Balloon Test Occlusion
For what conditions is a balloon test occlusion performed?
The arteries of the brain have a series of connections that form a circle at the base of the brain. This is known as the circle of Willis. They allow for is an alternative pathway for blood flow if one of the main arteries contributing to the circle is blocked. However, this circle is infrequently complete and the configuration varies widely between patients. Some pathologic conditions of the brain and its arteries may require intentionally blocking off one of the main arteries contributing to the circle. In the vast majority of cases, the carotid artery is closed, and blood flow from another artery travels around the circle to supply the area of the brain previously perfused by the carotid artery. Occasionally, it may be necessary to sacrifice a vertebral artery in the back part of the brain.
Why is a balloon test occlusion performed?
The reasons for sacrificing an artery are broad but can include traumatic injury with active, life-threatening bleeding; inoperable aneurysms or fistulas; or in association with tumors of the head and neck. The balloon test occlusion tells physicians whether or not it is safe to perform the procedure. In rare instances, a vessel needs to be closed without a test occlusion if it is an emergency in an unstable patient with uncontrolled bleeding. If the patient passes the balloon test occlusion, it is considered reasonable to close the vessel. If the patient does not pass the test, all efforts are made to pursue a ‘vessel-preserving’ open surgical or endovascular strategy.
How is a balloon test occlusion performed?
A balloon test occlusion is a simulation of closing the artery to see what the effects would be. This is done by obtaining arterial access in our standard fashion to place a catheter in the artery.
A special catheter with a balloon is inflated in the target artery, stopping blood flow. Then, a separate arterial access is obtained so that a second catheter can be navigated into the other arteries to perform angiograms to anatomically assess how the blood flow is being re-routed with the balloon inflated. There are known standards for the timing of the circulation that allow us to predict the risk of closing the blood vessel. Patients are awake during the procedure so that we may perform neurologic exams to monitor for changes.
There are a variety of ways to enhance the accuracy of the examination. Typically, we work with the Nuclear Medicine team who will inject the patient with a radiotracer material during balloon inflation. Patients are then imaged on nuclear medicine scanners for further quantitative information about brain perfusion.
Once all of the information is gathered, our neurovascular radiologists and other physician specialists meet for a multidisciplinary discussion to select the most appropriate treatment option for the affected blood vessel.