Conditions InDepth: Headache

Headache refers to head pain. There are several different types of headache, including:

  • Tension
  • Migraine
  • Cluster
  • Sinus

While the precise cause of many headaches remains unknown, several theories exist. The causes of a headache vary depending on the type of headache.

Tension headache refers to head pain associated with stress and muscle contraction. These headaches may occur only occasionally in response to a stressful event. They may also be chronic, occurring frequently. Some tension headaches are nearly constant, with daily pain that may vary in intensity. Tension headaches occur when muscles in the neck, face, and scalp contract and produce pain. The precise cause of this muscle contraction is unknown, but stress, anxiety , depression , eyestrain, and other factors may contribute.

Migraine is a type of recurring headache that involves blood vessels, nerves, and brain chemicals. Sensations such as visual changes, called auras, may precede a migraine. The International Headache Society recently developed a new system that classifies migraines as one of two types: migraine occurring with an aura (formerly called “classic”) and migraine occurring without an aura (formerly called “common"). Migraines may occur several times a week or once every couple of years. Migraines may be so severe that they interfere with your ability to work and carry on normal activities.

An internal or external trigger sets off a process that results in migraine headaches. The exact trigger is often unknown. It is possible that the nervous system reacts to the trigger by conducting electrical activity that spreads across the brain. This electrical activity leads to the release of brain chemicals that make blood vessels swell and become inflamed. Scientists think that it is this inflammatory process that causes the pain and other symptoms of a migraine headache.

Cluster headache is a type of severe, recurring pain that is located on one side of the head. It received its name from the clustering or pattern of frequent headaches that usually occur.

There are two main types of cluster headaches. Either type of headache may convert to the other type:

  • Episodic cluster headaches – (80% of all cases) occur one or more times daily for several months. The headaches then enter a period of remission and come back months or years later.
  • Chronic cluster headaches – (20% of all cases) occur almost daily with, at most, one headache-free week during a year.

The cause of cluster headaches is unknown.

Sinus headaches are associated with inflammation of the sinuses (called sinusitis ). The sinuses are hollow cavities in the skull. Colds and allergies cause inflammation of the nasal passages and can lead to sinusitis. Allergies and viral upper respiratory infections increase nasal secretions and cause tissue lining the nasal passages to swell. This results in nasal congestion and stuffiness. The nasal passages become blocked and normal drainage cannot occur. Secretions that are trapped in the sinuses may become infected with bacteria or, rarely, fungus. The swollen tissues or infection may create pain and pressure.

More than 45 million Americans suffer from regularly occurring headaches. More than 28 million of these people experience migraines.

What are the risk factors for headaches?
What are the symptoms of headaches?
How are headaches diagnosed?
What are the treatments for headaches?
Are there screening tests for headaches?
How can I reduce my risk of getting headaches?
What questions should I ask my healthcare provider?
What is it like to live with migraine headaches?
Where can I get more information about headaches?


National Headache Foundation website. Available at: .

The International Headache Society website. Available at: .

The Vestibular Disorders Association website. Available at: .

International classification of headache disorders. 2nd ed. Cephalalgia. 2004:24(suppl):1-160.

Interantional classification of headache disorders. 2nd ed. (1st revision.) Cephalalgia. 2005;25:460-465

Last reviewed February 2007 by David Juan, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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