Headache is pain felt in the head, face, scalp, or upper neck. The first clinical job is not to name every subtype. It is to decide whether the headache is a primary headache disorder or a warning sign from another disease.
A primary headache is the disease itself. Migraine, tension-type headache, and cluster headache are primary headaches. A secondary headache is caused by something else, such as bleeding, infection, trauma, tumor, cerebrospinal fluid leakage, medication overuse, or neuralgia (nerve pain). Headache is common, but a small fraction of headaches are dangerous, so a headache that is stronger, new, sudden, or different from the patient’s usual pattern calls for careful evaluation for secondary causes.
This split organizes everything else in the topic: the primary patterns are learned by their features, mechanisms, and treatments, while the secondary causes are learned as alarms to recognize.
Choose a route through the topic
- Headache Classification: the primary-versus-secondary split, the International Classification of Headache Disorders (ICHD) families, and why attack frequency changes management.
- Headache Clinical Presentation: migraine phases, tension-type pressure patterns, cluster and related one-sided autonomic syndromes, and how behavior during the attack helps separate them.
- Headache Pathophysiology: pain-sensitive structures, calcitonin gene-related peptide (CGRP) signaling, cortical spreading depression, triptan mechanisms, and the trigeminal-autonomic reflex.
- Headache Diagnosis: red flags and the SNOOP mnemonic, ICHD criteria for the common patterns, medication-overuse headache, and when to image.
- Headache Secondary Causes: subarachnoid hemorrhage, post-dural puncture headache, tumor and raised pressure, medication overuse, and the giant cell arteritis rule.
- Headache Treatment: acute versus preventive logic, cluster treatment, indomethacin-responsive headaches, medication-overuse withdrawal, and blood patch for spinal fluid leaks.
- Migraine versus Tension-Type versus Cluster Headache: a side-by-side comparison of the three classic primary patterns for rapid bedside separation.
- Headache Epidemiology: how common each headache pattern is, who it affects, and the pre-test probability (how likely a diagnosis is before further testing) behind pattern recognition.
- Headache Prognosis and Complications: chronification through medication overuse, prolonged or infarcting migraine variants, and the complications of a missed secondary cause.
- Headache Trigeminal Neuralgia: shock-like triggerable facial pain, its causes and drug and procedure ladder, and separation from cluster headache.
Start with classification if the names feel disorganized. The sequence then moves from the clinical patterns to the mechanisms behind them, the diagnostic approach and the secondary causes it must exclude, and treatment. The comparison keeps the three primary patterns distinct, epidemiology gives their relative frequency, prognosis covers what changes the outlook, and trigeminal neuralgia closes with facial pain that is not headache.