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 6.9 vs 5.1 with placebo (difference -1.8 days; the 30 mg twice-daily arm achieved -7.5, difference -2.4) 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 in PROGRESS: constipation (~10%), nausea (~10%); fatigue/somnolence also reported
  • 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:
    • If cost/access is a barrier: Start with topiramate or amitriptyline; expect ~30-40% will respond adequately
    • If prior oral preventive failure or intolerance: Proceed directly to CGRP mAb or atogepant
    • HER-MES and APPRAISE support early use of CGRP mAbs given superior tolerability and efficacy
  • 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

  1. Headache Classification Committee of the International Headache Society. The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018;38(1):1-211.
  2. 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.
  3. Silberstein SD, et al. Fremanezumab for the preventive treatment of chronic migraine (HALO CM). N Engl J Med. 2017;377(22):2113-2122.
  4. Detke HC, et al. Galcanezumab in chronic migraine: the randomized, double-blind, placebo-controlled REGAIN study. Neurology. 2018;91(24):e2211-e2221.
  5. Lipton RB, et al. Eptinezumab in patients with chronic migraine (PROMISE-2). Neurology. 2020;94(13):e1365-e1377.
  6. Reuter U, et al. Erenumab versus topiramate for the prevention of migraine (HER-MES). Lancet Neurol. 2022;21(4):341-351.
  7. Ailani J, et al. Atogepant for the preventive treatment of chronic migraine (PROGRESS). Lancet. 2024.
  8. Buse DC, et al. Chronic migraine epidemiology and outcomes — CaMEO study. Headache. 2019;59(8):1310-1323.
  9. Bigal ME, Lipton RB. Modifiable risk factors for migraine progression. Headache. 2006;46(9):1334-1343.