Headache Classification and Diagnosis

Primary Headache Disorders

The American Academy of Neurology and the American Headache Society acknowledge that primary headache disorders, including migraine, tension-type headache, and cluster headache, have no underlying pathologic cause, affecting a significant portion of the population 1, 2, 3
Migraine is characterized by unilateral, pulsatile pain of moderate to severe intensity that worsens with routine physical activity, and must have at least two of the following characteristics: unilateral location, throbbing character, worsening with routine activity, or moderate to severe intensity, according to the American Family Physician 2, 3, 4
Tension-type headache is distinguished by bilateral, pressing or tightening quality of mild to moderate intensity, not aggravated by routine physical activity, and lacks prominent associated symptoms, as noted by the American Family Physician and Nature Reviews Neurology 2, 3, 5
Cluster headache is strictly unilateral, severe to very severe pain lasting 15-180 minutes, requiring five attacks with frequency of 1-8 attacks per day, and is accompanied by ipsilateral cranial autonomic symptoms, as described by the American Family Physician and Nature Reviews Neurology 2, 3, 6
The prevalence of migraine affects 18% of women and 6.5% of men in the United States, while cluster headache affects ~0.1% of the general population, according to the Annals of Internal Medicine and Nature Reviews Neurology 1, 2

The American College of Radiology recognizes that secondary headaches result from underlying pathologic causes, including head and/or neck trauma, cranial or cervical vascular disorders, nonvascular intracranial disorders, substance use or withdrawal, infection, and disorders of homeostasis, as indicated by the Journal of the American College of Radiology 7
Red flags requiring investigation for secondary causes include thunderclap headache, focal neurologic signs or symptoms, unexplained fever, rapidly increasing headache frequency, headache awakening patient from sleep, and history of cancer or immunosuppression, as noted by Nature Reviews Neurology and the American Family Physician 2, 3

The International Headache Society classification system diagnoses headache syndromes, not patients, and a single patient can have more than one type of headache disorder simultaneously, as acknowledged by the Annals of Internal Medicine 1
Validated screening tools include the ID-Migraine questionnaire and the Migraine Screen Questionnaire (MS-Q), which have sensitivity and specificity values, and headache diaries to track frequency, intensity, and associated symptoms, as described by Nature Reviews Neurology 2, 4
Routine neuroimaging is NOT indicated for typical primary headaches without red flags, and when needed, MRI is preferred over CT, as recommended by Nature Reviews Neurology and Praxis Medical Insights 2, 4, 5