Primary or secondary headache or both?
The general rules for attribution to another disorder apply to 5. Headache attributed to trauma or injury to the head and/or neck.
- When a new headache occurs for the first time in close temporal relation to trauma or injury to the head and/or neck, it is coded as a secondary headache attributed to the trauma or injury. This remains true when the new headache has the characteristics of any of the primary headache disorders classified in Part One of ICHD-3.
- When a pre-existing headache with the characteristics of a primary headache disorder becomes chronic or is made significantly worse (usually meaning a two-fold or greater increase in frequency and/or severity) in close temporal relation to such trauma or injury, both the initial headache diagnosis and a diagnosis of 5. Headache attributed to trauma or injury to the head and/or neck (or one of its types or subtypes) should be given, provided that there is good evidence that the disorder can cause headache.
The types of 5. Headache attributed to trauma or injury to the head and/or neck are among the most common secondary headache disorders. During the first 3 months from onset they are considered acute; if they continue beyond that period they are designated persistent. This time period is consistent with ICHD-II diagnostic criteria, although the term persistent has been adopted in place of chronic.
There are no specific headache features known to distinguish the types of 5. Headache attributed to trauma or injury to the head and/or neck from other headache disorders; most often these resemble 2. Tension-type headache or 1. Migraine. Consequently their diagnosis is largely dependent upon the close temporal relation between the trauma or injury and headache onset. Consistently with those of ICHD-II, the diagnostic criteria of ICHD-3 for all types of 5. Headache attributed to trauma or injury to the head and/or neck require that headache must be reported to have developed within 7 days following trauma or injury, or within 7 days after regaining consciousness and/or within 7 days after recovering the ability to sense and report pain. Although this 7-day interval is somewhat arbitrary, and some experts argue that headache may develop after a longer interval in a minority of patients, there is not enough evidence at this time to change this requirement. Research is encouraged that tests the diagnostic criteria for A18.104.22.168 Delayed-onset acute headache attributed to moderate or severe traumatic injury to the head and A22.214.171.124 Delayed-onset acute headache attributed to mild traumatic injury to the head (see Appendix).
Headache may occur as an isolated symptom following trauma or injury or as one of a constellation of symptoms, commonly including dizziness, fatigue, reduced ability to concentrate, psychomotor slowing, mild memory problems, insomnia, anxiety, personality changes and irritability. When several of these symptoms follow head injury, the patient may be considered to have a post-concussion syndrome.
The pathogenesis of 5. Headache attributed to trauma or injury to the head and/or neck is often unclear. Numerous factors that may contribute to its development include, but are not limited to, axonal injury, alterations in cerebral metabolism, neuroinflammation, alterations in cerebral haemodynamics, underlying genetic predisposition, psychopathology and a patient’s expectations of developing headache after head injury. Recent research, using advanced neuroimaging modalities, suggests a potential for detecting brain structural, functional and metabolic abnormalities following minor trauma that are not detectable through conventional diagnostic tests. Post-traumatic sleep disturbances, mood disturbances and psychosocial and other stressors can plausibly influence the development and perpetuation of headache. The overuse of abortive headache medications may contribute to the persistence of headache after head injury through the development of 8.2 Medication-overuse headache. Clinicians must consider this possibility whenever a post-traumatic headache persists beyond the initial post-trauma phase.
Risk factors for the development of 5. Headache attributed to trauma or injury to the head and/or neck may include a previous history of headache, less severe injury, female gender and the presence of comorbid psychiatric disorders. The association between repetitive head trauma and the development of headache should be investigated further. The degree to which a patient’s expectation of headache following head injury and litigation regarding such headache promote its development and persistence is still widely debated. The majority of evidence suggests that malingering is a factor in only a small minority of patients.
It is recognized that some patients develop headache following very minor trauma to the head – so minor that it does not meet criteria even for mild traumatic brain injury. These headaches may begin after a single trauma or following repetitive minor head impacts (eg, in players of American football or rugby). However, headache due to very minor head trauma has not been adequately studied, so there are insufficient data to support its recognition and inclusion in ICHD-3. Research on headache following very minor trauma to the head, perhaps guided by the diagnostic criteria for A.5.8 Acute headache attributed to other trauma or injury to the head and/or neck and A.5.9 Persistent headache attributed to other trauma or injury to the head and/or neck, is encouraged.
Headache attributed to trauma or injury to the head and/or neck is also reported in children, although less often than in adults. The clinical presentations of the types are similar in children and adults, and the diagnostic criteria in children are the same.