Extracranial to intracranial EC-IC bypass is a surgical procedure to increase cerebral blood flow. This procedure entails connecting a branch of the external carotid artery usually the superficial temporal artery to a branch of the internal carotid artery usually the middle cerebral artery , either directly or via a vein graft.
This procedure is similar to cardiac bypass surgery where blocked heart arteries are bypassed. EC-IC bypass has been available as a potential treatment for ischemic stroke for the past 30 years. There has been much controversy concerning this procedure due to a large study conducted in the s. As a result, this procedure is only used in a very select group of patients.
The indications for EC-IC bypass are severe stenosis or occlusion of intracranial arteries with focal neurological symptoms, such as weakness or speech difficulties. This procedure is also used when an artery must be surgically occluded for the treatment of unclippable giant aneurysms.
In a cerebral artery bypass, the surgeon reroutes blood flow around a blocked or damaged artery to improve or restore blood flow to an oxygen-deprived ischemic area of the brain. A cerebral bypass can be performed in a variety of ways depending on where the blockage has occurred, the underlying condition being treated, and the size of the brain area to be revascularized.
There are two types of bypasses:. The first type uses a vessel graft — a length of artery or vein harvested from somewhere else in the body. The graft is connected above and below the blocked artery so that blood flow is rerouted bypassed through the graft. Common vessels used as a graft are the saphenous vein in the leg or the radial or ulnar arteries in the arm.
A separate incision is required to harvest the graft. Next, one end of the graft is connected to the external carotid artery ECA in the neck and then tunneled under the skin in front of the ear to the scalp. A hole is cut in the skull through which the graft is passed and connected to an artery in the brain.
This method is typically used when a large high-flow artery is affected or needs to be sacrificed to treat a tumor or aneurysm.
The other type does not use a vessel graft but a healthy donor artery that flows in the scalp or face. The donor artery is detached from its normal position on one end, redirected to the inside of the skull, and connected to an artery on the surface of the brain Fig.
The scalp artery now supplies blood to the brain and bypasses the blocked or damaged vessel. This method is typically used when a smaller low-flow artery has narrowed and is incapable of delivering enough blood to the brain.
The superficial temporal artery STA normally provides blood to the face and scalp. You can feel the pulse of the STA in front of your ear. The middle cerebral artery MCA normally provides blood to the frontal, temporal and parietal lobes of the brain. Blood flow through the MCA is often reduced when narrowing of the internal carotid artery occurs. If the STA is too small or unsuitable, another vessel such as the occipital artery may be used. Both types of bypasses require creating a hole in the skull to pass the vessel graft or scalp donor artery from outside the skull to the cerebral artery inside the skull.
Thus, this surgery is also called an extracranial—intracranial bypass EC-IC bypass. Cerebral bypass may be helpful in restoring blood flow and reducing the risk of stroke in conditions such as:. A cerebral bypass is performed by a neurosurgeon. Many neurosurgeons have specialized training in cerebrovascular surgery. Ask your surgeon about his or her training, especially if your case is complex. If the pre-surgical test results are positive, you will be scheduled for surgery.
Typically, a blood test, electrocardiogram EKG , and chest X-ray need to be performed. Discuss all medications prescription, over-the-counter, and herbal supplements you are taking with your health care provider. Some medications need to be continued or stopped the day of surgery. Stop taking all non-steroidal anti-inflammatory medicines Naprosyn, Advil, Motrin, Nuprin, Aleve, etc.
Stop smoking, chewing tobacco, and drinking alcohol 1 week before and 2 weeks after surgery because these activities can cause bleeding problems. You may also need to have clearance from your primary care physician or cardiologist if you have a history of other medical or heart conditions. No food or drink is permitted after midnight the night before surgery. It kills bacteria and reduces surgical site infections.
Avoid getting CHG in eyes, ears, nose or genital areas. Arrive at the hospital 2 hours before your scheduled surgery time to complete the necessary paperwork and pre-procedure work-ups. An anesthesiologist will talk with you and explain the effects of anesthesia and its risks.
An intravenous IV line and an arterial line will be placed in your arm. What happens during surgery varies depending on the type of bypass procedure. There are 7 steps to the procedure, which generally takes 3 hours.
Step 1. Once asleep, your head is placed in a 3-pin, skull-fixation device, which attaches to the table and holds your head in position during the procedure. The hair near the incision area is shaved and the scalp is prepped with an antiseptic. Step 2. A skin incision is made along the artery. Step 3. After the STA is freed, the muscle is cut and folded back to expose the bone. Step 4. The burr holes allow entrance of a special saw similar to a jigsaw.
The surgeon cuts an outline of a bone window. The bone flap is lifted and removed to expose the protective covering of the brain, called the dura. The dura is opened and folded back to expose the brain. Step 5: prepare the recipient artery Working under an operating microscope, the surgeon carefully locates a branch of the middle cerebral artery MCA suitable for bypass. The size of the recipient vessel must be a good match for the diameter of the donor vessel. Step 6.
The distal STA is cut and the end prepared for anastomosis. The surgeon then makes an opening in the side of the MCA vessel and sutures the two blood vessels together. Using a Doppler ultrasound or special fluorescent dye, good blood flow through the bypass is verified.
Step 7. The bone flap is replaced, but a hole is enlarged to allow passage of the bypass vessel without kinking or pressure. The bone flap is secured to the skull with titanium plates and screws Fig. The muscles and skin are sutured back together.
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