Neurology

Encephalitis

Encephalitis is inflammation of the brain parenchyma causing altered mental state, seizures or focal neurological dysfunction, usually from infection or autoimmunity; suspected herpes-simplex encephalitis needs immediate empirical intravenous aciclovir while investigations are arranged.

Definition

Encephalitis is inflammation of the brain parenchyma that causes a new change in cognition, behaviour or consciousness and/or seizures or focal neurological dysfunction, commonly with fever. It may be infectious, autoimmune, paraneoplastic or, less often, drug- or immune-therapy-related.

First principles

Encephalitis is a brain-function syndrome

Meningitis primarily inflames the meninges and causes headache, fever and neck stiffness. Encephalitis inflames brain tissue, so altered cognition, behaviour or consciousness, seizures and focal neurological signs are central. The syndromes overlap, and a patient with meningoencephalitis may need treatment for both until the cause is established.

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