Cerebral revascularization

Giant and complex aneurysms treatment with preservation of flow via bypass technique

Due to their anatomical characteristics and the complexity of the procedures required to obtain their complete occlusion, the treatment of giant intracranial aneurysms is a real challenge. Direct reconstructive strategies, whether by interventional neuroradiology (coils, stents) or microsurgical (clipping) means, are not always applicable and, in patients that would not tolerate parent or collateral artery sacrifice, the adjunction of a revascularization procedure using a bypass technique might be necessary. Cerebral arterial bypasses can be classified according to their function (3 types: flow replacement, flow reversal or protective), the branching mode of the graft used (3 types: pedicled, interpositional or in situ), the sites of anastomosis (2 types: extracranial-intracranial or intracranial-intracranial) and the class of flow they are supposed to provide (3 types: low-, intermediate- or high-flow). In this article, the authors review the different aspects in the management of patients with a giant intracranial aneurysm using a bypass: preoperative work-up, types of bypass and indications, surgical techniques and results.

Extracranial Posterior Communicating Artery Bypass for Revascularization of Patients With Common Carotid Artery Occlusion

BACKGROUND:

Extracranial-intracranial bypass surgery provides blood flow augmentation in patients suffering from intracranial or long-distance conductance artery stenosis or occlusion that otherwise cannot be treated. The standard procedure for these cases is an anastomosis between the superficial temporal and middle cerebral arteries. However, in patients presenting with common carotid artery occlusion, the superficial temporal artery is no longer sufficiently perfused. For these patients, alternative revascularization strategies have to be applied.

OBJECTIVE:

To describe a novel strategy for revascularization of patients with common carotid artery occlusion, ie, the extracranial posterior communicating artery bypass.

METHODS:

Two patients with chronic cerebrovascular compromise resulting in transitory ischemic attacks and/or border-zone infarctions caused by common carotid artery occlusion were referred to our institution. A radial artery bypass was established between the third segment of the vertebral artery and an M3 branch of the middle cerebral artery. The vertebral artery was exposed between the vertebral lamina of C1 and occipital bone via a paramedian incision. The bypass was tunneled subcutaneously, conducted intracranially via a tailored extended burr-hole craniotomy, and anastomosed to a recipient M3 vessel.

RESULTS:

The postoperative course of both patients was uneventful in terms of cerebral ischemia or bleeding complications. In both patients, postoperative angiographic controls revealed an excellent bypass function with markedly improved hemispheric filling of multiple middle cerebral artery branches. The patients were discharged without new neurological symptoms.

CONCLUSION:

Our extracranial posterior communicating artery bypass using a radial artery transplant from the vertebral artery to the middle cerebral artery is a useful tool to treat patients suffering from hemodynamic cerebrovascular compromise caused by common carotid artery occlusion.

Minimally occlusive laser vascular anastomosis (MOLVA): experimental study

BACKGROUND

Temporary occlusion of an intracranial artery during microvascular anastomosis is a major risk factor in cerebrovascular surgery. A new laser vascular welding technique that minimizes the occlusion time of the recipient vessel has been developed and is described in this report.

METHOD

A new minimally occlusive technique of end-to-side microvascular anastomosis was developed employing a diode laser in association with the application of a chromophore in our experimental model of double end-to-side anastomosis. The implantation of a vein graft on the patent carotid artery was obtained through the application of three interrupted sutures at each anastomotic site; the carotid was then clamped, two arteriotomies were performed, followed by the application of a fourth suture and of the laser welding procedure on each anastomosis. Monitoring of the temperature at the site of the anastomosis was introduced in order to control the welding technique.

FINDINGS

The time of the clamping of the carotid artery was 12 min to perform two end-to-side anastomoses (i.e., 6 min for each anastomosis). All bypasses were patent after a follow-up of 90 days and histological study confirmed good preservation of the vascular wall.

CONCLUSIONS

Our laser-assisted technique of vascular anastomosis reduces the duration of the clamping of the recipient artery down to 6 min. This technique can minimize the risk of cerebral ischemia associated with occlusion of a recipient artery in intracranial bypass procedures, promoting an improved vascular healing process with a lower risk of thrombosis and occlusion.

The Use of the Excimer Laser-assisted Anastomosis Technique Alleviates Neuroanesthesia During Cerebral High-flow Revascularization

In patients with complex intracranial aneurysms or skull base tumors, parent vessel occlusion and flow replacement by high-flow bypass surgery is a demanding therapy, both for the neurosurgeon and the neuroanesthesiologist. One reason for this is the need for prolonged temporary occlusion of a major cerebral artery, which carries a high risk of perioperative ischemia and necessitates versatile neuroprotective measures during anesthesia. Recently, a novel excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been introduced, circumventing the need for temporary occlusion of cerebral vessels. We hypothesized that the use of this ELANA technique would facilitate also the neuroanesthesiologic management of these patients. To test this, we reviewed the details of the neuroanesthesiologic management of patients undergoing ELANA high-flow bypass surgery at our institution. Twenty-nine patients with giant aneurysms (n=27) or skull base tumor (n=2) who were undergoing parent vessel occlusion and permanent flow replacement by high-flow bypass surgery using the ELANA technique were investigated retrospectively. The records of the patients were analyzed for induction and maintenance of anesthesia, fluid therapy, transfusion requirements, hemodynamic parameters, and brain protective strategies. Although we are not able to provide a sufficient body of cohort data to compare the neuroanesthesiologic management of patients undergoing the conventional anastomosis technique with management using the ELANA technique, in each of our reported cases the conventional anastomosis technique would have entailed a high probability of prolonged temporary occlusion that would, in turn, have warranted intensive brain-protective strategies. The observation that use of the ELANA technique precluded the necessity of brain-protective strategies without entailing perioperative cerebral infarction suggests that the ELANA technique supports the neurosurgeon in creating difficult permanent intracranial anastomoses and also facilitates neuroanesthesiologic management of patients undergoing cerebral high-flow revascularization procedures.

Modèle animal d'entraînement à l'anastomose temporosylvienne

BACKGROUND AND PURPOSE

Microsurgical training in neurosurgery is essential, the aim being to practise surgery with the microscope and to learn vascular and nervous anastomosis techniques. The objective of this project was to create a model simulating the human anatomy and surgical conditions.

TECHNIQUE

Rats were operated on using a plaster model mimicking a human hemicranium. The technique performed was an end to side anastomosis of the distal free end of the left carotid to the right carotid arteriotomy, using eight interrupted 10/0 sutures, at a depth of 5 cm. Early and delayed patency tests were performed.

DISCUSSION

Various models and techniques for training to microsurgical arterial anastomosis are described in the literature. The determining factor is the skill of the operator, which is in turn dependent on the level of training. This model allows the surgeon to gain significant technical experience with the EC-IC bypass, which is applicable to human neurosurgical practice and is indispensable for the prospective neurovascular surgeon.

Expanded polytetrafluoroethylene graft for bypass surgery using the excimer laser–assisted nonocclusive anastomosis technique

Object

Patients with complex craniocerebral pathophysiologies such as giant cerebral aneurysms, skull base tumors, and/or carotid artery occlusive disease are candidates for a revascularization procedure to augment or preserve cerebral blood flow. However, the brain is susceptible to ischemia, and therefore the excimer laser–assisted nonocclusive anastomosis (ELANA) technique has been developed to overcome temporary occlusion. Harvesting autologous vessels of reasonable quality, which is necessary for this technique, may at times be problematic or impossible due to the underlying systemic vascular disease. The use of artificial vessels is therefore an alternative graft for revascularization. Note, however, that it is unknown to what degree these grafts are subject to occlusion using the ELANA anastomosis technique. Therefore, the authors studied the ELANA technique in combination with an expanded polytetrafluoroethylene (ePTFE) graft.

Methods

The experimental surgeries involved bypassing the abdominal aorta in the rabbit. Ten rabbits were subjected to operations representing 20 ePTFE graft–ELANA end-to-side anastomoses. Intraoperative blood flow, follow-up angiograms, and long-term histological characteristics were assessed 75, 125, and 180 days postoperatively. Angiography results proved long-term patency of ePTFE grafts in all animals at all time points studied. Data from the histological analysis showed minimal intimal reaction at the anastomosis site up to 180 days postoperatively. Endothelialization of the ePTFE graft was progressive over time.

Conclusions

The ELANA technique in combination with the ePTFE graft seems to have favorable attributes for end-to-side anastomoses and may be suitable for bypass procedures.

Training in Cerebrovascular Disease: Do We Need to Change the Way We Train Residents?

WITH THE ONGOING development of endovascular techniques and technologies, treatment of cerebrovascular disease is evolving at a fast pace. For neurosurgery to maintain a leadership role in the treatment of these disorders, modifications in neurosurgical training programs are essential. In this article, we discuss the changes perceived to enable residents to acquire the multifaceted understanding and skill set necessary to meet the new clinical reality and prepare to become the leaders of tomorrow in the management of cerebrovascular disease.

ELANA: Excimer Laser-Assisted Nonocclusive Anastomosis for extracranial-to-intracranial and intracranial-to-intracranial bypass: a review

ELANA, excimer laser-assisted nonocclusive anastomosis, is a technique using an excimer laser/catheter system for intracranial bypass surgery of the brain. The technique has been developed over the past 12 years by Tulleken and colleagues at UMC Utrecht in The Netherlands for treatment of primarily untreatable giant aneurysms. We review here the emergence of transplanted conduit bypass as a valuable technique for managing these lesions and the subsequent development of ELANA bypass. The ELANA technique allows the operating surgeon to perform an extracranial-to-intracranial or intracranial-to-intracranial bypass using a transplanted large caliber conduit without occlusion of the recipient artery, thus eliminating intraoperative ischemic insult related to temporary occlusion time. We describe the ELANA technique, illustrate it with intraoperative photos, and review the relevant literature. ELANA is shown to be safe; we discuss its advantages over conventional techniques.

Long-term reendothelialization of excimer laser—assisted nonocclusive anastomoses compared with conventionally sutured anastomoses in pigs

Object. In contrast to conventional anastomosis methods, the excimer laser—assisted nonocclusive anastomosis (ELANA) technique involves a platinum ring and intima—adventitia apposition with a rim of medial and adventitial layers exposed to the bloodstream. The authors assessed the reendothelialization of porcine carotid arteries through ELANA compared with conventional anastomosis by using scanning electron microscopy.

Methods. In 28 pigs a bypass with one ELANA and one conventional anastomosis was made on the left common carotid artery. All patent anastomoses were evaluated intraoperatively with the aid of an ultrasonographic flowmeter and postoperatively by using scanning electron microscopy at 2 weeks, 2 months, 3 months, and 6 months thereafter. Twenty-four of 28 bypasses (48 of 56 end-to-side anastomoses) were fully patent at the time of evaluation. On scanning electron microscopic evaluation of the bypasses, all 48 patent anastomoses showed complete reendothelialization, including all 24 ELANAs in which the endothelium covered the rim and the laser-ablated edge completely. No endothelial difference was observed between conventional anastomoses and ELANAs, aside from the obvious anatomical differences like the platinum ring, which had been completely covered with endothelium. At 6 months postsurgery, remodeling of the ELANA was observed, leaving the ring covered with a layer of endothelium as the most narrow part of the anastomosis.

Conclusions. In long-term experiments, ELANA allows reendothelialization comparable to that achieved with conventional anastomosis. Considering its nonocclusive and high-flow characteristics, the ELANA technique is preferable in cerebral revascularization procedures.

The ELANA technique: high flow revascularization of the brain

High flow revascularization of the brain is hampered by the fact that temporary occusion of a major cerebral artery is necessary to create the distal anastomosis, which may result in brain ischemia. The excimer laser-assisted non-occlusive anastomosis (ELANA) technique circumvents this problem. In this paper we elucidate the development of a non-occlusive way to make anastomoses to the major cerebral arteries.

Wrapping and coating of cerebral aneurysms: history, evolution and surgical management after a re-bleed

Wrapping or coating of ruptured cerebral aneurysms was an acceptable method of surgical treatment until the 1980s. Occasionally, patients still present with a re-bleed. Management of these patients can be challenging. The author describes his experience of surgically treating ruptured aneurysms that have been previously wrapped. Technical issues in the surgical treatment are discussed with three illustrative cases of aneurysms at different locations encountered from 1999 to 2003. Despite operative difficulties satisfactory surgical results can be accomplished in the majority of these cases.