Chronic Migraine
Chronic migraine (CM) affects approximately 1-2% of the general population and represents the progression of episodic migraine into a near-daily headache disorder. It accounts for disproportionate disability, healthcare utilization, and lost productivity compared to episodic migraine. Recognition matters because CM responds to specific therapies — notably onabotulinumtoxinA and CGRP-targeted treatments — that are approved or studied specifically in this population.
Bottom Line
- Definition: ≥15 headache days/month for >3 months, with migraine features on ≥8 days
- Not all chronic daily headache is chronic migraine — rule out medication overuse headache (present in ~50-70% of CM patients), new daily persistent headache, and secondary causes
- OnabotulinumtoxinA is FDA-approved only for CM (≥15 days/month), not episodic migraine
- All CGRP monoclonal antibodies and atogepant (oral CGRP antagonist) have demonstrated efficacy in CM
- Chronification is often reversible — addressing modifiable risk factors and withdrawing overused medications can revert CM to episodic migraine
Diagnostic Criteria (ICHD-3)
- Headache (migraine-like or tension-type-like) on ≥15 days/month for >3 months
- Occurring in a patient who has had at least 5 attacks fulfilling criteria for migraine without aura or migraine with aura
- On ≥8 days/month for >3 months, the headache meets criteria for migraine (with or without aura), or is believed by the patient to be migraine and relieved by a triptan or ergot
- Not better accounted for by another ICHD-3 diagnosis
Practical Diagnostic Points
- The 8-day migraine threshold means not every headache day needs to be a full migraine attack — many days may be mild, tension-type-like headaches
- A headache diary for at least 1 month is essential for accurate diagnosis
- Patients often underreport headache frequency; ask specifically about mild headache days, not just severe attacks
- If the patient uses acute medication on ≥10-15 days/month, code both chronic migraine and medication overuse headache
Episodic vs Chronic: Key Distinctions
| Feature | Episodic Migraine | Chronic Migraine |
|---|---|---|
| Headache days/month | <15 | ≥15 (with ≥8 migraine days) |
| Headache character | Discrete attacks with clear onset/offset | Background headache with superimposed migraine attacks |
| OnabotulinumtoxinA | Not effective (EPISODIC trial negative) | FDA-approved (PREEMPT I & II) |
| CGRP mAbs | Effective | Effective (all four approved agents) |
| Medication overuse | Less common | Present in 50-70% |
| Psychiatric comorbidity | Common | Significantly higher rates of depression, anxiety, and sleep disorders |
Risk Factors for Chronification
Approximately 2.5-3% of episodic migraine patients progress to chronic migraine annually. Identifying and addressing modifiable risk factors is critical to prevention and reversal.
Modifiable
- Medication overuse: The single most important modifiable risk factor. Opioids (≥8 days/month) and barbiturate-containing compounds carry the highest risk. Triptans (≥10 days/month) and simple analgesics (≥15 days/month) also contribute.
- Obesity: Dose-dependent relationship; each 5-unit BMI increase raises CM risk by ~40%
- Caffeine overuse: >400 mg/day associated with chronification
- Sleep disorders: Insomnia, obstructive sleep apnea, and poor sleep hygiene
- Depression and anxiety: Bidirectional relationship; untreated mood disorders perpetuate chronification
- Stressful life events
Non-Modifiable
- Female sex (3:1 ratio)
- Higher baseline attack frequency (>4 attacks/month significantly increases risk)
- Cutaneous allodynia
- Lower socioeconomic status
- Head/neck injury
Medication Overuse Headache Overlap
Medication overuse headache (MOH) and chronic migraine are deeply intertwined. Per ICHD-3, MOH should be diagnosed alongside CM when acute medication use exceeds thresholds:
| Medication | Overuse Threshold | Risk Level |
|---|---|---|
| Opioids | ≥10 days/month | Highest |
| Barbiturate combinations | ≥10 days/month | High |
| Triptans | ≥10 days/month | Moderate |
| Combination analgesics | ≥10 days/month | Moderate |
| Simple analgesics (NSAIDs, acetaminophen) | ≥15 days/month | Lower |
Approach to MOH in Chronic Migraine
- Do not wait to withdraw overused medications before starting preventive therapy — start both simultaneously. The MOTS trial showed no-switching was non-inferior to switching for headache reduction.
- The MOH Treatment Strategies trial found withdrawal + preventive therapy achieved the highest MOH cure rate (97%) compared to preventive alone (74%)
- CGRP mAbs reduce headache frequency regardless of medication overuse status (post-hoc analyses of erenumab, fremanezumab, galcanezumab trials)
- OnabotulinumtoxinA is also effective in CM with MOH without requiring withdrawal first
- Bridge therapy during withdrawal: naproxen 500 mg BID scheduled for 2-4 weeks, or a short steroid taper (prednisone 60 mg x 5 days)
- Counsel patients that headaches typically worsen for 1-2 weeks after withdrawal before improving
Treatment of Chronic Migraine
Traditional Oral Preventives
Oral preventives remain a reasonable first-line option for CM, particularly when cost or access limits CGRP-targeted therapies. However, CM-specific trial data is limited for most agents:
- Topiramate: The only oral preventive with robust CM-specific data; 100 mg/day reduced headache days by ~3 days/month vs placebo
- Amitriptyline: Commonly used; may be particularly helpful when insomnia or tension-type features are prominent
- Propranolol/metoprolol: Useful when hypertension or anxiety are comorbid; less CM-specific evidence
- Valproate: Effective but limited by teratogenicity and weight gain
The HER-MES trial showed erenumab was significantly better tolerated than topiramate (discontinuation due to AEs: 10.6% vs 38.9%) with superior efficacy (≥50% responder rate: 55.4% vs 31.2%). The APPRAISE trial found patients were 6 times more likely to achieve ≥50% migraine day reduction with erenumab vs oral preventives.
OnabotulinumtoxinA (Botox)
- FDA-approved for CM only (not episodic migraine)
- PREEMPT I & PREEMPT 2: 155 units injected across 31 sites in head/neck every 12 weeks. Pooled analysis showed reduction of 8.4 headache days/month vs 6.6 with placebo (difference of ~1.8 days; both groups improved substantially from baseline).
- Benefit accumulates over 2-3 treatment cycles — assess after at least 2 rounds before deeming it a failure
- Can be combined with CGRP mAbs (complementary mechanisms)
CGRP Monoclonal Antibodies in CM
| Agent | CM Trial | MMD Reduction vs Placebo | ≥50% Responder Rate |
|---|---|---|---|
| Erenumab | Phase 2 CM study | -2.5 days (140 mg) | 41% vs 23% |
| Fremanezumab | HALO CM | -1.8 to -2.5 days | 38-41% vs 18% |
| Galcanezumab | REGAIN | -1.9 to -2.1 days | 28% vs 15% |
| Eptinezumab | PROMISE-2 | -2.1 to -2.6 days | 58-61% vs 39% |
Oral CGRP Antagonists (Gepants) for Prevention
Atogepant is the first oral CGRP receptor antagonist approved for migraine prevention, including chronic migraine:
- PROGRESS trial: Atogepant 60 mg once daily reduced monthly migraine days by 7.5 vs 5.1 with placebo (difference -2.4 days) in CM patients over 12 weeks
- ≥50% responder rate: 41% (atogepant 60 mg) vs 26% (placebo)
- Effective regardless of prior preventive failures (2-4 prior failures subgroup showed similar benefit)
- Common adverse events: constipation (7%), nausea (6%), fatigue (5%)
- Advantage: oral daily dosing may appeal to patients who prefer not to inject
- Consideration: requires hepatic monitoring; contraindicated with strong CYP3A4 inhibitors
Rimegepant (75 mg every other day) also has data supporting preventive use in episodic migraine and is used off-label in CM.
Combination Therapy
Combining onabotulinumtoxinA with a CGRP mAb is increasingly common in refractory CM:
- Mechanisms are complementary: onabotulinumtoxinA inhibits CGRP release from nerve terminals; mAbs block circulating CGRP or its receptor
- Retrospective studies suggest additive benefit in patients with inadequate response to either alone
- The COURAGE trial showed high satisfaction (70-73%) when combining ubrogepant (acute) with CGRP mAbs ± onabotulinumtoxinA for CM
Treatment Sequencing: A Practical Approach
- First-line options:
- Second-line:
- If CGRP mAb inadequate after 3 months: Add onabotulinumtoxinA (combination therapy)
- If onabotulinumtoxinA inadequate after 2 cycles: Add CGRP mAb
- Consider switching CGRP mAb class (ligand-targeting to receptor-targeting or vice versa)
- Refractory CM:
- Triple therapy: onabotulinumtoxinA + CGRP mAb + oral preventive (e.g., topiramate)
- Re-evaluate for MOH, psychiatric comorbidity, and secondary causes
- Consider neuromodulation devices as adjunct
- Acute treatment optimization: Use gepants (ubrogepant, rimegepant) or lasmiditan to avoid medication overuse; these can be used safely alongside CGRP mAb prevention
Reversion to Episodic Migraine
Chronic migraine is not a permanent state. With effective treatment and risk factor modification, many patients revert to episodic migraine:
- ~26% of CM patients remit to episodic within 2 years (CaMEO study)
- Predictors of remission: lower baseline headache frequency, absence of MOH, absence of depression, lower BMI
- Active management of modifiable risk factors significantly improves remission rates
Trial Comparison Table
| Trial | Year | Intervention | Population | Key Outcome |
|---|---|---|---|---|
| PREEMPT I | 2010 | OnabotulinumtoxinA 155-195 U | Chronic migraine | -8.4 vs -6.6 headache days/month; p<0.001 |
| PREEMPT 2 | 2010 | OnabotulinumtoxinA 155-195 U | Chronic migraine | -9.0 vs -6.7 headache days/month; p<0.001 |
| HALO CM | 2017 | Fremanezumab 225 mg monthly or 675 mg quarterly | Chronic migraine | -4.6 to -4.9 vs -2.5 MMD; p<0.001 |
| REGAIN | 2018 | Galcanezumab 120 mg or 240 mg | Chronic migraine | -4.8 vs -2.7 MMD; p<0.001 |
| PROMISE-2 | 2020 | Eptinezumab 100 mg or 300 mg IV | Chronic migraine | -7.7 to -8.2 vs -5.6 MMD; p<0.0001 |
| HER-MES | 2022 | Erenumab vs topiramate | Episodic + chronic migraine | Discontinuation: 10.6% vs 38.9%; ≥50% response: 55% vs 31% |
| APPRAISE | 2024 | Erenumab vs oral preventives | Episodic migraine, 1-2 prior failures | 6x more likely to achieve ≥50% MMD reduction |
| MOTS | 2022 | Switching vs no-switching overused meds | CM + medication overuse | No difference in headache days; MOH prevalence lower with switching |
| MOH Treatment Strategies | 2020 | Withdrawal + preventive vs either alone | Medication overuse headache | MOH cure: 97% (combo) vs 74% (preventive) vs 89% (withdrawal) |
References
- Headache Classification Committee of the International Headache Society. The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018;38(1):1-211.
- Dodick DW, et al. OnabotulinumtoxinA for treatment of chronic migraine: pooled results from the double-blind, randomized, placebo-controlled phases of the PREEMPT clinical program (PREEMPT). Headache. 2010;50(6):921-936.
- Silberstein SD, et al. Fremanezumab for the preventive treatment of chronic migraine (HALO CM). N Engl J Med. 2017;377(22):2113-2122.
- Detke HC, et al. Galcanezumab in chronic migraine: the randomized, double-blind, placebo-controlled REGAIN study. Neurology. 2018;91(24):e2211-e2221.
- Lipton RB, et al. Eptinezumab in patients with chronic migraine (PROMISE-2). Neurology. 2020;94(13):e1365-e1377.
- Reuter U, et al. Erenumab versus topiramate for the prevention of migraine (HER-MES). Lancet Neurol. 2022;21(4):341-351.
- Ailani J, et al. Atogepant for the preventive treatment of chronic migraine (PROGRESS). Lancet. 2024.
- Buse DC, et al. Chronic migraine epidemiology and outcomes — CaMEO study. Headache. 2019;59(8):1310-1323.
- Bigal ME, Lipton RB. Modifiable risk factors for migraine progression. Headache. 2006;46(9):1334-1343.