Table 1: Diagnostic Criteria for Encephalitis and Encephalopathy of Presumed Infectious or Autoimmune Aetiology (extracted from Venkatesan et al. )

Table 1: Diagnostic Criteria for Encephalitis and Encephalopathy of Presumed Infectious or Autoimmune Aetiology (extracted from Venkatesan et al. [2])

Major Criterion (required):

Patients presenting to medical attention with altered mental status (defined as decreased or altered level of consciousness, lethargy or personality change) lasting ≥24 h with no alternative cause identified.

Minor Criteria (2 required for possible encephalitis; ≥3 required for probable or confirmed^a encephalitis):

- Documented fever ≥38°C (100.4°F) within the 72 h before or after presentation

- Generalized or partial seizures not fully attributable to a pre-existing seizure disorder

- New onset of focal neurologic findings

- CSF WBC count ≥5/cubic mm

- Abnormality of brain parenchyma on neuroimaging suggestive of encephalitis that is either new from prior studies or appears acute in onset

- Abnormality on electroencephalography that is consistent with encephalitis and not attributable to another cause.

Abbreviations: CNS: Central Nervous System, CSF: Cerebral Spinal Fluid, EEG: Electroencephalogram, RBC: Red Blood Cell, WBC: White Blood Cell

^a Confirmed encephalitis requires one of the following: (1) Pathologic confirmation of brain inflammation consistent with encephalitis; (2) Defined pathologic, microbiologic, or serologic evidence of acute infection with a microorganism strongly associated with encephalitis from an appropriate clinical specimen; or (3) Laboratory evidence of an autoimmune condition strongly associated with encephalitis.