Headache is defined as a pain arising from the head or upper neck of the body. The pain originates from the tissues and structures that surround the skull or the brain because the brain itself has no nerves that give rise to the sensation of pain (pain fibers). The thin layer of tissue (periosteum) that surrounds bones, muscles that encase the skull, sinuses, eyes, and ears, as well as thin tissues that cover the surface of the brain and spinal cord (meninges), arteries, veins, and nerves, all can become inflamed or irritated and cause headache. The pain may be a dull ache, sharp, throbbing, constant, intermittent, mild, or intense.
Primary headaches are stand-alone illnesses caused directly by the overactivity of, or problems with, structures in the head that are pain-sensitive.
This includes the blood vessels, muscles, and nerves of the head and neck. They may also result from changes in chemical activity in the brain.
Common primary headaches include migraines, cluster headaches, and tension headaches.
Secondary headaches are symptoms that happen when another condition stimulates the pain-sensitive nerves of the head. In other words, the headache symptoms can be attributed to another cause.
A wide range of different factors can cause secondary headaches.
- alcohol-induced hangover
- brain tumor
- blood clots
- bleeding in or around the brain
- "brain freeze," or ice-cream headaches
- carbon monoxide poisoning
- teeth-grinding at night
- overuse of pain medication, known as rebound headaches
- panic attacks
The symptoms of a headache can depend on the type.
Tension headaches are the most common form of primary headache. Such headaches normally begin slowly and gradually in the middle of the day.
The person can feel:
- as if they have a tight band around the head
- a constant, dull ache on both sides
- pain spread to or from the neck
Tension-type headaches can be either episodic or chronic. Episodic attacks are usually a few hours in duration, but can last for several days. Chronic headaches occur for 15 or more days a month for a period of at least 3 months.
A migraine headache may cause a pulsating, throbbing pain usually only on one side of the head. The aching may be accompanied by:
- blurred vision
- sensory disturbances known as auras
Migraine is the second most common form of primary headache and can have a significant impact on the life of an individual. According to the WHO, migraine is the sixth highest cause of days lost due to disability worldwide. A migraine can last from a few hours to between 2 and 3 days.
Rebound or medication-overuse headaches stem from an excessive use of medication to treat headache symptoms. They are the most common cause of secondary headaches. They usually begin early in the day and persist throughout the day. They may improve with pain medication, but worsen when its effects wear off.
Along with the headache itself, rebound headaches can cause:
- neck pain
- a feeling of nasal congestion
- reduced sleep quality
Rebound headaches can cause a range of symptoms, and the pain can be different each day.
Cluster headaches usually last between 15 minutes and 3 hours, and they occur suddenly once per day up to eight times per day for a period of weeks to months. In between clusters, there may be no headache symptoms, and this headache-free period can last months to years.
The pain caused by cluster headaches is:
- often described as sharp or burning
- typically located in or around one eye
The affected area may become red and swollen, the eyelid may droop, and the nasal passage on the affected side may become stuffy and runny.