the medical condition characterized by an accumulation of cerebrospinal fluid (CSF) within the brain's ventricles. This condition occurs when there is an imbalance between the production and absorption of cerebrospinal fluid or when there is a blockage that prevents the normal flow of CSF. As a result, the excessive buildup of fluid can lead to increased intracranial pressure, which can have serious consequences on brain function and structure.

In contrast, meningitis refers to the inflammation of the protective membranes covering the brain and spinal cord, typically caused by an infection, not an accumulation of fluid. Encephalitis is the inflammation of the brain itself, often due to viral infections, and while it may involve changes in CSF levels, it does not specifically describe fluid accumulation like hydrocephalus does. Ataxia is a neurological sign involving a lack of voluntary coordination of muscle movements and does not pertain directly to the condition of CSF accumulation.

Therefore, recognizing that hydrocephalus specifically refers to the buildup of cerebrospinal fluid distinguishes it clearly from the other conditions listed.