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IHS Diagnosis ICD-10
1.5.1 Chronic migraine G43.3  


Migraine headache occurring on 15 or more days per month for more than 3 months in the absence of medication overuse.

Diagnostic criteria:

  1. Headache fulfilling criteria C and D for 1.1 Migraine without aura on ≥15 days/month for >3 months
  2. Not attributed to another disorder1;2


  1. History and physical and neurological examinations do not suggest any of the disorders listed in groups 5-12, or history and/or physical and/or neurological examinations do suggest such disorder but it is ruled out by appropriate investigations, or such disorder is present but headache does not occur for the first time in close temporal relation to the disorder.
  2. When medication overuse is present and fulfils criterion B for any of the subforms of 8.2 Medication-overuse headache, it is uncertain whether this criterion B is fulfilled until 2 months after medication has been withdrawn without improvement (see Comments).


Most cases of chronic migraine start as 1.1 Migraine without aura. Therefore, chronicity may be regarded as a complication of episodic migraine.

As chronicity develops, headache tends to lose its attack-wise (episodic) presentation although it has not been clearly demonstrated that this is always so.

When medication overuse is present (ie, fulfilling criterion B for any of the subforms of 8.2 Medication-overuse headache), this is the most likely cause of chronic symptoms. Therefore, the default rule is to code such patients according to the antecedent migraine subtype (usually 1.1 Migraine without aura) plus 1.6.5 Probable chronic migraine plus 8.2.8 Probable medication-overuse headache. When these criteria are still fulfilled 2 months after medication overuse has ceased, 1.5.1 Chronic migraine plus the antecedent migraine subtype should be diagnosed, and 8.2.8 Probable medication-overuse headache discarded. If at any time sooner they are no longer fulfilled, because improvement has occurred, code for 8.2.8 Medication-overuse headache plus the antecedent migraine subtype and discard 1.6.5 Probable chronic migraine.

These criteria require further study.