What is a headache?

Headache is defined as pain in the head that is located above the eyes or the ears, behind the head (occipital), or in the back of the upper neck. Headache, like chest pain or dizziness, has many causes

What are the causes of headaches?

There are two types of headaches: primary headaches and secondary headaches. Primary headaches are not associated with (caused by) other diseases. Examples of primary headaches are migraine headaches, tension headaches, and cluster headaches. Secondary headaches are caused by associated disease. The associated disease may be minor or serious and life threatening.

How common are primary and secondary headaches?

Tension headaches are the most common type of primary headache; as many as 90% of adults have had or will have tension headaches. Tension headaches are more common among women than men.

Migraine headaches are the second most common type of primary headache. An estimated 28 million people in the United States (about 12% of the population) will experience migraine headaches. Migraine headaches affect children as well as adults. Before puberty, boys and girls are affected equally by migraine headaches, but after puberty, more women than men are affected. An estimated 6% of men and up to 18% of women will experience a migraine headache.

In the United States, migraine headaches often go undiagnosed or are misdiagnosed as tension or sinus headaches. As a result, many migraine sufferers do not receive effective treatment.

Cluster headaches are a rare type primary headache, affecting 0.1% of the population. An estimated 85% of cluster headache sufferers are men. The average age of cluster headache sufferers is 28-30 years, although headaches may begin in childhood.

Secondary headaches have diverse causes, ranging from serious and life threatening conditions such as brain tumors, strokes, meningitis, and subarachnoid hemorrhages to less serious but common conditions such as withdrawal from caffeine and discontinuation of analgesics.
Many people suffer from "mixed" headache disorders in which tension headaches or secondary headaches trigger migraine headaches.

What causes primary headaches?

Migraine headache is caused by a combination of vasodilatation (enlargement of blood vessels) and the release of chemicals from nerve fibers that coil around the blood vessels. During a migraine attack, the temporal artery enlarges. (The temporal artery is an artery that lies on the outside of the skull just under the skin of the temple.) Enlargement of the temporal artery stretches the nerves that coil around the artery and causes the nerves to release chemicals. The chemicals cause inflammation, pain, and further enlargement of the artery. The increasing enlargement of the artery magnifies the pain.
Migraine attacks commonly activate the sympathetic nervous system in the body. The sympathetic nervous system is often thought of as the part of the nervous system that controls primitive responses to stress and pain, the so-called "fight or flight" response. The increased sympathetic nervous activity in the intestine causes nausea, vomiting, and diarrhea. Sympathetic activity also delays emptying of the stomach into the small intestine and thereby prevents oral medications from entering the intestine and being absorbed. The impaired absorption of oral medications is a common reason for the ineffectiveness of medications taken to treat migraine headaches. The increased sympathetic activity also decreases the circulation of blood, and this leads to pallor of the skin as well as cold hands and feet. The increased sympathetic activity also contributes to the sensitivity to light and sound sensitivity as well as blurred vision.

Tension headache does not have a clear cause. Many physicians attribute tension headaches to excess stress or a hectic day. There is also evidence that some tension headaches may have a cause that is similar to the cause of migraine headaches.

Cluster headache also does not have a clear cause, although alcohol and cigarettes can precipitate attacks.

What diseases cause secondary headaches?

Important examples of diseases causing secondary headaches include:

• Tumors in the brain, including tumors that have spread (metastasized) to the brain from another organ such as the lung or breast

• Subdural hematomas, which are collections of blood underneath the dura (the covering of the brain) due to bleeding from ruptured veins. Subdural hematomas typically occur in elderly individuals after a fall or other trauma to the head. Sometimes the fall can precede the visit to the doctor by weeks, and the elderly patients may not even recall the fall. Symptoms of subdural hematomas include chronic headaches, change in personality, and weakness of the extremities.

• Epidural hematomas, which are rapid collections of blood due to the rupture of arteries that run on the inner surface of the skull. Epidural hematomas usually are the result of skull fractures. The typical story is a head injury that causes a concussion with loss of consciousness and a skull fracture. The return of consciousness is followed by the sudden development of coma caused by an expanding hematoma.

• Infections such as meningitis caused by bacteria (meningococcus and pneumococcus), tuberculosis, Lyme disease, or cryptococcus

• Strokes due either to blood clots within the arteries of the brain or rupture of the blood vessels in the brain

• Subarachnoid hemorrhages which are caused by bleeding into the space between the brain and its outer arachnoid lining. The most common source of subarachnoid hemorrhage is an aneurysm, a ballooning of the weakened wall of an artery inside the head.

• Sudden onset of severe high blood pressure. (Chronic mild to moderate high blood pressure is not a common cause of headache).

• Temporal arteritis, a vasculitis (inflammation) of the temporal artery which runs beneath the skin of the temple. Temporal arteritis occurs primarily in older people and may be associated with fatigue, body aches, and anemia. Without proper treatment, temporal arteritis may lead to blindness and strokes.

• Acute angle glaucoma with sudden elevation of pressures inside the eyes

• Infections of the sinuses (sinusitis), ear (otitis), and teeth

• Hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormone

• Repeated carbon monoxide poisoning

• Parkinson's disease

• Medications such as indomethacin, estrogen, progestins, calcium channel blockers (commonly used for treating high blood pressure), and selective serotonin reuptake inhibitors (commonly used to treat depression)

• Overuse of over-the-counter or prescription pain relievers. Overuse of pain relievers causes the pain relievers to become less effective. As the effect of the pain reliever wears off, headaches recur (rebound headache).

• Cardiac ischemia (lack of blood supply to the muscles of the heart caused by coronary artery disease). Although cardiac ischemia is best known as a cause of either heart attacks or angina, it also may cause a headache. The headache may occur with or without the accompanying chest pain of a heart attack or angina. As with angina, in some individuals the headache may occur with exertion and subside with rest.

What are the symptoms of tension headaches?

Tension headaches often begin in the back of the head and upper neck as a band-like tightness or pressure. Tension headaches also are described as a band of pressure encircling the head with the most intense pain over the eyebrows. The pain of tension headaches usually is mild (not disabling) and bilateral (affecting both sides of the head). Tension headaches are not associated with an aura (see below) and are seldom associated with nausea, vomiting, or sensitivity to light and sound. Tension headaches usually occur sporadically (infrequently and without a pattern) but can occur frequently and even daily in some people. Most people are able to function despite their tension headaches.

What is the treatment for tension headaches?

Individuals with occasional tension headaches or mild migraine headaches that do not interfere with daily activities usually medicate themselves with over-the-counter (OTC, non-prescription) pain relievers (analgesics). Many OTC analgesics are available. OTC analgesics have been shown to be safe and effective for short-term relief of headache (as well as muscle aches, pains, menstural cramphs, and fever) when used according to the instructions on their labels.

There are two major classes of OTC analgesics: acetaminophen (Tylenol) and non-steroidal anti-inflammatory drugs (NSAIDs). The two types of NSAIDs are aspirin and non-aspirin. Examples of non-aspirin NSAIDs are ibuprofen (Advil, Nuprin, Motrin IB, and Medipren) and naproxen (Aleve). Some NSAIDs are available by prescription only. Prescription NSAIDs are usually prescribed to treat arthritis and other inflammatory conditions such as bursitis, tendonitis, etc. The difference between OTC and prescription NSAIDs may only be the amount of the active ingredient contained in each pill. For example, OTC naproxen (Aleve) contains 220 mg of naproxen per pill, whereas prescription naproxen (Naprosyn) contains 375 or 500 mg of naproxen per pill.

Acetaminophen reduces pain and fever by acting on pain centers in the brain. Acetaminophen is well tolerated and generally is considered easier on the stomach than NSAIDs. However, acetaminophen can cause severe liver damage in high (toxic) doses or if used on a regular basis over extended periods of time. In individuals who regularly consume moderate or large amounts of alcohol, acetaminophen can cause serious damage to the liver in lower doses that usually are not toxic. Acetaminophen also can damage the kidneys when taken in large doses. Therefore, acetaminophen should not be taken more frequently or in larger doses than recommended on the label.

NSAIDs relieve pain by reducing the inflammation that causes the pain (They are called non-steroidal anti-inflammatory drugs or NSAIDs because they are different from corticosteroids such as prednisone, prednisolone, and cortisone which also reduce inflammation). Corticosteroids, though valuable in reducing inflammation, have predictable and potentially serious side effects, especially when used long-term. NSAIDs do not have the same side effects that corticosteroids have.

Aspirin, Aleve, Motrin, and Advil all are NSAIDs and are similarly effective in relieving pain and fever. The main difference between aspirin and non-aspirin NSAIDs is their effect on platelets. Platelets are small particles in the blood that cause blood clots to form. Aspirin prevents the platelets from forming blood clots. Therefore, aspirin can increase bleeding by preventing blood from clotting though it also can be used therapeutically to prevent clots from causing heart attacks and strokes. The non-aspirin NSAIDs also have anti-platelet effects, but their anti-platelet action does not last as long as aspirin.

Aspirin, acetaminophen, and caffeine also are available combined in OTC analgesics for the treatment of headaches. Examples of such combination analgesics are Pain-aid, Excedrin, Fioricet, and Fiorinal.

Finding an effective analgesic or analgesic combination often is a process of trial and error because individuals respond differently to different analgesics. In general, a person should use the analgesic that has worked in the past. This will increase the likelihood that an analgesic will be effective and decrease the risk of side effects.

There are several precautions that should be observed with OTC analgesics:

• Children and teenagers should not use aspirin for the treatment of headaches, other pain, or fever, because of the risk of developing Reye's Syndrome, a life-threatening neurological disease that can lead to coma and even death.
• Patients with balance disorders or hearing difficulties should avoid using aspirin because aspirin may aggravate these conditions.
• Patients taking blood thinners such as warfarin (Coumadin) should not take aspirin and non-aspirin NSAIDs without a doctor's supervision because they add further to the risk of bleeding that is caused by the blood thinner.
• Patients with active ulcers of the stomach and duodenum should not take aspirin and non-aspirin NSAIDs because they can increase the risk of bleeding from the ulcer and impair healing of the ulcer.
• Patients with advanced liver disease should not take aspirin and non-aspirin NSAIDs because they may impair kidney function. Deterioration of kidney function in these patients can lead to rapid and life-threatening deterioration of their liver disease.
• Patients should not overuse OTC or prescription analgesics. Overuse of analgesics can lead to the development of tolerance (increasing ineffectiveness of the analgesic) and rebound headaches (return of the headache as soon as the effect of the analgesic wears off, usually in the early morning hours). Thus, overuse of analgesics can lead to a vicious cycle of more and more analgesics for headaches that respond less and less to treatment and occur more frequently.
  

How are migraine headaches prevented?

There are two ways to prevent migraine headaches: 1) by avoiding factors ("triggers") that cause the headaches, and 2) by preventing headaches with medications (prophylactic medications). Neither of these preventive strategies is 100% effective. The best one can hope for is to reduce the frequency of headaches.