What are the criteria for chronic migraine headaches and when to consider a trial of prophylactic therapy?

Criteria for Chronic Migraine and Prophylactic Therapy Indications

Chronic migraine is defined as headache occurring on ≥15 days/month for >3 months with migraine features on ≥8 days/month, and prophylactic therapy should be initiated in all patients meeting these criteria. 1

Diagnostic Criteria for Chronic Migraine

According to the International Classification of Headache Disorders (ICHD-3), chronic migraine is diagnosed when:

1. Headache (migraine-like or tension-type-like) occurs on ≥15 days/month for >3 months, fulfilling criteria 2 and 3 1
2. Attacks occur in an individual who has had at least five attacks fulfilling criteria for migraine without aura and/or migraine with aura
3. On ≥8 days/month for >3 months, any of the following criteria are met:
   • Criteria for migraine without aura
   • Criteria for migraine with aura
   • Headache believed by the patient to be migraine at onset and relieved by a triptan or ergot derivative 1

Criteria for Migraine Without Aura

1. At least five attacks fulfilling criteria 2-5
2. Headache attacks lasting 4-72 hours (untreated or unsuccessfully treated)
3. Headache has at least two of these characteristics:
   • Unilateral location
   • Pulsating quality
   • Moderate or severe intensity
   • Aggravation by routine physical activity
4. During headache, at least one of:
   • Nausea and/or vomiting
   • Photophobia and phonophobia 1

Criteria for Migraine With Aura

1. At least two attacks fulfilling criteria 2 and 3
2. One or more fully reversible aura symptoms (visual, sensory, speech/language, motor, brainstem, or retinal)
3. At least three of these characteristics:
   • At least one aura symptom spreads gradually over ≥5 minutes
   • Two or more symptoms occur in succession
   • Each symptom lasts 5-60 minutes
   • At least one symptom is unilateral
   • At least one symptom is positive
   • Aura is accompanied/followed by headache within 60 minutes 1

Indications for Prophylactic Therapy

Prophylactic therapy should be initiated when:

1. Headaches occur on ≥15 days/month for >3 months (chronic migraine) 1, 2
2. Frequent headaches causing significant disability despite acute treatment 3
3. Failure of or contraindication to acute treatments 3
4. Overuse of acute treatments (risk of medication overuse headache) 1, 3
5. Patient preference 3

Practical Assessment Tips

• Ask patients directly: "Do you feel like you have a headache of some type on 15 or more days per month?" 1
• Use a headache diary to accurately track frequency, as patients often underreport milder headaches 1
• Evaluate for medication overuse, which affects up to 73% of chronic migraine patients 1

First-Line Prophylactic Medications

For chronic migraine, evidence-based options include:

1. OnabotulinumtoxinA (Botox) - FDA-approved specifically for chronic migraine 1, 4
2. Topiramate - demonstrated efficacy in randomized controlled trials for chronic migraine 1
3. Other options with varying levels of evidence:
   • Gabapentin
   • Tizanidine
   • Fluoxetine
   • Amitriptyline
   • Valproate 1, 3

Common Pitfalls to Avoid

1. Failing to recognize medication overuse headache, which can perpetuate chronic migraine 2
2. Missing the diagnosis of chronic migraine (only 20% of patients who meet criteria are correctly diagnosed) 2
3. Not addressing modifiable triggers and risk factors:
   • Obesity
   • Caffeine use
   • Obstructive sleep apnea
   • Stress
   • Psychiatric comorbidities 1

Algorithm for Prophylactic Treatment Selection

1. First-line options:

   • For patients with chronic migraine: OnabotulinumtoxinA or topiramate 1, 4
   • For patients with comorbid depression/anxiety: Amitriptyline or venlafaxine 3, 5
   • For patients with hypertension: Beta-blockers (propranolol, metoprolol) 3, 5
   • For patients with high BMI: Topiramate (may assist with weight loss) 5

2. If first-line fails:

   • Try a different medication class
   • Consider combination therapy
   • Refer to headache specialist for refractory cases 1

Remember that chronic migraine is not static - patients may revert to episodic migraine or progress back to chronic migraine over time 1. Regular monitoring and adjustment of prophylactic therapy is essential for optimal management.