There is a threshold in migraine where the condition stops being a series of attacks and becomes a background state. Clinically, that line sits at fifteen or more headache days per month for longer than three months, with at least eight of those days carrying migraine features.
Crossing it changes the nature of the problem — and understanding why explains a great deal about why treatment that once worked stops working.
What changes in a chronified nervous system
Migraine is a neurological disorder, not a vascular one. The older explanation — vessels constrict, then swell, and the swelling hurts — has been superseded. Blood flow studies found that headache often begins while cerebral blood flow is still reduced and does not track the later increase, which is not what a dilation-causes-pain model predicts.
What actually happens involves activation of the trigeminovascular system, release of calcitonin gene-related peptide and related neuropeptides, sterile neurogenic inflammation around the meninges, and sensitization of second-order neurons in the brainstem.
Chronification is that sensitization becoming persistent. Several things shift:
Central sensitization. Second-order neurons in the trigeminal nucleus become progressively easier to activate. The system that once required a substantial trigger now fires on much less.
Cutaneous allodynia. Ordinary sensations become painful — hair brushing, glasses on the nose, a collar. This is a marker of sensitization and it predicts poorer response to acute treatment, because by the time allodynia appears the attack has moved beyond what abortive medication reaches well.
Loss of the between-attack baseline. In episodic migraine the system returns to normal between attacks. In chronic migraine it does not fully reset, so each attack starts from an already-elevated position.
Medication overuse. Frequent use of acute medications can itself drive chronification. This is common, treatable, and important to identify — but withdrawal should be managed with a physician, not attempted alone, as some medications require supervised tapering.
Why the neck matters more here than in episodic migraine
The trigeminal system is not sealed off from the neck.
Sensory fibers from the upper three cervical nerve roots converge with trigeminal fibers onto shared second-order neurons — the trigeminocervical complex. This is established neurophysiology. Dreyfuss, Michaelsen and Fletcher demonstrated the referral by provoking upper cervical joints in healthy volunteers and recording sensation in the occiput and head.
In episodic migraine, ongoing low-level input from the neck may be absorbed without consequence. In a sensitized system it is not. Continuous abnormal input arriving at an already-sensitized relay is exactly the kind of thing that keeps sensitization from resolving.
When the atlas sits misaligned beneath the skull, the mechanoreceptors in that region report from a distorted position, and the postural control centers in the brainstem set muscle tone around distorted information. Seaman and Winterstein described this as dysafferentation — abnormal mechanoreceptor input altering central processing, muscle tone and autonomic regulation. It is a coherent organizing framework that has not been validated in controlled trials.
This is a hypothesis about a maintaining factor, not a claim about cause. Migraine is substantially genetic and the neck does not create it. But maintaining factors matter enormously in a condition defined by failure to return to baseline.
The structural mechanisms, honestly tiered
The myodural bridge — anatomy established, clinical role preliminary. Gary Hack and colleagues described a dense connective tissue connection between the suboccipital muscles and the spinal dura, repeatedly confirmed since. The proposal that sustained suboccipital tension reaches pain-sensitive dural tissue follows logically from the anatomy but has not been demonstrated in controlled trials.
Craniocervical fluid dynamics — preliminary. Scott Rosa has published imaging observations and case series using upright MRI proposing that craniocervical misalignment can obstruct cerebrospinal fluid and venous flow, with correction improving it. This work consists of case series, book chapters and imaging observations rather than controlled trials; the method is proprietary and patented and the imaging technology commercially linked. A 2025 scoping review of weight-bearing MRI identified only nine qualifying studies, mostly small feasibility reports. Interesting and testable; not established.
Flanagan’s choke point — a single-author hypothesis. Michael Flanagan proposed the craniocervical junction as a choke point affecting cerebrospinal fluid circulation, venous drainage, arterial supply and brainstem regulation. Not validated in controlled trials.
What actually helps chronic migraine
Be direct about the hierarchy here. Chronic migraine has genuinely effective medical treatments and they should be pursued first.
See a headache specialist or neurologist. Chronic migraine is undertreated largely because people never get referred. Preventive medications, CGRP-targeting therapies and other options have real trial evidence behind them.
Get medication overuse assessed. This is frequently the reversible piece.
Keep a structured diary — headache days, medication days, sleep, cycle, triggers. This drives treatment decisions more than anything else.
Address sleep, which is bidirectional. Poor sleep worsens migraine and migraine worsens sleep.
Treat the neck as a possible maintaining factor, not the answer. If you have neck pain, restricted movement or tenderness at the base of the skull alongside the headaches, that is worth evaluating — but as one contributor among several.
Upper cervical evaluation
Assessment begins with specific testing to determine whether a misalignment is present at all. Where indicated, cone beam CT three-dimensional imaging locates the exact pattern on that individual’s anatomy. The correction is gentle and precisely directed, made without popping, twisting or yanking the neck, and the approach is oriented toward holding the correction, with follow-up testing determining whether an adjustment is needed rather than delivering one routinely.
Stated plainly: upper cervical care has not been demonstrated superior to other approaches for chronic migraine in head-to-head randomized trials. It is not a substitute for neurological care, and anyone presenting it as one is doing you a disservice.
Medical Disclaimer
This article is educational and does not constitute medical advice, diagnosis or treatment. Chronic migraine warrants medical evaluation. Do not stop or change prescribed medication without physician guidance. Seek emergency care immediately for sudden severe headache unlike any before, sudden vision loss, double vision, slurred speech, facial drooping, one-sided weakness, numbness or difficulty speaking, progressive weakness or loss of coordination, seizure, or headache with fever, neck stiffness and confusion.
Learn more about upper cervical evaluation and care at neckwise.com.
Written by Dr. Drew Hall, Upper Cervical Chiropractor.