| IHS | Diagnosis | ICD-10 |
|---|---|---|
| 9.2 | Headache attributed to systemic infection [A00-B97] | G44.881 |
| Coded elsewhere | Headache attributed to meningitis or encephalitis accompanying systemic infection should be coded accordingly under 9.1 Headache attributed to intracranial infection . | |
Diagnostic criteria:
- Headache with at least one of the following characteristics and fulfilling criteria C and D:
- diffuse pain
- intensity increasing to moderate or severe
- associated with fever, general malaise or other symptoms of systemic infection
- Evidence of systemic infection
- Headache develops during the systemic infection
- Headache resolves within 72 hours after effective treatment of the infection
Comments:
Headache in systemic infections is usually a relatively inconspicuous symptom and diagnostically unhelpful. These conditions are mostly dominated by fever, general malaise and systemic symptoms. Nevertheless, some systemic infections, particularly influenza, have headache as a prominent symptom along with fever and other symptoms. In other cases, systemic infection is accompanied by meningitis or encephalitis, and the headache should be coded to these disorders.
The great variability in their propensity for causing headache indicates that systemic infections do not have this effect simply through fever. The mechanisms causing headache include direct effects of the microorganisms themselves. In infectious disease, headache commonly coexists with fever and may be dependent on it, but headache can occur in the absence of fever. The presence or absence of fever may be used in the differential classification of headache. The exact cause of headache by fever is not elucidated. Some infective microorganisms may influence brainstem nuclei which release substances to cause headache, or endotoxins may activate inducible NOS causing production of nitric oxide (NO). The exact nature of these mechanisms remains to be investigated.
