Inflammation of brain parenchyma with neurological dysfunction
Encephalitis is defined as inflammation of the brain parenchyma associated with neurological dysfunction such as altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems, and motor and sensory deficits.
It is the result of direct inflammation of the brain tissue, as opposed to the inflammation of the meninges (meningitis), and can be the result of infectious or non-infectious causes. An aetiological agent is only identified in around 50% of cases.
Encephalitis is caused by a heterogeneous group of pathogens, but presents with a near-uniform neurological dysfunction.
A lumbar puncture is always recommended as long as there is no contraindication, and 2 out of the following 4 symptoms are present: fever, headaches, altered mental status of unknown aetiology, meningism.
The main differential to distinguish is encephalopathy secondary to metabolic or toxic disturbances. Once a primary central nervous system disease is diagnosed, the diagnostic approach is geared towards determining the aetiology and appropriate therapy.
Management consists of basic resuscitation measures ensuring adequacy of the airway, breathing, and circulation, and empirical antiviral therapy in cases of suspected viral encephalitis concurrently with diagnostic steps.