Concussion and Headache: Making Sense of Mild TBI and Post-traumatic Headache
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Both as a neurologist and the father of football-playing sons, I’ve heard a lot about traumatic brain injury (TBI) generally and concussion most of all. “Concussion” is a commonly used but poorly understood term that deserves some attempt at clarification, and if only due to its high prevalence and the persistent post-traumatic headache that may result from concussion the topic also calls for some attention.
Making sense of any medical disorder first requires a definition that is sensitive and specific and a uniform set of diagnostic criteria that are widely accepted. Once these are in place – and not before - prospective clinical trials can be initiated. If all goes well, those trials will yield ever-improving evidence-based management. In many ways, the present confusion and lack of evidence-based management for concussion and post-traumatic headache are analogous to what existed in the past for chronic daily headache.
Over 4% of the general population has near-daily or daily headache. One-half of those individuals – upwards of 6 million people in the United States – have chronic migraine, and yet only within the last 15 years has chronic migraine received formal designation as a primary headache disorder and have we had the criteria required to diagnose chronic migraine. With a definition and these criteria in hand, over a space of 15 years we have managed to develop no less than 6 safe, well-tolerated and effective evidence-based therapies for the suppression of chronic migraine.
Concussion and persistent post-traumatic headache are no less prevalent than chronic migraine - and no less deserving of effective diagnosis and management – but at present we have no such evidence-based pharmacologic therapy for post-traumatic headache.
Concussion is the clinically mildest of the TBIs. By definition, “concussion” implies a traumatically-induced physiologic disruption of brain function characterized by any period of loss of consciousness, any loss of memory for events immediately before or after the injury and no significant alteration of mental status at the time of injury (the Glasgow Coma scale Score, commonly used in the setting of TBI, must be greater than 12). Brain imaging – CT or MRI – performed acutely following concussion will be normal.
The post-concussive syndrome involves some combination of vestibulopathy (dysequlibrium/imbalance/”dizziness”), sensitivity to sound or motion, sleep disturbance, impaired cognition (issues with memory/”forgetfulness” and concentration), emotional disturbance (irritability, anxiety, depression) and – most common of the symptom group – headache. Especially when the circumstances of the TBI sound to have been relatively minor and the patient continues to report disabling symptoms even months following the injury, a large component of secondary gain is often suspected. In fact, the incidence of malingering in this clinical setting appears to be low, and more sophisticated neurodiagnostic testing may demonstrate findings that lend biologic credence to the symptoms. While with concussion brain imaging performed acutely is normal, those who develop the chronic symptoms of post-concussive syndrome may exhibit imaging evidence of thinning of brain cortex or “impaired functional connectivity” (presumably resulting from shear injury disrupting the white matter wiring of the brain).
Post-traumatic headache is tautologically defined as acute or persistent headache attributed to mild (essentially synonymous with “concussion”), moderate or severe traumatic injury to the head, with the headache having developed within 7 days of the head injury. “Persistent” post-traumatic headache (PPTH) implies that the headache has persisted for at least three months following the head injury.
Although it is often assumed that the symptoms (including headache) acutely resulting from concussion resolve spontaneously within days or a few weeks at most, one study of patients with TBI found that over 50% had persistent headache at three months. In another study involving patients with PPTH, over 2/3rds continued to have chronic headache even 2 years out from TBI.
What are the risk factors for developing persistent post-traumatic headache? Contrary to what one might expect, PPTH more commonly complicates mild TBI/concussion than it does more severe TBI. It is also more likely to occur in females, in individuals under the age of 60, in those with a prior history of TBI and in those with a pre-existing history of a primary head disorder (most commonly migraine; put simply, migraine brains do not like to be messed with). Interestingly, if the acute post-traumatic headache has features characteristic of migraine, the individual will be more likely to develop PPTH even if he/she has no antecedent history of migraine.
We currently lack any evidence-based therapies for prevention/suppression of PPTH, a regrettable deficiency given the high prevalence of the disorder, but this may be changing. Persistent post-traumatic headache typically comes in two flavors (ie, recognizable constellations of symptoms termed clinical phenotypes): one resembling chronic migraine and the other resembling chronic tension-type headache. OnabotulinumtoxinA (BotoxA) was approved for the suppression/prevention of primary chronic migraine in 2010, and in a recent pilot study investigators found that PPTH patients with the clinical phenotype of chronic migraine were significantly more likely to experience a clinically meaningful reduction in headache burden following treatment with BotoxA than patients with PPTH and the clinical phenotype of chronic tension-type headache. In another pilot study, investigators found that both BotoxA and erenumab (Aimovig), the latter another medication with a solid evidence base for use in primary chronic migraine, were effective in treating a high proportion of PPTH patients with the clinical phenotype of chronic migraine.
What to take away:
The most common symptom of the post-concussive syndrome is headache, and the syndrome itself typically does reflect persisting dysfunction of the central nervous system.
Persistent post-traumatic headache is a common and highly prevalent long-term complication of TBI… especially mild TBI/concussion.
Left untreated, the long-term prognosis for PPTH does not appear to be especially favorable.
At least for those patients with PPTH and the clinical phenotype of chronic migraine, use of evidence-based therapies indicated for suppression of primary chronic migraine may be effective.
