several methods have been used in cerebrovascular surgery to identify aneurysm obliteration or graft patency or residual nidus . the standard technique to assess anatomic results and confirm success or failure of cerebrovascular surgery is postoperative angiography . however , in case of abnormal finding in postoperative angiography , irreversible neurological deficit due to ischemic injury may have been developed already , or another surgical procedure could be required . numerous authors have recommended the application of intraoperative digital subtraction angiography ( dsa ) to readjust an imperfect procedure immediately5,13 ) . therefore , there is a need for a simple and reliable method with high resolution that allows intraoperative observation and documentation of blood flow in large and small vessels . indocyanine green ( icg ) fluorescence angiography is widely used in ophthalmology for the assessment of the retinal microcirculation in a variety of disorders . recently , many surgeons have advocated the use of microscope - integrated near infrared icg videoangiogrphy for intraoperative assessment3,4,16 ) . we report our early experience with intraoperative icg videoangiography during the surgical treatment of cerebrovascular disease . between august 2011 and april 2012 , 188 patients with cerebrovascular disease were surgically treated by the authors in our institution . the patients ' age ranged from 28 to 82 years ( mean 59.3 years ) . fifty - eight surgeries followed an acute subarachnoid hemorrhage ( sah ) , 69 operations were performed on patients with unruptured aneurysms , 42 cases of carotid endarterectomy ( cea ) were performed , 17 extracranial to intracranial ( ec - ic ) bypass surgeries were performed on patients with moyamoya or atherosclerotic occlusion or complex aneurysm , and two surgeries involved arteriovenous malformation ( avm ) . according to the aneurysm location , there were 55 anterior cerebral artery ( aca ) aneurysms , 41 middle cerebral artery ( mca ) aneurysms , 18 aneurysms of the internal cerebral artery ( ica ) , one aneurysm at the vertebrobasilar ( vb ) artery , and 12 multiple aneurysms . for aneurysm clipping , a pterional transsylvian , bifrontal interhemispheric , suboccipital approach was performed depending on site and size of the aneurysm . cea was performed for symptomatic patients with more than 50% carotid stenosis and for asymptomatic patients with more than 60% carotid stenosis by angiography . indications for ec - ic bypass surgery were hemodynamic compromise due to atherosclerotic stenooclusive cerebrovascular disease in seven patients , moyamoya syndrome or disease in six patients , and the presence of complex intracranial aneurysms in four patients ; the four patients were treated with aneurysm trapping ( n=3 ) and aneurysmorrhaphy ( n=1 ) . patients underwent direct revascularization either through a standard superficial temporal artery ( sta)-mca bypass ( n=14 ) , an occipital artery ( oa)-posterior inferior cerebellar artery ( pica ) bypass ( n=2 ) , or radial artery ( ra ) high - flow bypass ( n=1 ) . both of the patients with avm were spetzler - martin grade 1 and were scheduled for elective surgery . intraoperative icg videoangiography ( icg - va ) was done using an opmi pentero surgical microscope ( carl zeiss , jena , germany ) . the recommended dose of icg dye for va is 0.2 to 0.5 mg / kg , and the maximum daily dose should not exceed 5 mg / kg . for measurements , care was taken to uniformly illuminate the area of interest with the laser light source . at the time of angiography , icg was then administered intravenously by the anesthesiologist upon the request of the surgeon . half dose ( 0.2 to 0.3 mg / kg ) was used as a bolus ( standard dose of 25 mg dissolved in 5 ml water ) . anatomical results assessed by postoperative angiography included the remnant of aneurysm after clipping , patency of graft or recanalized internal carotid artery , and remnant of nidus . postoperative dsa and computed tomography ( ct ) angiography was used to confirm anatomical results on aneurysm patient at 14 days postoperatively . an almost unruptured aneurysm and sah patients whose condition was not satisfactory to perform dsa were examined by ct angiography . also , we performed ct angiography on the patients 7 days after cea . all patients received bypass surgery or surgical removal of avm were confirmed by dsa 7 days postoperatively . between august 2011 and april 2012 , 188 patients with cerebrovascular disease were surgically treated by the authors in our institution . the patients ' age ranged from 28 to 82 years ( mean 59.3 years ) . fifty - eight surgeries followed an acute subarachnoid hemorrhage ( sah ) , 69 operations were performed on patients with unruptured aneurysms , 42 cases of carotid endarterectomy ( cea ) were performed , 17 extracranial to intracranial ( ec - ic ) bypass surgeries were performed on patients with moyamoya or atherosclerotic occlusion or complex aneurysm , and two surgeries involved arteriovenous malformation ( avm ) . according to the aneurysm location , there were 55 anterior cerebral artery ( aca ) aneurysms , 41 middle cerebral artery ( mca ) aneurysms , 18 aneurysms of the internal cerebral artery ( ica ) , one aneurysm at the vertebrobasilar ( vb ) artery , and 12 multiple aneurysms . for aneurysm clipping , a pterional transsylvian , bifrontal interhemispheric , suboccipital approach was performed depending on site and size of the aneurysm . cea was performed for symptomatic patients with more than 50% carotid stenosis and for asymptomatic patients with more than 60% carotid stenosis by angiography . indications for ec - ic bypass surgery were hemodynamic compromise due to atherosclerotic stenooclusive cerebrovascular disease in seven patients , moyamoya syndrome or disease in six patients , and the presence of complex intracranial aneurysms in four patients ; the four patients were treated with aneurysm trapping ( n=3 ) and aneurysmorrhaphy ( n=1 ) . patients underwent direct revascularization either through a standard superficial temporal artery ( sta)-mca bypass ( n=14 ) , an occipital artery ( oa)-posterior inferior cerebellar artery ( pica ) bypass ( n=2 ) , or radial artery ( ra ) high - flow bypass ( n=1 ) . both of the patients with avm were spetzler - martin grade 1 and were scheduled for elective surgery . intraoperative icg videoangiography ( icg - va ) was done using an opmi pentero surgical microscope ( carl zeiss , jena , germany ) . the recommended dose of icg dye for va is 0.2 to 0.5 mg / kg , and the maximum daily dose should not exceed 5 mg / kg . for measurements , care was taken to uniformly illuminate the area of interest with the laser light source . at the time of angiography , icg was then administered intravenously by the anesthesiologist upon the request of the surgeon . half dose ( 0.2 to 0.3 mg / kg ) was used as a bolus ( standard dose of 25 mg dissolved in 5 ml water ) . anatomical results assessed by postoperative angiography included the remnant of aneurysm after clipping , patency of graft or recanalized internal carotid artery , and remnant of nidus . postoperative dsa and computed tomography ( ct ) angiography was used to confirm anatomical results on aneurysm patient at 14 days postoperatively . an almost unruptured aneurysm and sah patients whose condition was not satisfactory to perform dsa were examined by ct angiography . also , we performed ct angiography on the patients 7 days after cea . all patients received bypass surgery or surgical removal of avm were confirmed by dsa 7 days postoperatively . table 1 shows the classification of patients after icg - va by diagnosis and performed procedure . side effects or allergic reactions were not observed . if necessary , the videoangiographic study could be repeated within 15 minutes following clearance of the icg . in these cases , repeated injections did not pose any problems with respect to patient safety and image quality . the image quality and resolution allowed assessment of arterial branches , including small arteries ( < 0.5 mm in diameter ) . the icg - va proved to be an easy - to - use and practical procedure , adding no more than 3 minutes to the regular operation time . intraoperative icg - va demonstrated fully occluded aneurysm sac without vessel compromise in 119 cases ( 93.7% ) of 127 aneurysms . however , a small portion of the clipped aneurysm was filled with bright fluorescent material in 6 patients ( 4.7% : five unruptured cases and one sah case ) , and small perforators or branched arteries were not showed in two cases ( 1.6% ) . correction of the clip was done immediately by adding another clip on the previously clipped aneurysm in 4 patients and repositioning the clip in 4 patients . right after clip correction , we performed icg - va and the repeated va demonstrated good reduction ( table 3 ) . postoperative dsa was performed on 33 of 58 patients of sah and 4 of 69 unruptured aneurysms . postoperative angiographies showed 126 aneurysms ( 99.2% ) without residual aneurysm sac and vessel compromise , which are the same results of intraoperative icg - va . intraoperative findings of icg - va in relation to postoperative dsa are listed in table 2 . however , in one case of a ruptured left mca bifurcation aneurysm , postoperative ct angiography showed a 6 mm size remnant sac , although intraoperative icg - va did not show any residual site of the aneurysm . one month later , the patient had been scheduled for a cranioplasty due to a skull defect caused by severe brain swelling . during the operative procedure , we became aware that we could not identify the residual site mimicking the branched artery because of severe atherosclerosis . forty - two intraoperative icg - va were performed after endarterectomy . in all cases , the ica was demonstrated to be patent on icg - va by homogenous enhancement following excision of the plaque . at the distal end , postoperative ct angiography performed in 41 patients ( 97.6% ) at 7 days postoperatively showed good patency of ica without any stenosis . in one patient , postoperative ct angiography showed a segmental stenosis ( nascet , < 50% ) at the distal part of the endarterectomy site . we planned to follow the patient and to consider stent insertion if symptoms were appeared . intraoperative icg - va revealed adequate bypass patency in 14 ( 100% ) of 14 sta - mca bypasses , in one ( 50% ) of two oa - pica bypasses , and in one ( 100% ) high - flow bypass . in contrast , one patient undergoing oa - pica bypass surgery was found intraoperatively to have an occlusion of the bypass graft . in this case , the cause of failure was intimal injury of the donor vessel at the anastomotic site . following revision , revised bypass grafts finally exhibited good filling according to repeated icg - va . postoperative dsa was performed in all 17 patients who received bypass surgery . a comparison of the intraoperative findings of icg - va with the findings of postoperative dsa confirmed adequate bypass graft patency in 16 patients , which resulted in an early bypass patency rate of 94.1% . however , in one patient with complex supraclinoid ica aneurysm who were treated with ra - high flow bypass and aneurysm trapping , postoperative dsa showed an occlusion of ra graft though intraoperative icg - va have shown good patency . fortunately , the dsa demonstrated good collateral flow from posterior communicating artery , and the patient presented no neurological deficit although mild dysarthria was seen temporarily . both patients had an injection before and after resection of their avm . in both , icg - va before resection revealed arteriovenous shunting and helped the surgeon to discern the avm arteries , draining veins , and cortical veins . , we describe several cases that showed aneurysmal remnant through icg - va after clipping . ct angiography indicated a distal anterior cerebral artery aneurysm , the diameter was 8 mm . second was a 42-year - old woman showed convulsive seizure , the 7 mm sized aneurysm at mca bifurcation was detected incidentally on ct angiography . we performed clipping of the 5 mm sized aneurysm at anterior communicating artery disclosed by cerebral angiogram ( fig . 1e , f ) . in six cases including above three cases , after the clipping of the aneurysm all aneurysmal filling sites with fluorescent material were at the end of the clip blade . the brightness of fluorescence presented with two patterns ; it has become brighter gradually , or it has showed " blinking sign " caused by arterial pulsation . intraoperative icg - va demonstrated fully occluded aneurysm sac without vessel compromise in 119 cases ( 93.7% ) of 127 aneurysms . however , a small portion of the clipped aneurysm was filled with bright fluorescent material in 6 patients ( 4.7% : five unruptured cases and one sah case ) , and small perforators or branched arteries were not showed in two cases ( 1.6% ) . correction of the clip was done immediately by adding another clip on the previously clipped aneurysm in 4 patients and repositioning the clip in 4 patients . right after clip correction , we performed icg - va and the repeated va demonstrated good reduction ( table 3 ) . postoperative dsa was performed on 33 of 58 patients of sah and 4 of 69 unruptured aneurysms . postoperative angiographies showed 126 aneurysms ( 99.2% ) without residual aneurysm sac and vessel compromise , which are the same results of intraoperative icg - va . intraoperative findings of icg - va in relation to postoperative dsa are listed in table 2 . however , in one case of a ruptured left mca bifurcation aneurysm , postoperative ct angiography showed a 6 mm size remnant sac , although intraoperative icg - va did not show any residual site of the aneurysm . one month later , the patient had been scheduled for a cranioplasty due to a skull defect caused by severe brain swelling . during the operative procedure , we became aware that we could not identify the residual site mimicking the branched artery because of severe atherosclerosis . forty - two intraoperative icg - va were performed after endarterectomy . in all cases , the ica was demonstrated to be patent on icg - va by homogenous enhancement following excision of the plaque . at the distal end , postoperative ct angiography performed in 41 patients ( 97.6% ) at 7 days postoperatively showed good patency of ica without any stenosis . in one patient , postoperative ct angiography showed a segmental stenosis ( nascet , < 50% ) at the distal part of the endarterectomy site . we planned to follow the patient and to consider stent insertion if symptoms were appeared . intraoperative icg - va revealed adequate bypass patency in 14 ( 100% ) of 14 sta - mca bypasses , in one ( 50% ) of two oa - pica bypasses , and in one ( 100% ) high - flow bypass . in contrast , one patient undergoing oa - pica bypass surgery was found intraoperatively to have an occlusion of the bypass graft . in this case , the cause of failure was intimal injury of the donor vessel at the anastomotic site . following revision , revised bypass grafts finally exhibited good filling according to repeated icg - va . postoperative dsa was performed in all 17 patients who received bypass surgery . a comparison of the intraoperative findings of icg - va with the findings of postoperative dsa confirmed adequate bypass graft patency in 16 patients , which resulted in an early bypass patency rate of 94.1% . however , in one patient with complex supraclinoid ica aneurysm who were treated with ra - high flow bypass and aneurysm trapping , postoperative dsa showed an occlusion of ra graft though intraoperative icg - va have shown good patency . fortunately , the dsa demonstrated good collateral flow from posterior communicating artery , and the patient presented no neurological deficit although mild dysarthria was seen temporarily . both patients had an injection before and after resection of their avm . in both , icg - va before resection revealed arteriovenous shunting and helped the surgeon to discern the avm arteries , draining veins , and cortical veins . here , we describe several cases that showed aneurysmal remnant through icg - va after clipping . first case was a 62-year - old female presented with dizziness . ct angiography indicated a distal anterior cerebral artery aneurysm , the diameter was 8 mm . second was a 42-year - old woman showed convulsive seizure , the 7 mm sized aneurysm at mca bifurcation was detected incidentally on ct angiography . we performed clipping of the 5 mm sized aneurysm at anterior communicating artery disclosed by cerebral angiogram ( fig . 1e , f ) . in six cases including above three cases , after the clipping of the aneurysm all aneurysmal filling sites with fluorescent material were at the end of the clip blade . the brightness of fluorescence presented with two patterns ; it has become brighter gradually , or it has showed " blinking sign " caused by arterial pulsation . for a long time , icg dye has been used in ophthalmology to measure retinal blood flow with a clinically relevant complication rate of less than 0.1% ( hypotension , tachycardia , or an allergic reaction to iodine)7 ) . feindel et al.8,9 ) were the first to apply the concept of fluorescence angiography to the intraoperative visualization of cerebral microcirculation in patients undergoing neurosurgical procedure . icg - va has proven to be a practical and low - cost technique that can be easily applied in the neurosurgical operating room on a routine basis . one of the advantages of icg dye is that it can be administered intravenously as a bolus injection . therefore , the procedure can be performed any time during surgery , and repeated administration is possible if a minimum time interval of 15 minutes between repeated injections to allow clearance is maintained . icg - va is very simple and rapid , and there is no need to move the microscope from the surgical field or to interrupt the operation . in our study , the results of icg - va were available within 3 minutes for all patients . this simplicity and speed are very important advantages of icg - va for the neurosurgeon to act immediately to correct the mistake before critical cerebral injury can occur . in our experiences , icg - va is the most useful option in aneurysm surgery . its high resolution allows the neurosurgeon to identify the patency of all vessels within the surgical field . especially , icg - va is the most accurate tool to confirm complete aneurysmal occlusion and patency of very small perforating arteries . we need not puncture the clipped aneurysm sac to ensure no bleeding or to relieve concern about whether the very small perforator is patent or not . the rate of postoperative aneurysm remnants ranges from 4% to 19%1,6,14 ) and unexpected vessel occlusion ranges from 0.3% to 12% in aneurysm surgery . although postoperative detection of unexpected findings might necessitate reoperation , the results of such revision are not very good14 ) . similar to previous reports , in our study , eight clipping ( 6.3% ) of 127 operations were identified as an incomplete aneurysm occlusion or compromising vessel after icg - va . however , we could correct the clipping immediately and we did not need to reoperate except for one remnant . in a review of the literature , after icg - va in aneurysm surgery , the incidence of residual filling of aneurysm is 2% to 8% , and that of parent or branching artery occlusion is 4% to 12%10,17,22 ) . raabe et al.17 ) reported that clip adjustment was performed in 10 of 111 cases after clip application . wang et al.22 ) reported that clip reperforming was carried out in three of 101 aneurysm cases . the rates of concordance between intraoperative icg - va and postoperative dsa in previous reports as well as our study are 90% to 100%10,17,22 ) . however , the significant limitation of the icg angiographic view is the restriction to the angle of surgical approach for vessels covered by blood clots , aneurysm , or brain tissue that are not visible to the surgeon . in other words , icg - va captures only what is visible within the field of the microscope . in our case , the remnant aneurysm occurred because we ignored this fact and assumed the success of the icg - va , although marginal dissection was insufficient . moreover , repeated injections of icg for more information within a short interval may cause false positive findings . proximal - to - distal filling of arteries should be undertaken carefully to avoid misdiagnosing the retrograde filling of the branches distal to the aneurysm . icg - va was effective in identifying ica patency after cea according to our study . in 41 ( 97.6% ) of 42 patients , the results of intraoperative icg - va were the same as that of postoperative dsa with good patency except for one patient . however , icg - va was not sufficient to find the exact bounds of atherosclerosis before arteriotomy , although the fact that there was only one case in our study makes this conclusion tentative . haga et al.11 ) reported that icg - va was performed in all of 60 cea procedures and good patency could be identified . also , they reported that icg - va showed the exact location of stenosis before arteriotomy in some cases , although it was impossible in many more cases because of spontaneous fluorescence of calcified tissue . although there are a few reports on the application of icg - va during cea2 ) , in our opinion , icg - va is useful for intraoperative evaluation of the patency after cea because it is easy to handle and rapidly provides high - quality information on the blood stream of the cervical ica . in our one case , which icg - va was performed before and after arteriotomy , we could not find any advantage for finding the exact location of stenosis compared to inspection or palpation . because visualization of icg fluorescence may also be affected by the thickness and calcification , icg - va can be used selectively to predict the range of arteriotomy in cea . in bypass surgeries , icg - va even if there was one case of early graft failure , we thought that there had been spasm at the ra graft and the graft developed occlusion gradually after icg - va . in our study , excellent visualization of cererbral arteries , the bypass graft , and brain perfusion was noted in all cases . one case of 17 bypass surgeries was identified as a nonfunctioning oa - pica bypass , which could be revised successfully . the postoperative bypass patency rate has been reported to be only between 90% and 96%7,15,18 ) . there have been no possible methods that provide direct intraoperative inspection about the blood stream except intraoperative dsa . however , woitzik et al.23 ) reported the value of icg - va for the revision of four of 35 sta - mca bypasses . in addition , all four cases exhibited good filling of the bypass according to repeated icg - va . several subsequent studies19,21 ) have reported that icg - va has the potential to improve the outcomes of bypass surgery . however , it is hard to determine the direction of blood flow with icg - va , so we recommend additional doppler sonography to confirm the direction . previous reports about icg - va using avm are infrequent . in our two cases , icg - va before resection showed arteriovenous shunting and helped the surgeon to discern the avm arteries , draining veins , and cortical veins . however , both were only spetzler - martin ( s - m ) grade i avms . the finding that icg - va was useful for avm removal could reflect the superficial nature of the feeding arteries and draining veins in our cases . killory et al.12 ) reported that , although application of icg - va in 10 avms was ideal for early identification of avm arteries and veins , icg - va only complemented rather than replaced intraoperative dsa . this because , in their experience , icg - va is less useful with deep - seated lesions or when avm vessels are not on the surface , such as s - m grade iii or iv . killory et al . reported that icg is frequently of limited use for deep - seated avms that must be approached through a long , narrow corridor . however , our study had same result as study by takagi et al.,20 ) that icg - va is useful utility to determine the remnant of nidus postoperatively . it is well - known that icg - va can show feeder , draining vein , cortical vein , and nidus in avm surgery . icg - va clearly revealed arteriovenous shunting and helped the surgeon to discern the avm arteries , draining veins , and cortical veins in sequence from arterial phase to venous phase , distinctions that were not obvious with conventional intraoperative microscopic magnification . after review of the previous literature , we found that there was no consideration about the filling pattern of icg dye in incomplete clipped aneurysms . in our six incomplete clipped aneurysm cases , all aneurysmal filling sites with fluorescent material were the tip site of the clip blade . there was no case that icg filling was showed at the heel site of clip blade and we believe that is result of clip blade pressure force . furthermore , the brightness of fluorescence presented with two patterns : it has become brighter gradually , or it has showed " blinking sign " . this can be shown at incompletely clipped aneurysm with extremely minimal gap for contrast to flow , but can be seen or blink on arterial pulsation . this pattern is important to discern the residual icg filling of aneurysm from diffuse weak fluorescence of thrombus or atherosclerosis or calcification . it is very important to identify small perforator which is main factor of postoperative neurological deficit in cerebrovascular surgery . icg - va is the best way to identify small perforator compare to other methods such as intraoperative doppler . most ideal method is comparison of patency and brightness of small perforators before and after procedure via icg - va . however , most neurovascular surgeons can raise questions if unconfirmed perforators are less bright compare to adjacent arteries after procedure . in one of our cases with giant aneurysm at mca , after sta - m3 bypass surgery with aneurysmorrhaphy , icg - va showed a trace of fluorescence at a small perforator . we repeated open and closure of the aneurysm three or four times for identification of backflow of the perforator . however , the patency was retained according to postoperative dsa , and the patient had no neurological deficit , despite our concern ( fig . although it is difficult to establish the clear standard degree of the brightness of fluorescence , if the perforator is not complete dark with flow - free during icg - va and the procedure did not affect the perforator , it means that the flow have been weak even before procedure in our experience . also , brightness of contrast in perforator does not imply the patency , so the monitoring of motor or sensory evoked potentials can be helpful to determine the patency of perforator . it is well - known that icg - va can show feeder , draining vein , cortical vein , and nidus in avm surgery . icg - va clearly revealed arteriovenous shunting and helped the surgeon to discern the avm arteries , draining veins , and cortical veins in sequence from arterial phase to venous phase , distinctions that were not obvious with conventional intraoperative microscopic magnification . after review of the previous literature , we found that there was no consideration about the filling pattern of icg dye in incomplete clipped aneurysms . in our six incomplete clipped aneurysm cases , all aneurysmal filling sites with fluorescent material were the tip site of the clip blade . there was no case that icg filling was showed at the heel site of clip blade and we believe that is result of clip blade pressure force . furthermore , the brightness of fluorescence presented with two patterns : it has become brighter gradually , or it has showed " blinking sign " . this can be shown at incompletely clipped aneurysm with extremely minimal gap for contrast to flow , but can be seen or blink on arterial pulsation . this pattern is important to discern the residual icg filling of aneurysm from diffuse weak fluorescence of thrombus or atherosclerosis or calcification . it is very important to identify small perforator which is main factor of postoperative neurological deficit in cerebrovascular surgery . icg - va is the best way to identify small perforator compare to other methods such as intraoperative doppler . most ideal method is comparison of patency and brightness of small perforators before and after procedure via icg - va . however , most neurovascular surgeons can raise questions if unconfirmed perforators are less bright compare to adjacent arteries after procedure . in one of our cases with giant aneurysm at mca , after sta - m3 bypass surgery with aneurysmorrhaphy , icg - va showed a trace of fluorescence at a small perforator . we repeated open and closure of the aneurysm three or four times for identification of backflow of the perforator . however , the patency was retained according to postoperative dsa , and the patient had no neurological deficit , despite our concern ( fig . although it is difficult to establish the clear standard degree of the brightness of fluorescence , if the perforator is not complete dark with flow - free during icg - va and the procedure did not affect the perforator , it means that the flow have been weak even before procedure in our experience . also , brightness of contrast in perforator does not imply the patency , so the monitoring of motor or sensory evoked potentials can be helpful to determine the patency of perforator . icg - va is simple and provides real - time information of the patency of vessels including very small perforators within the field of the microscope and has a lower rate of adverse reactions . icg - va has the potential to achieve the goal of routine intraoperative vascular imaging during cerebrovascular surgery . however , icg - va is not a perfect method , and so a combination of monitoring tools assures the quality of cerebrovascular surgery .
objectiverecently , microscope - integrated near infrared indocyanine green videoangiography ( icg - va ) has been widely used in cerebrovascular surgery because it provides real - time high resolution images . in our study 
 , we evaluate the efficacy of intraoperative icg - va during cerebrovascular surgery.methodsbetween august 2011 and april 2012 , 188 patients with cerebrovascular disease were surgically treated in our institution . 
 we used icg - va in that operations with half of recommended dose ( 0.2 to 0.3 mg / kg ) . 
 postoperative digital subtraction angiography and computed tomography angiography was used to confirm anatomical results.resultsintraoperative icg - va demonstrated fully occluded aneurysm sack , no neck remnant , and without vessel compromise in 119 cases ( 93.7% ) of 127 aneurysms . 
 eight clipping ( 6.3% ) of 127 operations were identified as an incomplete aneurysm occlusion or compromising vessel after icg - va . in 41 ( 97.6% ) of 42 
 patients after carotid endarterectomy , the results were the same as that of postoperative angiography with good patency . 
 one case ( 5.9% ) of 17 bypass surgeries was identified as a nonfunctioning anastomosis after icg - va , which could be revised successfully . in the two patients of arteriovenous malformation , icg - va was useful for find the superficial nature of the feeding arteries and draining veins.conclusionicg-va is simple and provides real - time information of the patency of vessels including very small perforators within the field of the microscope and has a lower rate of adverse reactions 
 . however , icg - va is not a perfect method , and so a combination of monitoring tools assures the quality of cerebrovascular surgery .