What is the classification of headaches according to the International Classification of Headache Disorders (ICHD)?

Classification of Headache According to ICHD

The International Classification of Headache Disorders (ICHD-3) divides all headaches into three major categories: primary headaches (where no underlying structural cause exists), secondary headaches (caused by an underlying condition), and cranial neuralgias, central and primary facial pain, and other headaches. 1

Primary Headache Disorders

Primary headaches represent the majority of headache presentations in clinical practice (>90%) and include the following main types: 2

Migraine

Migraine without aura requires at least 5 attacks meeting all of the following criteria: 1, 3

• Duration: 4-72 hours when untreated or unsuccessfully treated 1
• At least two of these characteristics:
  • Unilateral location 1
  • Pulsating quality 1
  • Moderate or severe pain intensity 1
  • Aggravation by or causing avoidance of routine physical activity 1
• At least one of the following:
  • Nausea and/or vomiting 1
  • Both photophobia and phonophobia 1
• Not better accounted for by another ICHD-3 diagnosis 1

Migraine with aura requires at least 2 attacks with: 1, 3

• One or more fully reversible aura symptoms (visual, sensory, speech/language, motor, brainstem, or retinal) 1
• At least three of these six characteristics:
  • At least one aura symptom spreads gradually over ≥5 minutes 1
  • Two or more aura symptoms occur in succession 1
  • Each individual aura symptom lasts 5-60 minutes 1
  • At least one aura symptom is unilateral 1
  • At least one aura symptom is positive 1
  • The aura is accompanied with or followed by headache within 60 minutes 1

Chronic migraine is diagnosed when: 1, 4

• Headache occurs on ≥15 days/month for >3 months 1
• The patient has had at least 5 attacks fulfilling criteria for migraine without aura and/or migraine with aura 1
• On ≥8 days/month for >3 months, headache meets migraine criteria or is believed by the patient to be migraine at onset and relieved by a triptan or ergot derivative 1

Tension-Type Headache

Tension-type headache is characterized by: 1, 4

• Bilateral location with pressing/tightening (non-pulsatile) quality 1
• Mild to moderate intensity not aggravated by routine physical activity 1
• Absence of nausea or vomiting (anorexia may be present) 1
• Absence of both photophobia and phonophobia (one may be present) 1

Cluster Headache

Cluster headache requires 5 attacks with: 1

• Severe unilateral orbital, supraorbital, or temporal pain lasting 15-180 minutes untreated 1
• Frequency of one to eight attacks on any given day 1
• At least one of the following ipsilateral autonomic features:
  • Lacrimation 1
  • Nasal congestion or rhinorrhea 1
  • Forehead and/or facial sweating 1
  • Miosis, ptosis, or eyelid edema 1

Vestibular Migraine

Vestibular migraine requires: 3

• At least 5 episodes with vestibular symptoms of moderate/severe intensity lasting 5 minutes to 72 hours 3
• Current or previous history of migraine with or without aura 3
• One or more migraine features with at least 50% of vestibular episodes (headache with migraine characteristics, photophobia and phonophobia, or visual aura) 3

Secondary Headache Disorders

Secondary headaches account for <10% of headaches in practice and result from an underlying condition that can sometimes be life-threatening. 2 The ICHD-3 includes numerous secondary headache categories based on their etiology. 5, 6

Medication-Overuse Headache

This important secondary headache requires: 1

• Headache on ≥15 days/month in an individual with a pre-existing headache disorder 1
• Regular overuse for >3 months of acute headache medication: 1
  • Non-opioid analgesics on ≥15 days/month for ≥3 months, OR 1
  • Any other acute medication or combination on ≥10 days/month for ≥3 months 1

Cranial Neuralgias and Other Headaches

The third major category includes cranial neuralgias, central and primary facial pain, and other headache disorders that don't fit into the primary or secondary categories. 1, 5

Key Classification Principles

The ICHD classification is phenomenological rather than etiological, meaning it classifies based on headache features rather than underlying causes. 5 Importantly, the classification categorizes the headache disorder itself, not the patient—therefore, a single patient can have multiple concurrent headache diagnoses. 5

The ICHD-3 includes 14 different headache groups and more than 170 specific headache types, making it the most comprehensive headache classification system available. 5, 7 The classification prioritizes specificity over sensitivity, with "probable" diagnoses used when all criteria aren't fully met. 3