Post-traumatic headaches: Time for a revised classification?

Abstract

Post-traumatic headache (PTH) is among the most prevalent of the secondary headache disorders. As currently classified by the International Classification of Headache Disorders, 2nd edition (ICHD-2), PTH must start within 7 days of a mild, moderate, or severe traumatic brain injury (TBI). PTH transitions from an acute subtype to a chronic subtype 3 months after the injury (1). No other defining clinical characteristics set PTH apart from other primary or secondary headache disorders. In fact, most PTHs appear to have a phenotype indistinguishable from primary headache disorders and may respond to the same treatments as primary headache disorders (2,3). It seems altogether intuitive that headaches would occur acutely in the majority of individuals after a mild TBI (or concussion). More vexing, and controversial, is the link between head trauma and the subsequent development of chronic headaches (4,5). PTHs persist beyond the acute period in a significant proportion of patients. Up to 60% of TBI patients have chronic headaches persisting for up to 12 months (4,6). That chronic PTHs develop more often in mild versus moderate to severe TBI, in cases with impending litigation or in the setting of analgesic medication overuse, suggests a role for factors independent of trauma in the process of headache chronification (4,7,8). While each (or all) of these factors may be important in the genesis of chronic headaches in individual cases, there is a lack of evidence supporting them as unifying hypotheses to explain the spectrum of chronic PTHs in civilian and military patient populations. A better understanding of the processes leading to headache chronification after brain trauma is needed. Over the past 3 years, large epidemiological studies of headaches in military, civilian, and veteran populations with head trauma have been completed (9–11), providing a valuable opportunity to better understand and classify PTHs. In this issue, Lucas et al. (10) report the findings of a multi-center, longitudinal study of headaches in a population of 378 patients with moderate to severe TBI. The subjects underwent a baseline headache evaluation shortly after TBI and were then followed by telephone interview at 3, 6, and 12 months after injury to longitudinally assess headache incidence and headache characteristics. To our knowledge, this is one of the largest longitudinal studies of headaches in TBI patients. Many interesting findings emerge from this study, parts of which have been published previously (10, 11). The cumulative headache incidence in the study cohort was 71% over 12 months. Forty-three percent of patients had headaches at the baseline assessment shortly after TBI and this proportion was stable over the next 12 months. There were no differences in headache incidence between mild, moderate, and severe TBI patients. Eighteen percent of all patients had a history of headaches prior to TBI with 57% of these being migraine or probable migraine. Similar to previous studies, pre-traumatic headache and female sex were risk factors for reporting headaches after TBI. Migraine and probable migraine were the most common headache types after trauma, accounting for 52% of headaches at baseline and 60% of headaches 6 months after injury. Migrainous headaches were 2–3fold more common than tension-type headaches (TTHs; 7–21%) at all time points. The high prevalence of migraine observed by Lucas et al. (10) sharply contrasts with older studies which suggested a higher prevalence of TTH after TBI, but are similar to the findings of recent studies in military and veteran populations which found migraine in 60 to over 90% of cases (2,3,9,12). Comparing PTH studies and study populations can be difficult, but the accumulation of