What Is a Headache?

A headache is the sensation of pain in the head, areas of the face, and sometimes the upper neck. The brain itself is not sensitive to pain, even though it may feel that way during a severe headache. The actual structures that are sensitive to pain include facial bones, eyes, nose, ears and mouth. During a headache, only part of the head may feel pain, such as the temples, or the whole head may be affected. Pain may be severe, moderate, or minor, and it may be described as sharp or dull. With some headaches, other symptoms may occur, such as light sensitivity and nausea.

While scientists do understand what triggers headaches, the exact molecular basis of headaches as a disease is not understood completely. It may be a dysfunction of the neurotransmitter serotonin. According to this theory, an abnormal release of the serotonin causes a shift in blood flow from the arteries to the veins, which then causes changes in the nerves and nerve centers, resulting in a headache.

Depending on the cause and type of headache, different areas of the head will be affected by pain. Vascular headaches, such as migraines, cause pain in the very sensitive large blood vessels in the head. Problems with the jaws and teeth also may cause pain in these areas and thus cause a headache. Muscle contraction or tension headaches result from neck spasms, thus pain from these headaches will include the neck. Headaches also may be caused by eyestrain or stuffed sinuses.

Brain aneurysms may cause sudden and intense head pain. Bacterial meningitis also may cause intense pain, usually in reaction to light, resulting from an infection of the meninges, the tissue surrounding brain nerves and the spinal cord. Brain tumors and head and neck trauma also cause head pain. Withdrawal from over-the-counter and prescription drugs may result in head pain. People who overuse headache medications may experience rebound headaches.

Headaches tend to run in families, so researchers do believe there is a genetic component. The majority of Americans, over 70 percent, have experienced some kind of headache during the past year. Over 40 million Americans experience headaches on a regular basis.

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