Superficial temporal-middle cerebral artery bypass. A detailed analysis of multiple pre- and postoperative angiograms in 40 consecutive patients

Flow replacement bypass for aneurysms: decision-making using intraoperative blood flow measurements

PURPOSE

There is much debate regarding the optimal strategy for extracranial-intracranial (EC-IC) bypass for complex aneurysms. We introduce the concept of a flow replacement bypass which aims to compensate for loss of flow in the efferent vessels of the aneurysm. The strategy to achieve this utilizes direct intraoperative flow measurements to guide optimal revascularization by matching graft flow to demand.

METHODS

We reviewed all EC-IC bypass cases performed over a 6-year period. We identified cases in which intraoperative flow measurements using an ultrasonic flow probe were utilized to determine the revascularization strategy and analyzed the decision-making paradigm.

RESULTS

Twenty-three cases were analyzed. For terminal aneurysms, flow measurement in the affected vessel at baseline predicted the flow required for full replacement: middle cerebral artery (MCA), 50 +/- 25 cc/min (n = 9); posterior inferior cerebellar artery (PICA), 13 +/- 7 cc/min (n = 4); posterior cerebral artery (PCA), 33 cc/min (n = 1); and superior cerebellar artery (SCA), 10 cc/min (n = 1). For proximal internal carotid artery (ICA) aneurysms (n = 8), the flow deficit from baseline during carotid temporary occlusion was measured (26 +/- 18 cc/min, an average of 44% drop from baseline). The adequacy of flow from the superficial temporal artery (STA) or occipital artery (OA), when available, was assessed prior to bypass, and STA, OA, or vein interposition grafts were used accordingly. Measurement of bypass flow following anastomosis confirmed not only patency but sufficient flow in all cases: MCA 50 +/- 25 cc/min, PICA 18 +/- 9 cc/min, PCA 64 cc/min, SCA 12 cc/min, ICA 36 +/- 25 cc/min (STA), and >200 cc/min (vein).

CONCLUSIONS

Direct intraoperative measurement of flow deficit in aneurysm surgery requiring parent vessel sacrifice can guide the choice of flow replacement graft and confirm the subsequent adequacy of bypass flow.

Evaluation of extracranial-intracranial bypass using quantitative magnetic resonance angiography

OBJECT

To date, angiography has been the primary modality for assessing graft patency following extracranial-intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography.

METHODS

One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery). There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean +/- standard error of the mean, 37 +/- 13 ml/minute compared with 105 +/- 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02).

CONCLUSIONS

Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.

Delayed re-opening of an STA-MCA bypass graft

We describe the case of a 47-year-old female with symptomatic right MCA stenosis who had undergone cerebral revascularization through a superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass. Despite clear patency in the operating room, post-operative angiography showed no flow in the bypass. Her ipsilateral internal carotid artery (ICA) was widely patent. She remained asymptomatic and follow-up angiography four years later showed a widely patent bypass graft in the setting of critical stenosis of the ipsilateral ICA. That the graft was found opened up and supplying the hemisphere was presumably stimulated by an increased "demand" and flow gradient promoting its patency.

Evaluation of extracranial-intracranial arterial bypass function with magnetic resonance angiography

Extracranial-intracranial (EC/IC) arterial bypass surgery is a valuable therapeutic modality in the field of cerebrovascular surgery. The assessment of bypass patency and its functional parameters are of utmost importance in the postoperative course. The present study examined the potential role of quantitative MR-based volume flow measurement techniques for the investigation of bypass patency. Forty-one patients with steno-occlusive cerebrovascular disease treated with EC/IC bypass surgery underwent conventional angiographic (CA) and two-dimensional cine-phase MR-based angiographic assessment (MRA) of bypass function. CA bypass function was evaluated as poor (grade I), moderate (grade II), or extensive (grade III) and was compared with quantitative volume flow measurements (BVF) obtained in MRA studies. Bypass filling was classified as grade I in 15% of the cases, grade II and grade III in 36% and 49% of the studies, respectively. Mean BVF differed significantly in the different grades: 31.94 +/- 9.8 ml/min in grade I, 73.6 +/- 16.7 ml/min in grade II, and 97.2 +/- 26.6 ml/min in grade III. BVF values of 48 ml/min or lower (n = 6) were specific for grade I bypass function, while only BVF values higher than 111 ml/min (3/20, 15%) are specific for extensive angiographic bypass function. The assessment of EC/IC bypass patency with quantitative BVF measurements provides exact, investigator-independent information under physiological conditions. MRA is well correlated with the angiographic bypass grading system.

Bypass to the intracranial internal carotid artery

Extracranial to intracranial internal carotid artery bypass surgery with vein is well described for a number of diverse conditions. They provide high blood flow with good initial patency. However, long term patencies for specific graft types remains unknown. This is an analysis of consecutive interposition saphenous vein bypass cases between the common carotid artery (CCA) and the intracranial internal carotid artery (ICA) where the distal anastomosis was placed end-to-end immediately proximal to the posterior communicating artery in 55 patients undergoing 57 bypass procedures (bilateral in 2 cases). Twenty-five patients underwent grafting for planned vessel obliteration where the pathology required vessel sacrifice. Twenty-eight patients had bypass grafting for stroke risk reduction in the setting of threatening stroke and 4 patients had bypass grafts for emergency revascularisation in the setting of stroke in evolution. Patients were assessed preoperatively and at follow-up with modified Rankin scores. Procedural related complications included a 7% mortality and 7% functional decline. Early graft occlusion occurred in 5% of grafts leading to death in each case. A further patient died of rupture at the distal anastomosis site. In surviving patients, patency was present in 100% at last follow-up (mean 5 years and maximum 11 years) with no patient sustaining new hemispheric ischemic events. One patient developed a delayed asymptomatic stenosis within the vein graft requiring stenting. Because of the high initial management risks this technique of common carotid to intracranial internal carotid artery saphenous vein bypass surgery should be reserved for patients at considerable risk by alternate management. However, once the acute postoperative period is past the bypass appears to be robust and capable of supplying the entire distribution of a normal internal carotid artery.

Intracranial vascular anastomosis using the microanastomotic system. Technical note

The authors describe the use of a microanastomotic device to perform intracranial end-to-end vascular anastomoses. Direct end-to-end anastomosis was performed between the superficial temporal artery and branches of the middle cerebral artery (MCA) in three patients. Two patients had moyamoya disease, with severe proximal MCA disease, and one suffered an internal carotid artery occlusion with poor collateral flow. All patients reported a history of recent ischemic symptoms. Each anastomosis was accomplished in less than 15 minutes with technically satisfactory results. Postoperative angiographic studies demonstrated patency of the bypasses in all patients.

Extracranial-intracranial saphenous vein bypass for carotid or vertebral artery dissections: a report of six cases

The management of carotid or vertebral artery dissections has generally been either conservative (with anticoagulation) or surgical (by proximal ligation or trapping procedures). However, identification and management of those patients with a high risk of stroke recurrence have been difficult. Six patients with carotid or vertebral artery dissections underwent a total of seven surgical procedures involving intracranial interpositional saphenous vein bypass grafts anastomosed distally beyond the point of dissection with trapping of the intermediate diseased section of the artery. It is suggested that this procedure be used in patients who have bilateral carotid or vertebral artery disease, persistent angiographic abnormalities (particularly aneurysms), or recurring ischemic events while undergoing anticoagulation therapy, or in whom anticoagulation is undesirable. This procedure has benefits over current surgical options because of the maintenance of high flow, the avoidance of abnormal watershed areas of flow, and the elimination of the risk of emboli. The procedure is compared to previous techniques of extracranial-intracranial bypass.

Superficial temporal-middle cerebral artery bypass: clinical pre- and postoperative angiographic correlation

Between 1974 and 1982, an anastomosis between a pedicle of the superficial temporal artery (STA) and a cortical branch of the middle cerebral artery (MCA) was performed in 163 carotid systems in 157 patients for internal carotid artery occlusion in whom postoperative angiograms were available for analysis. The angiographic opacification of the arterial system was correlated with the patient's preoperative neurological function and stroke in the follow-up period. From this analysis, the following observations were made: 1) 96% of bypasses were patent; 2) 80% of bypasses achieved a high or medium MCA filling score; 3) there was hypertrophy of the STA in 70% of the cases; 4) greater bypass filling occurred in hemispheres with nonvisualized preoperative collateral circulation than in those with readily visualized collateral flow; 5) a meaningful correlation between angiographically assessed postoperative bypass function and stroke rate was not possible because only four patients suffered an ipsilateral hemispheric stroke in the 8-year follow-up period; and 6) patients who were neurologically unstable before the procedure were at greatest risk for a stroke in the follow-up period. It is apparent that objective analysis of the effectiveness of an STA-MCA bypass, or any other form of extracranial bypass, must await the development of new diagnostic studies in which high-resolution three-dimensional quantification of cerebral blood flow is possible. These studies will necessarily be correlated with preoperative and follow-up clinical data.

Radiologic evaluation of extracranial to Sylvian middle cerebral artery bypass

At this institution a new procedure has been developed that involves anastomosing one of the branches of the superficial temporal artery to one of the major trunks of the middle cerebral artery in the Sylvian fissure. This procedure has been performed in 22 cases to date. Clinical indications for this procedure have fallen into four major categories. This new type of anastomosis produces greater bypass flow than conventional cortical middle cerebral artery anastomoses, and may be a better therapeutic alternative in certain clinical situations. The preoperative and postoperative angiographic evaluation of these patients is discussed. The radiologic results in this series of patients are reviewed.

Critique of the extracranial-intracranial bypass study

The potential benefit of extracranial-intracranial anastomosis was evaluated by a multicenter international cooperative study headed by the group in London, Ontario, Canada. The final conclusion of the study was that the extracranial-intracranial anastomosis did not provide any benefit over the treatment with aspirin. Several objections and shortcomings have been identified in this study. In our evaluation it cannot be concluded that EC-IC bypass surgery is not effective in reducing stroke in all patient populations.

Extraintracranial anastomosis performed by means of biological gluing materials: experimental and clinical study

A new surgical technique of extraintracranial anastomosis (EIA) is reported. End-to-side microvascular anastomosis is performed by applying four crossed-fixing sutures and by mantling a hemostatic sponge muff (eg, Spongostan) impregnated with fibrinogen-thrombin glue. Histopathological studies of microvascular anastomosis in animals and clinical results of 70 EIA operations showed that this surgical technique of anastomosis has certain advantages, namely that it reduces the number of sutures needed, is less traumatic to the vascular wall, ensures elastic vascular junction, and the glue and Spongostan used possess high biological inertness that provides a better physiological connection of vessels than conventional suturing. The highly hermetic vascular junction and absence of blood flow at the anastomosis site are achieved without additional suturing. The duration of the operation is significantly reduced. A full EIA function sets in comparatively early.

The extracranial-intracranial bypass study: how will the outcome affect us?

Extracranial-intracranial bypass is now a commonly performed procedure in centres with a high level of neurosurgical and vascular expertise. Bypass of surgically inaccessible stenoses or occlusions appears to be a logical technique to prevent future stroke but there is much uncertainty about the clinical indications for surgery and even the natural history of the lesions being bypassed. To answer these questions, the International EC/IC Bypass Study was set up in 1977 with relatively broad entry criteria. The data will be analysed in June 1985 and if the results support the use of bypass as a means of preventing subsequent stroke, the procedure should become firmly established. However, if the results are negative, or inconclusive, rather than discard the procedure, subsets of higher risk patients should be sought, in particular using newer methods of assessing cerebral perfusion and metabolism.

Ophthalmopneumoplethysmography (OPG-Gee) without and with bypass-compression for quantification of hemodynamic significance of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis

The Extracranial-Intracranial (EC/IC) Bypass Procedure is a new method in order to try to increase the Intracranial Perfusion Pressure (ICPP). Postoperative patency of the bypass can be shown by means of Seldinger angiography. By this method no information however is obtained on the hemodynamic function of the bypass. OPG-Gee measures the Ophthalmic Artery Pressure (OAP) which is related to the ICPP. In this study OPG-Gee is performed without and subsequently with compression of the bypass. Quantification of the hemodynamic significance of the bypass is obtained by measuring the pressure decay in the ophthalmic arteries during this procedure. The Rest Pressure Difference (RPD), i.e. the pressure difference between the two ophthalmic arteries without bypass compression is measured. By subtracting the RPD from the BCD the remaining pressure is called the Net Bypass Pressure (NBP), i.e. the pressure difference, which the EC/IC bypass contributes to the ICPP. If, however, at constant systemic arterial blood pressure (SABP) the OAP drops during bypass compression on both sides, we hypothesize that the NBP is the sum of both drops, because, as a result of the interhemispheric steal mechanism, the less perfused hemisphere steals from the better perfused hemisphere. In a group of 40 patients OPG-Gee without and subsequently with bypass compression was applied. Twenty two of 40 OPG-Gee's showed NBP's of 4 mm of mercury or more (55%). In the group of 29 patients with unilateral internal carotid artery occlusion in 21 patients (72%) an NBP of 4 mm of mercury or more was found (mean of 13 mm of mercury).(ABSTRACT TRUNCATED AT 250 WORDS)

Occlusion of internal carotid artery. Further clinical angiographic, and therapeutic considerations

Patients with occlusion of ICA have been reviewed. Further ischemic attacks have been observed in 25-30%. The cause of the ischemia was generally embolization by way of collateral circulation through the ECA. Treatment of these patients is considered.

DSA evaluation of the STA-MCA bypass

Continuing improvements in intravenous DSA techniques have now shown it to be useful in the angiographic evaluation of STA-MCA bypass function. Both patent and non-patent bypasses were observed in this study. Diagnostically adequate spatial resolution and signal to noise ratio were achieved by electronic magnification and integration techniques. Patient positioning was important and the projection which gave optimal visualization of the STA-MCA bypass, free of vessel overlap, was a 40 degrees oblique, 20 degrees craniocaudal view on the side of interest. Intravenous DSA can complement, and in some cases may supplant, conventional arteriography in the radiologic evaluation of STA-MCA bypass surgery.

Cortical artery aneurysm formation after extracranial to intracranial bypass surgery. Case report

An aneurysm of the recipient cortical artery developed 13 months after an extracranial-intracranial bypass procedure. A high transcranial pressure gradient between the scalp and the cortical arteries may have contributed to this unusual complication.

Short vein grafts for cerebral revascularization

Experience with the use of a short saphenous vein bypass graft for cerebral revascularization is reviewed. Twenty patients with symptomatic atherosclerotic occlusive disease underwent a total of 21 bypass procedures. Cerebral revascularization was performed using a short (5 to 10 cm) saphenous vein graft (SVG) extending from the superficial temporal artery (STA) trunk anterior to the ear in 19 bypasses, or from the occipital artery (OA) immediately behind the mastoid process to the posterior temporal or angular branch of the middle cerebral artery (MCA) in two bypasses. The early patency rate for the SVG bypasses was 90%. Two of the four patients with SVG occlusion were found to have substantial resolution of a severe inaccessible internal carotid artery stenosis that was present preoperatively. Filling of multiple major branches of the MCA through the SVG was seen in 90% of patients on late postoperative conventional angiography. The STA trunk or proximal OA was consistently found to be enlarged on the late studies. None of the patients had recurrence of cerebral transient ischemic attacks. The procedure may be useful as a primary means of cerebral revascularization or as an alternative approach when a scalp artery cannot be used because of its small size, severity of arteriosclerotic changes (a common occurrence), or damage during its dissection. Cerebral blood flow studies suggest that the use of a short SVG has a more favorable effect upon the cerebral circulation than the conventional bypass procedure.

Follow-up of patients with proved occluded internal carotid artery. Clinical and angiographic correlation

Patients with angiographically proven occluded ICA were subjected to a clinical follow-up. In about 25%, further ischemic attacks ipsilateral to the occluded ICA occurred. The pathogenesis of ischemia and the management of these patients is discussed.

Morphological and clinical analysis of extra-intracranial bypass. 1. Clinical and angiographical analysis

In this morphological-clinical analysis it was possible to study the clinical and angiographical results of extra-intracranial bypass in a continued series. Small changes in management result from the indications in the groups with TIA's and completed strokes. Preoperative angiographical findings allow determination of the most favourable bypass-feeder taking into consideration age and morphology. From the postoperative dilatation of the donor artery conclusions may be drawn as to the indication for operation with respect to the angiogram and the choice of the branch of the superficial temporal artery.

Morphological and clinical analysis of extra-intracranial bypass. 2. Histological and histometrical evaluation with correlation of angiographical findings

Rest segments of superficial temporal arteries obtained during STA-MCA anastomoses were studied histologically and histometrically. Aging was found to be associated with thickening of the intimal layer and thinning of the medial layer. In comparison with the young patients, the old patients showed a larger internal diameter of the superficial temporal artery and a larger ratio of the thickness of the intimal layer to the medial layer. The internal diameter calculated angiographically and the internal diameter estimated histologically correlated well. The dilatation ratio of the superficial temporal artery did not correlate with dimensional data assessed histologically.

Dependency on bypass circulation: a case study

In a case of consecutive occlusion of both internal carotid arteries bilateral STA-MCA anastomoses were established. Since a series of angiographic examinations were undertaken, dynamics and probable efficacy of both natural and artificial collateral circulations could be followed up in a two-year period. Objectively in the evaluation of anastomoses was enhanced by direct percutaneous STA-angiography (STAG), in order to delineate the vascular territory irrigated exclusively by the anastomosis. By demonstrating exactly the functional capacity of anastomoses in correlation with the clinical course, dependency on bypass circulation could be assessed.

Ultrasonic evaluation of superficial temporal artery-middle cerebral artery anastomosis

Ultrasonic Doppler studies were made pre- and postoperatively in 22 patients undergoing STA-MCA anastomosis. A quantitative evaluation of the bypass was attempted by determining the STA blood flow velocity and pattern. The STA velocity on the Doppler sonogram was compared with the degree of intracranial vascular filling via anastomotic channels and the STA diameter on angiogram. The STA velocity was increased and the blood flow pattern of STA altered from an external carotid pattern to an internal carotid pattern in a patent bypass. The results were in good agreement with angiographic findings. The are of intracranial vascular filling via a vewly formed bypass on angiogram was proportional to the increase in STA velocity. As the STA diameter enlarged, the STA velocity increased progressively. It is suggested the Doppler flowmetry is reliable as a semi-quantitative means of evaluationg the STA-MCA anastomosis.

Influence of superficial temporal artery to middle cerebral artery bypass on cerebral blood flow in dogs with middle cerebral artery occlusion

Eight dogs had a superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis, followed immediately by ligation of the ipsilateral middle cerebral artery. Subsequently, utilizing the radioactive microsphere technique, regional cerebral blood flow determinations were made both before and after ligation of the superficial temporal artery. A significant reduction in blood flow of 20-35% was noted in both cerebral hemispheres, caudate and thalamic nuclei, brain stem and cerebellum following occlusion of the bypass. It is our impression that this generalized reduction in flow is due to a redistribution of blood from normal areas previously supplied by the bypass. This implies that the newly created extracranial to intracranial arterial anastomosis reduces the shunting of blood from zones of higher to zones of lower flow through the circle of Willis and leptomeningeal collaterals. It also suggests a mechanism for the development in neurological function referable to areas of the brain remote from the bypass which is detected in some patients after STA-MCA anastomosis.

Angiographic aspects of extra-intracranial arterial bypass (EIAB) for cerebral arterial occlusive disease

Fifty extra-intracranial arterial anastomoses were performed in 48 patients. The importance of a precise angiographic study in the pre- and post-operative period is emphasized. The different angiographic patterns of the anastomosis, its variation in time, the possible cause of failure, and the role played by the EIAB on the cerebral blood flow are described and discussed. The problems of extension and time of the postoperative angiographic examination, are also discussed.