Prospective observational multicenter study in European ICUs. All patients admitted to the ICU for probable or confirmed Acute encephalitis (2013 IDSA - Infectious Disease Society of America criteria) will be included. Factors associated with a poor prognosis will be identified by multivariate analysis using a logistic regression.

Primary objective :

evaluate the correlation between mRs score and the baseline characteristics Functional outcomes will be evaluated using the modified Rankin score (mRS) score, which is one of the most frequently used scores in acute neurological diseases [18]. A poor outcome will be defined by a mRS score > 2 (functional dependence or death). The investigator usually evaluates this score if the patient is still in the hospital 90 days after admission. Patients discharged from hospital within 90 days following ICU admission without major disability (mRS 0, 1 or 2) are considered to have a good outcome. Patients discharged within 90 days with a disability will be classified for the study according to the latest available data. Patients will not be contacted directly by the investigator for the study purposes.

Secondary objectives :

To identify additional prognosis factors : the clinical, radiological, biological and neurophysiological factors associated with poor outcome for patients admitted to the ICU with AE

• Day 28 mortality, in-ICU mortality, in-hospital mortality

• Major systemic complications (septic shock, hyponatremia, nosocomial pneumonia, catheter-related BSI, overt gastroenteral bleeding, pulmonary embolism)

• Major intracranial complications during ICU stay

  • Status epilepticus
  • Brain death
  • Empyema/cerebral abscess
  • Cerebral ischemia
  • Intracranial bleeding

• ICP monitoring

• Neurosurgery

The cause of death will be categorized into 2 categories:

• Systemic causes (cardiovascular failure, MOF)
• Neurological cause (Diffuse neurologic injury or withdrawal of care)

Inclusion Criteria:

• Age ≥ 18 years

• non-opposition to participate in the study (or consent if applicable according to local legislation)

• Impaired consciousness (altered mentation, stupor, or personality changes) for a duration ≥ 24 h, without obvious explanation

• A score on the Glasgow Coma Scale < or =13 at ICU admission

• A Cerebrospinal fluid pleocytosis > = 5 cell / mm3

• At least 2 of the following :

  • Fever (≥ 38.0 °C) within 72 hours before or after admission
  • Generalized or partial seizures non-attributable to pre-existing epilepsy
  • New onset focal neurological deficit
  • Parenchymal abnormalities on MRI compatible with AE
  • EEG alterations compatible with AE.

Exclusion Criteria:

• CSF or neuroimaging not available (s) or not performed.
• febrile encephalopathy associated with another diagnosis (sepsis, neurological disease with aspiration pneumonia ... )

1000 patients admitted to the ICU for AE (5 consecutive patients in each participating ICU, targeted number of ICUs in Europe : 200).