Encephalitis

Encephalitis is inflammation of the brain parenchyma. Infection—especially herpes simplex virus (HSV)—is a major cause, but an autoimmune process can produce a similar syndrome when antibodies or immune cells disrupt neuronal function. Inflammation causes neuronal dysfunction and cerebral edema; the result may be altered behaviour, impaired memory or language, seizures, focal neurological deficits, and increased intracranial pressure (ICP). The experienced nurse often notices a change in the person before a dramatic neurological deficit appears. A previously appropriate patient becomes unusually irritable, disinhibited, withdrawn, confused, or unable to find words. That behavioural change matters because the temporal lobes, which support memory, language, and emotional regulation, are commonly affected in HSV encephalitis. Fever, headache, or a seizure strengthens the concern, but their absence does not make encephalitis safe to dismiss. Encephalitis differs from uncomplicated meningitis by the degree of brain dysfunction. Meningitis more typically produces fever, headache, photophobia, and neck stiffness; encephalitis produces altered cognition, behaviour, consciousness, seizures, or focal findings. The conditions can coexist, so neck stiffness does not rule encephalitis out. Stroke, hypoglycaemia, intoxication, medication effects, metabolic delirium, and a...