Subarachnoid hemorrhage overview

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Subarachnoid Hemorrhage Microchapters


Patient Information





Differentiating Subarachnoid Hemorrhage from other Diseases

Epidemiology and Demographics

Risk Factors


Natural History, Complications and Prognosis


History and Symptoms

Physical Examination

Laboratory Findings



Other Imaging Findings

Other Diagnostic Studies


Medical Therapy


Primary Prevention

Secondary Prevention

AHA/ASA Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage (2012)

Risk Factors/Prevention
Natural History/Outcome
Clinical Manifestations/Diagnosis
Medical Measures to Prevent Rebleeding
Surgical and Endovascular Methods
Hospital Characteristics/Systems of Care
Anesthetic Management
Cerebral Vasospasm and DCI
Seizures Associated With aSAH
Medical Complications

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]


Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space surrounding the brain, i.e., the area between the arachnoid membrane and the pia mater. It may arise due to trauma or spontaneously, and is a medical emergency which can lead to death or severe disability even if recognized and treated in an early stage. Treatment is with close observation, medication and early neurosurgical investigations and treatments. Subarachnoid hemorrhage causes 5% of all strokes. 10-15% die before arriving in hospital, and average survival is 50%.[1]


Spontaneous SAH is most often due to rupture of cerebral aneurysms (85%), which are weaknesses in the wall of the arteries of the brain that enlarge. While most cases of SAH are due to bleeding from small aneurysms, there is evidence from research that larger aneurysms (which are rarer) are still more likely to rupture. A further 10% of cases is due to non-aneurysmal perimesencephalic hemorrhage, in which the blood is limited to the area of the midbrain. No aneurysms are generally found. The remaining 5% are due to vasculitic damage to arteries, other disorders affecting the vessels, disorders of the spinal cord blood vessels, and bleeding into various tumors.

Risk Factors

Risk factors for subarachnoid hemorrhage are smoking, hypertension (high blood pressure) and excessive alcohol intake; all are associated with a doubled risk for SAH. Some protection of uncertain significance is conferred by Caucasian ethnicity, hormone replacement therapy, a higher than normal cholesterol and the presence of diabetes mellitus.[2]


History and Symptoms

The classic symptom of subarachnoid hemorrhage is thunderclap headache ("most severe ever" headache developing over seconds to minutes). This headache is often described like being "kicked in the head".[3] 10% of all people with this symptom turn out to have a subarachnoid hemorrhage, and is the only symptom in about a third of all SAH patients. Other presenting features may be vomiting (non-specific), seizures (1 in 14) and meningism. Confusion, decreased level of consciousness or coma may be present. Intraocular hemorrhage (bleeding into the eyeball) may occur. Subhyaloid hemorrhages may be visible on fundoscopy (the hyaloid membrane envelopes the vitreous body).

Laboratory Findings

A lumbar puncture (removal of cerebrospinal fluid/CSF with a needle from the lumbar sac under local anesthetic) will identify another 3% of the cases by demonstrating xanthochromia (yellow appearance of centrifugated fluid) or bilirubin (a breakdown product of hemoglobin) in the CSF.


  1. Van Gijn J, Kerr RS, Rinkel GJ. Subarachnoid haemorrhage. Lancet 2007;369:306-18. PMID 17258671.
  2. Feigin VL, Rinkel GJ, Lawes CM; et al. (2005). "Risk factors for subarachnoid hemorrhage: an updated systematic review of epidemiological studies". Stroke. 36 (12): 2773–80. doi:10.1161/01.STR.0000190838.02954.e8. PMID 16282541.
  3. Longmore, Murray (2007). Oxford Handbook of Clinicial Medicine. Oxford. p. 841. ISBN 0-19-856837-1. Unknown parameter |coauthors= ignored (help)