panencephalitis

Panencephalitis is a term used to describe inflammation of the entire brain (pan- meaning all, encephalon). It denotes a pattern of diffuse brain involvement rather than a single disease. The most well-described form is subacute sclerosing panencephalitis (SSPE), a rare, progressive, and usually fatal encephalitis caused by a persistent, mutated measles virus that remains in the brain years after initial infection. In a broader sense, panencephalitis can occur with various infectious, autoimmune, toxic, or inflammatory processes that affect widespread brain tissue.

Subacute sclerosing panencephalitis typically begins with subtle behavioral or cognitive changes, followed by neurological decline. Patients may develop personality alterations, memory impairment, myoclonus, seizures, ataxia, and progressive motor dysfunction. Over time there is increasing rigidity, spasticity, and autonomic disturbance. Diagnosis relies on a combination of clinical features, electroencephalography showing periodic generalized complexes, and cerebrospinal fluid or serologic evidence of measles exposure or infection. Neuroimaging often reveals widespread, progressive brain involvement.

Treatment for panencephalitis is mainly supportive and aims to alleviate symptoms and slow progression when possible. In SSPE, antiviral and immunomodulatory therapies (for example, intraventricular interferon or ribavirin in some regimens) have been used in attempts to modify the course, though evidence is variable. Vaccination against measles is the most effective preventive strategy, reducing the risk of SSPE by preventing the initial measles infection.

Prognosis varies by underlying etiology; SSPE generally follows a progressive course over months to years and is frequently fatal.