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Posttraumatic headache may be associated with reduced pain thresholds



Posttraumatic headache may be associated with quantitative changes in photosensitivity and allodynia, according to results of a pilot study presented at the annual meeting of the American Headache Society. The findings suggest that patients with posttraumatic headache have abnormal, multimodal sensory processing, said Amaal J. Starling, MD, a neurologist at Mayo Clinic in Phoenix.

Dr. Amaal J. Starling, neurologist at Mayo Clinic, Phoenix

Dr. Amaal J. Starling

Mild traumatic brain injury (TBI) is a growing public health problem. Headache is the most common symptom after mild TBI, and often the most debilitating symptom for these patients. No Food and Drug Administration–approved treatments are available for patients with posttraumatic headache, and about three-quarters of these patients report that current treatments bring them no relief.

Identifying novel targets and developing new treatment options will require a deeper understanding of the pathophysiology of posttraumatic headache, said Dr. Starling. She and her colleagues conducted a pilot study to characterize allodynia, cutaneous heat pain thresholds, photophobia, and light-induced pain thresholds objectively in patients with posttraumatic headache, compared with healthy controls.

Participants were exposed to a bright-light stressor

The researchers enrolled 20 patients between ages 18 years and 65 years with posttraumatic headache attributed to mild TBI in their study. They matched these patients by age with 20 healthy controls. Dr. Starling and colleagues evaluated all participants prospectively using the Allodynia Symptom Checklist (ASC-12), Photosensitivity Assessment Questionnaire (PAQ), State-Trait Anxiety Inventory (STAI), and Beck Depression Inventory (BDI).

The investigators performed quantitative sensory testing to measure each participant’s cutaneous forearm heat pain threshold. Using a progressive light stimulation device, they quantified each participant’s light-induced pain threshold. Finally, Dr. Starling and colleagues obtained participants’ cutaneous heat pain thresholds immediately after, 10 minutes after, and 40 minutes after exposing them to a bright-light stressor.

The researchers found no significant differences between groups in age, gender, or race. The population’s average age was 41 years. Approximately 70% of the sample was female. Among participants with posttraumatic headache, the average time since the onset of posttraumatic headache was 46 months. The average number of headache days per month in that group was 17.2, which represented “a significantly high headache burden,” said Dr. Starling. Approximately 80% of patients with posttraumatic headache had headaches with a migraine phenotype.

Patients’ pain thresholds were lower

STAI and BDI scores were significantly higher among patients with posttraumatic headache, compared with controls. Mean PAQ score was 0.62 among patients and 0.24 among controls, representing significantly greater photophobia symptom severity among patients, said Dr. Starling.

Light-induced pain thresholds were significantly lower in patients with posttraumatic headache (median, 90.5 lux), compared with healthy controls (median, 863.5 lux), independent of depression and anxiety. Allodynia symptom severity was significantly higher in patients with posttraumatic headache (mean ASC-12 score, 5.7), compared with controls (mean ASC-12 score, 0.98).

In addition, the mean baseline cutaneous heat pain threshold was 40.8° C in patients with posttraumatic headache and 44.4° C in healthy controls. When participants were subjected to the bright-light stressor, the immediate change in heat pain threshold was significant in patients with posttraumatic headache (−1.9° C), compared with healthy controls. The difference between groups was not significant at 10 and 40 minutes after exposure to the stressor, however. The light intensity inducing moderate pain was 688 lux in patients with posttraumatic headache, compared with 6,000 lux in healthy controls.

“Our next steps are going to be replicating this [study] in a larger population, as well as determining whether any type of intervention would change these different types of sensory sensitivities and thresholds,” said Dr. Starling. She and her colleagues will use this human research model to examine whether posttraumatic headache differs from other headache disorders such as migraine and to examine potential differences between acute and persistent posttraumatic headache.

The study was funded through an intramural Mayo Clinic early career research award.

SOURCE: Starling AJ et al. AHS 2019. Abstract OR14.

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