Health
Fact-checked

At WiseGEEK, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

Learn more...

What is a Subarachnoid Hemorrhage?

Niki Foster
Niki Foster
Niki Foster
Niki Foster

A subarachnoid hemorrhage is a type of stroke characterized by bleeding in the area between the arachnoid membrane and the pia mater, two membranes that cover the brain. The arachnoid membrane and pia mater are the two innermost meninges, membranes covering the structures of the central nervous system. The pia mater is delicate and adheres to the brain surface, while the arachnoid layer is made of spider-web-like connective tissue and helps cushion the central nervous system. Subarachnoid hemorrhage may be due to head trauma or a ruptured aneurysm in the brain.

The most common symptom of subarachnoid hemorrhage is a sudden, intense headache known as a thunderclap headache. Many patients experience no other symptoms. However, vomiting, delirium, neck stiffness, seizure, coma, and weakness on one side of the body may also accompany subarachnoid hemorrhage.

Cocaine abuse can cause a subarachnoid hemorrhage.
Cocaine abuse can cause a subarachnoid hemorrhage.

In severe cases, brain herniation may occur, resulting in the dilation of one pupil and failure of the pupil to contract in response to light. Intraocular or subhyaloid hemorrhage, bleeding into the eye or its surrounding membrane, respectively, also rarely occurs. Subarachnoid hemorrhage also triggers the release of adrenalin and other hormones, resulting in a spike in blood pressure and increased heartbeat. Cardiac arrhythmia, accumulated fluid in the lungs, and even cardiac arrest can follow.

A subarachnoid hemorrhage may result in coma.
A subarachnoid hemorrhage may result in coma.

Subarachnoid hemorrhage is most often caused by a ruptured cerebral aneurysm, a weakened area in a cerebral artery that becomes enlarged. Other possible causes include other blood vessel disorders, head injury, cocaine abuse, sickle cell anemia, and blood clotting disorders or anticoagulant medication. Subarachnoid hemorrhage is always an emergency and should be treated as soon as possible. Half of all cases are fatal and many people who survive suffer cognitive or neurological impairment.

A subarachnoid hemorrhage may be due to a ruptured aneurysm in the brain.
A subarachnoid hemorrhage may be due to a ruptured aneurysm in the brain.

Subarachnoid hemorrhage patients are stabilized as quickly as possible. Depending upon the severity of the condition, immediate surgery may be required to remove the blood and close off the bleeding site. Other patients are stabilized for a longer period of time and undergo a femoral angiogram to discover the source of the bleeding. The aneurysm may be treated with clipping or coiling. Clipping requires opening the skull and placing clips on the artery around the aneurysm, while coiling is performed by running a catheter through the arteries and placing platinum coils by the aneurysm, causing a blood clot that destroys the aneurysm.

Niki Foster
Niki Foster

In addition to her role as a WiseGEEK editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology.

Learn more...
Niki Foster
Niki Foster

In addition to her role as a WiseGEEK editor, Niki enjoys educating herself about interesting and unusual topics in order to get ideas for her own articles. She is a graduate of UCLA, where she majored in Linguistics and Anthropology.

Learn more...

Discuss this Article

Post your comments
Login:
Forgot password?
Register:
    • Cocaine abuse can cause a subarachnoid hemorrhage.
      By: HamsterMan
      Cocaine abuse can cause a subarachnoid hemorrhage.
    • A subarachnoid hemorrhage may result in coma.
      By: Monkey Business
      A subarachnoid hemorrhage may result in coma.
    • A subarachnoid hemorrhage may be due to a ruptured aneurysm in the brain.
      By: joshya
      A subarachnoid hemorrhage may be due to a ruptured aneurysm in the brain.
    • A subarachnoid hemorrhage may be caused by a head injury.
      By: Alen-D
      A subarachnoid hemorrhage may be caused by a head injury.
    • The most common symptom of a subarachnoid hemorrhage is a thunderclap headache.
      By: vladimirfloyd
      The most common symptom of a subarachnoid hemorrhage is a thunderclap headache.
    • The accumulation of fluid in the lungs may follow a subarachnoid hemorrhage.
      By: decade3d
      The accumulation of fluid in the lungs may follow a subarachnoid hemorrhage.