There are over 200 types of headache, and the causes range from harmless to life-threatening. The description of the headache, together with findings on neurological examination, determines the need for any further investigations and the most appropriate treatment.
The most common types of headache are the "primary headache disorders", such as tension-type headache and migraine. They have typical features; migraine, for example, tends to be pulsating in character, affecting one side of the head, associated with nausea, disabling in severity, and usually lasts between 3 hours and 3 days. Rarer primary headache disorders are trigeminal neuralgia and cluster headache.
Headaches may be caused by problems elsewhere in the head or neck. Some of these are not harmful, such as cervicogenic headache (pain arising from the neck muscles). Medication overuse headache may occur in those using excessive painkillers for headaches, parodoxically causing worsening headaches.
A number of characteristics make it more likely that the headache is due to potentially dangerous secondary causes; some of these may be life-threatening or cause long-term damage.
"Thunderclap headache" may be the only symptom of subarachnoid hemorrhage.Headache with fever may be caused by meningitis, particularly if there is meningism , and confusion may be indicative of encephalitis.Headache that is worsened by straining or a change in position may be caused by increased pressure in the skull; this is often worse in the morning and associated with vomiting. Raised intracranial pressure may be due to brain tumors, idiopathic intracranial hypertension (IIH, more common in younger overweight women) and occasionally cerebral venous sinus thrombosis.Headache together with weakness in part of the body may indicate a stroke or brain tumor. Headache in older people, particularly when associated with visual symptoms or jaw claudication, may indicate giant cell arteritis (GCA), in which the blood vessel wall is inflamed and obstructs blood flow.Angle closure glaucoma may lead to headache, particularly around the eye, as well as visual abnormalities, nausea, vomiting and a red eye with a dilated pupil.