Posttraumatic headache is difficult to define and there is debate about the specificity of the 7-day headache onset criterion in the current definition. There is limited evidence available to guide decision making about this criterion.
A nested cohort study of 193 treatment-seeking veterans who met criteria for persistent headache attributed to mild traumatic injury to the head, including some veterans with delayed headache onset up to 90 days post-injury, was undertaken. Survival analysis examined the proportion of participants reporting headache over time and differences in these proportions based on sex, headache phenotype, and mechanism of injury.
127 participants (66%; 95% CI: 59-72%) reported headache onset within 7 days of head injury and 65 (34%) reported headache onset between 8 days and 3 months after head injury. Fourteen percent of participants reported pre-existing migraine before head injury, and there was no difference in the proportion of veterans with pre-existing migraine based on headache onset. Headache onset times were not associated with sex, headache phenotype, or mechanism of injury. There were no significant differences in proportion of veterans with headache onset within 7 days of head injury based on headache phenotype (70% migraine onset within 7 days, 70% tension-type headache within 7 days, 56% cluster headache within 7 days; ≥ .364). Similar findings were observed for head injury (64% blast, 60% blunt; = .973). There were no significant differences observed between headache onset groups for psychiatric symptoms (Posttraumatic Stress Disorder Checklist for = 1.3, 95% CI = -27.5, 30.1; Patient Health Questionnaire-9 Item = 3.5, 95% CI = -6.3, 3.7; Generalized Anxiety Disorder Screener = 6.5, 95% CI = -2.7, 15.6).
Although most of the sample reported headache onset within 7 days of head injury, one-third experienced an onset outside of the diagnostic range. Additionally, veterans with headache onset within 7 days of head injury were not meaningfully different from those with later onset based on sex, headache phenotype, or mechanism of head injury. The ICHD-3 diagnostic criteria for 7-day headache onset should be expanded to 3 months.