Headache attributed to viral encephalitis

Diagnostic criteria:
A. Headache fulfilling criteria for 9.1.2 Headache attributed to viral meningitis or encephalitis
B. Either or both of the following:

    1. neuroimaging shows diffuse brain oedema
    2. at least one of the following:

      a) altered mental state
      b) focal neurological deficits
      c) seizures.

Comment: Headache attributed to viral encephalitis should be suspected whenever headache is associated with altered mental state (including impaired vigilance), focal neurological deficits and/or seizures. Pain is usually diffuse, with the focus in frontal and/or retro-orbital areas, severe or extremely severe, throbbing or pressing type. Other commonly associated neurological deficits are disturbances of speech or hearing, double vision, loss of sensation in some parts of the body, muscle weakness, partial paralysis in the arms and legs, ataxia, hallucinations, personality changes, loss of consciousness and/or memory loss.