Unruptured cerebral aneurysms
- About unruptured cerebral aneurysms
- Diagnosis of unruptured cerebral aneurysms
- Treatment of unruptured cerebral aneurysms
About unruptured cerebral aneurysms
If you are found to have a cerebral aneurysm
(about unruptured aneurysms)
Cerebral aneurysms and subarachnoid hemorrhage
Cerebral aneurysms may cause subarachnoid hemorrhage
A "cerebral aneurysm" is a swelling in a blood vessel in the brain at the point where it divides into two branches. Cerebral aneurysms may suddenly burst, causing hemorrhage beneath the arachnoid membrane, which covers the surface of the brain; hence the name "subarachnoid hemorrhage." If a cerebral aneurysm ruptures and causes a subarachnoid hemorrhage, one-third of patients die, one-third experience persistent paralysis or some other disability, and only one-third are able to return to their previous condition and lead normal lives. It is thus important to provide treatment before a subarachnoid hemorrhage occurs. Cerebral aneurysms that have not yet burst are called "unruptured cerebral aneurysms. " Most patients with unruptured aneurysms display no symptoms at all until the aneurysm starts to bleed; however, the aneurysm may sometimes compress a cerebral nerve, even in the absence of hemorrhage, causing symptoms such as impaired eye movement. Some individuals are genetically predisposed to cerebral aneurysm, so patients with a family member who has suffered subarachnoid hemorrhage have a higher chance of discovering a cerebral aneurysm in tests compared with others.
[ Human brain observed from its inferior aspect ]
Cerebral arteries are running over the brain surface under the arachnoid membrane.
A cerebral aneurysm arises from the cerebral artery.
[ Subarachnoid hemorrhage: rupture of a cerebral aneurysm ]
Subarachnoid hemorrhage is caused by the rupture of a cerebral aneurysm
between the brain surface and the arachnoid membrane.
Risk of hemorrhage by unruptured cerebral aneurysms
The risk of unruptured cerebral aneurysms rupturing and causing a subarachnoid hemorrhage varies depending on the size of the aneurysm. The following information is taken from results published by the Japan Neurological Society in 2012. The larger a cerebral aneurysm, the greater the chance of its rupturing, and smaller aneurysms are less likely to break. On average, cerebral aneurysms more than 5–7 mm in size rupture and cause hemorrhage at a rate of around 1% (one in 100 people) each year. Aneurysms that are smaller than this have a far lower risk of hemorrhage, while larger ones have a higher risk. The hemorrhage rate also varies depending on the site of the aneurysm. For example, aneurysms of the anterior communicating artery, or those at the bifurcation of the internal carotid artery and the posterior communicating artery, are believed to rupture more easily, even if they are small in size. The risk of rupture also differs depending on the shape of the aneurysm. The rupture rate is approximately 1.6-times higher for those aneurysms showing a small swelling on the lesion wall.
[ A high-risk cerebral aneurysm for bleeding ]