Your headache symptoms can help your doctor determine its cause and the appropriate treatment. Most headaches aren't the result of a serious illness, but some may result from a life-threatening condition requiring emergency care.
Headaches are generally classified by cause:
A primary headache is caused by overactivity of or problems with pain-sensitive structures in your head. A primary headache isn't a symptom of an underlying disease.
Chemical activity in your brain, the nerves or blood vessels surrounding your skull, or the muscles of your head and neck (or some combination of these factors) can play a role in primary headaches. Some people may also carry genes that make them more likely to develop such headaches.
The most common primary headaches are:
Migraine (with and without aura)
Tension headache (also known as tension-type headache)
Trigeminal autonomic cephalalgia (TAC), such as cluster headache and paroxysmal hemicrania
A few headache patterns also are generally considered types of primary headache, but are less common. These headaches have distinct features, such as an unusual duration or pain associated with a certain activity.
Although generally considered primary, each could be a symptom of an underlying disease. They include:
Chronic daily headaches (for example, chronic migraine, chronic tension-type headache, or hemicranias continua)
Some primary headaches can be triggered by lifestyle factors, including:
Alcohol, particularly red wine
Certain foods, such as processed meats that contain nitrates
Changes in sleep or lack of sleep
A secondary headache is a symptom of a disease that can activate the pain-sensitive nerves of the head. Any number of conditions — varying greatly in severity — may cause secondary headaches.
Possible causes of secondary headaches include:
Arterial tears (carotid or vertebral dissections)
Blood clot (venous thrombosis) within the brain — separate from stroke
Brain aneurysm (a bulge in an artery in your brain)
Brain AVM (brain arteriovenous malformation) — an abnormal formation of brain blood vessels
Carbon monoxide poisoning
Chiari malformation (structural problem at the base of your skull)
Ear infection (middle ear)
Encephalitis (brain inflammation)
Giant cell arteritis (inflammation of the lining of the arteries)
Glaucoma (acute angle closure glaucoma)