Extracranial—intracranial bypass in the treatment of occlusive cerebrovascular disease and intracranial aneurysms in the United States between 1992 and 2001: a population-based study

Self-closing Nitinol U-Clips for intracranial arterial microanastomosis: a preliminary experience on seven cases

PURPOSE

To report experience on the use of self-closing nitinol U-Clips for different types of intracranial arterial microanastomosis.

METHODS

We treated 7 patients (3 females and 4 males, age ranging from 25 to 68 yo) admitted from November 2005 to January 2008 to the Neurological Institute C. Besta of Milan. One patient had cerebral hypoperfusion and the others a complex intracranial aneurysm. In each patient a bypass procedure was completed by using self-closing Nitinol U-Clips for intracranial arterial microanastomoses.

RESULTS

The total time of temporary occlusion was 15.71 +/- 4.386 min. Bypass patency was confirmed intraoperatively by near-infrared indocyanine green videoangiography and microdoppler in each patient. No spasm of the graft was encountered and immediate post-operative bypass patency was confirmed in 6/7 patients. The graft thrombosed in 1 patient with antiphospholipid syndrome. 1 patient died from a massive Subarachnoid Hemorrhage due to rupture of an aneurysm while waiting for an endovascular procedure. In the 5 patients at the last follow-up, long-term patency of the bypass was confirmed and no neurological deficits occurred related to the procedure.

CONCLUSION

This is the first report of the use of U-Clips for intracranial microanastomosis. Our data indicated that it is a safe technique, reduces the time taken to perform an anastomosis and the risk of an ischemic complication. Further studies of the longer-term patency of bypass as performed with U-Clips are required.

The evolution of cerebral revascularization surgery

Among the relatively few surgeons to be awarded the Nobel Prize was Alexis Carrel, a French surgeon and pioneer in revascularization surgery at the turn of the 20th century. The authors trace the humble beginnings of cerebral revascularization surgery through to the major developments that helped shape the modern practice of cerebral bypass surgery. They discuss the cornerstone studies in the development of this technique, including the Extracranial/Intracranial Bypass Study initiated in 1977. Recent innovations, including modern techniques to monitor cerebral blood flow, microanastomosis techniques, and ongoing trials that play an important role in the evolution of this field are also evaluated.

The acetazolamide challenge: techniques and applications in the evaluation of chronic cerebral ischemia

The acetazolamide (ACZ) challenge test is a useful clinical tool and a reliable predictor of critically reduced perfusion. In patients with chronic steno-occlusive disease, the ability to maintain normal cerebral blood flow by reducing vascular resistance secondary to autoregulatory vasodilation is compromised. Identification of the presence and degree of autoregulatory vasodilation (reflecting the cerebrovascular reserve) is a significant prognostic factor in patients with chronic cerebrovascular disease. The pharmacologic challenge of a vasodilatory stimulus such as ACZ can also be used to optimize the treatment strategies for these patients. The pathophysiology, methods, and clinical applications of the ACZ challenge test are discussed in this article.

The plastic surgeon's role in extracranial-to-intracranial bypass using a reverse great saphenous vein graft

BACKGROUND

Extracranial-to-intracranial bypass is used for flow replacement and diversion that prevent the serious complications associated with sudden ligation of the middle cerebral artery for treatment of complex tumors or aneurysms. Extracranial-to-intracranial bypass is a demanding procedure that requires experience in advanced microsurgical techniques. In this article, the authors review the first report of an extracranial-to-intracranial bypass performed by a plastic surgeon with emphasis on indications for microsurgical involvement in neurosurgical practice and on description of the surgical technique.

METHODS

Between April of 2004 and October of 2006, three extracranial-to-intracranial bypass cases were performed including one for a complex aneurysm rupture and two for resections of cranial base tumors. In every case, the intracranial approach was used by the neurosurgeon. The bypass was performed by interposing a reverse great saphenous vein graft between the superficial temporal artery, in end-to-end anastomosis, and the second segment of the middle cerebral artery, in end-to-side anastomosis.

RESULTS

In each case, postoperative cerebral angiography demonstrated complete patency of the extracranial-to-intracranial bypass. Neither of the two surviving patients at a mean follow-up of 13 months had deterioration of neurologic function, postoperative stroke, or surgery-related death. One of the patients was dead before the 6-month follow-up.

CONCLUSIONS

The reverse great saphenous vein graft is a good option for extracranial-to-intracranial bypass, with the advantages of high-flow graft, wide lumen, adequate length, easy harvest, and minimal donor-site morbidity. The plastic surgery/neurosurgery alliance allows scope for improved outcomes in complex neurosurgical cases and continues to push the frontiers of reconstructive microsurgery.

Vascular neurosurgery following the International Subarachnoid Aneurysm Trial: modern practice reflected by subspecialization

OBJECT

In this paper the authors' goal was to report on and examine (in the context of a large hospital with good endovascular intervention provisions) the activities of a neurosurgeon with a dedicated vascular interest in the era after the International Subarachnoid Aneurysm Trial in the United Kingdom. They also aimed to establish therapeutic trends and outcomes.

METHODS

The authors reviewed the multidisciplinary team activity of 1 neurosurgeon and 2 interventional radiologists during a period of 22 months (2005-2007). They reviewed 281 aneurysm interventions; the majority was used to treat subarachnoid hemorrhage. Data analysis showed a strong preference for endovascular treatment for acute rupture (86.6 vs 13.4%), with a progressively greater role for open microsurgery in the more elective context (57% endovascular vs 43% surgical). They also reviewed 66 interventions for arteriovenous malformations, of which only 6 were surgical. These data are compared against a sample year from 2001 to 2002 (pre-International Subarachnoid Aneurysm Trial), showing comparable rates of surgically treated aneurysms versus endovascularly treated aneurysms, but an increase overall in the number of patients requiring open surgery.

RESULTS

The authors found that excellent outcomes for microsurgical clipping compared with endovascular therapy can be achieved within the current climate. These and previously published data strongly support a continuing role for vascular neurosurgery as a subspecialist interest in combination with a dedicated endovascular service and a multidisciplinary team.

CONCLUSIONS

Despite a trend to prefer coiling for ruptured aneurysms, the authors have shown that there is still a vital role for open surgery in the management of the ruptured and unruptured aneurysm. They consider the remaining role for surgery for arteriovenous malformations within the modern era of endovascular therapy.

Trends in the use of vagus nerve stimulation for epilepsy: analysis of a nationwide database

Object

Vagus nerve stimulation (VNS) plays a significant role in the treatment of intractable epilepsy. The goal of this study was to analyze trends in the use of VNS for epilepsy in the US by using a nationwide database.

Methods

Data for patients undergoing VNS were obtained from the nationwide inpatient sample for the years 1998–2005. Trends regarding number of procedures, length of stay (LOS), hospital charges, patient sex, and payer information were retrieved and analyzed.

Results

The number of VNS procedures for epilepsy increased between 1998 and 2003 but decreased in the subsequent 2 years. The LOS and hospital charges showed yearly increases. Female patients underwent VNS implantation more than males did, and most procedures were performed in the 18- to 64-year-old age group. The combination of Medicare and Medicaid provided most of the funding for VNS from 2002 through 2005. The VNS procedures were performed mostly in teaching hospitals.

Conclusions

Trends from a national database reveal consistent use of VNS for intractable epilepsy. Greater use of the procedure appears to be reflected in the female population, and the procedure has been performed most often at tertiary care teaching hospitals, where a comprehensive evaluation for all forms of therapy is arguably best able to target appropriate patients for appropriate therapies. With the recent application of VNS to target populations without epilepsy, such as patients with refractory depression, the trend of continued use of this treatment for epilepsy appears likely.

Self-closing surgical clips for use in pericallosal artery–pericallosal artery side-to-side bypass

The authors demonstrate the feasibility of a new procedure to create intracranial interrupted microvascular anastomosis. Self-closing nitinol surgical clips were used for a pericallosal artery–pericallosal artery side-to-side bypass in a 52-year-old man harboring an unruptured large aneurysm located on the right A2 segment. The outflow artery was found to arise from the dome of the aneurysm, which was considered unsuitable for stand-alone clip ligation or coil occlusion. After bypass patency was intraoperatively confirmed using near-infrared indocyanine green videoangiography, the aneurysm and feeding artery were embolized with coils and safely occluded. Both postoperative courses were uneventful. The patient was discharged neurologically intact on the 5th postembolization day. Postprocedure angiography demonstrated no ipsilateral aneurysm filling and excellent bilateral distal outflow from the left anterior cerebral artery.

Identification of the optimal cortical target point for extracranial-intracranial bypass surgery in patients with hemodynamic cerebrovascular insufficiency

OBJECT

The objective of this report is to describe a new approach to identify the optimal cortical target point for extracranial-intracranial (EC-IC) bypass surgery, to reliably find suitable recipient vessels for the anastomosis.

METHODS

Thirty consecutive patients (17 men and 13 women; mean age 54.6 +/- 11.79 years [+/- standard deviation]) with hemodynamic cerebrovascular insufficiency due to stenoocclusive arterial disease underwent EC-IC bypass surgery. The end of the Sylvian fissure was identified preoperatively using a specially designed template and external landmarks. At surgery, a 3-cm trephination was made, centered over the target point as determined by the template. The number, diameter, and length of the exposed cortical arteries were assessed using photographs and indocyanine green (ICG) angiograms.

RESULTS

At least 1 recipient artery appropriate for anastomosis (>or= 1 mm) was found in every craniectomy. The mean number of suitable recipient arteries per craniotomy was 2.09 +/- 0.87, the mean diameter was 1.28 +/- 0.24 mm, and the mean length 10.83 +/- 4.87 mm. Bypass patency was confirmed by intraoperative ICG angiography, postoperative computed tomography angiography, and digital subtraction angiography, and reached 100%.

CONCLUSIONS

Performing a 3-cm craniectomy over the described target point, reliably allows access to suitable recipient arteries for EC-IC bypass surgery.

Microvascular Anastomosis Training Model Based on a Turkey Neck with Perfused Arteries

Objective:

The microvascular anastomosis (MA) technique remains an important aspect of modern neurosurgical practice. Specialized training is essential for mastering the anastomosis of small vessels. To minimize animal use and to create a simple but realistic training model, we developed a pulsatile perfused arteries model based on turkey carotid arteries for microvascular anastomosis training.

Methods:

Approximately 10-cm-long segments of turkey necks were used as a material to set up this model. The diameter of turkey carotid arteries at the neck level was found to be between 1 and 3 mm. Both carotid arteries on the neck segment were cannulated and incorporated into a closed circulation circuit consisting of silicone tubes and an infusion pump that provided continuous arterial-like flow and pulsation during the MA training. Tubing connection with both proximal and distal ends of the carotid arteries allowed circulatory patency during vessel clamping and anastomosis creation. Different fluids ranging from simple water to various colored solutions or even whole blood could be used for vascular perfusion in this experimental setup. Fluid output was maintained between 11 and 16 ml/min. Minimum pressure was set at 80 cm/H20, and maximum pressure was set at 160 cm/H20. Mean fluid flow through the arteries was 8 to 13 ml/min. End-to-end, end-to-side, and side-to-side MA may be performed on this model.

Results:

This training model provides several advantages: the materials are easily obtainable and inexpensive, pulsatile flow through the arteries is realistic, the model is easy to manage, and there is no need for special facilities for animal care or anesthesia that are required for live animals. The diameter and structure of turkey carotid arteries are essentially identical to the human cortical vessels and distal branches of the superficial temporal artery.

Conclusion:

The pulsatile perfused carotid arteries model presents a realistic MA training model. It provides an inexpensive and simple setup for educational purposes. This technique can minimize live animal and anesthesia needs for MA training. Wide use of this model may enhance and popularize MA training and education.

Superficial temporal artery to middle cerebral artery bypass: past, present, and future

OBJECT

The aim of this study was to review the historical developments and current status of superficial temporal artery (STA) to middle cerebral artery (MCA) bypass.

METHOD

A literature review was performed to review the origins and current uses of the STA bypass procedure in neurosurgery.

RESULTS

The idea of providing additional blood supply to the brain to prevent stroke and maintain neurological function has been present in the mind of neurosurgeons for many decades. In 1967 the first STA-MCA bypass was done by M. G. Yaşargil, and an enormous step was made into the field of microneurosurgery and cerebral revascularization. During the decades that followed, this technique was used as an adjuvant or a definitive surgical treatment for occlusive disease of the extracranial and intracranial cerebral vessels, skull base tumors, aneurysms, carotid-cavernous fistulas, cerebral vasospasm, acute cerebral ischemia, and moyamoya disease. With the results of the first randomized extracranial-intracranial (EC-IC) bypass trial and the development of endovascular techniques such as angioplasty for intracranial atherosclerotic disease and cerebral vasospasm, the indications for STA-MCA bypass became limited. Neurosurgeons continued to perform EC-IC bypasses as an adjuvant to clipping of aneurysms and in the treatment of skull base tumors and moyamoya disease; the procedure is less commonly used for atherosclerotic carotid artery occlusion (CAO) with definite evidence of hemodynamic insufficiency. The evidence that patients with symptomatic CAO and "misery perfusion" have an increased stroke risk has prompted a second trial for evaluating EC-IC bypass for stroke prevention. The Carotid Occlusion Surgery Study is a new trial designed to determine whether STA-MCA bypass can reduce the incidence of stroke in these patients. New trials will also reveal the role of the STA-MCA bypass in the prevention of hemorrhages in moyamoya disease.

CONCLUSIONS

The role of STA-MCA bypass in the management of cerebrovascular disease continues to be refined and evaluated using advanced imaging techniques and by performing randomized trials for specific purposes, including symptomatic CAO.

Flow-assisted surgical cerebral revascularization

✓Extracranial–intracranial bypass surgery has advanced from a mere technical feat to a procedure requiring careful patient selection and a justifiable decision-making paradigm. Currently available technologies for flow measurement in the perioperative and intraoperative setting allow a more structured and analytical approach to decision making. The purpose of this report is to review the use of flow measurement in cerebral revascularization, presenting algorithms for flow-assisted surgical planning, technique, and surveillance.

EC-IC bypass: The failure of a clinical trial? Applicability to PFO closure trials

Extracranial-to-intracranial (EC-IC) bypass surgery was used to prevent stroke in patients with carotid occlusion and inadequate collateral flow. Because of inappropriate proliferation of EC-IC bypass, a randomized clinical trial was carried out. The failure of the trial may have been related to inappropriate patient selection and all eligible patients not being randomized. Subsequent study has identified criteria for patient selection and new trials are underway. The present patent foramen ovale closure trials share many of the same difficulties, including overuse of the procedure and interventionalists reluctant to randomize patients. If these trials are not properly done we will be in the same situation in 20 years that the EC-IC trialists are facing today. Improvements in patient selection criteria, randomization of all eligible patients, and better statistical parameters will increase the likelihood of future trials getting the correct answer the first time. The importance of carefully done observational trials should not be overlooked.

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.

SELF-CLOSING U-CLIPS FOR INTRACRANIAL MICROANASTOMOSES IN HIGH-FLOW ARTERIAL BYPASS

OBJECTIVE

Self-closing nitinol U-clips (Medtronic, Inc., Minneapolis, MN) have been used to create vascular microanastomoses by vascular surgeons. This device eliminates the need for suture management and knot tying. Therefore, a high-quality interrupted microvascular anastomosis can be obtained in a shorter period of time. This is the first report of a U-clip intracranial arterial microanastomosis for a high-flow extracranial-intracranial bypass using a radial artery graft.

CLINICAL PRESENTATION

A 24-year-old woman with a history of chronic headache was admitted to the National Neurological Institute Carlo Besta after a brain computed tomographic scan revealed a giant serpentine aneurysm of her right middle cerebral artery. Magnetic resonance angiography and four-vessel angiography confirmed the diagnosis and ruled out other lesions.

INTERVENTION

A radial artery graft was used to create a high-flow bypass between the external carotid artery and the postaneurysmal M2 segment of the right middle cerebral artery. Nitinol self-closing U-clips were used for the interrupted intracranial microanastomosis. After intraoperative near-infrared indocyanine green video angiography confirmed the bypass patency, the aneurysm could be trapped.

CONCLUSION

The postoperative course was uneventful. The patient was discharged on the seventh postoperative day and was neurologically intact. Postoperative angiography documented the successful exclusion of the aneurysm and the presence of revascularization of the distal branches of the right middle cerebral artery through the bypass. This case demonstrates the efficacy of U-clips for intracranial microanastomoses.

Is Extracranial-Intracranial Bypass Surgery Effective in Certain Patients?

The role of surgical revascularization for patients who have ischemic disease remains controversial. Despite the previous EC-IC bypass trial that failed to demonstrate the benefit from STA-MCA bypass compared with medical therapy, however, there is mounting evidence that the procedure should be considered in selected patients. Bypass remains a mainstay of treatment in moyamoya disease and in flow replacement in the setting of planned vessel sacrifice.