Dr. Robert Solomon has been treating patients with brain aneurysms for a very long time, and he has seen it all. Some of the most challenging to treat, he says, are the amorphous or “giant” aneurysms of the basilar artery.
Researchers* at the Cerebrovascular Center pulled together 22 years of Dr. Solomon’s case files and found the best way to treat these unwieldy aneurysms may be to head them off at the pass and clip the basilar artery itself.
The basilar artery is a large blood vessel located at the lower part of the brain that is formed when two of the major suppliers of oxygen-rich blood, the vertebral arteries, come together at the back of the brain (see image below right).
Because the brain is so vital to life, the human body has given it a redundant blood supply. That means that if one vessel in the brain gets blocked off, blood can be automatically re-routed. This happens in two ways. First, all the major arteries to the brain come together inside the brain to form a circle (the Circle of Willis, image below right) that collectively can feed the whole brain. This way blood can be re-routed from the other major vessels if one fails.
The brain also has what is called collateral circulation. Collateral blood vessels are normally closed, but when a larger vessel gets blocked, they can open up and re-rout the blood between vessels. Over time these tiny vessels will grow and become permanent.
Sometimes a surgeon needs to block an artery on purpose. This may be the case when it supplies an oddly-shaped or giant aneurysm that is at risk of bursting. A giant aneurysm (larger than 2.5 cm in diameter) in the basilar artery can be particularly hard to treat however, because of its location. It lies deep in the brain near parts that control vital functions like breathing and heart rate.
An aneurysm occurs when the wall of a blood vessel grows weak and starts to balloon out. These enlarged areas of the vessel are at risk of bursting and causing a brain bleed. They can also be a problem if the increase in size presses on vital brain structures.
A number of surgical methods are used to treat aneurysms. Because they are often balloon like in shape, they can be blocked off at their base, using a tiny clip, and closed off. Once it is no longer fed with blood, the aneurysm shrinks away. More recently surgeons have been able to insert a coil into the aneurysm itself using minimally invasive endovascular techniques.
The problem with oddly-shaped and giant aneurysms is that they often don’t have a distinct “neck” that can be clipped, or they are just too big to be reliably coiled. Surgeons are seeing that the rate of recurrence of these kinds of aneurysm after these procedures are not always optimal. When this is the case, occlusion (blocking off) of the basilar artery itself can be the most effective and least risky procedure.
Researchers in the Cerebrovascular Center looked through 22-years of Dr. Solomon’s case files and found all his patients who had gone through this procedure. They had records of these patients during the procedure, at their one month and one year follow-ups, and up to 18 years after. They wanted to see how patients fared over all, especially in terms of neurological symptoms (indications of brain damage) and recurrence of the aneurysm.
The results were exceptional. At the one month follow-up, 80% of the patients studied had no neurological problems. Upon long term follow-up (an average of 3.5 years) none of the patients had any lasting deficits. In fact, one patient who had weakness in his arms and legs before surgery was completely normal by his 2-year follow up.
According to the authors:
“No patients suffered a recurrence of symptoms or necessitated re-operation. No patients suffered a hemorrhage at any point after occlusion, and of the four patients who presented with a subarachnoid hemorrhage, none suffered a re-bleed.”
Based on their research, they also outlined a number of patient criteria associated with an optimal outcome. First they said, patients were only considered for a surgical block of the basilar artery when direct surgical or endovascular intervention on the aneurysm itself was not considered safe. Then they considered any previous treatment failures, the size of the aneurysm, whether it had a distinct neck, and the health and position of the surrounding blood vessels.
It was also critically important, they said, that there was good collateral circulation. This was tested before surgery using a balloon test occlusion as a kind of trial run. With this procedure, surgeons can see if it will be safe to block the vessel by inflating a balloon inside the artery. This temporarily blocks the blood flow allowing them to see if it is re-routed.
The authors concluded that surgical blocking of the basilar artery is an effective treatment with a high rate of cure for patients with complex basilar artery aneurysms.
*The authors of this study, Complex Basilar Artery Aneurysms Treated with Surgical Basilar Occlusion: A Modern Series are: resident physicians Christopher P Kellner and Raqeeb Haque; and from the Cerebrovascular Center, Dr. Philip M. Meyers, Dr. Sean D. Lavine, Dr. E. Sander Connolly, and the Department Chair Dr, Robert A. Solomon.
To learn more about the treatment of aneurysms see Dr. Solomon’s Brain Aneurysm Primer Video.
First published Aug 15, 2010
Updated Feb 27, 2017
Images in the post are in the public domain
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