Headache is pain experienced in the head. It is a symptom rather than a single disease: it may be the main manifestation of a primary headache disorder, such as migraine, or result from another medical condition. Headaches vary in location, intensity, duration, frequency, and accompanying symptoms. Recurrent headache disorders can cause substantial disability and interfere with everyday activities. (ninds.nih.gov)
Classification
The International Classification of Headache Disorders (ICHD-3), published by the International Headache Society, organizes headaches into primary headache disorders, secondary headache disorders, and painful cranial neuropathies and other facial pains. These categories distinguish headache disorders in their own right from headaches attributed to another cause. (ichd-3.org)
Primary headaches include migraine, tension-type headache, cluster headache, and several less common disorders. Secondary headaches are attributed to conditions such as head or neck injury, vascular disease, infection, altered intracranial pressure, exposure to a substance, or substance withdrawal. Disorders of the eyes, teeth, sinuses, and other head or neck structures can also produce secondary headache or facial pain. (ichd-3.org)
A person may have more than one headache disorder. The classification therefore permits separate diagnoses for distinct headache types, including a primary disorder occurring together with medication-overuse headache. (ichd-3.org)
Pain mechanisms
Headache involves activation or altered processing of pain signals associated with pain-sensitive structures in and around the head. Secondary conditions can stimulate nerve endings through pressure, traction, or other effects. The nervous system processes these signals, producing the experience of head pain. (ninds.nih.gov)
Migraine is a neurobiological disorder involving interactions among nerve signals, chemical messengers, and blood vessels. Its mechanisms include the trigeminovascular system and sensitization of pain pathways; it is not adequately explained as a purely vascular disorder. Tension-type headache also has a neurobiological basis, rather than being simply a psychological response to stress. Its precise mechanisms remain incompletely understood. (ichd-3.org)
Major primary headache disorders
Migraine
Migraine commonly produces attacks of moderate or severe headache, often pulsating and affecting one side of the head, although bilateral pain also occurs. Routine physical activity may aggravate the pain. Associated symptoms include nausea, vomiting, and sensitivity to light and sound. In adults, untreated or unsuccessfully treated migraine headache typically lasts 4–72 hours. (ichd-3.org)
Some attacks involve aura, consisting of transient neurological symptoms, commonly visual or sensory disturbances. Aura usually precedes or accompanies the headache, but can also occur without headache. Migraine may include symptoms before the headache and after it resolves, such as fatigue or changes in activity. (ichd-3.org)
Tension-type headache
Tension-type headache typically causes bilateral, pressing or tightening pain of mild to moderate intensity. Episodic attacks last from 30 minutes to seven days and are not aggravated by ordinary activities such as walking. Nausea and vomiting are absent in the diagnostic criteria for episodic tension-type headache; sensitivity to either light or sound may occur, but not both together. (ichd-3.org)
The disorder is classified into infrequent episodic, frequent episodic, and chronic forms. Tenderness of muscles surrounding the skull may be present, but is not required for diagnosis. (ichd-3.org)
Cluster headache
Cluster headache causes severe or very severe attacks of strictly unilateral pain, usually around or above an eye or in the temple. Untreated attacks typically last 15–180 minutes and may occur from once every other day to eight times daily during an active period. (ichd-3.org)
Accompanying features include tearing, eye redness, nasal congestion, a runny nose, eyelid swelling or drooping, and restlessness or agitation. Symptoms around the eye and nose occur on the same side as the pain. Attacks often recur in bouts lasting weeks or months, separated by remission periods. (ichd-3.org)
Secondary headache and medication overuse
Secondary headache encompasses many different mechanisms and diseases, rather than one characteristic pain pattern. Recognized categories include headache attributed to infection, cranial or cervical vascular disorders, nonvascular intracranial disorders, trauma, and disturbances of homeostasis. Classification depends on evidence linking the headache to the underlying condition, not merely on the coexistence of two diagnoses. (ichd-3.org)
Medication-overuse headache is a secondary disorder occurring in a person with a pre-existing headache disorder who regularly overuses medication intended for acute headache relief. ICHD-3 defines it by headache on at least 15 days per month and medication overuse for more than three months. The medication-use threshold is at least 10 or 15 days per month, depending on the drug class. It usually, but not invariably, resolves after overuse ends. Migraine or tension-type headache can be diagnosed alongside it. (ichd-3.org)
Clinical assessment
Diagnosis rests on the headache history and clinical assessment. Important features include onset, duration, frequency, location, accompanying symptoms, medication use, and changes from the established pattern. A headache diary can document these features over time. (nice.org.uk)
Features relevant to possible secondary causes include sudden onset with rapidly maximal intensity, worsening headache with fever, new neurological deficits, impaired consciousness, recent trauma, positional headache, and a substantial change in headache characteristics. These features inform decisions about further investigation; they do not identify a specific cause by themselves. (nice.org.uk)
Magnetic resonance imaging and computed tomography can investigate suspected structural or vascular causes. Primary headache diagnosis does not ordinarily depend on imaging, and incidental imaging abnormalities may be unrelated to the pain. (nice.org.uk)
Treatment and population burden
Treatment differs by diagnosis and distinguishes acute attack relief from preventive treatment. Established approaches include analgesic medicines for tension-type headache, migraine-specific medicines such as triptans, and oxygen or rapidly delivered triptans for cluster headache. Management also accounts for medication overuse, adverse effects, and coexisting conditions. (nice.org.uk)
Headache disorders are a major public health concern because recurrent pain affects work, education, family life, and quality of life. The World Health Organization identifies under-recognition, limited access to appropriate diagnosis and treatment, and insufficient professional training as barriers to care. The burden extends beyond individual attacks to lost productivity and the continuing effects of recurrent illness. (who.int)
References
- Headache | National Institute of Neurological Disorders and Strokeninds.nih.gov
- Migraine and other headache disorderswho.int
- Classification - ICHD-3ichd-3.org
- How to use the classification - ICHD-3ichd-3.org
- 1 Migraine without aura - ICHD-3ichd-3.org
- Migraine - ICHD-3ichd-3.org
- Tension-type headache (TTH) - ICHD-3ichd-3.org
- 1 Infrequent episodic tension-type headache - ICHD-3ichd-3.org
- 1 Cluster headache - ICHD-3ichd-3.org
- 2 Medication-overuse headache (MOH) - ICHD-3ichd-3.org
- Recommendations: Headaches in over 12s: diagnosis and managementnice.org.uk
- Headaches: Full guidelinenice.org.uk