|9||HEADACHE ATTRIBUTED TO INFECTION|
|Coded elsewhere||Headache disorders attributed to extracranial infections of the head (such as ear, eye and sinus infections) are coded as subtypes of 11. Headache or facial pain attributed to disorder of cranium, neck, eyes, ears, nose, sinuses, teeth, mouth or other facial or cranial structures .|
Primary or secondary headache or both?
When a new headache occurs for the first time in close temporal relation to an infection, it is coded as a secondary headache attributed to the infection. This is also true if the headache has the characteristics of migraine, tension-type headache or cluster headache. When a pre-existing primary headache is made worse in close temporal relation to an infection, there are two possibilities, and judgment is required. The patient can either be given only the diagnosis of the pre-existing primary headache or be given both this diagnosis and the diagnosis of headache attributed to the infection. Factors that support adding the latter diagnosis are: a very close temporal relation to the infection, a marked worsening of the pre-existing headache, very good evidence that the infection can aggravate the primary headache and, finally, improvement or resolution of the headache after relief from the infection.
Definite, probable or chronic?
A diagnosis of Headache attributed to an infection usually becomes definite only when the headache resolves or greatly improves after effective treatment or spontaneous remission of the infection. If the infection cannot be treated effectively or does not remit spontaneously, or when there has been insufficient time for this to happen, a diagnosis of Headache probably attributed to infection is usually applied.
This is not the case for 9.1.1 Headache attributed to bacterial meningitis. It is recognised that this headache may become chronic. When the causative infection is effectively treated or remits spontaneously but headache persists after 3 months, the diagnosis changes to 9.4.1 Chronic post-bacterial meningitis headache.
In other cases when the infection is eliminated but headache does not resolve or markedly improve after 3 months, a diagnosis of A9.4.2 Chronic post-non-bacterial infection headache may be considered. This is described only in the appendix as such headaches have been poorly documented, and research is needed to establish better criteria for causation.
Headache is a common accompaniment of systemic viral infections such as influenza. It is also common with sepsis; more rarely it may accompany other systemic infections.
In intracranial infections headache is usually the first and the most frequently encountered symptom. Occurrence of a new type of headache which is diffuse, pulsating and associated with a general feeling of illness and/or fever should direct attention towards an intracranial infection even in the absence of a stiff neck. Unfortunately, there are no good prospective studies of the headaches associated with intracranial infection and precise diagnostic criteria for these subtypes of headache cannot be developed in all cases.