High-flow extra-intracranial bypass surgery in the treatment of giant aneurysms and tumors of the skull base

This surgery may be indicated in patients with a giant aneurysm or a tumor of the skull base to occlude the Internal Carotid Artery (ICA). When there is an insufficient system of intracranial collaterals such an intervention is only justified after the construction of an extra-intracranial bypass. The conventional extra-intracranial bypass that was designed by Yasargil and Donaghy consists of an anastomosis between a branch of the superficial temporal artery (diameter 1-1.5 mm) and a peripheral branch of the Middle Cerebral Artery (MCA) (diameter 1-1.2 mm). This elegant and safe procedure does have one obvious disadvantage: because of the small size of the recipient artery the maximal flow through the bypass is low (10-25 cc/min). To use a major brain artery as recipient is not permitted because the temporary occlusion of such an artery, necessary to make the end-to-end anastomosis, is very likely to induce brain ischemia in these patients with poor intracranial collaterals. To make high flow revascularization of the brain possible, utilizing a major brain artery as recipient, we developed in the experimental animal laboratory a non-occlusive anastomosis technique. The experiments are performed in rabbits and pigs. A donor vessel (common carotid artery or a piece of vein) is connected with its down-stream end either to the exterior of the opposite common carotid artery (pig) or the abdominal aorta (rabbit). The basis of a successful anastomosis proved to be a platinum ring with a diameter of 2.8 mm that was first stitched to the outside of the recipient artery by way of 8 zero sutures that passed through the recipient wall only superficially and penetrated the wall of the donor fully. An Excimer laser catheter consisting of 180 fibres (diameter 65 micron) arranged around a thin-walled catheter with a diameter of 2.2 mm and a metal grid mounted in its lumen, 0.5 mm from the tip, is introduced in the donor vessel via an artificial side branch. When the tip of the catheter, which is guided to its correct position by the platinum ring at the anastomosis site, touches the wall of the recipient artery, a vacuum is induced in the catheter and maintained for two minutes to obtain a firm fixation of the tip to the wall. The Excimer laser apparatus is now activated for 5 seconds (40 Hz, 10 mJ per pulse) punching out a full thickness disc of the recipient artery wall that stays fixed to the tip because of the vacuum in the catheter and is removed when the catheter is pulled out of the donor vessel. The Excimer Laser Assisted Non-Occlusive Anastomosis (ELANA) is now completed. After proving the ELANA to yield a high patency rate and to be very safe in 50 rabbits we transferred the technique to the clinic seven years ago and since then made 130 high flow bypasses utilizing the ELANA in patients where either the ICA had to be occluded in the treatment of a giant aneurysm or a skull base tumor or the ICA was spontaneously occluded causing a progressive stroke in the ipsilateral cerebral hemisphere. The technical details of the ELANA method and the indications for high flow revascularization of the brain will be discussed.