Post-Traumatic Headaches After Accidents: Causation
A patient who develops headaches after a motor vehicle accident may have more than one potential source of head pain. The collision may produce a traumatic brain injury, whiplash-associated headache, cervical soft-tissue injury, cervicogenic headache, a new post-traumatic headache with migraine-like features, or a significant worsening of a pre-existing migraine disorder. For personal injury attorneys, the important medical question is therefore not simply whether the client reports headaches after the collision. The stronger question is whether the clinical record establishes a medically reasonable connection between the traumatic event, the timing of symptom development, objective examination findings, diagnostic criteria, and the patient’s change from their pre-accident condition.
This guide explains how clinicians evaluate post-injury headaches using accident chronology, previous headache history, neurological and cervical examination, appropriate diagnostic testing, formal headache classifications, and longitudinal documentation.
Consider a patient who experienced two migraines per month before a rear-end collision. Before the crash, those headaches were predictable, usually responded to medication, and rarely interfered with work.
Following the collision, the patient develops neck pain immediately and begins experiencing headaches four or five days each week. The headaches now start near the upper neck, move toward the temple, and are accompanied by nausea, light sensitivity, dizziness, and difficulty concentrating.
Calling every episode simply a “migraine” would miss part of the clinical picture.
Calling everything “whiplash” would also be incomplete.
For an attorney reviewing the medical file, several causation questions should immediately follow:
That distinction is central to a defensible medical-causation analysis.
For a broader discussion of how injury chronology and objective evidence fit together, see Dr. Jimenez’s Accident Injury Medical Causation in El Paso.
Post-traumatic headache is a secondary headache disorder. It may follow mild, moderate, or severe traumatic brain injury.
Under the International Classification of Headache Disorders, Third Edition, or ICHD-3, a headache attributed to traumatic head injury generally has a close temporal relationship to the injury. The standard criteria use headache onset within seven days of the head injury, recovery of consciousness, or discontinuation of medication that prevented the patient from recognizing or reporting the headache.
A headache lasting less than three months is classified as acute. A headache continuing beyond three months is classified as persistent (Headache Classification Committee of the International Headache Society [IHS], 2018).
The classification system also recognizes delayed-onset categories in its appendix, which matters when the history is clinically persuasive but headache onset does not fit neatly within the primary seven-day criterion.
Most importantly, post-traumatic headache does not have to “look different” from migraine. Modern research shows that post-traumatic headache frequently develops migraine-like or tension-type features. A throbbing headache with nausea, light sensitivity, and sound sensitivity after traumatic brain injury can therefore still represent a secondary post-traumatic headache rather than simply a spontaneous recurrence of primary migraine (Díaz & Lehman, 2026).
Attorneys can review Dr. Jimenez’s Traumatic Brain Injuries section for additional clinical context.
Whiplash creates a different mechanism.
The ICHD-3 describes whiplash as a sudden acceleration-deceleration movement of the head resulting in flexion and extension of the neck. Motor vehicle collisions are a common setting.
For an acute headache attributed to whiplash, the patient must have experienced whiplash associated with neck pain and/or headache, and the headache ordinarily develops within seven days. Persistent headache attributed to whiplash continues longer than three months (IHS, 2018).
This creates an important medical-legal distinction.
A patient does not necessarily need to strike their head against the steering wheel, window, or headrest to develop a trauma-related headache. Rapid acceleration-deceleration can injure cervical muscles, ligaments, joints, discs, and related pain-generating structures without a direct head impact.
Document the collision mechanism rather than reducing it to “car accident.”
Relevant details can include:
The site’s Whiplash Injuries resource and Collision & Injury Dynamics section provide useful background on these mechanisms.
A pre-existing migraine diagnosis does not automatically defeat accident causation.
Instead, the clinician should determine the patient’s baseline.
ICHD-3 specifically recognizes circumstances in which a pre-existing primary headache disorder becomes significantly worse in close temporal relationship to a condition capable of producing headache. The classification notes that significant worsening usually means at least a two-fold increase in headache frequency and/or severity (IHS, 2018).
This is why the pre-accident record can be so valuable.
Suppose a patient had:
Before the crash:
Two migraine days per month, severity 5/10, no missed work.
After the crash:
Twelve headache days per month, severity commonly 7-9/10, new cervical pain, dizziness, photophobia, sleep disturbance, and missed work.
The fact that migraine existed before the collision does not answer the causation question. The relevant inquiry becomes whether the collision caused a documented aggravation or produced a superimposed secondary post-traumatic headache.
A strong record compares the patient’s pre-injury and post-injury state rather than pretending the prior disorder did not exist.
Dr. Jimenez’s Headache and Migraine Treatment resource discusses migraine, cervicogenic headache, and post-whiplash headache patterns in greater detail.
A motor vehicle collision can injure the cervical spine while simultaneously producing neurological symptoms associated with concussion.
These conditions are not mutually exclusive.
A patient may have:
A cervicogenic headache is attributed to a disorder of the cervical spine or its associated soft tissues.
ICHD-3 emphasizes that causation should not be based on imaging alone. Evidence may include a temporal relationship between the cervical disorder and headache, improvement of headache as the cervical disorder improves, reduced cervical range of motion that provokes headache, or response to diagnostic blockade of a cervical structure (IHS, 2018).
That limitation matters in personal injury cases because degenerative abnormalities are common.
An MRI showing cervical degeneration does not independently establish that degeneration caused the patient’s post-accident headaches. Conversely, pre-existing degeneration does not automatically eliminate the possibility that trauma aggravated a previously asymptomatic or stable condition.
Clinical correlation remains essential.
For attorneys, one of the most valuable sections of a medical report is often the timeline.
A useful chronology identifies:
Before the accident: previous migraine frequency, neck symptoms, neurological history, medications, prior accidents, and functional status.
At the accident: collision mechanics, head position, direct impact, acceleration-deceleration movement, loss or alteration of consciousness, confusion, amnesia, dizziness, nausea, neck pain, and immediate headache.
Hours to days later: headache onset, sleep disturbance, photophobia, phonophobia, concentration problems, dizziness, neck stiffness, and changes in activity tolerance.
During recovery: headache frequency, severity, duration, triggers, functional limitations, examination changes, response to treatment, and progression toward baseline.
Temporal association by itself does not prove causation. But when chronology aligns with a recognized injury mechanism and is supported by clinical findings, it becomes an important component of medical reasoning.
Do not evaluate post-injury headache only by asking, “How bad is your pain?”
The examination may include assessment of:
Mild traumatic brain injury can produce headaches along with dizziness, balance problems, nausea, light or noise sensitivity, cognitive slowing, memory problems, and sleep disturbance. Some symptoms occur immediately, while others may become apparent hours or days later (Centers for Disease Control and Prevention [CDC], 2025).
A normal neurological examination does not necessarily exclude mild traumatic brain injury, but abnormal neurological findings can substantially change the urgency and scope of diagnostic investigation.
Not every patient with post-accident headache needs every available imaging study.
Testing should be driven by the history, examination, red flags, and suspected diagnosis.
Post-traumatic headache itself is considered a red-flag context when deciding whether imaging is appropriate. The American College of Radiology identifies MRI of the head or noncontrast CT of the head as usually appropriate initial imaging options in patients with headache accompanied by red-flag features, including post-traumatic onset (American College of Radiology, 2022).
Depending on the circumstances, clinicians may also investigate the cervical spine or vascular structures.
A sudden unusual headache or neck pain associated with focal neurological deficits deserves particularly careful evaluation because vascular disorders such as cervical carotid or vertebral artery dissection must be considered in the appropriate clinical setting.
Imaging should support clinical decision-making—not replace it.
A defensible personal injury record should show the reasoning behind the diagnosis.
Important elements include:
Electronic notes can be organized so that attorneys, insurers, and claims-review systems—including systems using Colossus-style data review—can identify objective findings and functional change. However, never alter the clinical record to produce a desired insurance score. Documentation should reflect what the patient reported, what the clinician actually observed, and why the resulting diagnosis and care plan were medically reasonable.
The Initial Chiropractic Examination page illustrates the importance of history, examination, diagnosis, and individualized clinical planning.
The practice is one of the few El Paso clinics bringing medical direction, chiropractic care, rehabilitation, neurological and musculoskeletal assessment, diagnostic coordination, acupuncture, and electroacupuncture into a coordinated injury-care environment. The clinic’s website identifies Dr. Cardenas as medical director and collaborative physician and describes its multidisciplinary injury-recovery model.
Once the clinic has appropriately evaluated dangerous neurological or vascular conditions, it may consider conservative care based on the patient’s diagnosis. Chiropractic treatment can focus on restoring cervical mechanics and mobility; rehabilitation can rebuild movement and physical tolerance; and acupuncture or electroacupuncture may be incorporated for symptom management when clinically appropriate. The goals are practical: reduced pain, better mobility, improved sleep, restored physical function, and support for nervous-system recovery, coordinated with the patient’s existing physicians and specialists.
The patient remains the informed decision-maker throughout the process.
For attorneys, “Did the client have headaches after the accident?” is rarely enough.
The stronger inquiry is:
What headache disorder is present, what changed from the patient’s pre-accident baseline, when did that change occur, what trauma mechanism could reasonably produce it, what objective findings support or challenge the diagnosis, and what competing causes were considered?
A well-supported causation opinion does not require pretending that every symptom is new.
It requires accurately separating:
That distinction protects both the patient’s medical interests and the integrity of the legal record.
Clinical causation and legal proximate causation are related but not identical. The healthcare provider’s role is to explain the medical relationship between the traumatic event, the patient’s condition, and the available evidence. The attorney, and ultimately the legal fact-finder, determines how that evidence satisfies the applicable legal standard.
American College of Radiology. (2022). ACR Appropriateness Criteria®: Headache.
Centers for Disease Control and Prevention. (2025). Symptoms of mild TBI and concussion.
Díaz, P. G., & Lehman, A. B. (2026). Phenotype-guided management of post-traumatic headache: An update on pathophysiology and treatment. Current Pain and Headache Reports, 30(1), 98. https://doi.org/10.1007/s11916-026-01535-y
Headache Classification Committee of the International Headache Society. (2018). The International Classification of Headache Disorders, 3rd edition. Cephalalgia, 38(1), 1-211.
Schwedt, T. J. (2024). Posttraumatic headache. Continuum, 30(2), 411-424. https://doi.org/10.1212/CON.0000000000001410
Medical-Legal Disclaimer: This article is intended for educational purposes and does not establish a diagnosis, treatment recommendation, standard of care, or legal opinion in an individual case. Medical causation should be determined from the complete history, examination, diagnostic evidence, and applicable clinical criteria.