Which statement best defines encephalitis?

• A. Inflammation of the meninges covering the brain and spinal cord.
• B. Brain tissue infection due to bacteria.
• C. Inflammation of the brain usually caused by a virus.
• D. A collection of pus localized in an area of the brain.

Answer: (C)

Encephalitis is inflammation of the brain tissue itself, which disrupts how neurons work and can cause fever, confusion, seizures, and other neurological changes. It is most commonly caused by a viral infection, which is why this statement emphasizes that viral etiology. This sets it apart from meningitis, which involves inflammation of the membranes surrounding the brain and spinal cord, and from a brain abscess, which is a localized collection of pus in the brain. While bacterial infections of the brain can occur, the classic description of encephalitis centers on viral inflammation of the brain tissue, often requiring imaging and cerebrospinal fluid analysis for diagnosis and antiviral treatment when appropriate.