Prior to the international cooperative study with regard to EC/IC bypass surgery, STA-MCA anastomosis had often been used with little knowledge of its fundamental theory. Even now, many points still remain to be clarified with reference to the selection of candidates. The use of bypass surgery should not be restricted only to cases involving cerebral ischemia. It can also be used for cases in which a neck clipping of aneurysm is difficult, proximal clipping or trapping of the parent artery being the only choice. For such situations, STA-MCA anastomosis is the most common procedure. It must be kept in mind, however, that STA-MCA anastomosis is not suitable in such instance as for the reconstruction of the anterior cerebral artery when, as is sometimes seen, the amount of blood flow through the STA may be insufficient to maintain the brain function. Under such circumstances, not only should STA-MCA anastomosis be performed but also other reconstructive procedures, depending on the needs presented by each case. In this regard, the authors have used a radial artery graft instead of a saphenous vein graft for patients with a cavernous giant aneurysm and have obtained satisfactory results. This technique, termed as a "high flow" bypass, still has probelms to be solved. Based on their experience, the beneficial features of a radial artery graft are : the graft provides an appropriate caliber that compares to that of the recipient artery, the removal and suturing is easier, rotation and kinking is avoided, and a good patency is achieved. The prefecture's policy on how to proceed with STA-MCA anastomosis is herein stated, this surgery entailing a long radial artery graft and A_3-A_3 side-to-side anastomosis. New methods and equipments that have proven to be more useful have been incorporated into the procedure. Details of the previous bypass cases and the results are not given in this paper, and only the most crucial points of their bypass procedure are explained to make an accurate suture and to ensure that the temporary clip is used for the shortest time. Summary is follows : (1) Clear visualization of the cut wall of the arteries is required for better anastomosis. The authors stained the cut wall with a pyoktanine blue solution and placed a green dam under the recipient artery. (2) The length of the incision in the recipient artery should be adjusted to suit the size of donor artery ostium. This can be done by laying the donor artery close to the recipient artery. (3) To avoid a dry thread sticking to the surrounding structures or a thread being soaked in cerebrospinal fluid, semi-wet surgical technique is advised by continuous drainage of the cerebrospinal fluid by a small tube and by pouring saline onto the brain surface. (4) A thread used for the corner stitches, a 9.0 or 10.0 monofilament nylon, should be placed through the cut wall of the donor artery before the temporary occlusion of the recipient artery ; (5) Exchange of surgical instruments should be kept to a minimum during the surgery. For the bypass procedure, suturing should be carried out by using forceps. (6) So as to perform the anastomosis smoothly, put the needles and thread on a gelform sheet, 1 by 2 cm wide, in front of the recipient artery.

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Over the past 10 years, the authors have surgically performed 38 acute cerebral revascularizations, each within 24 hours. The patients had been evaluated by angiography, CT scans, single photon emission CT (SPECT), and/or electroencephalogram (EEG) topography. Of this number, 19 cases had an internal carotid artery (ICA) occlusion and/or a middle cerebral artery (MCA) occlusion, and for treatment, 33 conventional superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis were performed. Additionally, 5 ICA-occluded patients with a poor STA were given an extracranial -intracranial bypass with an interposed radial artery graft. The postoperative results, classified on the basis of morbidity, were graded as excellent, good, fair, or poor. Twenty-six patients were graded as excellent or good, 6 fair or poor, and the remaining 6 patients did not survive. Acute cerebral revascularization patients showing some low flow patterns on SPECT (over 40% of normal values) , with normal to slight low density visualizations on routine CT, and with a sufficient collateral circulation were considered to present good prognosis. Although many other researchers support the authors' view on the usefulness of immediate, high-flow revascularization for patients manifesting acute cerebral ischemia, whether such therapy is beneficial remains controversial. Further, the prognosis for ICA-occluded patients with a poor collateral circulation continues to be pessimistic, and new therapeutic methods to assist them must be devised.

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To clarify the efficacy of a STA-SCA bypass for those with a vertebrobasilar occlusive disease, the authors have investigated the operative complications and the clinical course of 3O such patients given a STA-SCA bypass, said patients also the subjects of a subsequent follow-up study. Results have shown that no serious surgical complications occurred, and postoperative angiograms have revealed that bypass patency was achieved in all cases. Further, the patients' outcomes on discharge have been excellent, with no morbidity and only one death due to a myocardial infarction. During the follow-up study 4 patients manifested ischemic symptoms, 2 patients experiencing a TIA and another two a completed stroke, one being a supratentorial infarction due to an internal carotid artery occlusion, and the other a small pontine infarction. There also were two deaths, one due to a cardiac infarction and the other to diabetes mellitus. The remaining cases, however, had favorable outcomes. Based on these results, the authors conclude that an STA-SCA bypass provides an effective therapy for vertebrobasilar ischemia, and that this procedure should be the first choice for posterior fossa revascularization, since it can be performed with little risk of surgical and/or systemic complications.

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A TIA, due to a vertebro-basilar insufficiency, frequently occurs because of stenosis in the first portion of the extracranial vertebral artery (VA). In this report, the authors review the operative techniques involved in VA reconstructions, and discuss the advantages and disadvantages of each method. Exposure of the VA can be achieved by a supraclavicular approach, after which, to describe the easier technique, the kinking and coiling of the VA can be corrected by removing the fibrous adhered tissue and the perivascular sympatheticus of the VA and C6 process. The VA is then wrapped with an artificial vessel (Dacron) to protect VA recoiling after this correction. Various surgical reconstructions have been proposed for a stenosis of VA origin, and though a vertebral artery endarterectomy is a technique that has been much described in reports, especially by cardiovascular surgeons, the disadvantage of this procedure is that often a sternotomy or the cutting of the clavicle is necessary to expose the extensive operating field. Moreover, the procedure is technically difficult to accomplish because the area is restricted and the VA wall is thin and fragile. Also, since the surgical intervention is relatively minor, many cases have been reported wherein the successful transposition of the VA to the carotid artery have been described. However, this procedure requires the simultaneous cross clamping of the CCA and the VA, entailing a higher risk of brain ischemia. In certain case, when the VA is transposed to the SA, the VA may not be long enough, thereby restricting the anastomotic area considerably and causing tension at the anastomotic site. Therefore, to avoid this problem in a vertebral artery reconstruction, the authors have used a short vein bypass between the VA and SA, and while two anastomoses are required, the manipulation of the anastomosis is rather easy and the carotid flow is not interrupted. They thus have found that transpositions of the vertebral artery to the SA or a vein bypass are safe and relatively easy procedures. It also should be stressed that intraoperative monitoring of the VA stump pressure and the ABR is extremely important during the surgical reconstruction of the VA.

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The benefits of a carotid endarterectomy can be realized only if the perioperative morbidity and mortality are kept to a minimum, and in this regard, the biggest problem this operation presents is the management of cerebral ischemia while the carotid artery is occluded. In this paper the authors outline an approach to treating a symptomatic carotid artery bifurcation disease with a defined protocol for a microsurgical endarterectomy that utilizes mannitol protection during the potential period of a focal, temporary, cerebral ischemia. This protocol includes the use of the operating microscope, the avoidance of an internal shunt, the administration of mannitol before and during carotid clamping, and strict control of postoperative hypertension. Using this protocol, 126 consecutive endarterectomies were performed in 120 patients, and the authors report a combined permanent morbidity and mortality rate of 2.5%. Details of this procedure and intraoperative monitoring are discussed.

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Replacement of the cavernous portion of the internal carotid artery (ICA) by a saphenous vein graft, a procedure known as a Fukushima Bypass, has enabled the authors to perform more aggressive, radical surgery for cases manifesting cavernous lesions. Using this procedure, we have performred bypass surgery for 25 cases presenting tumors and vascular lesions. This has led us to apportion this surgical technique into three classification, depending on the anastomotic site, and representative cases and surgical techniques they have used are presented. Fukushima Bypass I (C5-C3) In the usual frontotemporal approach, the anterior triangle, anterolateral triangle, lateral loop, and Glasscock triangle are exposed extradurally, and the vein graft is anastomosed to the petrous ICA (proximal C5), which is exposed approximately 8 to 10 mm. The vein is then placed beneath the temporal lobe and anastomosed (distal C3). Preservation of the tensor tympani muscle, the auditory tube, and the cochlea is indispensable. Fukushima Bypass II (high cervical-C5) A high cervical-C5 ICA is replaced by a saphenous vein graft for lesions int the high cervical area that extend to the infratemporal area. A high cervical, small, skin incision and a subtemporal craniotomy provide a satisfactory operative field. Fukushima Bypass III (high cervical-C3) For lesions that extend widely from the cavernous sinus to the petrous ICA, the artery between the high cervical portion and the ICA siphon area is anastomosed to a saphenous vein graft. The above techniques have been used since 1988, and their usefullness and safety have been confirmed. The author therefore hope that they will be more widely used in the surgical treatment of skull-based tumors and vascular lesions.

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Extracranial-Intracranial (EC/IC) artery bypass surgery is indicated when the cerebral circulation shows what is called "misery perfusion", a condition, diagnosable through SPECT, that shows a decrease in the cerebral blood flow (CBF), an increase in the cerebral blood volume (CBV), due to compensatory vasodilation that occurs under 1owered cerebral perfusion pressure, and an elongated mean transit time (MTT) of the cerebral blood flow, the latter reported to correlate well with the oxygen extraction fraction (OEF). In 1971, the long saphenous vein was first used as an interposition graft in EC/IC bypass surgery. Since that time the use of this graft has spread, so that today long vein grafts are not only used for treating occlusive vascular disease but also for such anomalies as a giant aneurysm that cannot be approached directly. Further, the use of a long vein graft extends the choice of both the donor and recipient vessels, i.e., the extracranial carotid or the subclavian artery can serve as the donor vessel and the intracranial carotid, the proximal middle cerebral, the anterior cerebral, the posterior cerebral, or the superior cerebellar artery, to name a few, as the recipient vessel. Also, one of the merits of a long vein graft is that the bypass flow through it is twice that of a STA-MCA bypass. This can sometimes become a demerit, however, for this greater flow has occassionally provoked postoperative hyperperfusion. Follow-up studies of vein grafts used in cardiovascular surgery have revealed that the patency of saphenous vein grafts is far longer than that of radial artery grafts, due to intimal changes that occur through hyperplasia, but skillful surgical and pharmacologic techniques are required to maintain good patency of the vein graft peri- and postoperatively. Finally, because such bypass surgery may involve greater surgical risk, a preoperative evaluation of the entire body, especially of the heart, is mandatory. Further, the intra- and postoperative control of the blood pressure is essential so as to ensure the success of long vein graft bypass surgery.

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The authors discuss a new system that has been developed for intraoperative spatial monitoring. Named the "NEURO-SAT", it is comprised of frameless iso-centric stereotactic mechanism and a three-dimensional (3-D) digitizer. The 3-D digitizer's multi-articulated arm has three joints that form Cartesian coordinates, two quadrant arcs that form an iso-center system, a microdrive, and a probe holder. This frameless iso-centric mechanism is useful for open stereotaxy. Further, routine CT- or MRI-guided stereotactic surgery also is possible, due to the system's high level of accuracy. Before surgery, CT and/or MR images are acquired after placing three or four external markers on the scalp. Then, using an image scanner, CT or MR images are entered into a computer and stored on a floppy disk. After the patient's head has been fixed on the operating table, NEURO-SAT is used to read the spatial points of these external markers on the scalp. During the procedure, the coordinates on the patient's head are automatically entered into the computer and matched with those of the NEURO-SAT and the CT/MR images on the CRT display. The authors have used this system in 31 cases of an open craniotomy and 41 cases of burr hole surgery, both types of surgery having been carried out by using the stereotactic function and the 3-D spatial monitoring function in parallel. Errors in mechanical accuracy of this system were under 0.8 mm, and the maximum error during operation is presumed not to have exceeded 2 mm. Because of these results, it is felt that this new system provides a more dependable method for performing image-guided surgery than currently available conventional instruments.

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Reported is a case of an intracranial arteriovenous malformation (AVM) with right-sided aortic arch that were found in a 26-year-old male who suddenly experienced a headache and a speech disturbance. A neurological examination revealed motor aphasia and right hemiparesis, a CT scan showed a left frontal hematoma, and a cerebral angiogram demonstrated a left frontal AVM. Further, an aortogram revealed a right -sided aortic arch with mirror-image branching and aneurysmal dilatation of the right ductus arteriosus. Five cases of an intracranial AVM associated with a congenital heart disease have been previously reported, leading some authors to suspect a comcomitant developmental disturbance of the cardiovascular and cerebrovascular angiogenesis. Informatively, only one previous case of a right-sided aortic arch has been reported in the literature. In this case, no apparent relationship was found between the intracranial AVM and the cardiovascular anomalies. The developmental process of the cerebral vasculature is discussed and a comparison is made between the present case and previously reported cases.

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A rare case is reported of a distal posterior inferior cerebellar artery (PICA) aneurysm associated with a megadolichobasilar anomaly. This 71-year-old woman was deeply comatose on admission and a thick and diffuse subarachnoid hemorrhage was disclosed in a CT scan. A right vertebral angiography revealed a megadolichobasilar anomaly and an aneurysm located at the junction of the posterior medullary and the supratonsillar segments (the choroidal point) of the left PICA. She underwent a successful neck clipping of the aneurysm 16 days later. Over the next one and half months her level of consciousness gradually improved so that she was able to open and close her eyes and to grasp and release hands to a verbal command. Mild left oculomotor palsy, which was regarded as a pathognomonic sign suggesting a megadolichobasilar anomaly was presented. Unfortunately she suffered from respiratory failure and died on the 73rd postoperative day. Incidence of the megadolichobasilar anomaly was reported approximately 1.5% in autopsy. Correlation between the megadolichobasilar anomaly and this rare aneurysm, constituting less than 0.5% of all intracranial aneurysms, is discussed.

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