Brain Aneurysm Resource Center

What went on in my head?

Michael Chen, MD

Even with accurate, detailed medical knowledge, it is hard to know for sure how people will do after they survive a ruptured brain aneurysm.  I’ve seen some patients do amazingly well, and are essentially back to normal.  I’ve seen others who need to stay in nursing homes and cannot take care of their own daily activities.  Obviously, there are several factors that determine the severity of actual brain injury after a ruptured brain aneurysm.  What I hope to do in the next few paragraphs is describe what goes on in your head after a brain aneurysm ruptures.

Brain aneurysms are a problem with the arteries, which transmit blood under pressure, pumped by the heart, as opposed to veins, which transmit blood under very low pressure after it has passed through your tissues or organs.  As such, when an aneurysm ruptures, blood enters, under considerable pressure, into the spinal fluid space that normally surrounds your brain.  Because the skull is a fixed volume in adults, any increase in volume within the skull (blood, in this case), quickly increases the pressure within the skull.  This mechanical pressure can damage the brain by having a squeezing effect, otherwise referred to as mass effect.  In more severe situations, a part of the brain may herniate into a space that it shouldn’t be in.  The severity of this mass effect initially is an important determinant of how much neurologic injury a patient will sustain.

As mentioned, earlier, blood enters under pressure into the spinal fluid space that normally surrounds the brain.  This spinal fluid space is also referred to as the subarachnoid space, which is enveloped by a tissue layer called the arachnoid membrane.  Under normal circumstances, spinal fluid has a vital role in maintaining normal health and function of the neurons in the brain, and as such, does recirculate.  About a soda can of spinal fluid is formed each day (very slow rate) and gets reabsorbed into the veins at certain locations.

Depending on how much blood enters this space from the ruptured aneurysm, spinal fluid may not be able to drain normally.  As a result, spinal fluid builds up, further increasing the pressure within the skull.  This is called hydrocephalus, and may be a reason why you need a drain in the first day or so, and why you may need a permanent drain or shunt to provide an alternative drainage route for the spinal fluid that continues to be produced by your body.  Hydrocephalus can contribute to disability.

The major blood vessels at the base of the brain that are most likely to develop aneurysms are suspended within the spinal fluid with little supporting tissue surrounding it.  As such, when an aneurysm ruptures, blood actually surrounds the surface of these blood vessels.  This blood settles, coagulates and then the body through several reactions, tries to clear this blood.  As the blood is “digested” by the white blood cells in the body, some of the by-products may be irritating to the normal surrounding tissues, including the arteries in the brain.  The normal muscle layer that makes up the wall of the artery may become irritated by this blood and contract, narrowing the vessel, compromising blood flow to the brain.  This may lead to ischemic strokes, or brain injury from insufficient blood flow.  This is yet another factor that may contribute to neurologic disability.

There are several other processes that occur including seizures, infections, blood clots in the legs, and heart problems, among others.  The prolonged intensive care unit stay, often around 2 weeks, also takes its toll on your overall medical health.  Frequent neurologic exams in the intensive care unit significantly disturb sleep.

During your follow-up visit, try to ask you physician, who knows your particular case in detail, to explain what went on when your aneurysm ruptured.  Hopefully by then, you’ll begin to have a better sense of what to expect in the future.