Postsurgical observations of mean hemispheric cerebral blood flow with patients receiving high-flow EC-IC bypass using a radial artery graft (preliminary report, one-year observation of 10 hemispheres)

Vascular responses to abrupt blood flow change after bypass surgery for complex intracranial aneurysms

BACKGROUND

Bypass surgery for complex intracranial aneurysms (IAs) results in drastic blood flow changes in intracranial arteries. The aim of the study was to elucidate how vessels adapt to blood flow changes after bypass surgery with phase-contrast magnetic resonance imaging (PC-MRI).

METHODS

This is a prospective observational study to assess changes of the blood flow in intracranial arteries after bypass surgery for IAs. Flow rates and vessel diameters were measured with PC-MRI in 52 intracranial arteries of 7 healthy volunteers and 31 arteries of 8 IA patients who underwent bypass surgery. Wall shear stress (WSS) was calculated with the Hagen-Poiseuille formula. In 18 arteries of 5 patients, the same measurement was performed 1, 3, and 12 months after surgery.

RESULTS

PC-MRI showed a strong positive correlation between the flow rate and the third power of vessel diameter in both healthy volunteers (r = 0.82, P < 0.0001) and IA patients (r = 0.90, P < 0.0001), indicating the constant WSS. Of the 18 arteries in 5 patients, WSS increased in 7 arteries and decreased in 11 arteries immediately after surgery. In the WSS-increased group, WSS returned to the preoperative value in the third postoperative month. In the WSS-decreased group, WSS increased in the 12th month, but did not return to the preoperative level.

CONCLUSIONS

In a physiological state, WSS was constant in intracranial arteries. Changed WSS after bypass surgery tended to return to the preoperative value, suggesting that vessel diameter and flow rate might be controlled so that WSS remains constant.

Risk factors for neurological worsening and symptomatic watershed infarction in internal carotid artery aneurysm treated by extracranial-intracranial bypass using radial artery graft

OBJECT

The revascularization technique, including bypass created using the external carotid artery (ECA), radial artery (RA), and M2 portion of middle cerebral artery (MCA), has remained indispensable for treatment of complex aneurysms. To date, it remains unknown whether diameters of the RA, superficial temporal artery (STA), and C2 portion of the internal carotid artery (ICA) and intraoperative MCA blood pressure have influences on the outcome and the symptomatic watershed infarction (WI). The aim of the present study was to evaluate the factors for the symptomatic WI and neurological worsening in patients treated by ECA-RA-M2 bypass for complex ICA aneurysm with therapeutic ICA occlusion.

METHODS

The authors measured the sizes of vessels (RA, C2, M2, and STA) and intraoperative MCA blood pressure (initial, after ICA occlusion, and after releasing the RA graft bypass) in 37 patients. Symptomatic WI was defined as presence of the following: postoperative new neurological deficits, WI on postoperative diffusion-weighted imaging, and ipsilateral cerebral blood flow reduction on SPECT. Neurological worsening was defined as the increase in 1 or more modified Rankin Scale scores. First, the authors performed receiver operating characteristic curve analysis for continuous variables and the binary end point of the symptomatic WI. The clinical, radiological, and physiological characteristics of patients with and without the symptomatic WI were compared using the log-rank test. Then, the authors compared the variables between patients with and without neurological worsening at discharge and at the 12-month follow-up examination or last hospital visit.

RESULTS

Symptomatic WI was observed in 2 (5.4%) patients. The mean MCA pressure after releasing the RA graft (< 55 mm Hg; p = 0.017), mean (MCA pressure after releasing the RA graft)/(initial MCA pressure) (< 0.70 mm Hg; p = 0.032), and mean cross-sectional area ratio ([RA/C2 diameter]2 < 0.40 mm [p < 0.0001] and [STA/C2 diameter]2 < 0.044 mm [p < 0.0001]) were related to the symptomatic WI. All preoperatively independent patients remained independent (modified Rankin Scale score < 3). After adjusting for age and sex, left operative side (p = 0.0090 and 0.038) and perforating artery ischemia (p = 0.0050 and 0.022) were related to neurological worsening at discharge (11 [29%] patients) and at the 12-month follow-up or last hospital visit (8 [22%] patients).

CONCLUSIONS

Results of the present study showed that the vessel diameter and intraoperative MCA pressure had impacts on the symptomatic WI and that operative side and perforating artery ischemia were related to neurological worsening in patients with complex ICA aneurysms treated by ECA-RA-M2 bypass.

Impact of cervical internal carotid clamping and radial artery graft bypass on cortical arterial perfusion pressure during craniotomy

Strategic cervical internal carotid occlusion is employed either temporarily or permanently in various neurosurgical procedures. The aim of the present study was to assess changes in cortical arterial pressure during cervical internal carotid cross-clamping before and after the placement of radial artery (RA) graft bypass in the treatment of complex carotid artery aneurysms. Perfusion pressure of the middle cerebral artery (MCA) was assessed in 22 patients with complex carotid aneurysm treated with RA graft bypass. Regional cerebral blood flow was assessed postoperatively using single-photon computed tomography. Mean cortical blood pressure (mcBP) was found to be 48.2 ± 24.2 and 97.0 ± 24.0 % of baseline after clamping the cervical internal carotid artery and opening the RA graft bypass, respectively. Cerebral perfusion pressure estimated by the mcBP failed to sustain a critical limit of greater than 70 mmHg under craniotomy in 16 out of 20 (80 %) patients. There was an inverse correlation in mcBP between the baseline and after the placement of the RA graft bypass (r = 0.66, P < 0.005). Postoperative regional cerebral blood flow in the MCA territory on the ipsilateral side of the aneurysm was 97 ± 7 % of that of the contralateral side after internal carotid artery (ICA) ligation combined with RA graft bypass. Substantial pressure reductions in cerebral cortical arteries were observed during the cervical internal carotid cross-clamping. Perfusion pressure in peripheral cortical arteries after the placement of the RA graft bypass was comparable to the state before ICA clamping.

Changing Treatment Strategy From Clipping to Radial Artery Graft Bypass and Parent Artery Sacrifice in Patients With Ruptured Blister-Like Internal Carotid Artery Aneurysms

BACKGROUND:

Blood blister-like aneurysms (BBAs) are aneurysms with ill-defined fragile necks arising from an internal carotid artery (ICA) and associated with high mortality.

OBJECTIVE:

To describe strategies and outcomes in patients in whom radial artery (RA) graft bypass with ICA sacrifice was considered as the primary treatment during the acute phase of subarachnoid hemorrhage.

METHODS:

The authors analyzed the clinical records of 20 patients who were treated between 2004 and 2011 at their hospital and affiliate institutions.

RESULTS:

A majority of the patients were treated during the acute phase (&lt;24 hours, n = 15). A favorable outcome was achieved in 18 (90%) patients. The treatment strategies used were as follows: (1) ICA trapping/external carotid artery (ECA)-RA-middle cerebral artery (MCA) bypass (n = 13), (2) ICA trapping/superficial temporal artery-MCA bypass (n = 2), (3) aneurysm clipping with RA-MCA temporary bypass (n = 3), (3) aneurysm clipping with proximal ICA ligation and ECA-RA-MCA bypass (n = 1), and (4) direct clipping (n = 1). Postoperative infarction was observed in 6 patients and was ascribed to vasospasm (n = 1), retrograde thrombosis associated with trapping (n = 2), and reasons unrelated to the surgical procedures (n = 3).

CONCLUSION:

Trapping with RA graft bypass demonstrated favorable results in patients with internal carotid BBAs. Although trapping/RA graft bypass is a definitive treatment for BBAs located proximal to the origin of the posterior communicating artery, some distal BBAs preclude ICA trapping to spare the perforating arteries.

Extracranial-intracranial bypass surgery using a radial artery interposition graft for cerebrovascular diseases

OBJECTIVE

To investigate the efficacy of extracranial-intracranial (EC-IC) bypass surgery using a radial artery interposition graft (RAIG) for surgical management of cerebrovascular diseases.

METHODS

The study involved a retrospective analysis of 13 patients who underwent EC-IC bypass surgery using RAIG at a single neurosurgical institute between 2003 and 2009. The diseases comprised intracranial aneurysm (n=10), carotid artery occlusive disease (n=2), and delayed stenosis in the donor superficial temporal artery (STA) following previous STA-middle cerebral artery bypass surgery (n=1). Patients were followed clinically and radiographically.

RESULTS

Bypass surgery was successful in all patients. At a mean follow-up of 53.4 months, the short-term patency rate was 100%, and the long-term rate was 92.3%. Twelve patients had an excellent clinical outcome of Glasgow Outcome Scale (GOS) 5, and one case had GOS 3. Procedure-related complications were a temporary dysthesia on the graft harvest hand (n=1) and a hematoma at the graft harvest site (n=1), and these were treated successfully with no permanent sequelae. In one case, spasm occurred which was relieved with the introduction of mechanical dilators.

CONCLUSION

EC-IC bypass using a RAIG appears to be an effective treatment for a variety of cerebrovascular diseases requiring proximal occlusion or trapping of the parent artery.

The efficacy of direct extracranial-intracranial bypass in the treatment of symptomatic hemodynamic failure secondary to athero-occlusive disease: a systematic review

OBJECTIVE

The 1985 International Extracranial-Intracranial (EC-IC) Bypass Trial failed to show a benefit following surgery in patients with varying degrees of angiographic ICA stenosis. More recent studies using modern technology to identify appropriate candidates, however, have generated promising findings. As a result, controversy exists regarding the role of this technique in the treatment of symptomatic athero-occlusive disease. To this end, we performed a systematic review and quantitative analysis of the literature to determine if a subset of patients with symptomatic hemodynamic failure secondary to athero-occlusive disease may benefit from direct EC-IC bypass.

METHODS

We performed a MEDLINE (1985-2007) database search using the following keywords, singly and in combination: EC-IC bypass, hemodynamic failure and misery perfusion. Additional studies were identified manually by scrutinizing references from identified manuscripts, major neurosurgical journals and texts, and personal files. Our literature search divided studies into three categories: natural history of patients with stage I hemodynamic failure (16 studies, 2320 patients), natural history of patients with stage II hemodynamic failure (3 studies 163 patients), and outcomes of patients with hemodynamic failure treated by EC-IC bypass (23 studies 506 patients).

RESULTS

Patients with severe stage I and stage II hemodynamic failure are at higher risk of cerebral infarction than those with mild disease (p=.014, OR 1.17-4.08 and p=0.10, OR 0.89-3.63, respectively). Additionally, patients with severe hemodynamic failure respond better to surgery than those with mild disease (p=0.03, OR 0.16-0.92).

CONCLUSIONS

Patients with severe hemodynamic failure secondary to athero-occlusive disease appear to benefit from direct EC-IC bypass surgery. As a result, the conclusions of the 1985 International EC-IC Bypass Trial may not be applicable to this subset of patients. A randomized clinical trial involving this patient population is warranted.

Extracranial-intracranial bypass to reduce the risk of ischemic stroke in intracranial aneurysms of the anterior cerebral circulation: a systematic review

BACKGROUND AND PURPOSE

If clip application or coil placement for treatment of intracranial (IC) aneurysms is not feasible, the parent vessel can be occluded to induce thrombosis of the aneurysm. In the case that such an occlusion cannot be tolerated without subsequent sequel, the additional construction of an extracranial (EC)-IC bypass is needed for sufficient ipsilateral revascularization. Hitherto, the effectiveness of this combined treatment option was not investigated in a controlled randomized trial or in a review. The aim of the current report was to analyze clinical effectiveness of EC-IC bypass for cerebral revascularization in patients with Hunterian ligation in case of otherwise untreatable aneurysm of the anterior cerebral circulation. Special reference was given to different hemodynamic subgroups.

METHODS

A computerized database search was conducted from November 1985 to November 2002 using MEDLINE, relevant Internet sources, and full-text journal articles using appropriate indexed terms. Journal of Neurosurgery, Neurosurgery, Acta Neurochirurgica, and Stroke were manually searched for the period November 1985 to November 2002 and checked reference lists of all relevant articles for additional eligible studies. Language restriction was done for English, French, and German. Reports dealing with EC-IC bypass surgery for cerebral revascularization in case of aneurysm of the anterior cerebral circulation were reviewed when appropriate. Studies were included that contained evaluable data on clinical state, preoperative and postoperative hemodynamic state, surgical outcome, and follow-up. A statistical analysis was performed for different outcome parameters and clinical effectiveness in the included studies.

RESULTS

Overall, 20 studies were included, each with a study quality of 0-1. The postoperative outcome related to death or stroke depended mainly on preoperative hemodynamic subgroups (cerebral blood flow [CBF]/cerebral blood volume [CBV]; oxygen extraction fraction [OEF]). The final functional status was worse the more CBF/CBV ratio and OEF increased. Perioperative risk for death (0.8%) or stroke (1.5%) during the first month after operation was similar to the death or stroke rate during the following 2 to 12 months after operation. Neurologic function was improved over the preoperative state in 74% of the patients and was unchanged in 9%. The modified Rankin scale score was postoperatively 0 to 1 in 81% and 2 in 6% of the patients. Long-term patency was excellent, with 2.3% failure rate per year after the first year after surgery. There was no de novo aneurysm formation in the follow-up.

CONCLUSION

Neurologic function and subsequent stroke attributable to hemodynamic insufficiency in patients with otherwise untreatable IC aneurysm improves significantly by EC-IC bypass surgery if the brain area corresponding to the impaired neurologic function remains viable. The hemodynamic parameters observed for patients who experience improved neurologic function or diminished stroke risk profile after EC-IC bypass surgery contain both significantly elevated OEF and CBF/CBV. Therefore, hemodynamic state represents an important indicator for EC-IC bypass surgery. The large amount of data leads to narrow stroke with no significant heterogeneity, and the overall results are, therefore, likely to be statistically robust.

The extracranial-intracranial bypass trial: implications for future investigations

The 1985 International Extracranial-Intracranial (EC-IC) Bypass Trial failed to show a surgical benefit of EC-IC bypass in patients with varying degrees of angiographic stenosis. This study was limited by the technology available at the time it was conducted. In the 20 years since, there has been considerable progress in imaging techniques that now enable the identification of a subset of stroke patients with hemodynamic ischemia. In the present study, the authors review the relevant literature and propose a reevaluation of the benefits of the EC-IC bypass procedure using these new imaging techniques. The authors reviewed the admission criteria for the EC-IC Bypass Trial in the light of more recently discovered neurovascular physiology and showed that the imaging criteria used in that trial are not physiologically adequate. A MED-LINE (1985-2007) database search for EC-IC case studies was conducted, and additional studies were identified manually by scrutinizing references from identified manuscripts, major neurosurgical journals and texts, and personal files.

Superficial temporal artery graft for bypass of the maxillary to proximal middle cerebral artery using a transantral approach: an anatomical and technical study

CONCLUSION

Using a transantral approach, we examined a new bypass of the maxillary artery (MA) to proximal middle cerebral artery (MCA). The caliber of the MA was suitable to provide sufficient blood flow. The length of the graft was shorter and it had a straighter course in the new technique than in previously described techniques.

OBJECTIVE

To examine a new bypass of the MA to proximal MCA using a transantral approach as an alternative to other forms of anterior circulation bypass surgery.

MATERIAL AND METHODS

The method was applied to five adult cadavers bilaterally. The MA and its branches were easily found after removal of the posterior sinus wall using a transantral approach. Then, a hole was created in the sphenoid bone 5-6 mm lateral to the posteroinferior edge of the superior orbital fissure extradurally. After the carotid and sylvian cisternae had been opened, the M2 segment of the MCA was exposed. The MA was transected just before the origin of the descending palatine artery branch. After opening the dura over the hole, the MA was passed through the hole to reach the intracranial cavity. The proximal side of the superficial temporal artery graft was anastomosed end-to-end with the MA and the distal side was anastomosed end-to-side with the M2 segment of the MCA.

RESULTS

The mean caliber of the MA was 2.4+/-0.3 mm before the origin of the descending palatine artery branch. The mean caliber of the largest trunk of the M2 segment of the MCA was 2.3+/-0.3 mm. The average length of the graft was 24+/-3 mm.

Experience from "double-insurance bypass." Surgical results and additional techniques to achieve complex aneurysm surgery in a safer manner

BACKGROUND

"Double-insurance bypass" was recently advocated to avoid the risk of cerebral ischemia during prolonged temporary occlusion of the carotid artery. For large aneurysms needing temporary but prolonged obliteration of the internal carotid artery (ICA). We have attempted the double-insurance bypass in 15 patients and, herein, report the efficacies and limitations of the procedure, and surgical techniques to make this procedure safer.

METHODS

We treated 15 patients with complex internal carotid aneurysms by clipping surgery with the aid of radial artery (RA) to proximal middle cerebral artery (MCA) bypass, so-called double-insurance bypass. We analyzed surgical results of the procedure.

RESULTS

In 11 patients, the duration of temporary occlusion of the ICA could be prolonged for as long as 110 minutes (mean, 45 minutes) without any ischemic complications. One patient in the earlier period of our experience suffered extended cerebral infarction due to possible restricted blood flow through the RA, because the brachial artery was compressed by the firm shoulder joint and neighboring structures. Thereafter, we routinely monitored the blood pressure of MCA (MCABP) and never experienced such cortical infarctions. Another 3 patients, however, experienced ischemia in the territory of perforating arteries that originated from a segment that could not be perfused by the RA-MCA bypass.

CONCLUSIONS

In combination with monitoring of MCABP, the double-insurance bypass can be a safer and more potent adjunctive procedure for the treatment of complex internal carotid aneurysms which require prolonged temporary occlusion of the ICA.

Microsurgical anatomy of cerebral revascularization. Part I: Anterior circulation

Object. Revascularization is an important component of treatment for complex aneurysms that require parent vessel occlusion, skull base tumors that involve major vessels, and certain ischemic diseases. In this study, the authors examined the microsurgical anatomy of cerebral revascularization in the anterior circulation by demonstrating various procedures for bypass surgery.

Methods. Twenty-five adult cadaveric specimens were studied, using 3 to 40 magnification, after the arteries and veins had been perfused with colored silicone. The microsurgical anatomy of cerebral revascularization in the anterior circulation was examined with the focus on the donor, recipient, and graft vessels. The techniques discussed in this paper include the superficial temporal artery (STA)—middle cerebral artery (MCA), middle meningeal artery (MMA)—MCA, and side-to-side anastomoses; short arterial and venous interposition grafting; and external carotid artery/internal carotid artery (ICA)—M2 and ICA—ICA bypasses. Bypass procedures for cerebral revascularization are divided into two categories depending on their flow volume: low-flow and high-flow bypasses. A low-flow bypass, such as the STA—MCA anastomosis, is used to cover a relatively small area, whereas a high-flow bypass, such as the ICA—ICA anastomosis, is used for larger areas. Cerebral revascularization techniques are also divided into two types depending on the graft materials: pedicled arterial grafts, such as STA and occipital artery grafts, and free venous or arterial grafts, which are usually saphenous vein and radial artery grafts. Pedicled arterial grafts are mainly used for low-flow bypasses, whereas venous or arterial grafts are used for high-flow bypasses.

Conclusions. It is important to understand the methods of bypass procedures and to consider indications in which cerebral revascularization is needed.

Radial Artery Graft for Bypass of the Maxillary to Proximal Middle Cerebral Artery: An Anatomic and Technical Study

OBJECTIVE

In this study, we aimed to investigate the use of a radial artery graft for bypass of the maxillary artery (MA) to the proximal middle cerebral artery (MCA) as an alternative to superficial temporal artery-to-MCA anastomosis or extracranial carotid-to-MCA bypass using long grafts.

METHODS

Five adult cadavers were used bilaterally. After a frontotemporal craniotomy and a zygomatic arch osteotomy, the MA was found easily 1 to 2 cm inferior to the infratemporal crest. A hole was created with a 4-mm-tip drill in the sphenoid bone 2 to 3 mm lateral to the foramen rotundum extradurally, and the dura over the hole was opened. After the carotid and sylvian cisterns had been opened, the M2 segment of the MCA was exposed. The graft was passed through the hole to reach the M2 segment. Then, the MA was freed from the surrounding tissue and was transected before the infraorbital artery branch. The radial artery graft was anastomosed end-to-end to the MA proximally and end-to-side to the M2 segment of the MCA distally.

RESULTS

The mean thickness of the MA before the infraorbital artery branch was 2.6 ± 0.3 mm. The mean thickness of the largest trunk of the MCA was 2.3 ± 0.3 mm. The average length of the graft was 36 ± 5.5 mm.

CONCLUSION

MA-to-MCA bypass is as feasible as proximal MCA revascularization using long vein grafts. The thickness of the MA provides sufficient flow; the length of the graft is short, and it has a straight course. MA-to-proximal MCA bypass may be an alternative to superficial temporal artery-to-MCA as well as extracranial carotid-to-MCA bypasses.

Proximal superficial temporal artery to proximal middle cerebral artery bypass using a radial artery graft: an anatomic approach

We present the use of radial artery graft for bypass of the proximal superficial temporal artery to the proximal middle cerebral artery. Six adult cadaver sites were used bilaterally. After apterional incision, 2x2-cm minicraniectomy was performed which began 2 cm behind the zygomatic process of the frontal bone. The superficial temporal artery was transsected before exposing the zygomatico-orbital artery branch. The proximal side of the radial artery graft was anastomosed end-to-end to the proximal superficial temporal artery and the distal side end-to-side to the proximal middle cerebral artery. The mean calibers of the proximal superficial temporal artery and largest trunk of the middle cerebral artery were 2.25+/-0.35 mm and 2.3+/-0.3 mm, respectively. The average graft length was 85+/-5.5 mm. We conclude that such bypasses are simpler than proximal middle cerebral artery revascularization using long vein grafts. This method proves that the caliber of the proximal superficial temporal artery is more suited to providing sufficient flow than the distal superficial temporal artery, and the graft is short. Such bypasses to the middle cerebral artery may be an alternative to those from the distal superficial temporal artery or extracranial carotid artery.

Venous and arterial bypass grafts for difficult tumors, aneurysms, and occlusive vascular lesions: evolution of surgical treatment and improved graft results

OBJECTIVE: In the treatment of patients with cranial base tumors, unclippable aneurysms, or medically intractable ischemia, it may be necessary to use high-flow bypass grafts. The indications, surgical techniques and complications are discussed. METHODS: During a 10-year period, 99 saphenous vein grafts and 3 radial artery grafts were performed for 101 patients, i.e., 72 with neoplasms, 23 with aneurysms, and 6 with ischemia. Clinical follow-up monitoring of the patients was by direct examination or telephone interview, with a mean follow-up period of 41.2 months (range, 5-147 mo). Radiological follow-up monitoring was by magnetic resonance imaging, magnetic resonance angiography, or three-dimensional computed tomographic angiography, with a mean follow-up period of 32 months (range, 1-120 mo). During the follow-up period, there was one late graft occlusion and one graft stenosis. RESULTS: The use of intraoperative angiography improved the patency rate from 90 to 98% and reduced the incidence of perioperative stroke from 13 to 9.5%. Ninety-two percent of the patients were in excellent or good neurological condition at the time of discharge from the hospital, compared with 95% before surgery. The perioperative mortality rate was 2%. Other complications included three intracranial hematomas, rupture of a vein graft in a patient with Marfan's syndrome, and five tumor resection-related problems. The long-term survival rates for patients who received grafts were excellent for patients with benign tumors, fair to poor for patients with malignant tumors, good for patients with aneurysms, and excellent for patients with ischemia. CONCLUSION: The results of saphenous vein and radial artery grafting have been greatly improved by the use of intraoperative angiography, improvements in surgical techniques, and improved perioperative treatment.