Headache is the symptom of pain anywhere in the region of the head or neck. It occurs in migraines (sharp, or throbbing pains), tension-type headaches, and cluster headaches. Frequent headaches can affect relationships and employment. There is also an increased risk of depression in those with severe headaches.
Headaches can occur as a result of many conditions whether serious or not. There are a number of different classification systems for headaches. The most well-recognized is that of the International Headache Society. Causes of headaches may include dehydration, fatigue, sleep deprivation, stress, the effects of medications, the effects of recreational drugs, viral infections, loud noises, common colds, head injury, rapid ingestion of a very cold food or beverage, and dental or sinus issues.
Treatment of a headache depends on the underlying cause, but commonly involves pain medication. A headache is one of the most commonly experienced of all physical discomforts.
About half of adults have a headache in a given year. Tension headaches are the most common, affecting about 1.6 billion people (21.8% of the population) followed by migraine headaches which affect about 848 million (11.7%).
There are more than 200 types of headaches. Some are harmless and some are life-threatening. The description of the headache and findings on neurological examination, determine whether additional tests are needed and what treatment is best.
Primary vs. secondary headaches
Headaches are broadly classified as “primary” or “secondary”. Primary headaches are benign, recurrent headaches not caused by underlying disease or structural problems. For example, migraine is a type of primary headache. While primary headaches may cause significant daily pain and disability, they are not dangerous. Secondary headaches are caused by an underlying disease, like an infection, head injury, vascular disorders, brain bleed or tumors. Secondary headaches can be harmless or dangerous. Certain “red flags” or warning signs indicate a secondary headache may be dangerous.
90% of all headaches are primary headaches. Primary headaches usually first start when people are between 20 and 40 years old. The most common types of primary headaches are migraines and tension-type headaches. They have different characteristics. Migraines typically present with pulsing head pain, nausea, photophobia (sensitivity to light) and phonophobia (sensitivity to sound). Tension-type headaches usually present with non-pulsing “bandlike” pressure on both sides of the head, not accompanied by other symptoms. Other very rare types of primary headaches include:
cluster headaches: short episodes (15–180 minutes) of severe pain, usually around one eye, with autonomic symptoms (tearing, red eye, nasal congestion) which occur at the same time every day. Cluster headaches can be treated with triptans and prevented with prednisone, ergotamine or lithium.
trigeminal neuralgia or occipital neuralgia: shooting face pain
hemicrania continua: continuous unilateral pain with episodes of severe pain. Hemicrania continua can be relieved by the medication indomethacin.
primary stabbing headache: recurrent episodes of stabbing “ice pick pain” or “jabs and jolts” for 1 second to several minutes without autonomic symptoms (tearing, red eye, nasal congestion). These headaches can be treated with indomethacin.
primary cough headache: starts suddenly and lasts for several minutes after coughing, sneezing or straining (anything that may increase pressure in the head). Serious causes (see secondary headaches red flag section) must be ruled out before a diagnosis of “benign” primary cough headache can be made.
primary exertional headache: throbbing, pulsatile pain which starts during or after exercising, lasting for 5 minutes to 24 hours. The mechanism behind these headaches is unclear, possibly due to straining causing veins in the head to dilate, causing pain. These headaches can be prevented by not exercising too strenuously and can be treated with medications such as indomethacin.
primary sex headache: dull, bilateral headache that starts during sexual activity and becomes much worse during orgasm. These headaches are thought to be due to lower pressure in the head during sex. It is important to realize that headaches that begin during orgasm may be due to a subarachnoid hemorrhage, so serious causes must be ruled out first. These headaches are treated by advising the person to stop sex if they develop a headache. Medications such as propranolol and diltiazem can also be helpful.
hypnic headache: moderate-severe headache that starts a few hours after falling asleep and lasts 15–30 minutes. The headache may recur several times during night. Hypnic headaches are usually in older women. They may be treated with lithium.
Headaches may be caused by problems elsewhere in the head or neck. Some of these are not harmful, such as cervicogenic headache (pain arising from the neck muscles). Medication overuse headache may occur in those using excessive painkillers for headaches, paradoxically causing worsening headaches.
More serious causes of secondary headaches include:
meningitis: inflammation of the meninges which presents with fever and meningismus, or stiff neck
bleeding inside the brain (intracranial hemorrhage)
subarachnoid hemorrhage (acute, severe headache, stiff neck without fever)
ruptured aneurysm, arteriovenous malformation, intraparenchymal hemorrhage (headache only)
brain tumor: dull headache, worse with exertion and change in position, accompanied by nausea and vomiting. Often, the person will have nausea and vomiting for weeks before the headache starts.
temporal arteritis: inflammatory disease of arteries common in the elderly (average age 70) with fever, headache, weight loss, jaw claudication, tender vessels by the temples, polymyalgia rheumatica
acute closed angle glaucoma (increased pressure in the eyeball): headache that starts with eye pain, blurry vision, associated with nausea and vomiting. On physical exam, the person will have a red eye and a fixed, mid dilated pupil.
Post-ictal headaches: Headaches that happen after a convulsion or other type of seizure, as part of the period after the seizure (the post-ictal state)
Gastrointestinal disorders may cause headaches, including Helicobacter pylori infection, celiac disease, non-celiac gluten sensitivity, irritable bowel syndrome, inflammatory bowel disease, gastroparesis, and hepatobiliary disorders. The treatment of the gastrointestinal disorders may lead to a remission or improvement of headaches.
The brain itself is not sensitive to pain, because it lacks pain receptors. However, several areas of the head and neck do have pain receptors and can thus sense pain. These include the extracranial arteries, middle meningeal artery, large veins, venous sinuses, cranial and spinal nerves, head and neck muscles, the meninges, falx cerebri, parts of the brainstem, eyes, ears, teeth and lining of the mouth. Pial arteries, rather than pial veins are responsible for pain production.
Headaches often result from traction to or irritation of the meninges and blood vessels. The nociceptors may be stimulated by head trauma or tumors and cause headaches. Blood vessel spasms, dilated blood vessels, inflammation or infection of meninges and muscular tension can also stimulate nociceptors and cause pain. Once stimulated, a nociceptor sends a message up the length of the nerve fiber to the nerve cells in the brain, signaling that a part of the body hurts.
Primary headaches are more difficult to understand than secondary headaches. The exact mechanisms which cause migraines, tension headaches and cluster headaches are not known. There have been different hypotheses over time which attempt to explain what happens in the brain to cause these headaches.
Migraines are currently thought to be caused by dysfunction of the nerves in the brain. Previously, migraines were thought to be caused by a primary problem with the blood vessels in the brain. This vascular theory, which was developed in the 20th century by Wolff, suggested that the aura in migraines is caused by constriction of intracranial vessels (vessels inside the brain), and the headache itself is caused by rebound dilation of extracranial vessels (vessels just outside the brain). Dilation of these extracranial blood vessels activates the pain receptors in the surrounding nerves, causing a headache. The vascular theory is no longer accepted. Studies have shown migraine head pain is not accompanied by extracranial vasodilation, but rather only has some mild intracranial vasodilation.
Currently, most specialists think migraines are due to a primary problem with the nerves in the brain. Auras are thought to be caused by a wave of increased activity of neurons in the cerebral cortex (a part of the brain) known as cortical spreading depression followed by a period of depressed activity. Some people think headaches are caused by the activation of sensory nerves which release peptides or serotonin, causing inflammation in arteries, dura and meninges and also cause some vasodilation. Triptans, medications which treat migraines, block serotonin receptors and constrict blood vessels.
People who are more susceptible to experience migraines without headache are those who have a family history of migraines, women, and women who are experiencing hormonal changes or are taking birth control pills or are prescribed hormone replacement therapy.
Tension headaches are thought to be caused by activation of peripheral nerves in the head and neck muscles
Cluster headaches involve overactivation of the trigeminal nerve and hypothalamus in the brain, but the exact cause is unknown.
Approximately 64–77% of people have a headache at some point in their lives. During each year, on average, 46–53% of people have headaches. Most of these headaches are not dangerous. Only approximately 1–5% of people who seek emergency treatment for headaches have a serious underlying cause.
More than 90% of headaches are primary headaches. Most of these primary headaches are tension headaches. Most people with tension headaches have “episodic” tension headaches that come and go. Only 3.3% of adults have chronic tension headaches, with headaches for more than 15 days in a month.
Approximately 12–18% of people in the world have migraines. More women than men experience migraines. In Europe and North America, 5–9% of men experience migraines, while 12–25% of women experience migraines.
Cluster headaches are very rare. They affect only 1–3 per thousand people in the world. Cluster headaches affect approximately three times as many men as women.
The first recorded classification system was published by Aretaeus of Cappadocia, a medical scholar of Greco-Roman antiquity. He made a distinction between three different types of headache: i) cephalalgia, by which he indicates a shortlasting, mild headache; ii) cephalea, referring to a chronic type of headache; and iii) heterocrania, a paroxysmal headache on one side of the head. Another classification system that resembles the modern ones was published by Thomas Willis, in De Cephalalgia in 1672. In 1787 Christian Baur generally divided headaches into idiopathic (primary headaches) and symptomatic (secondary ones), and defined 84 categories.