Primary or secondary headache or both?
When a 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 (beta). 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 subtypes) should be given.
The subtypes 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 three 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 subtypes of 5. Headache attributed to trauma or injury to the head and/or neck from other headache types; most often these resemble tension-type headache or 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 (beta) for all subtypes require that headache must be reported to have developed within seven days of trauma or injury, or within seven days after regaining consciousness and/or the ability to sense and report pain when these have been lost following trauma or injury. Although this seven-day interval is somewhat arbitrary, and although 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.
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, 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 abnormalities following minor trauma that are not detectable through conventional diagnostic tests. Post-traumatic sleep disturbances, mood disturbances and psychosocial 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 such 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. Those with pending litigation and those without are similar regarding headache characteristics, cognitive test results, treatment responses and improvement in symptoms over time. Furthermore, symptom resolution does not typically occur following legal settlements. In Lithuania, for example, a country in which there is little expectation of developing headache after head injury, and a lack of insurance against personal injury, rates of 5.2 Persistent headache attributed to traumatic injury to the head are low.
5. 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 subtypes are similar in children and adults, and the diagnostic criteria in children are the same.