Brain Aneurysm (2003)

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Alter­nate name: Cere­bral Aneurysm


The term Brain aneurysm(also called a cere­bral aneurysm) refers to a con­di­tion where a weak­ness in the wall of a blood ves­sel (artery) in the brain causes the ves­sel to bal­loon out­wards. This bal­loon­ing leads to a stretch­ing and thin­ning of the artery wall over time. Aneurysms may form in dif­fer­ent parts of the body but a brain aneurysm is located inside the head, in an artery that sup­plies the brain with blood.



The aneurysm can look like:

  1. a sin­gle bulge on one side of the blood ves­sel (called a sac­cu­lar or berry aneurysm)
  2. or like a bulge in the mid­dle of the blood ves­sel (called a fusiform aneurysm)


The dan­ger asso­ci­ated with an aneurysm is related to the thin wall of the bulging, or bal­loon­ing ves­sel. Under pres­sure from the blood flow­ing in the artery, a brain aneurysm can leak or burst (rup­ture). If this occurs blood will go into the space (sub­arach­noid space) around the brain. This type of bleed­ing is called a sub­arach­noid hem­or­rhage(SAH) and is con­sid­ered a med­ical emer­gency. For addi­tional infor­ma­tion on sub­arach­noid hem­or­rhages see the patient guide, Sub­arach­noid Hemorrhage.

Brain aneurysms can occur any­where in the brain but most often are found where blood ves­sels branch apart, or where the blood flows at a higher pressure.


  • It is esti­mated that 3 to 5 per­cent of the adult pop­u­la­tion have a brain aneurysm.
  • Althoug aneurysms can occur at any age, they hap­pen most often in peo­ple 3560 years of age.
  • Aneurysms occur slightly more often in women than in men.


A brain aneurysm that has not leaked or rup­tured usu­ally will not cause any symp­toms. Brain aneurysms may develop silently, with­out any warning.

Rarely, very large aneurysms may cause symp­toms such as:

  • Headaches
  • Dou­ble vision or loss of vision
  • Pain above or behind an eye
  • Droopy eye­lid
  • Big­ger eye pupil
  • Loss of feel­ing (numb­ness) of the face
  • Seizures


Brain aneurysms can develop for a vari­ety of rea­sons. Some risk fac­tors that have been linked to devel­op­ing an aneurysm include:

  • Fam­ily his­tory of brain aneurysms
  • Smok­ing
  • Hyper­ten­sion
  • Ath­er­o­scle­ro­sis (hard­en­ing of the arteries)
  • Exces­sive use of alcohol
  • Use of cocaine
  • Head injury
  • Some inher­ited genetic dis­or­ders (e.g. Marfan’s syn­drome, poly­cys­tic kid­ney disorder)
  • Infec­tions of the heart or brain

How­ever, brain aneurysms can occur in peo­ple with­out any risk factors.


CT scan, Mag­netic Res­o­nance Imag­ing (MRI), and cere­bral angiogram are the main diag­nos­tic tests to find out if you have an aneurysm.


The treat­ment for a brain aneurysm may vary and depends on the size and loca­tion of the aneurysm.

  • If the aneurysm is small, or in an area of the brain where it is not likely to rup­ture, then your doc­tor may rec­om­mend obser­va­tion. This means that you would have an MRI or cere­bral angiogram from time to time to make sure the aneurysm is not get­ting any bigger.
  • In cases where the aneurysm is felt to be more at a risk of rup­tur­ing, then your doc­tor may rec­om­mend either a sur­gi­cal clip­ping or an endovas­cu­lar coil­ing for your aneurysm.

Sur­gi­cal clip­ping involves an oper­a­tion to reach the aneurysm through an open­ing in the skull (called a cran­iotomy). A small metal clip is placed at the base of the aneurysm, so that the aneurysm is closed off from the rest of the blood ves­sel. The surgery for the clip­ping of an aneurysm is explained in more detail in the patient guide, Aneurysm Clipping.

Endovas­cu­lar coil­ing involves plac­ing soft spi­rals made out of plat­inum inside the aneurysm. Dur­ing an angiogram, a tube (catheter) is inserted into an artery in the groin and care­fully advanced into the brain. Using this catheter, the radi­ol­o­gist will fill the aneurysm with plat­inum coils. The pro­ce­dure for endovas­cu­lar coil­ing is explained in more detail in the patient guide, Endovas­cu­lar Treat­ment of Cere­bral Aneurysm With Plat­inum Coils (GDC).

The result of a suc­cess­ful sur­gi­cal clip­ping or endovas­cu­lar coil­ing is that blood flows nor­mally through the artery, but no longer enters the aneurysm itself. With no blood flow­ing into the aneurysm it is no longer at risk of leak­ing or rupturing.


Whether your treat­ment involves obser­va­tion, or you are wait­ing for coil­ing or clip­ping, there are a few things that you should doto lower your risk of an aneurysm rupture.

  • Stop smok­ing
  • Con­trol your blood pressure
  • Avoid any med­ica­tions and nat­ural or herbal prod­ucts that “thin” the blood (we could make a sep­a­rate list for these)

Signs of an aneurysm rupture

Sud­den onset of a severe headache (often reported as the worse headache of the person’s life) with either:

  • Nau­sea and/​or vomiting
  • Drowsi­ness or confusion
  • Loss of consciousness
  • Seizure
  • Dif­fi­cul­ties to speak
  • Weak­ness or paral­y­sis of your arms or legs

The rup­ture of an aneurysm is con­sid­ered a med­ical emer­gency. If you expe­ri­ence any of the above signs you must seek imme­di­ate med­ical assistance.

Infor­ma­tion about InfoNEURO
Neuro-​Patient Resource Cen­tre
Mon­treal Neu­ro­log­i­cal Hosp­tial Room 354
Tel: (514) 3985358
E-​mail: infoneuro@​muhc.​mcgill.​ca
Web site: http://​infoneuro​.mcgill​.ca/

This infor­ma­tion is for edu­ca­tional pur­poses only, and is not intended to replace the advice of a pro­fes­sional health­care prac­ti­tioner, or to sub­sti­tute for med­ical care.

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Writer: Shar­ron Runions MSc(A), CNN©, Clin­i­cal Nurse Spe­cial­ist.
Edi­tors: Dr. David Sin­clair (Neu­ro­surgery), Dr. Robert Coté pro­fes­sional (Neu­rol­ogy), Eileen Beany Peter­son (Med­ical Librar­ian).

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