Subarachnoid hemorrhage

Injury	Disease	Nutrition	Poison

Symptoms	Surgery	Test	Special Topic

Central nervous system

Subarachnoid hemorrhage

Definition:

Subarachnoid hemorrhage is bleedingbetween the middle membrane covering of the brain and the brain itself. Specifically it occurswithin the cerebrospinal fluid-filled spaces surrounding the brain (also known as the subarachnoid space). Patients with subarachnoid hemorrhage usually complain of the"the worst headache of their lives."

Alternative Names:
Hemorrhage - subarachnoid
Causes, incidence, and risk factors:

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Subarachnoid hemorrhage occurs in approximately 1 out of 10,000 people. About 5 to 10% of strokes are caused by subarachnoid hemorrhage. It is most common in people 20 to 60 years old. It is slightly more common in women than men.

The most common cause of any form of subarachnoid hemorrhage is trauma. The most common cause of subarachnoid hemorrhage in young adults is a ruptured cerebral aneurysm.

A small percentage of subarachnoid hemorrhages have a nonaneurysmal pattern to them. They occur spontaneously, and are usually localized to the area in the brain called the perimesencephalic cisterns. The usual outcome for this type of hemorrhage is excellent. Unlike the majority of hemorrhages that are caused by arterial ruptures, this type is thought to be caused by a ruptured vein or capillary.

Subarachnoid hemorrhage occurs when there is bleeding into the space between the brain and the arachnoid membrane (the middle membrane covering the brain). This may occur from a ruptured cerebral aneurysm or arteriovenous malformation, but some result from unidentified causes.

Risks include: disorders associated with aneurysm or weakened blood vessels, including a history of polycystic kidney disease, fibromuscular dysplasia (FMD), other connective tissue disorders, aneurysms in other blood vessels, high blood pressure, and smoking.

The disorder may cause permanent brain damage from ischemia (loss of blood flow) or from the presence of blood in and around the tissues of the brain.

References:

Kirmani JF, Alkawi A, Ahmed S, et al.Endovascular treatment of subarachnoid hemorrhage. Neurol Res. 2005;27 Suppl 1:103-7.

Edlow JA. Diagnosis of subarachnoid hemorrhage. Neurocrit Care. 2005;2(2):99-109.

Bird S. Failure to diagnose: subarachnoid haemorrhage. Aust Fam Physician. 2005 Aug;34(8):682-3.

Marx J. Rosen?s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:2362-2363.