Symptoms of SAH include a severe headache with a rapid onset ("thunderclap headache"), vomiting, confusion or a lowered level of consciousness, and sometimes seizures.[1] The diagnosis is generally confirmed with a CT scan of the head, or occasionally by lumbar puncture. Treatment is by prompt neurosurgery or radiologically guided interventions with medications and other treatments to help prevent recurrence of the bleeding and complications. Surgery for aneurysms was introduced in the 1930s, but since the 1990s many aneurysms are treated by a less invasive procedure called "coiling", which is carried out by instrumentation through large blood vessels.
SAH is a form of stroke and comprises 1-7% of all strokes.[2] It is a medical emergency and can lead to death or severe disability¡ªeven when recognized and treated at an early stage. Up to half of all cases of SAH are fatal and 10¨C15% die before reaching a hospital,[1] and those who survive often have neurological or cognitive impairment.
The classic symptom of subarachnoid hemorrhage is thunderclap headache (a headache described as "like being kicked in the head",[4] or the "worst ever", developing over seconds to minutes). This headache often pulsates towards the occiput (the back of the head).[5] About one-third of sufferers have no symptoms apart from the characteristic headache, and about one in ten people who seek medical care with this symptom are later diagnosed with a subarachnoid hemorrhage.[1] Vomiting may be present, and 1 in 14 have seizures.[1] Confusion, decreased level of consciousness or coma may be present, as may neck stiffness and other signs of meningism.[1] Neck stiffness usually presents six hours after initial onset of SAH.[6] Isolated dilation of a pupil and loss of the pupillary light reflex may reflect brain herniation as a result of rising intracranial pressure (pressure inside the skull).[1] Intraocular hemorrhage (bleeding into the eyeball) may occur in response to the raised pressure: subhyaloid hemorrhage (bleeding under the hyaloid membrane, which envelops the vitreous body of the eye) and vitreous hemorrhage may be visible on fundoscopy. This is known as Terson syndrome (occurring in 3-13% of cases) and is more common in more severe SAH.
Oculomotor nerve abnormalities (affected eye looking downward and outward and inability to lift the eyelid on the same side) or palsy (loss of feeling) may indicate bleeding from the posterior communicating artery. Seizures are more common if the hemorrhage is from an aneurysm; it is otherwise difficult to predict the site and origin of the hemorrhage from the symptoms.[1] SAH in a person known to have fits is often diagnostic of an arteriovenous malformation.
As a result of the bleeding, the body releases large amounts of adrenaline and similar hormones. This leads to a sharp increase in the blood pressure; the heart comes under substantial strain, and neurogenic pulmonary edema (accumulation of fluid in the lungs), cardiac arrhythmias (irregularities in the heart rate and rhythm), electrocardiographic changes (in 27% of cases)[8] and cardiac arrest (in 3% of cases) may occur rapidly after the onset of hemorrhage.
Subarachnoid hemorrhage may also occur in people who have suffered a head injury. Symptoms may include headache, decreased level of consciousness and hemiparesis (weakness of one side of the body). SAH is a frequent occurrence in traumatic brain injury, and carries a poor prognosis if it is associated with deterioration in the level of consciousness.
