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For potential surgical resection of ICA or CCA (cancer or other complex
skull base or head and neck surgery.
(the
image shows a test occlusion of the right internal
carotid artery, demonstrating a large cavernous aneurysm)
Condition
Sometimes it is necessary to block off one of the four major arteries that
supply the brain. Occluding one of these arteries may be important in the
treatment of certain types of tumors that surround one of these arteries. If
the tumor is surrounding or next to a blood vessel, it may be necessary to
remove the artery along with the tumor to achieve a cure. Another situation
is when there is an aneurysm, a large dilation of the artery.
Some aneurysms can most safely be treated by
blocking off the artery along with the aneurysm. In both of these cases your
doctors want to make sure you will tolerate blocking off the blood vessel.
In most people, the four major blood vessels, two carotid arteries in the
front part of your neck and two vertebral arteries buried deep in the back
of your neck, have connections called collaterals, much like pipes in a
house.
If one artery is plugged, the other arteries, by
way of connections, can supply blood to your brain. Not every person has
these connections however, and the balloon test occlusion test is important
to determine the presence or absence of these connections, and to determine
if the collaterals are sufficient to allow a major blood vessel to be
blocked without causing a stroke.
Procedure
The procedure first involves an angiogram, which is described on another
page in our website. After pictures are taken of the blood vessels, a
catheter with a small balloon on the end is directed from the femoral artery
at the groin into the blood vessel of interest, usually one of the carotid
arteries. This tube is placed through the same hole as the other catheter
and it is not necessary to stick the artery again. After the balloon is
placed in the artery to be tested it is gently inflated to occlude flow
through the artery. If you have good connections or collaterals, the other
arteries send enough blood to the brain so there is no change in the brain
function. In this case the balloon is usually left in place for thirty
minutes, then deflated and removed. If your brain lacks these connections,
not enough blood gets to the brain and you develop weakness in an arm, or
difficulty speaking. In this event the balloon is immediately deflated and
removed; once blood flow is restored the weakness goes away, usually within
seconds. This test is often combined with a brain scan that helps measure
the amount of blood flowing to the brain. This test is done after the
balloon test occlusion and takes about thirty minutes. Once these tests are
completed you will be asked to stay on your back for 2-5 hours after which
you may go home.
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