Neuropsychological sequelae of acute-onset sporadic viral encephalitis.

Acute encephalitis is an inflammation of the brain parenchyma. In the USA, by estimation, 20,000 cases occur every year. A variety of cognitive deficits may persist after the acute stage, and they are often the sole cause of disability. Recent literature demonstrates the heterogeneity of both amnestic disorders and the outcome following encephalitis. Herpes simplex virus is the most commonly recognised single aetiology of sporadic encephalitis and it may be the cause of the most severe symptoms. Antiviral medication, however, seems to have improved the cognitive outcome when compared to the historical, untreated cases. The cognitive sequelae following herpes simplex virus encephalitis (HSVE) are best known and most commonly described, e.g., in textbooks, but they do not represent the typical symptomatology of encephalitis in general. Much less is unfortunately known about other types of encephalitis, those that account perhaps up to 80% of all cases, where both mild and severe defects have been observed. This article summarises the current knowledge.