Headaches

Primary headaches occur independently and are not caused by another medical condition. It's uncertain what sets the process of a primary headache in motion. A cascade of events that affect blood vessels and nerves inside and outside the head causes pain signals to be sent to the brain. Brain chemicals called neurotransmitters are involved in creating head pain, as are changes in nerve cell activity (called cortical spreading depression). Migraine, cluster, and tension-type headache are the more familiar types of primary headache.

Secondary headaches are symptoms of another health disorder that causes pain-sensitive nerve endings to be pressed on or pulled or pushed out of place. They may result from underlying conditions including fever, infection, medication overuse, stress or emotional conflict, high blood pressure, psychiatric disorders, head injury or trauma, stroke, tumors, and nerve disorders (particularly trigeminal neuralgia, a chronic pain condition that typically affects a major nerve on one side of the jaw or cheek).

Headaches can range in frequency and severity of pain. Some individuals may experience headaches once or twice a year, while others may experience headaches more than 15 days a month. Some headaches may recur or last for weeks at a time. Pain can range from mild to disabling and may be accompanied by symptoms such as nausea or increased sensitivity to noise or light, depending on the type of headache.

Why Headaches Hurt

Information about touch, pain, temperature, and vibration in the head and neck is sent to the brain by the trigeminal nerve, one of 12 pairs of cranial nerves that start at the base of the brain.

The nerve has three branches that conduct sensations from the scalp, the blood vessels inside and outside of the skull, the lining around the brain (the meninges), and the face, mouth, neck, ears, eyes, and throat.

Brain tissue itself lacks pain-sensitive nerves and does not feel pain. Headaches occur when pain-sensitive nerve endings called nociceptors react to headache triggers (such as stress, certain foods or odors, or use of medicines) and send messages through the trigeminal nerve to the thalamus, the brain's "relay station" for pain sensation from all over the body. The thalamus controls the body's sensitivity to light and noise and sends messages to parts of the brain that manage awareness of pain and emotional response to it. Other parts of the brain may also be part of the process, causing nausea, vomiting, diarrhea, trouble concentrating, and other neurological symptoms.

When to See a Doctor

Not all headaches require a physician's attention. But headaches can signal a more serious disorder that requires prompt medical care. Immediately call or see a physician if you or someone you're with experience any of these symptoms:

Sudden, severe headache that may be accompanied by a stiff neck.
Severe headache accompanied by fever, nausea, or vomiting that is not related to another illness.
"First" or "worst" headache, often accompanied by confusion, weakness, double vision, or loss of consciousness.
Headache that worsens over days or weeks or has changed in pattern or behavior.
Recurring headache in children.
Headache following a head injury.
Headache and a loss of sensation or weakness in any part of the body, which could be a sign of a stroke.
Headache associated with convulsions.
Headache associated with shortness of breath.
Two or more headaches a week.
Persistent headache in someone who has been previously headache-free, particularly in someone over age 50.
New headaches in someone with a history of cancer or HIV/AIDS.

Diagnosing Your Headache

How and under what circumstances a person experiences a headache can be key to diagnosing its cause. Keeping a headache journal can help a physician better diagnose your type of headache and determine the best treatment. After each headache, note the time of day when it occurred; its intensity and duration; any sensitivity to light, odors, or sound; activity immediately prior to the headache; use of prescription and nonprescription medicines; amount of sleep the previous night; any stressful or emotional conditions; any influence from weather or daily activity; foods and fluids consumed in the past 24 hours; and any known health conditions at that time. Women should record the days of their menstrual cycles. Include notes about other family members who have a history of headache or other disorder. A pattern may emerge that can be helpful to reducing or preventing headaches.

Once your doctor has reviewed your medical and headache history and conducted a physical and neurological exam, lab screening and diagnostic tests may be ordered to either rule out or identify conditions that might be the cause of your headaches. Blood tests and urinalysis can help diagnose brain or spinal cord infections, blood vessel damage, and toxins that affect the nervous system. Testing a sample of the fluid that surrounds the brain and spinal cord can detect infections, bleeding in the brain (called a brain hemorrhage), and measure any buildup of pressure within the skull. Diagnostic imaging, such as with Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), can detect irregularities in blood vessels and bones, certain brain tumors and cysts, brain damage from head injury, brain hemorrhage, inflammation, infection, and other disorders. Neuroimaging also gives doctors a way to see what's happening in the brain during headache attacks. An electroencephalogram (EEG) measures brain wave activity and can help diagnose brain tumors, seizures, head injury, and inflammation that may lead to headaches.

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