Encephalitis Brain Inflammation

Encephalitis is inflammation of the brain parenchyma that produces neurologic dysfunction. The finding that changes the clinical priority is altered mental status: a reduced level of consciousness, new personality or behavior change, or a new cognitive deficit, usually lasting at least 24 hours. Fever, headache, seizures, speech disturbance, and focal neurologic deficits commonly accompany it. Meningitis primarily inflames the meninges and can cause fever, headache, photophobia, and neck stiffness without primary brain dysfunction. The two conditions frequently occur together as meningoencephalitis, so neck stiffness does not rule encephalitis in or out. A patient with fever and a new change in behavior or consciousness should be treated as having possible encephalitis until the cause is clarified. Causes fall into two management pathways: - Infectious encephalitis occurs when a pathogen directly invades brain tissue. Herpes simplex virus is the most important treatable cause of sporadic encephalitis in North America. Other causes include West Nile and other arboviruses, enteroviruses, varicella-zoster virus, rabies virus, and measles. - Immune-mediated or autoimmune encephalitis occurs when the immune system attacks neuronal surface or intracellular antigens, such as...