A person's head may hurt as the result of a primary headache syndrome or an underlying medical condition. Approximately 90 percent of all headaches are considered primary headaches, according to Cleveland Clinic. Secondary headaches are caused by a variety of conditions, some of which are life-threatening.
Of the types of primary headaches, tension-type headaches are the most common. Migraines and cluster headaches are also classified as primary headache syndromes. Migraines are more common in women, while cluster headaches are more prevalent in men. Cleveland Clinic notes that migraines affect anywhere from 12 to 18 percent of the population. Migraine and cluster headaches may involve the cranial blood vessels and trigeminal nerve.
A secondary headache is a symptom of another medical condition. Some of these conditions are minor and go away within a few days or weeks. They include sinusitis, ear infection and influenza. Some of the conditions responsible for secondary headaches are very serious. Mayo Clinic explains that stroke, meningitis, brain aneurysm or carbon monoxide poisoning may cause this type of headache.
People with primary headache disorders typically experience headaches in a stable pattern. These headaches may be triggered by light, hormonal changes, certain foods or strong odors. A secondary headache may be accompanied by seizures or fainting. Patients may also describe secondary headaches as very abrupt or the worst headaches of their lives, according to the American Headache Society.