Approximately 75% are attributed to "primary" headaches: headache disorder, non-specific headache, idiopathic<unk>  or uncertain headache disorder. The remainder are secondary to a number of conditions, including: * Subarachnoid hemorrhage (10–25% of all cases of<unk>  * Cerebral venous sinus thrombosis * Cervical artery dissection * Hypertensive emergency (severely raised blood pressure) * Spontaneous intracranial hypotension (unexplained low cerebrospinal fluid pressure) * Stroke (headache occurs in about 25% of strokes but usually not<unk>  character) * Retroclival hematoma (hematoma behind the clivus in the skull, usually due to physical trauma but sometimes spontaneous) * Pituitary apoplexy (infarction or hemorrhage of the pituitary gland) * Colloid cyst of the third ventricle * Meningitis, sinusitis * Reversible cerebral vasoconstriction syndrome (previously Call-Fleming syndrome, several subtypes) * Primary cough headache, primary exertional headache, and primary sexual headache The most important of the secondary causes are subarachnoid hemorrhage, cerebral venous sinus thrombosis, and dissection of an artery in the neck. In subarachnoid hemorrhage, there may be syncope (transient loss of consciousness), seizures, meningism (neck pain and stiffness), visual symptoms, and vomiting. 50–70% of people with subarachnoid hemorrhage have an isolated headache without decreased level of consciousness. The headache typically persists for several days. Cerebral venous sinus thrombosis, thrombosis of the veins of the brain, usually causes a headache that reflects raised intracranial pressure and is therefore made worse by anything that makes the pressure rise further, such as coughing. In 2–10% of cases, the headache is of<unk>  character. In most cases there are other neurological abnormalities, such as seizures and weakness of part of the body, but in 15–30% the headache is the only abnormality. Carotid artery dissection and vertebral artery dissection (together cervical artery dissection), in which a tear forms inside the wall of the blood vessels that supply the brain, often causes pain on the affected side of the head or neck. The pain usually precedes other problems that are caused by impaired blood flow through the artery into the brain; these may include visual symptoms, weakness of part of the body, and other abnormalities depending on the vessel affected.
Thunderclap headache
External compression headache
Cold-stimulus headache
Ictal headache
Tension headache
Lupus headache
Vascular headache
Cluster headache