This form of hemorrhage has a slightly different cause, although the results are as disastrous as other forms of CVA. Near the base of the brain is an arterial ring called the “Circle of Willis”. Frequently, a small bulge may occur on this particular artery, called a “berry aneurysm.” It is relatively common for this to rupture suddenly (for similar reasons as with any rupturing, weakened vessel wall). However, instead of rupturing into the brain substance, being on the outer part of the brain, it may rupture into the space outside the actual brain substance. Alternatively, it may gradually exude blood and leak over a period of time, thus releasing irritating blood into the cerebrospinal fluid that bathes the brain.
The patient may suffer from recurring headaches, or the person may have been entirely free from them, the incident heralding the first sign that all is not well. Intense headache is rapidly followed by coma. About thirty percent of patients die in the first attack, and death may ensue within twenty-four to thirty-six hours or even later on during the first fortnight if fresh bleeding occurs from the rupture.
However, the patient may regain consciousness and start to improve. Severe headaches may persist for two to three weeks. Slow physical and intellectual recovery may gradually follow. As with any coma, the patient is treated as a medical emergency, although there are certain features indicating this type of disorder (after investigatory tests).
If this is suspected, then the patient may be considered to be a neurosurgical emergency for surgical intervention may save the patient from further attacks and may prolong life and bring it back to reasonable normality. However, experience shows that a high proportion of survivors have another attack (from a fresh site) within two years.