What are the clinical features of encephalitis?

The most characteristic or 'typical' clinical picture, with acute-subacute presentation, consists of the appearance of: fever (97%); alteration of the level of consciousness (92%, from obnubilation to coma); alteration of the contents of consciousness, behavior or personality (85%, confusion, disorientation, inappropriate behavior and agitation); headache, with or without vomiting (81%); language disorders (76%) and seizure activity (67%, of motor focal type, although they can also be generalized or partial complex).
In other cases, the onset of the clinical picture is more insidious or manifests itself in its 'atypical form' (3-20% of cases) as a subacute feverish or even afebrile encephalopathy with alterations in the level of consciousness or behavior (confused with 'true psychiatric cases') in the absence of signs of neurological focalization and seizure activity.