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. Diagnosis
The most important initial investigation is computed tomography of the brain, which is very sensitive for subarachnoid hemorrhage. If this is normal, a lumbar puncture is performed, as a small proportion of SAH is missed on CT and can still be detected as xanthochromia.If both investigations are normal, the specific description of the headache and the presence of other abnormalities may prompt further tests, usually involving magnetic resonance imaging (MRI). Magnetic resonance angiography (MRA) may be useful in identifying problems with the arteries (such as dissection), and magnetic resonance venography (MRV) identifies venous thrombosis. It is not usually necessary to proceed to cerebral angiography, a more precise but invasive investigation of the brains blood vessels, if MRA and MRV are normal. Epidemiology
Incidence of thunderclap headache has been estimated at 43 per 100,000 people every year. Approximately 75% are attributed to "primary" headaches: headache disorder, non-specific headache, idiopathic thunderclap headache or uncertain headache disorder.
The remainder are secondary to a number of conditions, including:
Subarachnoid hemorrhage (10–25% of all cases of thunderclap headache)
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 thunderclap 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 headacheThe 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 thunderclap character.