Subarachnoid hemorrhage
Key points
- Subarachnoid hemorrhage is a disorder involving bleeding between the middle membrane covering of the brain and the brain itself, within the cerebrospinal fluid-filled spaces surrounding the brain (also known as the subarachnoid space).
- Subarachnoid hemorrhage occurs in approximately 1 out of 10,000 people.
- A neuromuscular examination usually shows irritated meninges (the tissues covering the brain).
- Treatment goals include lifesaving measures, relief of symptoms, repair of the cause of the bleeding, and prevention of complications.
Alternative names
Hemorrhage - subarachnoid
Definition
Subarachnoid hemorrhage is a disorder involving bleeding between the middle membrane covering of the brain and the brain itself, within the cerebrospinal fluid-filled spaces surrounding the brain (also known as the subarachnoid space).
Causes, incidence, and risk factors
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. In the case of spontaneous subarachnoid hemorrhage, 95% of the cases are a result of a ruptured 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.
Symptoms
- Headache
o Sudden onset
o Described as the "worst ever experience"
o Can be preceded by a popping or snapping sensation in the head
o Pain described as a new type
o Generalized pain, often worse near the back of the head - Nausea and vomiting may accompany the headache
- Decreased consciousness and alertness
o Temporary or progressively worsens to coma and death - Difficulty seeing or changes in vision
o Double vision
o Blind spots
o Temporary loss of vision in one eye - Stiff neck
Written and revised by
David Cohen, M.D.
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