It also revealed a surprisingly high frequency of misdiagnosis. The original sample included 500 patients drawn from the Stanford Research Repository Cohort Discovery Tool, but a review found 200 records that were misdiagnosed and had to be excluded.
“It’s very easy to label someone who suffered a head injury and say this is the reason why they have this (headache),” said lead author Tommy Chan, MBBS, a headache fellow in the department of neurology at Stanford (Calif.) University, in an interview. Such patients are often seen by ED or primary care physicians who do not have a lot of experience with posttraumatic headache, and that can lead to negative consequences if a low-pressure headache is mistaken as stemming from a skull fracture. “It’s a very different treatment plan for one versus the other,” said Dr. Chan in an interview.
He noted that it can help to take a patient history that includes the preaccident headache frequency and determine if there was a change in frequency post injury.
Dr. Chan presented the results at the virtual annual meeting of the American Headache Society.
“The results are what one might expect, although we haven’t studied it enough to really know. We haven’t systematically characterized these risk factors for chronic posttraumatic headache very well, [so] it’s useful to have this information,” said Andrew Charles, MD, professor neurology at the University of California, Los Angeles, and director of the UCLA Goldberg Migraine Program, who was not involved in the study. However, Dr. Charles emphasized the need to confirm the results prospectively.
Defining risk factors
The analysis found that a history of migraines, medication overuse, psychological disorders, and new posttraumatic headache–associated comorbidities were all associated with a greater risk for persistent posttraumatic headache. None of those came as a surprise, “but we live in a world where medicine is practiced based on evidence, and providers want to see data to support that. I think that this will help with resource allocation. It’s important to address [a patient’s] overuse of medications, or if they’re having psychological symptoms,” said Dr. Chan.
A total of 150 patients in the analysis had acute posttraumatic headache (mean duration, 0.7 months) while 150 had persistent posttraumatic headache (mean duration, 24 months; P < .00001). Clinical factors associated with risk of persistent headache included a history migraine (relative risk, 2.4; P < .0001), a previous head injury (odds ratio, 5.8; P < .0001), medication overuse (RR, 2.6; P < .0001), preexisting psychological history (OR, 5; P < .0001), and new posttraumatic headache–associated comorbidities, such as vertigo or posttraumatic stress disorder (RR, 9.8; P < .0001).
Identifying patient subgroups
The researchers also identified four subcategories of patients with persistent posttraumatic headache, each with differing risk factors and clinical characteristics. It’s too soon to use these identifiers to make clinical recommendations, but Dr. Chan hopes that further study of these groups will be informative. “It might point us toward (the idea) that each patient population is actually different, even within the chronic persistent posttraumatic headache population, we can’t group them all under the same umbrella term. If we can tease out that a patient has truly had a head injury, but no history of migraine, no overuse of medication, no psychological history, and no other associated symptoms, this would be a very interesting population to study because they would help us understand the pathophysiology [of persistent posttraumatic headache].”
Although the study was conducted by defining persistent posttraumatic headache as lasting at least 3 months, Dr. Chan took issue with that commonly held definition. That choice is arbitrary, with no pathophysiological basis or data to support it, and is based more on clinical trials testing preventative treatments. But when it is used in clinical practice, it can muddy communication with patients. “When this timeline is told to a patient, and when it’s not achieved, they might become disappointed. We should not put too much emphasis on time. Everybody is different,” he said.
The study did not receive any funding. Dr. Chan had no relevant financial disclosures. Dr. Charles consults for consults for Amgen, BioHaven, Eli Lilly, Novartis, and Lundbeck.