Persistent Headache After Brain Injury May Signal Hidden Brain Dysfunction, Researchers Propose

When someone survives a traumatic brain injury, the medical team’s attention usually focuses on the acute crisis: the Glasgow Coma Scale score, pupillary responses, and what CT or MRI scans reveal about structural damage. Yet for a large proportion of survivors, the most disabling problem arrives later and never fully leaves. Post-traumatic headache, a secondary headache attributed to traumatic injury to the head, is among the most frequent neurological symptoms reported after traumatic brain injury, and when it persists for more than three months it is classified as persistent post-traumatic headache under the International Classification of Headache Disorders. A new opinion article published in Frontiers in Human Neuroscience argues that this stubborn, often overlooked symptom deserves far more scientific attention, not merely as a source of suffering but as a potential clinical window into brain dysfunction that conventional assessments fail to capture.

The article, authored by Denise Franco de Almeida Duarte, Jader Vinicius da Silva Rocha, and colleagues from the Federal University of Espírito Santo, Santa Catarina State University, and the Baylor Scott & White Research Institute, advances a deliberately cautious hypothesis. The researchers propose that when a headache persists months after a traumatic brain injury, its persistence may serve as a clinical signal warranting investigation of ongoing functional or biological abnormalities that are not fully characterized by structural imaging. Crucially, the authors are explicit about what they are not claiming: persistent post-traumatic headache is not proposed as a validated biomarker, a prognostic indicator, or a surrogate measure of any specific underlying mechanism. Instead, they frame it as an observable clinical feature whose persistence should prompt scientists and clinicians to look deeper.

The motivation for this framework comes from a well-recognized gap in traumatic brain injury care. Acute severity measures such as the Glasgow Coma Scale, pupillary reactivity, and structural imaging remain essential for early clinical decisions and are strongly associated with mortality and short-term disability. However, these tools were designed to characterize the initial injury and estimate acute outcomes, and their ability to account for persistent symptoms is limited. Patients with apparently similar initial injury profiles can follow markedly different long-term trajectories, with some experiencing persistent headache, fatigue, cognitive impairment, sleep disturbances, emotional symptoms, and reduced quality of life while others recover more fully. This variability suggests that the extent of the initial injury alone does not capture the biological processes that shape long-term recovery.

One candidate process is neuroinflammation. Traumatic brain injury initiates a cascade of biological events that can extend well beyond the acute phase. Acute activation of microglia and astrocytes, the brain’s resident immune cells, contributes to tissue responses following injury, but experimental studies suggest that sustained or dysregulated inflammatory activity may persist, potentially altering the blood-brain barrier and disrupting neuronal function. Animal work has shown that chronic cortical inflammation mediated by microglia can drive neuronal dysfunction long after the initial trauma, and microglial depletion during the chronic phase of experimental injury has been reported to reduce neurodegeneration and neurological deficits. The authors, however, are careful to note that evidence for persistent neuroinflammation derives predominantly from experimental studies and broader traumatic brain injury populations, and should not be interpreted as proof that neuroinflammation directly causes persistent post-traumatic headache. It provides a biologically plausible framework that requires specific validation in patients with the condition.

Altered pain processing offers a second, and in some respects better-supported, line of evidence. Studies conducted specifically in patients with persistent post-traumatic headache have identified sensory abnormalities, including cephalic allodynia, hyperalgesia, and altered pain modulatory responses, supporting abnormal nociceptive processing in at least a subset of patients. The authors emphasize that central sensitization should be distinguished from nociplastic pain and other forms of altered nociceptive signaling, because these related concepts are not interchangeable. Adding to this picture, experimental work has demonstrated hypersensitivity to calcitonin gene-related peptide, or CGRP, a key molecule in headache biology, in people with post-traumatic headache, lending support to the involvement of CGRP-related nociceptive pathways. Even so, these findings do not establish central sensitization as a universal mechanism or demonstrate a single pathophysiological pathway underlying the condition.

A complementary perspective comes from network neuroscience, which conceptualizes neurological dysfunction as arising from disturbances in interactions among distributed brain networks rather than exclusively from focal structural damage. Traumatic brain injury studies have demonstrated persistent structural network abnormalities during recovery, and neuroimaging studies focused on post-traumatic headache have identified alterations in resting-state functional connectivity involving pain-processing, pain-modulatory, and affective networks. One particularly striking finding involved disruption of functional connectivity between the periaqueductal gray, a brainstem region central to pain modulation, and the default mode network, which predicted the development of persistent post-traumatic headache in patients with mild traumatic brain injury. These findings provide more direct, though still limited, evidence that persistent headache may be associated with measurable alterations in brain network function.

The authors also confront an important alternative explanation: persistent post-traumatic headache may simply reflect a greater overall symptom burden rather than a distinct biological state. Headache commonly co-occurs with sleep disturbance, fatigue, cognitive complaints, anxiety, and depression, and these factors may independently influence both headache persistence and measures of brain function. Pre-existing headache disorders, injury severity, medication use, cervical or extracranial pain generators, and psychological and behavioral factors may further contribute to clinical heterogeneity. Consequently, the presence or severity of persistent headache cannot currently be assumed to indicate the presence, type, or magnitude of persistent brain dysfunction. The co-occurrence of headache with other post-traumatic symptoms may reflect partially overlapping, independent, or mutually reinforcing mechanisms rather than different expressions of a single persistent biological condition.

What distinguishes this opinion article is that it generates testable predictions rather than resting on plausibility alone. If persistent post-traumatic headache is genuinely associated with ongoing post-traumatic dysfunction beyond overall symptom burden, then individuals with the condition should demonstrate reproducible functional or biological abnormalities when compared with appropriately matched traumatic brain injury survivors who do not have persistent headache. These associations should remain detectable after accounting for injury severity, pre-existing headache, headache phenotype, psychological symptoms, sleep disturbance, and medication use. Longitudinal studies should further determine whether changes in headache frequency, intensity, or disability are accompanied by changes in candidate neurophysiological, neuroimaging, or molecular measures. Conversely, the authors note, failure to identify reproducible associations after controlling for confounders would argue against the hypothesis or restrict its applicability to specific patient subgroups.

Testing the hypothesis will require prospective studies that combine detailed headache phenotyping with objective measures of brain function and biology. Quantitative electroencephalography, neuroimaging-derived connectivity measures, and molecular or inflammatory markers are candidate approaches, and artificial intelligence and machine-learning methods may help identify multidimensional patterns or patient phenotypes within these datasets. The authors stress, however, that machine learning is an analytical tool rather than a biological measure, and that no candidate approach can currently be considered a validated biomarker of persistent post-traumatic headache. Their value lies in testing whether persistent headache is systematically associated with measurable patterns of post-traumatic dysfunction beyond headache severity and overall symptom burden. Candidate measures should not be treated as biomarkers until their reproducibility, specificity, longitudinal behavior, and clinical relevance have been established in affected populations.

The practical implications could be significant if the framework survives prospective validation. Traumatic brain injury remains a major cause of death and disability worldwide, particularly among young adults and people of working age, and advances in prehospital care, neurosurgery, and intensive care have improved survival while increasing attention to long-term quality of life. A clinically accessible signal, such as a headache that refuses to resolve, could eventually help identify survivors who might benefit from additional biological assessment, prognostic stratification, or mechanism-based interventions. The authors recommend that future research compare traumatic brain injury survivors with persistent headache, survivors without persistent headache, and, where appropriate, individuals with primary headache disorders, to determine which findings are specific to the post-traumatic condition, to traumatic brain injury more broadly, or to chronic headache irrespective of trauma. Stratification by injury severity will also be necessary, because mechanisms and recovery trajectories may differ between mild and moderate-to-severe injury. For now, the message is one of disciplined optimism: persistent post-traumatic headache may offer a window into the injured brain, but the view through it must still be verified.

Subject of Research: Post-traumatic headache as a clinical indicator of persistent brain dysfunction after traumatic brain injury

Article Title: Post-traumatic headache as a window into persistent brain dysfunction after traumatic brain injury: an opinion article

Article References: Duarte, D. F. D. A., Rocha, J. V. D. S., Dias, F. M. V., Koerich, M. H. A. D. L., Almeida, V. C. R. D., Almeida, R. F. D., Silva Filho, W. G. D., & Arêas, F. Z. D. S. (2026). Post-traumatic headache as a window into persistent brain dysfunction after traumatic brain injury: an opinion article. Frontiers in Human Neuroscience, 20, Article 1946999. https://doi.org/10.3389/fnhum.2026.1946999

Image Credits: AI Generated

DOI: 10.3389/fnhum.2026.1946999

Keywords: post-traumatic headache, traumatic brain injury, neuroinflammation, central sensitization, brain connectivity, CGRP, Glasgow Coma Scale, functional connectivity, biomarkers, network neuroscience, neurorehabilitation, mild TBI