Changes Proposed by DHHS in the Definition of Encephalopathy in the Aids to Interpretation of the Vaccine Injury Table

  • The term encephalopathy means any acute or chronic significant acquired abnormality of, or injury to, or impairment of function of, the brain.

    • Acute encephalopathy shall be defined as follows: An acute encephalopathy should be sufficiently severe to require health care intervention and hospitalization.

    • For children less than 24 months of age who present without an associated seizure event, an acute encephalopathy shall be defined as a significantly decreased level of consciousness, specifically stupor or coma, lasting for at least 24 hours. Those children less than 24 months of age who present following a seizure shall be viewed as having an acute encephalopathy if their stupor or coma persists beyond 24 hours and cannot be attributed to a postictal state or medication.

    • For children 24 months of age or older, an acute encephalopathy is one that persists for at least 24 hours and that is characterized by at least two of the following:

      • a significant change in mental status that is not medication related; specifically a confusional state or a delirium, or a psychosis;

      • a significantly decreased level of consciousness, which is independent of a seizure and cannot be attributed to the effects of medication; or

      • a seizure associated with loss of consciousness.

    • Increased intracranial pressure may be a clinical features of acute encephalopathy in any age group.

    • The following clinical features alone, or in combination, do not qualify as evidence of an acute encephalopathy or a significant change in either mental status or level of consciousness as de scribed above: Sleepiness, irritability (fussiness), high-pitched and unusual screaming, persistent inconsolable crying, and bulging fontanelle. Seizures in themselves are not sufficient to constitute a diagnosis of encephalopathy. In the absence of other evidence of an acute encephalopathy, seizures shall not be viewed as the first symptom or manifestation of the onset of an encephalopathy.

  • Chronic encephalopathy is defined as persistence of the acute findings over an extended period, usually several months to years beyond the acute episode. Individuals who return to a normal neurologic state after the acute encephalopathy shall not be presumed to have suffered residual neurologic damage from the vaccine; any subsequent chronic encephalopathy shall not be presumed to be a sequela of the acute encephalopathy. Children with evidence of a chronic encephalopathy secondary to genetic, prenatal, or perinatal factors shall not be considered to have a condition set forth in the Vaccine Injury Table.

Source: Adapted from U.S. Department of Health and Human Services (1992).

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