Indocyanine green (ICG) fluorescence videoangiography is now widely used for the intraoperative assessment of vessel patency, providing high quality, valuable, real-time imaging of cerebrovascular anatomy.
Preservation of adequate blood flow and exclusion of flow from lesions are key concepts of vascular neurosurgery.
The overlay of fluorescence videoangiography within the field of view of the white light operative microscope allows real-time assessment of the blood flow within vessels during simultaneous surgical manipulation. This technique could improve intraoperative decision making during complex neurovascular procedures 1).
Simal-Julián et al. conducted a review to identify and assess the impact of all of the methodological variations of conventional ICGVA applied in the field of neurovascular pathology that have been published to date in the English literature. A total of 18 studies were included in this review, identifying four primary methodological variants compared to conventional ICGVA: techniques based on the transient occlusion, intra-arterial ICG administration via catheters, use of endoscope system with a filter to collect florescence of ICG, and quantitative fluorescence analysis. These variants offer some possibilities for resolving the limitations of the conventional technique (first, the vascular structure to be analyzed must be exposed and second, vascular filling with ICG follows an additive pattern) and allow qualitatively superior information to be obtained during surgery. Advantages and disadvantages of each procedure are discussed. More case studies with a greater number of patients are needed to compare the different procedures with their gold standard, in order to establish these results consistently 2).
Intraoperative indocyanine green videoangiography (ICG-VA) has been widely used in vascular surgery, where vessels are clearly shown as white on a black background. However, other structures cannot be observed during ICG-VA.
Is not absolutely reliable as a stand-alone method during clipping of ophthalmic artery aneurysms and can be complemented with IA. ICGA can be used either as an alternative or complementary technique to IA during aneurysm surgery 3).
It can assist in intraoperative surgical management and/or stroke prevention particularly during aneurysm clipping, EC-IC bypass and AVM/DAVF surgery 4), and to document the intraoperative vascular flow 5).
Indocyanine green (ICG) angiography is commonly used to map the vascular configuration of cerebral arteriovenous malformations (AVMs) during resection.
ICG-VA is a safe and effective technique for locating the ICA in skull-base expanded endonasal surgery. Furthermore, this technique can provide real-time guidance for the surgeon and increase safety for the patient 6).
Sato et al. developed a new, high-resolution intraoperative imaging system (dual-image VA [DIVA]) to simultaneously visualize both light and near-infrared (NIR) fluorescence images from ICG-VA, allowing observation of other structures.
The operative field was illuminated via an operating microscope by halogen and xenon lamps with a filter to eliminate wavelengths over 780 nm. In the camera unit, visible light was filtered to 400-700 nm and NIR fluorescence emission light was filtered to 800-900 nm using a special sensor unit with an optical filter. Light and NIR fluorescence images were simultaneously visualized on a single monitor.
The system clearly visualized the operative field together with fluorescence-enhanced blood flow. In aneurysm surgeries, we could confirm incomplete clipping with the neck remnant or with remnant flow into the aneurysm. In cases of arteriovenous malformation or arteriovenous fistula, feeding arteries and draining veins were easily distinguished.
This system allows observation of the operative field and enhanced blood flow by ICG together in real time and may facilitate various types of neurovascular surgery 7).
Indocyanine Green Video-angiography (ICGV) is becoming routine in intracranial aneurysm surgery, in order to assess intra-operatively both sac obliteration and vessel patency after clipping.
Its a safe and effective modality of intraoperative blood flow assessment and reduces the incidence of postoperative ischaemic complications 8).
However, ICGV-derived data have been reported to be misleading at times. Della Puppa et al., noted that a simple intra-operative maneuver (the “squeezing maneuver”) allows the detection of deceptive ICGV data on aneurysm exclusion and allows potential clip repositioning. The “squeezing maneuver” is based on a gentle pinch of the dome of a clipped aneurysm when ICGV documents its apparent exclusion.
Data from 23 consecutive patients affected by intracranial aneurysms who underwent the “squeezing maneuver” were retrospectively analyzed. The clip was repositioned in all cases when the dyeing of the sac was visualized after the maneuver.
In 22% of patients, after an initial ICGV showing the aneurysm exclusion after clipping, the squeezing maneuver caused the prompt dyeing of the sac; in all cases the clip was consequently repositioned. A calcification/atheroma of the wall/neck was predictive of a positive maneuver (p= 0.0002). The aneurysm exclusion rate at post-operative radiological findings was 100%.
With the limits of this small series, the “squeezing maneuver” appears helpful in the intra-operative detection of misleading ICGV data, mostly when dealing with aneurysms with atheromasic and calcified walls 9).
In selected cases, endoscopic ICG angiographies (e-ICG-A) provides the neurosurgeon with information that cannot be obtained by microscopic ICG angiography (m-ICG-A). E-ICG-A is capable of emerging as a useful adjunct in aneurysm surgery and has the potential to further improve operative results 10).
Indocyanine green (ICG) videoangiography (VA) in cerebral aneurysm surgery allows confirmation of blood flow in parent, branching, and perforating vessels as well as assessment of remnant aneurysm parts after clip application. A retrospective analysis from Two hundred forty-six procedures were performed in 232 patients harboring 295 aneurysms. The patients, whose mean age was 54 years, consisted of 159 women and 73 men. One hundred twenty-four surgeries were performed after subarachnoid hemorrhage, and 122 were performed for incidental aneurysms. Single aneurysms were clipped in 185 patients, and multiple aneurysms were clipped in 47 (mean aneurysm diameter 6.9 mm, range 2-40 mm). No complications associated with ICG-VA occurred. Intraoperative microvascular Doppler ultrasonography was performed before ICG-VA in all patients, and postoperative digital subtraction angiography (DSA) studies were available in 121 patients (52.2%) for retrospective comparative analysis. In 22 (9%) of 246 procedures, the clip position was modified intraoperatively as a consequence of ICG-VA. Stenosis of the parent vessels (16 procedures) or occlusion of the perforators (6 procedures), not detected by micro-Doppler ultrasonography, were the most common problems demonstrated on ICG-VA. In another 11 procedures (4.5%), residual perfusion of the aneurysm was observed and one or more additional clips were applied. Vessel stenosis or a compromised perforating artery occurred independent of aneurysm location and was about equally common in middle cerebral artery and anterior communicating artery aneurysms. In 2 procedures (0.8%), aneurysm puncture revealed residual blood flow within the lesion, which had not been detected by the ICG-VA. In the postoperative DSA studies, unexpected small (< 2 mm) aneurysm neck remnants, which had not been detected on intraoperative ICG-VA, were found in 11 (9.1%) of 121 patients. However, these remnants remained without consequence except in 1 patient with a 6-mm residual aneurysm dome, which was subsequently embolized with coils.
Its a helpful intraoperative tool and led to a significant intraoperative clip modification rate of 15%. However, small, < 2-mm-wide neck remnants and a 6-mm residual aneurysm were missed by intraoperative ICG-VA in up to 10% of patients. Results in this study confirm that DSA is indispensable for postoperative quality assessment in complex aneurysm surgery 11).
ICG video-angiography is a time-efficient and safe alternative to intra-operative spinal angiography. It provided useful information on haemodynamic changes intraoperatively and completeness of treatment 12).
Has the potential to shorten operating times, gives additional reassurance of completeness of surgical treatment and preservation of normal spinal vasculature 13).
Serves an important role in the microsurgical treatment of spinal dural arteriovenous fistula DAVF. It is simple and provides real-time information about the precise location of spinal DAVF and result after obliteration of spinal DAVF 14).
It has been established as a noninvasive technique to gauge the patency of a bypass graft; however, intraoperative graft patency may not always correlate with graft flow. Altered flow through the bypass graft may directly cause delayed graft occlusion.
Januszewski et al. report on 3 types of flow that were observed through cerebral revascularization procedures in 48 bypass procedures.
After anastomosis, bypass patency was assessed first using a noninvasive technique and then with ICG videoangiography, and flow through the graft was characterized. Patients who received a vein or radial artery graft were also evaluated with intraoperative angiography.
Thirty-three patients eligible for analysis were retrospectively analyzed. The patients had undergone extracranial-intracranial (EC-IC) or IC-IC bypass for ischemic stroke (13 patients), moyamoya disease (10 patients), and complex aneurysms (10 patients; 6 giant or large aneurysms, 2 carotid blister-like aneurysms, and 2 dissecting posterior inferior cerebellar artery [PICA] aneurysms). Thirty-six bypasses were performed including 26 superficial temporal artery (STA)-middle cerebral artery (MCA) bypasses (2 bilateral and 1 double-barrel), 6 EC-IC vein grafts, 1 EC-IC radial artery graft, 1 PICA-PICA bypass, 1 MCA-posterior cerebral artery bypass, and 1 occipital artery-PICA bypass. Robust anterograde flow (Type I) was noted in 31 grafts (86%). Delayed but patent graft enhancement and anterograde flow (Type II) was observed in 4 cases (11%); 1 of these cases with an EC-IC vein graft degraded gradually to very delayed flow with no continuity to the bypass site (Type III). Additionally, 1 STA-MCA bypass graft revealed no convincing flow (Type III). The 5 patients with Type II or III grafts were evaluated with a flow probe and reexploration of the bypass site, and in all cases the reason the graft became occluded was believed to be recipient-vessel competitive flow. In no case was there evidence of stenosis or a technical issue at the site of the anastomosis. Three patients with Type II and the 1 patient with Type III flow (11% of procedures) did not have a patent bypass on postoperative imaging.
The type of flow observed through the graft has a direct relationship with postoperative imaging findings. Despite the possibility of competitive flow, Type III and some Type II flows through the graft indicate the need for graft evaluation and anastomosis exploration 15).