OBJECTIVE: Superficial temporal artery to middle cerebral artery (STA-MCA) direct bypass surgery is the most common surgical procedure to treat moyamoya disease (MMD). Here, we aim to compare the performance of the 3D exoscope in bypass surgery with the gold standard operative microscope.
METHODS: All direct STA-MCA bypass procedures performed at a single university hospital for MMD between 2015 and 2023 were considered for inclusion. Data were retrospectively collected from patient files and surgical video material. From 2020 onwards, bypass procedures were exclusively performed using a digital three-dimensional exoscope as visualization device. Results were compared with a microsurgical bypass control group (2015-2019). The primary endpoint was defined as total duration of surgery, duration of completing the vascular anastomosis (ischemia time), bypass patency, number of stiches to perform the anastomosis, added stiches after leakage testing of the anastomosis and the Glasgow outcome scale (GOS) at last follow-up as secondary outcome parameter.
RESULTS: A total of 16 consecutive moyamoya patients underwent 21 STA-MCA bypass procedures. Thereof, six patients were operated using a microscope and ten patients using an exoscope (ORBEYE® n = 1; AEOS® n = 9). Total duration of surgery was comparable between devices (microscope: 313 min. ± 116 vs. exoscope: 279 min. ± 42; p = 0.647). Ischemia time also proved similar between groups (microscope: 43 min. ± 19 vs. exoscope: 41 min. ± 7; p = 0.701). No differences were noted in bypass patency rates. The number of stiches per anastomosis was similar between visualization devices (microscope: 17 ± 4 vs. exoscope: 17 ± 2; p = 0.887). In contrast, more additional stiches were needed in microscopic anastomoses after leakage testing the bypass (p = 0.035).
CONCLUSIONS: Taking into account the small sample size, end-to-side bypass surgery for moyamoya disease using a foot switch-operated 3D exoscope was not associated with more complications and led to comparable clinical and radiological results as microscopic bypass surgery.

Extracranial-to-intracranial (EC-IC) surgical bypass improves cerebral blood flow (CBF) and cerebrovascular vasoreactivity (CVR) for patients with carotid occlusion. Bypass graft patency and contribution of the graft to the postoperative increase in CVR are challenging to assess. To assess the effectiveness of 4D flow magnetic resonance imaging (MRI) to evaluate bypass graft patency and flow augmentation through the superficial temporal artery (STA) before and after EC-IC bypass.
Three consecutive patients undergoing EC-IC bypass for carotid occlusion were evaluated pre- and postoperatively using CVR testing with pre- and poststimulus 4D flow-MRI for assessment of the bypass graft and intracranial vasculature.
Preoperatively, 2 patients (patients 1 and 3) did not augment flow through either native STA. The third, who had evidence of extensive native EC-IC collateralization on digital subtraction angiography (DSA), did augment flow through the STA preoperatively (CVR = 1). Postoperatively, all patients demonstrated CVR > 1 on the side of bypass. The patient who had CVR > 1 preoperatively demonstrated the greatest increase in resting postoperative graft flow (from 40 to 130 mL/minute), but the smallest CVR, with a poststimulus graft flow of 160 mL/minute (CVR = 1.2). The 2 patients who did not demonstrate augmentation of graft flow preoperatively augmented postoperatively from 10 to 20 mL/minute (CVR = 2.0) and 10-80 mL/minute (CVR = 8.0), respectively. Intracranial flow was simultaneously interrogated. Two patients demonstrated mild reductions in resting flow velocities in all interrogated vessels immediately following bypass. The patient who underwent CVR testing on postoperative day 48 demonstrated a stable or increased flow rate in most intracranial vessels.
Four-dimensional flow MRI allows for noninvasive, simultaneous interrogation of the intra- and extracranial arterial vasculature during CVR testing, and reveals unique paradigms in cerebrovascular physiology. Observing these flow patterns may aid in improved patient selection and more detailed postoperative evaluation for patients undergoing EC-IC bypass.

A double anastomosis using a single superficial temporal artery (STA) donor branch for both a proximal side-to-side (S2S) and a distal end-to-side anastomosis is a novel direct bypass technique for use in selected patients necessitating flow augmentation.
To describe the single-vessel double anastomosis (SVDA) technique, including its indications, advantages, and limitations, in addition to reporting our cases series of patients who underwent a SVDA bypass surgery.
Patients undergoing a SVDA bypass at a single institution between January 2010 and February 2016 were retrospectively reviewed. Intraoperative flow data was collected, including STA cut-flow, bypass flows, and cut flow index (CFI). Bypass patency was assessed by cerebral angiography and quantitative magnetic resonance angiography with noninvasive optimal vessel analysis. Adverse events occurring during the hospital stay and clinical status at last follow up was recorded.
Seven patients underwent SVDA bypass. Mean follow-up was 14.5 mo. Initial CFI for the S2S bypasses averaged 0.56 ± 0.25 and CFI after the SVDA averaged 1.15 ± 0.24. There was a statistically significant average difference in CFI before and after the SVDA bypass (p < .013). Thirteen bypasses (93%) were patent postoperatively, and remained patent at last follow up. Four patients experienced various postoperative complications. None of the patients had a new stroke since hospital discharge.
SVDA is a novel technique that can be advantageous for selected cases of extracranial-to-intracranial bypass. Expertise in bypass procedures is a necessary prerequisite. Graft patency rates and complications appear comparable to other bypass techniques.

Over the last years, intraoperative use of fluorescein is gaining ground in the field of neurosurgery, due to development of a microscope-integrated YELLOW 560 module, with reported experiences in brain malignancies, aneurysms, and arteriovenous malformation surgery. The aim of this study is to determine the feasibility and value of fluorescein videoangiography during bypass procedures.
The authors enrolled 11 patients who underwent extracranial-to-intracranial bypass for moyamoya disease, atherosclerotic steno-occlusive cerebrovascular disease, and flow replacement during a giant middle cerebral artery (MCA) aneurysm treatment. Patients underwent fluorescein videoangiography using microscope-integrated fluorescence module.
In all 11 cases, good bypass patency was intraoperatively demonstrated through fluorescein videoangiography and confirmed by post-operative digital subtraction angiography or computed tomographic angiography. The technique seems to be less sensible than standard indocyanine green videoangiography in terms of flow velocity assessment during first pass and does not benefit from a dedicated software to perform hemodynamic parameter analysis (i.e., FLOW 800). Fluorescein videoangiography was able to show a higher number of vessels than indocyanine green videoangiography, providing an extremely well-defined view of cortical vascular network, also in deeper cortical areas. In case of deep-seated anastomosis, it allowed real-time manipulation of neurovascular structures, making it possible a safe analysis of vessels in deep surgical field during videoangiography observation.
Fluorescein videoangiography is a cost-effective, easy-to-use, fast and safe intraoperative tool and is useful to assess graft patency and extent of cortical vascular network also in deeper cortical areas. In case of deep-seated anastomosis, it provides the great advantage of performing real-time manipulation of neurovascular structures during videoangiography observation. It could represent a valuable complementary or alternative technique to assess intraoperative bypass function.

OBJECTIVE: Intracranial revascularization surgeries are an effective treatment for moyamoya disease and other intracranial vascular obliterative diseases. However, in some cases, wound-related complications develop after surgery. Although the incidence of wound complication is supposed to be higher than that with a usual craniotomy, this complication has rarely been the focus of studies in the literature that report the outcomes of revascularization surgeries. Here, the relationship between intracranial revascularization surgeries and their complications is statistically assessed.
METHODS: Between October 2004 and February 2010, 71 patients were treated using cerebral revascularization surgeries on 98 sides of the head. The relationship between wound complications and operative technique was retrospectively assessed. Multivariate logistic regression analysis was performed to identify the risk factors of wound complication, including operative technique, age, sex, diabetes mellitus (DM), hypertension, hyperlipidemia, and smoking history.
RESULTS: In total, there were 21 (21.4%) operative wound complications. Of these 21 complications, there were 14 (66.7%) minor complications and 7 (33.3%) major complications. No statistically significant relationship was found between wound complications and any surgical procedure. A trend toward severer complications was demonstrated for the procedures that used both STA branches (\"double\" procedures) in comparison with the procedures that used only 1 STA branch (\"single\" procedures, p=0.016, Cochran-Armitage trend test). Multivariate logistic regression analysis also revealed that double procedures demonstrated a significantly higher incidence of wound complications than single procedures (OR 3.087, p=0.048). DM was found to be a risk factor for wound complication (OR 9.42, p=0.02), but age, sex, hypertension, and hyperlipidemia were not associated with the incidence of complications. Even though the blood supply to the scalp is abundant due to 5 arteriovenous systems, sometimes cutaneous necrosis develops after intracranial revascularization surgeries. The galeal blood supply is thought to be crucial for preventing wound-related complications. Special care is also thought to be required for DM patients.
CONCLUSIONS: Revascularization surgeries seemed to demonstrate a higher risk of wound-related complications. Double-type procedures, which use both branches of the STA, and a history of DM were found to be risk factors for wound-related complications. Attention should be paid to the design of the galeal incision and vessel harvest line. Also, special attention should be paid to patients with DM.

OBJECTIVE: Anesthetic management of extracranial to intracranial (EC-IC) bypass for complex intracranial aneurysms is challenging as the goals involve balancing the cerebral perfusion during parent artery clamping and avoiding factors that predispose to rupture of the unsecured aneurysm. There is very sparse literature available on anesthetic management for this procedure.
METHODS: A retrospective review of the records of 20 patients undergoing EC-IC bypass was performed with an objective of assessing the efficacy and outcomes of anesthetic management in the absence of advanced neurological monitoring.
RESULTS: A total of 20 patients underwent EC-IC bypass as an adjunct cerebral revascularization in the management of complex intracranial aneurysms. Intraoperatively normotension and normocarbia were maintained. During the EC-IC bypass, when the temporary clamp was applied, mild hypertension (increase from baseline by 20%) and hypervolemia (central venous pressure increased to 12 mmHg) were maintained. Cerebral protection during temporary clipping of intracranial vessel was provided using moderate hypothermia to 34°C and intravenous thiopentone. Temporary clip time ranged from 15 min to 54 min (mean-25 min). All patients except one were extubated post-operatively (19/20 = 95%). None of the patients had rupture of aneurysm in the peri-operative period. Three patients developed neurologic events (3/20 = 15%). One patient had cerebral vasospasm and two patients developed cerebral infarction. Two patient subsequently improved and one succumbed to the neurological deterioration (mortality 1/20 = 5%).
CONCLUSIONS: Adherence to the principal goals for the procedure, avoidance of hemodynamic fluctuations such as hypotension and hypertension, maintenance of normocarbia, and cerebral protection, result in favorable neurological outcome even in the absence of advanced neuromonitoring.