Headache
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I now have comprehensive content from multiple authoritative textbooks. Here is the full classification overview:
Headache: Classification & Types
The International Headache Society's International Classification of Headache Disorders, 3rd edition (ICHD-3, 2018) is the universally accepted framework. It divides headaches into 4 main parts.
The Big Picture: Primary vs. Secondary
| Feature | Primary Headache | Secondary Headache |
|---|---|---|
| Definition | Headache IS the disorder itself | Headache is a SYMPTOM of an underlying condition |
| Cause | No identifiable structural/organic cause | Caused by an exogenous or identifiable disease |
| Examples | Migraine, tension-type, cluster | Meningitis, SAH, tumor, trauma |
| Prevalence | ~90% of all headaches | ~10% of all headaches |
According to Harrison's Principles of Internal Medicine 22E, tension-type headache accounts for 69% and migraine for 16% of all primary headaches. Among secondary headaches, systemic infection is the most common cause (63%).
PART ONE: Primary Headaches (ICHD-3)
1. Migraine (most disabling primary headache)
| Subtype | Key Features |
|---|---|
| 1.1 Migraine without aura | Unilateral, pulsating, moderate-severe, aggravated by activity; nausea/photophobia |
| 1.2 Migraine with aura | Preceded by reversible neurologic symptoms (visual, sensory, speech) |
| 1.2.2 Brainstem aura | Dysarthria, vertigo, diplopia, ataxia - must have 2+ brainstem symptoms |
| 1.2.3 Hemiplegic migraine | Fully reversible motor weakness; familial (FHM 1-4) or sporadic |
| 1.2.4 Retinal migraine | Monocular visual disturbance with headache |
| 1.3 Chronic migraine | ≥15 headache days/month for >3 months, ≥8 fulfilling migraine criteria |
| 1.4 Complications | Status migrainosus, persistent aura, migrainous infarction, migraine-triggered seizure |
| 1.6 Episodic syndromes | Cyclical vomiting, abdominal migraine, benign paroxysmal vertigo/torticollis |
2. Tension-Type Headache (most common headache overall - 69%)
| Subtype | Frequency |
|---|---|
| 2.1 Infrequent episodic | <1 day/month |
| 2.2 Frequent episodic | 1-14 days/month |
| 2.3 Chronic | ≥15 days/month for >3 months |
- Character: Bilateral, pressing/tightening (non-pulsating), mild-to-moderate intensity
- No nausea, no aggravation by routine activity
- May have photophobia OR phonophobia (not both)
3. Trigeminal Autonomic Cephalalgias (TACs)
| Type | Duration | Key Feature | Gender |
|---|---|---|---|
| Cluster headache | 15-180 min | Unilateral periorbital/temporal; ipsilateral autonomic signs (ptosis, lacrimation, rhinorrhea); extreme severity | M > F (4:1) |
| Paroxysmal hemicrania | 2-30 min | Similar to cluster but more frequent (>5/day); responsive to indomethacin | F > M |
| SUNCT/SUNA | 1-600 sec | Very short, very frequent; conjunctival injection + tearing | M > F |
| Hemicrania continua | Continuous | Unilateral continuous + superimposed severe attacks; indomethacin-responsive | F > M |
4. Other Primary Headache Disorders
- Primary cough headache
- Primary exercise headache
- Primary headache associated with sexual activity (coital cephalalgia)
- Primary thunderclap headache
- Cold-stimulus headache ("ice cream headache")
- External pressure headache
- Primary stabbing headache ("ice pick")
- Nummular headache
- Hypnic headache (wakes patient from sleep)
- New daily persistent headache (NDPH)
PART TWO: Secondary Headaches (ICHD-3 codes 5-12)
These headaches have a temporal relationship to an underlying cause:
| Code | Category | Key Examples |
|---|---|---|
| 5 | Trauma/injury to head or neck | Post-traumatic headache, whiplash |
| 6 | Cranial/cervical vascular disorder | SAH, stroke, carotid dissection, venous sinus thrombosis, RCVS |
| 7 | Nonvascular intracranial disorder | Intracranial hypertension (pseudotumor cerebri), low CSF pressure, neoplasm |
| 8 | Substance or its withdrawal | Medication overuse headache (MOH), alcohol, caffeine withdrawal |
| 9 | Infection | Meningitis, encephalitis, systemic infection |
| 10 | Disorder of homeostasis | Hypertensive headache, hypoxia, dialysis headache |
| 11 | Cranium, neck, eyes, ears, sinuses, teeth | Cervicogenic headache, sinusitis, glaucoma, TMJ disorders |
| 12 | Psychiatric disorder | Somatization, psychotic disorder |
PART THREE: Painful Cranial Neuropathies & Other Facial Pain
| Code | Type |
|---|---|
| 13.1 | Trigeminal neuralgia (tic douloureux) - electric shock-like, triggered by light touch |
| 13.2 | Glossopharyngeal neuralgia |
| 13.4 | Occipital neuralgia |
| 13.7 | Optic neuritis |
| 13.10 | Tolosa-Hunt syndrome (painful ophthalmoplegia) |
| 13.12 | Burning mouth syndrome |
Clinical Memory Aid: Primary vs. Secondary Headache Features
Features suggesting SECONDARY (worrisome) headache - the "SNOOP4" mnemonic:
- S - Systemic symptoms (fever, weight loss, immunosuppression)
- N - Neurologic symptoms or signs
- O - Onset: sudden/thunderclap ("worst headache of my life" = SAH until proven otherwise)
- O - Older age (new headache >50 = consider giant cell arteritis, mass lesion)
- P - Progressive worsening pattern
- P - Postural component (positional headache = think CSF pressure changes)
- P - Precipitated by Valsalva (cough, sneeze, strain = consider Chiari, mass)
- P - Papilledema on exam
Sources: Harrison's Principles of Internal Medicine 22E | Bradley & Daroff's Neurology in Clinical Practice | Neuroanatomy Through Clinical Cases, 3rd Ed | Adams & Victor's Principles of Neurology, 12th Ed
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