A headache is pain in any part of the head, including the scalp, upper neck, face, and interior of the head. Headaches are one of the most common reasons people visit a doctor.
Headaches interfere with the ability to work and do daily tasks. Some people have frequent headaches. Other people hardly ever have them.
Causes of Headache
Although headaches can be painful and distressing, they are rarely due to a serious condition. Headaches can be divided into two types:
Primary headaches: Not caused by another disorder
Secondary headaches: Caused by another disorder
Primary headache disorders include
Cluster headache Cluster Headaches A cluster headache causes severe pain that is felt at the temple or around the eye on one side of the head and that lasts a relatively short time (usually 30 minutes to 1 hour). It is accompanied... read more and other trigeminal autonomic cephalgias, including chronic paroxysmal hemicrania, hemicrania continua, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing Short-Lasting Unilateral Neuralgiform Headache With Conjunctival Injection and Tearing (SUNCT) Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT), a rare disorder, resembles cluster headaches. It usually causes short but frequent bouts of pain... read more (SUNCT)
Trigeminal autonomic cephalgias are rare.
Secondary headaches may result from disorders of the brain, eyes, nose, throat, sinuses, teeth, jaws, ears, or neck or from a bodywide (systemic) disorder.
Common causes
The two most common causes of headache are primary headaches:
Less common causes
Less often, headaches are due to a less common primary headache disorder called cluster headache Cluster Headaches A cluster headache causes severe pain that is felt at the temple or around the eye on one side of the head and that lasts a relatively short time (usually 30 minutes to 1 hour). It is accompanied... read more or to one of the many secondary headache disorders (see table Some Causes and Features of Headaches Some Causes and Features of Headaches 
). Some secondary headache disorders are serious, particularly those that involve the brain, such as meningitis Introduction to Meningitis Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space). Meningitis can be... read more , a brain tumor Overview of Brain Tumors A brain tumor can be a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body... read more , or bleeding within the brain (intracerebral hemorrhage Intracerebral Hemorrhage An intracerebral hemorrhage is bleeding within the brain. Intracerebral hemorrhage usually results from chronic high blood pressure. The first symptom is often a severe headache. Diagnosis is... read more ).
Fever can cause headaches, as can many infections that do not specifically involve the brain. Such infections include Lyme disease Lyme Disease Lyme disease is a tick-transmitted infection caused by Borrelia species, primarily by Borrelia burgdorferi and sometimes by Borrelia mayonii in the United States. These... read more 
, Rocky Mountain spotted fever Rocky Mountain Spotted Fever (RMSF) Rocky Mountain spotted fever is a potentially fatal rickettsial infection that is transmitted by dog ticks and wood ticks. It causes a rash, headache, and high fever. People become infected... read more 
, and influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more .
Headaches also commonly occur when people stop consuming caffeine or stop taking pain relievers (analgesics) after using them for a long time (called medication overuse headache Medication Overuse Headache A medication overuse (rebound) headache occurs when people who take too many headache drugs have a headache for more than 15 days a month for more than 3 months. Medication overuse headache... read more ).
Contrary to what most people think, eye strain and high blood pressure (except for extremely high blood pressure) do not typically cause headaches.
Evaluation of Headache
Doctors focus on the following:
Determining whether the headache has another cause (that is, whether it is a secondary headache)
Checking for symptoms suggesting that the headache is caused by a serious disorder
If no cause is identified, they focus on identifying which type of primary headache is present.
Warning signs
In people with headaches, certain characteristics are cause for concern:
Changes in sensation or vision, sudden weakness, loss of coordination, seizures, difficulty speaking or understanding speech, or changes in levels of consciousness such as drowsiness or confusion (suggesting a brain disorder)
A fever and a stiff neck that makes lowering the chin to the chest painful and sometimes impossible
A very sudden, severe headache (thunderclap headache)
Tenderness at the temple (as when combing hair) or jaw pain when chewing
The presence of cancer or a disorder that weakens the immune system (immunodeficiency disorder Disorders That Can Cause Immunodeficiency
), such as AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more 
Use of a drug that suppresses the immune system Some Drugs That Can Cause Immunodeficiency
(immunosuppressant)Symptoms that affect the whole body such as fever or weight loss
A headache that progressively worsens (in frequency or severity)
Red eyes and halos seen around lights
Very high blood pressure
Headaches that begin after age 50
When to see a doctor
People who have any warning sign should see a doctor immediately. The presence of a warning sign may suggest that the headaches may be caused by a serious disorder, as for the following:
A severe headache with a fever and a stiff neck: Meningitis Introduction to Meningitis Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space). Meningitis can be... read more —a life-threatening infection of the fluid-filled space between the tissues covering the brain and spinal cord (meninges)
A thunderclap headache: A subarachnoid hemorrhage Subarachnoid Hemorrhage (SAH) A subarachnoid hemorrhage is bleeding into the space (subarachnoid space) between the inner layer (pia mater) and middle layer (arachnoid mater) of the tissues covering the brain (meninges)... read more
(bleeding within the meninges), which is often due to a ruptured aneurysmTenderness at the temple, particularly in older people who have lost weight and have muscle aches: Giant cell arteritis Giant Cell Arteritis Giant cell arteritis is chronic inflammation of large and medium arteries of the head, neck, and upper body. Typically affected are the temporal arteries, which run through the temples and provide... read more
Headaches in people who have cancer or a weakened immune system (due to a disorder or drug): Meningitis or spread of cancer to the brain
If people with none of the above symptoms or characteristics start having headaches that are different from any they have had before or if their usual headaches become unusually severe, they should call their doctor. Depending on their other symptoms, the doctor may ask them to come for an evaluation.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the pain and tests that may need to be done (see table Some Causes and Features of Headaches Some Causes and Features of Headaches ).
Doctors ask about the characteristics of the headache:
How often it occurs
How long it lasts
Where the pain is
How severe is it
What the pain is like (for example, whether it is throbbing, dull, or like a knife)
Whether any symptoms accompany it
How long a sudden headache takes to reach its maximum intensity
What triggers the headache, what makes it worse, and what relieves it
Other questions may include
Whether people have had headaches before
Whether the headaches recur and, if so, when did they start and how often do they occur
Whether the current headache is the same or different from previous headaches
Doctors also ask about risk factors for headache. They include
Whether people take or have stopped taking certain drugs
Whether they have a disorder that may account for the headache
Whether they have family members with severe headaches
Whether they have had a recent head injury
Whether they have had a spinal tap recently
People can think about how to answer the above questions and write the answers down before they go to the doctor. Sometimes doctors ask people to fill out a headache questionnaire that covers most of the relevant questions. People may complete the questionnaire before their visit and bring the results with them. Having this information written down can save time and help guide the evaluation.
A general physical examination is done. It focuses on the head and neck and on brain, spinal cord, and nerve function (neurologic examination Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the nervous system. Examination of the nervous system—the... read more ). An eye examination The Eye Examination A person who has eye symptoms should be checked by a doctor. However, some eye disorders cause few or no symptoms in their early stages, so the eyes should be checked regularly (every 1 to 2... read more is sometimes also done.
Testing
Most people do not need testing. However, if doctors suspect a serious disorder, tests are done. For some suspected disorders, tests are done as soon as possible. In other cases, testing can be done within one or more days.
Magnetic resonance imaging (MRI) and/or magnetic resonance angiography (which provides detailed images of blood vessels) or, if MRI is not available or contraindicated, computed tomography (CT) is done as soon as possible if people have
A thunderclap headache
Changes in levels of consciousness, such as drowsiness or confusion
A fever and a stiff neck that makes lowering the chin to the chest painful and sometimes impossible
Swelling of the optic nerve (papilledema Papilledema Papilledema is a condition in which increased pressure in or around the brain causes the part of the optic nerve inside the eye to swell. Visual symptoms may be fleeting disturbances in vision... read more ), detected by eye examination with an ophthalmoscope
Symptoms that suggest a serious bodywide response to an infection (sepsis Sepsis and Septic Shock Sepsis is a serious bodywide response to bacteremia or another infection plus malfunction or failure of an essential system in the body. Septic shock is life-threatening low blood pressure ... read more ), such as a certain type of rash or shock
Symptoms that suggest a brain disorder, such as changes in sensation or vision (including double vision), sudden weakness, loss of coordination, seizures, or difficulty speaking or understanding speech
Extremely high blood pressure
A head injury causing headache and loss of consciousness
If people have a thunderclap headache, magnetic resonance angiography Magnetic resonance angiography (MRA) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more 
is done immediately.
MRI is done within a day or so if people have conditions such as the following:
Cancer
A weakened immune system (due to a disorder such as AIDS or a drug)
MRI or CT (if MRI is not available or is contraindicated) is done within a few days if people have certain other characteristics, such as the following:
Headaches that begin after age 50
Weight loss
Double vision
A new headache that is worse when the person awakens in the morning or that awakens the person from sleep
An increase in the frequency, duration, or intensity of chronic headaches
A spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more 
(lumbar puncture) is usually done if
Acute meningitis Acute Bacterial Meningitis Acute bacterial meningitis is rapidly developing inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid... read more or encephalitis Encephalitis Encephalitis is inflammation of the brain that occurs when a virus directly infects the brain or when a virus, vaccine, or something else triggers inflammation. The spinal cord may also be involved... read more (a brain infection) is suspected.
People have a thunderclap headache (suggesting subarachnoid hemorrhage Subarachnoid Hemorrhage (SAH) A subarachnoid hemorrhage is bleeding into the space (subarachnoid space) between the inner layer (pia mater) and middle layer (arachnoid mater) of the tissues covering the brain (meninges)... read more
) even when results of CT or MRI or other imaging tests are normal.People have a weakened immune system.
The headache is worsening and doctors suspect idiopathic intracranial hypertension Idiopathic Intracranial Hypertension Idiopathic intracranial hypertension is characterized by increased pressure within the skull (intracranial pressure). What triggers the disorder is unknown. People have daily or near daily headaches... read more or chronic meningitis. Subacute and Chronic Meningitis Subacute meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space) when it develops... read more
Usually, doctors do CT or MRI before the spinal tap if they think that pressure within the skull may be increased—for example, by a mass (such as a tumor, an abscess, or a hematoma). A spinal tap can be dangerous if pressure within the skull is increased. When spinal fluid is removed and pressure within the skull is increased, parts of the brain may suddenly shift downward. If these parts are pressed through the small openings in the tissues that separate the brain into compartments, a life-threatening disorder called brain herniation Herniation: The Brain Under Pressure 
results.
Other tests are done within hours or days, depending on the examination results and the causes that are suspected.
Treatment of Headache
Treatment of headache depends on the cause.
If the headache is a tension headache or if it accompanies a minor viral infection, people can take acetaminophen or a nonsteroidal anti-inflammatory drug Nonsteroidal Anti-Inflammatory Drugs Pain relievers (analgesics) are the main drugs used to treat pain. Doctors choose a pain reliever based on the type and duration of pain and on the drug's likely benefits and risks. Most pain... read more (NSAID) to relieve the pain.
Essentials for Older People
If headaches begin after age 50, doctors usually assume they result from another disorder until proved otherwise. Many disorders that cause headaches, such as giant cell arteritis, brain tumors, and subdural hematomas (which may result from falls), are more common among older people.
Treatment of headaches may be limited in older people. Older people are more likely to have disorders that prevent them from taking some of the drugs used to treat migraines and cluster headaches (triptans and dihydroergotamine—see table Some Drugs Used to Treat Migraines Some Drugs Used to Treat Migraines ). These disorders include angina, coronary artery disease, and uncontrolled high blood pressure.
If older people need to take drugs to treat headaches that can make them feel drowsy, they must be monitored closely.
Key Points
Most headaches do not have a serious cause, particularly if the headaches began at a young age, if they have not changed over time, and if results of the examination are normal.
If headaches occur frequently or if warning signs Warning signs A headache is pain in any part of the head, including the scalp, upper neck, face, and interior of the head. Headaches are one of the most common reasons people visit a doctor. Headaches interfere... read more are present, people should see a doctor.
Most headaches do not require testing.
Doctors can usually determine the type or cause of headaches based on the medical history, symptoms, and results of a physical examination.
If doctors suspect that the cause is a serious disorder (such as a hemorrhage or an infection), MRI is usually done, often immediately.
If doctors suspect meningitis, encephalitis, or a subarachnoid hemorrhage, a spinal tap is done, usually after CT or MRI done to exclude abnormalities that increase pressure within the skull.
