Vertebrobasilar insufficiency. Part 2. Microsurgical treatment of intracranial vertebrobasilar disease

Posterior circulation transient ischemic attacks have an associated risk of subsequent infarction of approximately 5% per year. Intracranial vertebrobasilar thrombo-occlusive lesions appear particularly likely to result in repetitive ischemic symptoms and in infarction due to hemodynamic insufficiency. The authors present their experience with 45 patients with symptomatic intracranial vertebrobasilar vascular disease despite maximal medical therapy. The specific operative approaches for intracranial vertebral artery endarterectomy and extracranial to intracranial posterior circulation revascularization procedures are outlined.     

Natural history of subclavian steal syndrome

Eighty-two patients presenting with subclavian steal syndrome (36 men, 46 women; median age, 66.5 years) were studied. All patients underwent clinical and noninvasive evaluation. Diagnosis was based on both a 20 mmHg difference in blood pressure between arms and reversed blood flow in the vertebral artery. Twenty-one patients (25.6%) had a transient ischemic attack or cerebrovascular accident before the study. In 16 patients (19.5%), the anterior circulation was involved and the vertebrobasilar circulation was effected in 5 patients (4.8%). Fifty-five patients were followed for one to six years (mean 4.1 years). During this period three patients died. Noninvasive studies showed that 39 patients (70.9%) had progression of disease in the carotid arteries and that 10 of these 39 (12.1%) exhibited a transient ischemic attack or cerebrovascular accident, and eight patients (9.7%) required carotid endarterectomy. No patient had a stroke involving the vertebrobasilar circulation, but four patients (4.8%) had a transient ischemic attack. Three other patients had revascularization procedures performed for arm ischemia. Patients with subclavian steal syndrome are more likely to experience a transient ischemic attack or cerebrovascular accident involving the carotid circulation than the vertebrobasilar circulation. Noninvasive evaluation of the carotid arteries and the posterior circulation should be included in the long-term follow-up of these patients.     

Microsurgical anatomy of cerebral revascularization. Part II: posterior circulation

OBJECT: Revascularization is an important component of treatment for complex aneurysms, skull base tumors, and vertebrobasilar ischemia in the posterior circulation. In this study, the authors examined the microsurgical anatomy related to cerebral revascularization in the posterior circulation and demonstrate various procedures for bypass surgery. METHODS: The microsurgical anatomy of cerebral and cerebellar vessels as they relate to revascularization procedure and techniques, including extracranial-to-intracranial bypass grafting, arterial interposition grafting, and side-to-side anastomosis, were examined by performing stepwise dissections in 22 adult cadaveric specimens. The arteries and veins in the specimens were perfused with colored silicone. Dominant cerebral and cerebellar revascularization procedures in the posterior circulations include superficial temporal artery (STA)-posterior cerebral artery (PCA), STA-superior cerebellar artery (SCA), occipital artery (OA)-anterior inferior cerebellar artery, OA-posterior inferior cerebellar artery (PICA), and PICA-PICA anastomoses. These procedures are effective in relatively small but critical areas including the brainstem and cerebellum. For revascularization of larger areas a saphenous vein graft is used to create a bypass between the PCA and the external carotid artery. Surgical procedures are generally difficult to perform in deep and narrow operative spaces near critical vital structures. CONCLUSIONS: Although a clear guideline for cerebral revascularization procedures has not yet been established, it is important to understand various microsurgical techniques and their related anatomical structures. This will help surgeons consider surgical indications for treatment of patients with vertebrobasilar ischemia caused by aneurysms, tumors, or atherosclerotic diseases in the posterior circulation.     

Vertebrobasilar occlusion therapy of giant aneurysms. Significance of angiographic morphology of the posterior communicating arteries

The clinical and angiographic records were reviewed for 71 patients with giant aneurysms of the posterior circulation, who underwent therapeutic occlusion of the basilar artery or both vertebral arteries. This treatment is used when the aneurysm neck cannot be surgically clipped, and occlusion of the parent artery is performed to initiate thrombosis within the lumen. In these cases, collateral blood flow to the brain stem is supplied mainly by the posterior communicating arteries. Consequently, their angiographic morphology (patency, size, and number) is demonstrated as a preoperative indicator of whether the patient will be able to tolerate vertebrobasilar occlusion. Vertebral angiograms with carotid artery compression (the Allcock test) will often be needed to provide this information. The data relating posterior communicating artery morphology to clinical outcome in 71 cases of attempted vertebrobasilar occlusion are presented. The use and accuracy of carotid artery compression studies are also discussed. It is essential for the radiologist to supply the neurosurgeon with this valuable information in every case of giant posterior circulation aneurysm.     

Revascularizing the upper basilar circulation with saphenous vein grafts: operative technique and lessons learned

BACKGROUND: The purpose of this study was to report our operative technique and lessons learned using saphenous vein conduits to revascularize the rostral basilar circulation (ie, bypass to the posterior cerebral or superior cerebellar arteries). We also review the evolution of this technique for the treatment of vertebrobasilar insufficiency (VBI) and complex posterior fossa aneurysms. METHODS: Data were collected retrospectively for 8 consecutive patients undergoing rostral basilar circulation saphenous vein bypass grafts at our institution between 1989 and 2004 for the treatment of VBI or in conjunction with Hunterian ligation of complex posterior circulation aneurysms. The indications for treatment, pre- and postoperative neurologic status, angiographic results, operative complications, and long-term clinical outcomes were analyzed for each patient. RESULTS: With clinical and angiographic follow-up ranging from 3 months to 15 years, 7 of 8 bypasses remained patent, 3 of 3 aneurysms remained obliterated, and 4 of 5 patients with VBI experienced resolution of their preoperative symptoms. There were no surgery-related deaths, but 2 patients did experience major neurologic morbidity. The outcomes for the 217 total patients reported in the literature were as follows: 135 excellent (62%), 26 good (12%), 30 poor (14%), and 26 dead (12%). CONCLUSIONS: Despite the risk of serious neurologic complications with this procedure, when one considers the natural history of untreated patients, saphenous vein revascularization of the rostral basilar circulation remains an acceptable option. Although surgical technique has varied, patient selection criteria, graft patency, and patient outcomes have been relatively constant over the past 25 years.     

Cerebral blood flow and metabolism following superficial temporal artery to superior cerebellar artery bypass for vertebrobasilar occlusive disease.

In order to clarify the effectiveness of extracranial-intracranial bypass operations in patients with vertebrobasilar occlusive disease, the authors used positron emission tomography to investigate the cerebral blood flow (CBF) and metabolism of eight patients undergoing superficial temporal artery (STA)-superior cerebellar artery (SCA) bypass procedures. In the preoperative studies, CBF in the region of the posterior fossa was low and the oxygen extraction fraction (OEF) was high, the so-called "misery perfusion syndrome." Such changes were evident in both the posterior circulation and the anterior circulation regions. Postoperatively, there was a significant increase in CBF, a significant decrease in the OEF not only in the region of posterior circulation but also over the entire brain, and a disappearance of the uncoupling between CBF and oxygen metabolism. The STA-SCA bypass procedure is effective in improving CBF and metabolism in patients with vertebrobasilar occlusive disease.     

Revascularization of the Posterior Circulation

The primary objective of revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke. Specific anatomical and neurophysiologic characteristics such as posterior communicating artery size affect the susceptibility to ischemia. Current indications for revascularization include symptomatic vertebrobasilar ischemia refractory to medical therapy and ischemia caused by parent vessel occlusion as treatment for complex aneurysms. Treatment options include endovascular angioplasty and stenting, surgical endarterectomy, arterial reimplantation, extracranial-to-intracranial anastomosis, and indirect bypasses. Pretreatment studies including cerebral blood flow measurements with assessment of hemodynamic reserve can affect treatment decisions. Careful blood pressure regulation, neurophysiologic monitoring, and neuroprotective measures such as mild brain hypothermia can help minimize the risks of intervention. Microscope, microinstruments and intraoperative Doppler are routinely used. The superficial temporal artery, occipital artery, and external carotid artery can be used to augment blood flow to the superior cerebellar artery, posterior cerebral artery, posterior inferior cerebellar artery, or anterior inferior cerebellar artery. Interposition venous or arterial grafts can be used to increase length. Several published series report improvement or relief of symptoms in 60 to 100% of patients with a reduction of risk of future stroke and low complication rates.     

Hemodynamic evaluation of vertebral arteries by duplex ultrasound

In summary, vertebral artery hemodynamics can be readily evaluated both qualitatively and quantitatively. Duplex ultrasonography provides a very reliable noninvasive technique for this assessment. Flow in the vertebral artery system can be noninvasively quantified in greater than 95 per cent of all patients examined using this technique, and such measurements help identify subgroups of patients whose symptoms may be related to posterior circulation ischemia. Further evaluation of the spectral flow patterns is often helpful in diagnosing the cause of these ischemic symptoms. Unfortunately, quantitative flows are rarely obtained during routine carotid ultrasound studies. Such data, however, may provide an objective basis for the following kinds of surgical decisions: 1. Recommendations for carotid surgery in patients with high-grade carotid stenosis but nonlocalizing symptoms. 2. Recommendations for no surgery in patients who have vertebrobasilar symptoms but diminished flow characteristic of poor cardiac output. 3. Recommendations for surgery to augment vertebral artery flow in patients who have vertebrobasilar symptoms, decreased vertebral flow on the basis of proximal stenosis, and normal carotid artery flow. Obviously, there is a need to confirm these hypotheses by studying patients thoroughly before and after surgery. Other investigators must begin gathering data on vertebral artery flow to determine its impact and utility in making surgical decisions.     

Complications of intracranial bypass for vertebrobasilar insufficiency

The authors' initial experience with intracranial revascularization of vertebrobasilar insufficiency, reported previously, fortunately yielded reasonably good results with high patency rates but in some cases there were significant, albeit temporary, complications. Since that time, major brain-stem strokes have occurred in two patients following superficial temporal to superior cerebellar artery bypass procedures. This occurrence has caused the authors to reassess their experience with this procedure and review the published literature with regard to complications. This review and the results of the international bypass study on anterior circulation ischemia suggest that a very cautious and conservative approach should be taken prior to considering intracranial bypass to the superior cerebellar or posterior cerebral artery.     

Cerebral revascularization performed using posterior inferior cerebellar artery-posterior inferior cerebellar artery bypass. Report of four cases and literature review

Cerebral revascularization is often required for the surgical treatment of complex intracranial aneurysms. In certain anatomical locations, vascular anatomy and redundancy make in situ bypass possible. The authors present four patients who underwent revascularization performed using the rarely reported posterior inferior cerebellar artery (PICA)-PICA in situ bypass after their aneurysms had been trapped. At Barrow Neurological Institute, between 1991 and the present, four male patients underwent PICA-PICA by-passes to treat aneurysms involving the vertebral artery, the PICA, or both. The mean age of these patients was 34 years (range 5-49 years). Follow-up studies revealed patent bypasses and no evidence of infarction. Patient outcomes were excellent or good. Multiple surgical techniques have been described for revascularization of at-risk cerebral territories. Often, the blood supply must be derived from extracranial sources through a mobilized pedicle or interposited graft. Certain anatomical locations such as the vertebrobasilar junction, the anterior circle of Willis, and the middle cerebral artery bifurcation are amenable to in situ bypass because there is vessel redundancy or proximity to the contralateral analogous vessel. The advantages of an in situ bypass include one suture line, a short bypass distance, and a close match with the caliber of the recipient graft. Although technically challenging, this technique can be successful and should be considered for appropriate candidates.     

Transluminal stent-assisted angiplasty of the intracranial vertebrobasilar system for medically refractory, posterior circulation ischemia: early results

OBJECTIVE: Symptomatic vertebrobasilar artery stenosis portends a poor prognosis, even with medical therapy. Surgical intervention is associated with considerable morbidity, and percutaneous angioplasty alone has demonstrated mixed results, with significant complications. Recent advances in stent technology have allowed for a novel treatment of symptomatic, medically refractory, vertebrobasilar artery stenosis. We report on a series of patients with medically refractory, posterior circulation stenosis who were treated with transluminal angioplasty and stenting at two medical centers in the United States. METHODS: A retrospective analysis of data for 11 consecutive patients with symptomatic, medically refractory, intracranial, vertebral or basilar artery stenosis was performed. All patients were treated with percutaneous transluminal angioplasty and stenting. Short-term clinical and angiographic follow-up data were obtained. RESULTS: Among 11 patients who were treated with stent-assisted angioplasty of the basilar or vertebral arteries, there were three periprocedural deaths and one delayed death after a pontine stroke. Other complications included a second pontine infarction, with subsequent residual diplopia. The remaining seven patients (64%) experienced symptom resolution and have resumed their preprocedural activities of daily living. Angiographic follow-up examinations demonstrated good patency of the stented lesions for five of seven survivors (71%); one patient exhibited minimal intrastent intimal hyperplasia, and another patient developed new stenosis proximal to the stent and also developed an aneurysm within the stented portion of the basilar artery. The last patient exhibited 40% narrowing of the treated portion of the vessel lumen. CONCLUSION: Recent advances in stent technology allow negotiation of the proximal posterior circulation vasculature. Although the treatment of vertebrobasilar artery stenosis with angioplasty and stenting is promising, long-term angiographic and clinical follow-up monitoring of a larger patient population is needed.     

Superficial temporal and occipital artery bypass pedicles to superior, anterior inferior, and posterior inferior cerebellar arteries for vertebrobasilar insufficiency

Eighty-three patients underwent 85 intracranial to extracranial pedicle bypass anastomosis procedures to the posterior circulation. There were 15 patients with occipital artery (OA) to posterior inferior cerebellar artery (PICA) anastomosis, 20 patients with OA to anterior inferior cerebellar artery (AICA) anastomosis, and 50 patients with superficial temporal artery (STA) to superior cerebellar artery (SCA) anastomosis. All patients had transient ischemic attacks (TIA's) suggestive of vertebrobasilar ischemia. Twenty-seven patients had crescendo TIA's or stroke in evolution and were considered to be clinically unstable. All patients had severe bilateral distal vertebral artery or basilar artery disease. Twenty-two patients had bilateral vertebral artery occlusion and three had basilar artery occlusion. In this series, 69% had complete resolution of symptoms; the mortality rate was 8.4% and the morbidity rate 13.3%. Clinically stable patients did better than unstable patients. The STA-SCA anastomosis was well tolerated and technically less demanding than the OA-PICA or OA-AICA anastomosis procedures. Patients with symptomatic severe bilateral vertebral or basilar artery disease have a grave prognosis and the option of a surgical arterial pedicle revascularization procedure should be offered to them.     

Exacerbation of Major Artery Aneurysms after Revascularization in Patients with Moyamoya Disease: Two Case Reports

The natural history of aneurysms of the major arteries after revascularization in moyamoya disease has yet to be documented. At our institute, we treated two patients with moyamoya disease-associated aneurysms involving major arteries of the posterior cerebral circulation. The aneurysms became enlarged at an early stage after revascularization, necessitating coil embolization. Although cerebral blood flow was improved in the anterior circulation, revascularization for these patients did not decrease hemodynamic stress in the posterior circulation and was not able to attenuate aneurysmal growth. Therefore, patients with moyamoya disease-associated aneurysms of the major arteries should be carefully monitored after revascularization.     

The role of cerebral revascularization in patients with intracranial aneurysms

Cerebral revascularization offers an important adjunct to parent-vessel ligation in the treatment of large and otherwise inaccessible intracranial aneurysms. Good or excellent outcomes can be expected in approximately 80% of patients. Poor outcomes and ischemic complications were highest in posterior circulation lesions. Cranial neuropathies from mass effect associated with giant aneurysms of the cavernous and intradural internal carotid artery will improve and be cured in the majority of patients treated with universal revascularization approach. In combination with open parent vessel ligation or endovascular occlusion, durable protection from subarachnoid hemorrhage can be achieved.     

Anastomosis of occipital artery to anterior inferior cerebellar artery for vertebrobasilar junction stenosis

A new approach to revascularization of the posterior fossa for vertebrobasilar insufficiency due to vertebrobasilar junction stenosis is reported. The procedure involves anastomosing the occipital artery to a branch of the anterior inferior cerebellar artery. Rationale for the procedure and surgical technique are discussed.     

Saphenous vein bypass grafts for giant aneurysms and intracranial occlusive disease

The authors report their experience with the use of saphenous vein bypass grafts for treating advanced occlusive disease in the posterior circulation (77 patients, all of whom had failed medical management and showed severe ischemic symptoms), deteriorating patients with giant aneurysms of the posterior circulation (nine patients), progressive ischemia in the anterior circulation (26 patients, none of whom had a normal examination), and giant aneurysms in the anterior circulation (20 patients, all of whom presented with mass effect or subarachnoid hemorrhage). Graft patency in the first 65 cases treated was 74%. However, after significant technical changes of vein-graft preparation and construction of the proximal anastomosis, patency in the following 67 cases was 94%. Excellent or good results (including relief of deficits existing prior to surgery) were achieved in 71% of patients with advanced occlusive disease in the posterior circulation, 44% of those with giant aneurysms of the posterior circulation, 58% of those with ischemia of the anterior circulation, and 80% of those with giant aneurysms of the anterior circulation. Mean graft blood flow at surgery in the series was 100 ml/min for posterior circulation grafts and 110 ml/min for anterior circulation grafts. Experience to date indicates that this is a useful operation, and is particularly applicable to patients who are neurologically unstable from advanced intracranial occlusive disease in the posterior circulation or with giant aneurysms in the anterior circulation. The risk of hyperfusion breakthrough with intracerebral hematoma restricts the technique in patients with progressing ischemic symptoms in the anterior circulation, and the intolerance of patients with fusiform aneurysms in the posterior circulation to the iatrogenic vertebrobasilar occlusion limits the applicability of this approach to otherwise inoperable lesions in that system.     

Surgical treatment of unruptured aneurysms of the posterior circulation

With the ever-increasing number of intact aneurysms revealed by modern imaging, the options for their management are assuming great importance. While some knowledge has emerged as to their natural history and the results of surgical treatment of those in the anterior circulation, little information has been published concerning unruptured aneurysms arising from the posterior circulation. The authors report their experience since 1971 with 167 patients operated on for 179 unruptured vertebrobasilar aneurysms up to 25 mm in diameter. Overall, 160 aneurysms were treated by direct clip obliteration, while 19 were managed by alternative methods. Fifty-three patients (32%) had solitary aneurysms and the other 114 patients (68%) had multiple aneurysms or an associated arteriovenous malformation, which were commonly treated concurrently. Many of these coexisting vascular anomalies had ruptured in the recent or remote past, adding to the complexity of management and interpretation of specific surgical results related to the intact posterior circulation aneurysm. There were 78 documented postoperative complications including 23 systemic complications, seven postoperative hematomas, six brain injuries from retraction, five cases of aseptic meningitis, three instances of seizures, three wound infections, and three patients with hydrocephalus. Multiple complications occurred in 23 patients. Seventy-one of the patients with these untoward events recovered, without disability, with time or treatment. There were only six poor results and one death in the series, resulting in a 4.2% combined morbidity/mortality rate. However, since two of these poor outcomes and the single death were attributable to a coexisting aneurysm, the actual surgical morbidity related specifically to the posterior circulation aneurysm was only 2.4%. This experience suggests that non-giant, intact vertebrobasilar aneurysms can be obliterated surgically at a very low risk, and this treatment should eliminate the greater lifetime risk related to an unsecured aneurysm.     

Perioperative- and long-term mortality rates after major vascular surgery: the relationship to preoperative testing in the medicare population.

Debate continues regarding the value of cardiovascular testing and coronary revascularization before major vascular surgery. Whereas recent guidelines have advocated selective preoperative testing, several authors have suggested that it is no longer necessary in an era of low perioperative cardiac morbidity and mortality. We used data from a random sample of Medicare beneficiaries to determine the mortality rate after vascular surgery, based on the use of preoperative cardiac testing. A 5% nationally random sample of the aged Medicare population for the final 6 mo of 1991 and first 11 mo of 1992 was used to identify a cohort of patients who underwent elective infrainguinal or abdominal aortic reconstructive surgery. Use within the first 6 mo of 1991 was reviewed to determine if preoperative noninvasive cardiovascular imaging or coronary revascularization was performed. Thirty-day (perioperative) and 1-yr mortalities were assessed. Perioperative mortality was significantly increased for aortic surgery (209 of 2865 or 7.3%), compared with infrainguinal surgery (232 of 4030 or 5.8%); however, 1-yr mortality was significantly increased for infrainguinal surgery (16.3% vs 11.3%, P < 0.05). Stress testing, with or without coronary revascularization, was associated with improved short-and long-term survival in aortic surgery. The use of stress testing with coronary revascularization was not associated with reduced perioperative mortality after infrainguinal surgery. Stress testing alone was associated with reduced long-term mortality in patients undergoing infrainguinal revascularization. IMPLICATIONS: Analysis of the Medicare Claims database suggests that vascular surgery is associated with substantial perioperative and long-term mortality. The reduced long-term mortality in patients who had previously undergone preoperative testing and coronary revascularization reinforces the need for a prospective evaluation of these practices.     

Long-term outcomes in adult patients with ischemic-type moyamoya disease involving posterior circulation

Background

The object of this study was to compare the long-term outcomes in adult patients with moyamoya disease (MMD) with posterior circulation involvement (PCi) treated through surgical revascularization with those in adult patients without PCi.

Methods

The records of 32 consecutive adult patients with ischemic-type MMD who were treated with revascularization were reviewed. Twelve of these patients (38 %) had PCi at initial onset. Clinical characteristics of the patients with PCi were compared to those without PCi. Neurological outcomes were assessed using the modified Rankin Scale (mRS) in the preoperative and postoperative follow-up periods. A five-year Kaplan-Meier stroke risk was calculated.

Results

The frequency of presenting with infarction was significantly higher among patients with PCi than among those without PCi (p?=?0.006). mRS scores in the preoperative period were significantly higher in patients with PCi than in patients without PCi (p?=?0.0004). There were no significant differences in mRS scores between the preoperative and postoperative follow-up period in patients with PCi (p?=?0.3), nor were there any between the preoperative and postoperative follow-up periods in patients without PCi (p?=?0.2). The five-year Kaplan-Meier risk of surgical morbidity and ipsilateral stroke was 14.3 % in surgically treated hemispheres with PCi versus 14.9 % in surgically treated hemispheres without PCi (p?=?0.96).

Conclusions

PCi at initial onset was significantly correlated with poor outcome. Revascularization for the middle cerebral artery territory in patients with PCi was effective at preventing recurrent ischemic stroke.     

Four cases of abducens palsy caused by a vascular lesion of the vertebrobasilar system

Several pathological conditions are responsible for abducens palsy, but a lesion of the vertebral artery (VA) has rarely been recognized as one of the causes. It has been reported that a high percentage of cases of abducens palsy are involved with ruptured dissecting aneurysms of the VA. We investigate the vertebrobasilar anatomy in 4 patients, suffering with abducens palsy. One patient revealed a fusiform dilatation of the vertebral artery on the same side as the abducens palsy. Three patients were noted to have stenosis of the vertebral artery from the origin of the posterior inferior cerebellar artery (PICA) to the union. Finally, four patients were found to have abnormal vertebrobasilar anatomy, which was on the same side as the abducens palsy. It is conceivable that changes of vertebrobasilar circulation may cause abducens palsy through direct compression, or ischemic events.