3D exoscopic versus microscopic superficial temporal artery to middle cerebral artery bypass surgery for moyamoya disease - a comparative series.

PURPOSE: 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). CONCLUSION: 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.

Long-term risk of hemorrhage and mortality after treatment of high-grade intracranial dural arteriovenous fistulas.

BACKGROUND: Despite recent multi-institutional efforts, long-term data on clinical and radiological outcomes after treatment of high-grade dural arteriovenous fistulas (dAVFs) remain scarce. This study aimed to evaluate the long-term risk of hemorrhage and fistula-related mortality after treatment. METHODS: Retrospective analysis of all consecutive patients primarily diagnosed with a high-grade dAVF (Cognard grade 2b, 2a+b, 3, 4) between January 2012 and September 2022 at a large neurovascular center. Primary endpoints were intracranial hemorrhage (ICH) and all-cause mortality after treatment; secondary endpoints were angiographic occlusion, complication rate and neurological deficits. RESULTS: A total of 121 patients underwent 141 treatments (122 endovascular therapy (EVT), 5 radiotherapy, 14 surgery) of which 12 patients (10%) underwent retreatment. Follow-up was available in all patients for a median of 4.2 (IQR 2.5 to 6.6) years. Eleven patients (9%) died during the follow-up period, of which three deaths (2%) occurred after hemorrhagic presentation, one of them attributable to treatment. One death (0.8%) was due to delayed hemorrhage after partial occlusion from EVT. No other post-treatment bleedings occurred. Angiographic follow-up after multimodality treatment was available in 93% of patients after a median of 6 months; the overall occlusion rate was 90%. The overall rate of complications was 25% after EVT and 14% after surgery. The rates of new transient and permanent neurological deficits after EVT were 9% and 3%, respectively. CONCLUSIONS: The long-term rate of re-bleeding or dAVF-related mortality was low when high rates of angiographic occlusion were achieved. The risk for treatment-related complications leading to neurological sequela was low.

Digital exoscope versus surgical microscope in spinal dural arteriovenous fistula surgery: a comparative series.

OBJECTIVE: Surgical treatment of spinal dural arteriovenous fistulas (DAVFs) has been reported to be superior to endovascular treatment in terms of occlusion of the fistula. Despite the increased availability of digital 3D exoscopes, the potential benefits of using an exoscope in spinal DAVF surgery have not been studied. The purpose of this study was to report and compare the results of exoscope- and microscope-assisted surgery for spinal DAVFs. METHODS: All consecutive adult patients (≥ 18 years of age) treated surgically for spinal DAVFs from January 2016 to January 2023 in a tertiary neurosurgical referral center were included. All patients were operated on by one neurosurgeon. Their pre- and postoperative clinical findings, imaging studies, and intra- and postoperative events were evaluated and surgical videos from the operations were analyzed. RESULTS: Altogether, 14 patients received an operation for spinal DAVF during the study period, 10 (71%) with an exoscope and 4 (29%) with a microscope. The DAVFs were most commonly located in the lower parts of the thoracic spine in both groups. The duration of exoscopic surgeries was shorter (141 vs 151 minutes) and there was less blood loss (60 vs 100 ml) than with microscopic surgeries. No major surgical complications were observed in either group. Of the 14 patients, 10 had gait improvement postoperatively: 7 (78%) patients in the exoscope group and 3 (75%) in the microscope group. None of the patients experienced deterioration following surgery. CONCLUSIONS: Exoscope-assisted surgery for spinal DAVFs is comparable in safety and effectiveness to traditional microscopic surgery. With practice, experienced neurosurgeons can adapt to using the exoscope without major additional risks to the patient.

Long-term treatment outcomes and natural course of low-grade intracranial dural arteriovenous fistulas.

OBJECTIVE: In contrast to high-grade dural arteriovenous fistula (dAVF), low-grade dAVF is mainly associated with tinnitus and carries a low risk of morbidity and mortality. It remains unclear whether the benefits of active interventions outweigh the associated risk of complications in low-grade dAVF. METHODS: The authors conducted a retrospective single-center study that included all consecutive patients diagnosed with an intracranial low-grade dAVF (Cognard type I and IIa) during 2012-2022 with DSA. The authors analyzed symptom relief, symptomatic angiographic cure, treatment-related complications, risk for intracerebral hemorrhage (ICH), and mortality. All patients were followed up until the end of 2022. RESULTS: A total of 81 patients were diagnosed with a low-grade dAVF. Of these, 48 patients (59%) underwent treatment (all primary endovascular treatments), and 33 patients (41%) did not undergo treatment. Nine patients (19%) underwent retreatments. Angiographic follow-up was performed after median (IQR) 7.7 (6.1-24.1) months by means of DSA (mean 15.0, median 6.4 months, range 4.5-83.4 months) or MRA (mean 29.3, median 24.7 months, range 5.9-62.1 months). Symptom control was achieved in 98% of treated patients after final treatment. On final angiographic follow-up, 73% of patients had a completely occluded dAVF. There were 2 treatment-related complications resulting in 1 transient (2%) and 1 permanent (2%) neurological complication. One patient showed recurrence and progression of a completely occluded low-grade dAVF to an asymptomatic high-grade dAVF. No cases of ICH- or dAVF-related mortality were found in either treated patients (median [IQR] follow-up 5.1 [2.0-6.8] years) or untreated patients (median [IQR] follow-up 5.7 [3.2-9.0] years). CONCLUSIONS: Treatment of low-grade dAVF provides a high rate of symptom relief with small risks for complications with neurological sequela. The risks of ICH and mortality in patients with untreated low-grade dAVF are minimal. Symptoms may not reveal high-grade recurrence, and radiological follow-up may be warranted in selected patients with treated low-grade dAVF. An optimal radiographic follow-up regimen should be developed by a future prospective multicenter registry.

Digital 3D Exoscope is Safe and Effective in Surgery for Intradural Extramedullary Tumors: A Comparative Series.

BACKGROUND: Digital 3D exoscopes have been shown to be comparably safe and effective as surgical microscopes in complex microneurosurgical procedures. However, the results of exoscopic spinal tumor surgeries are scarce. The purpose of this study is to compare results of a transition from microscope to exoscope in surgeries for spinal intradural extramedullary tumors. METHODS: We included all consecutive patients with intradural extramedullary spinal tumors operated on by the senior author during January 2016 to October 2023. The 3D exoscope was used in the latter half of the series from November 2020. We evaluated pre- and postoperative clinical findings, imaging studies, intra- and postoperative events, and analyzed surgical videos from the operations retrospectively. RESULTS: We operated 35 patients (exoscope n = 19, microscope n = 16) for intradural extramedullary tumors (meningioma n = 18, schwannoma n = 12, other n = 5). Tumors in the cervical and thoracic spine were more common than in the lumbar region. The duration of surgery was slightly longer (median 220 vs. 185 minutes) in the exoscope group. However, the rate of gross total resection of the tumor was higher (81% vs. 67%) and the tumors more often located anteriorly to the spinal cord (42% vs. 13%) in the exoscope group. No major complications (i.e., permanent motor deficit or postoperative hematoma) occurred in either group. We saw postoperative gait improvement in 81% and 85% of the patients with preoperative deterioration of gait after exoscopic and microscopic surgeries, respectively. CONCLUSIONS: This study demonstrates that exoscope-assisted surgery for spinal intradural extramedullary tumors is comparable in safety and effectiveness to traditional microscopic surgery.

Exoscopic resection of giant olfactory groove meningioma.

Olfactory groove meningiomas represent 8%-13% of all intracranial meningiomas. Gross-total resection for large (4-6 cm) and giant (> 6 cm) cases remains challenging due to their relationship with critical neurovascular structures and extensive frontal lobe edema. A variety of transcranial and endoscopic approaches have been described. This 2D operative video shows the use of a digital 3D exoscope in the removal of a giant olfactory groove meningioma through a lateral supraorbital approach in a 57-year-old woman with visual impairment and apathy. The exoscope provides a very good angulated view of the subfrontal area on both sides of the anterior cranial fossa even through a small craniotomy. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23125.

Exoscopic extradural anterior clinoidectomy.

Extradural anterior clinoidectomy is a resourceful technique to decompress the optic nerve as well as increase exposure of the parasellar region during extensive approaches. Despite requiring adjunctive epidural bone work, this technique allows safe optic nerve mobilization and early devascularization for anterior clinoidal meningioma resection. This 2D operative video describes right optic nerve decompression by extradural anterior clinoidectomy and subsequent resection of a right Al-Mefty type III clinoid meningioma under exoscope magnification. The patient was a 50-year-old woman with a 1-year history of right visual acuity impairment and papillary atrophy. The exoscope allows a 360° view around the anterior clinoid, improving maneuverability. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23118.

How I do it: surgery for spinal arteriovenous malformations.

BACKGROUND: Spinal arteriovenous malformations (AVM) are rare lesions. They may present with intramedullary hemorrhage or edema, often inducing severe neurological deficits. Active treatment of spinal AVMs is challenging even for experienced neurosurgeons. METHOD: Anticipation of anatomy and AVM angiocharacteristics from preoperative imaging is key for successful treatment. Information gathered from MRI and DSA has to be then matched to intraoperative findings. This is a prerequisite for reasonably safe and structured lesion removal. CONCLUSION: We provide a structured approach for surgical treatment of spinal AVMs, supplemented by high-resolution video and imaging material.

Herpesviruses, polyomaviruses, parvoviruses, papillomaviruses, and anelloviruses in vestibular schwannoma.

Etiology of vestibular schwannoma (VS) is unknown. Viruses can infect and reside in neural tissues for decades, and new viruses with unknown tumorigenic potential have been discovered. The presence of herpesvirus, polyomavirus, parvovirus, and anellovirus DNA was analyzed by quantitative PCR in 46 formalin-fixed paraffin-embedded VS samples. Five samples were analyzed by targeted next-generation sequencing. Viral DNA was detected altogether in 24/46 (52%) tumor samples, mostly representing anelloviruses (46%). Our findings show frequent persistence of anelloviruses, considered normal virome, in VS. None of the other viruses showed an extensive presence, thereby suggesting insignificant role in VS.

Three-Dimensional Exoscopic Versus Microscopic Resection of Vestibular Schwannomas: A Comparative Series.

BACKGROUND: Microsurgical resection of vestibular schwannoma (VS) is highly challenging, especially because surgical treatment nowadays is mainly reserved for larger (Koos grade 3 and 4) tumors. OBJECTIVE: To assess the performance of three-dimensional exoscope use in VS resection in comparison with the operative microscope. METHODS: Duration of surgery and clinical and radiological results were collected for 13 consecutive exoscopic schwannoma surgeries. Results were compared with 26 preceding microsurgical resections after acknowledging similar surgical complexity between groups by assessment of tumor size (maximum diameter and Koos grade), the presence of meatal extension or cystic components, and preoperative hearing and facial nerve function. RESULTS: Total duration of surgery was comparable between microscopically and exoscopically operated patients (264 minutes ± 92 vs 231 minutes ± 84, respectively; P = .276). However, operative time gradually decreased in consecutive exoscopic cases and in a multiple regression model predicting duration of surgery, and exoscope use was associated with a reduction of 58.5 minutes (95% CI -106.3 to -10.6; P = .018). Tumor size was identified as the main determinant of duration of surgery (regression coefficient = 5.50, 95% CI 3.20-7.80) along meatal extension and the presence of cystic components. No differences in postoperative hearing preservation and facial nerve function were noted between the exoscope and the microscope. CONCLUSION: Resection of VS using a foot switch-operated three-dimensional exoscope is safe and leads to comparable clinical and radiological results as resection with the operative microscope.

How I do it: lateral approach for craniocervical junction tumors.

BACKGROUND: The far lateral approach has been developed to access lesions at the craniocervical junction and upper cervical spinal canal. Associated morbidity triggered the development of less invasive tailored approaches. METHOD: In this lateral approach to the craniocervical junction, the occipital condyle is kept intact, vertebral artery manipulation is minimized, and the sigmoid sinus is not skeletonized. A linear incision through skin and muscles and use of an abdominal wall fat graft minimize the risk of cerebrospinal fluid leakage. CONCLUSIONS: The exposure provided is sufficient for the majority of tumors in this region and allows for low complication rates.

3D Exoscopes are Noninferior to Operating Microscopes in Aneurysm Surgery: Comparative Single-Surgeon Series of 52 Consecutive Cases.

OBJECTIVE: The literature on exoscope use in cerebrovascular neurosurgery is scarce, mainly comprising small case series and focused on visualization quality and ergonomics. As these devices become widely used, direct comparison to the operating microscope regarding efficacy and patient safety is necessary. METHODS: Fifty-two consecutive clipping procedures, performed by 1 senior vascular neurosurgeon, were analyzed. Either an operating microscope with a mouth switch (25 cases with 27 aneurysms; 13 ruptured) or a three-dimensional exoscope with a foot switch (27 cases with 34 aneurysms; 6 ruptured) were used. Durations of major surgical stages, number of device adjustments, numbers of clip repositionings and clips implanted were extracted from surgical videos. Demographic data, imaging characteristics, clinical course and outcomes were extracted from digital patient records. RESULTS: Duration of surgery and different stages did not differ between devices, except for final site inspection. The number of device adjustments was higher with the exoscope. With progressive experience in exoscope use, the number of device adjustments increased significantly, whereas surgery duration remained unchanged. Favorable outcome (modified Rankin Scale score 0-2) was observed in 80% and 88% of patients in the microscope and exoscope groups, respectively. Ischemic events were found in 2 patients in each group; no other complications occurred. CONCLUSIONS: In aneurysm clipping, three-dimensional exoscopes are noninferior to operating microscopes in terms of surgery duration, safety, and outcomes, based on our limited series. Progressive experience enables the surgeon to perform significantly more device adjustments within the same amount of surgical time.

Visualization and Maneuverability Features of a Robotic Arm Three-Dimensional Exoscope and Operating Microscope for Clipping an Unruptured Intracranial Aneurysm: Video Comparison and Technical Evaluation.

BACKGROUND: In recent years, three-dimensional (3D) digital exoscope systems have been developed and reported to form an adequate alternative to the conventional operating microscope. OBJECTIVE: To illustrate essential and practical features in a surgical video comparing a robotic arm 3D digital exoscope and a conventional operating microscope to clip a middle cerebral artery aneurysm. METHODS: We used a mouth switch-controlled operating microscope (OPMI PENTERO 900; Carl Zeiss Meditec AG) and robotic arm-controlled 3D digital Aeos exoscope (Aesculap Inc). We assessed the following visualization and optical features: overall visualization quality, color and contrast quality, range and quality of magnification, and adjustment of focus. In addition, we assessed maneuverability for changing surgical site within and viewing angle of the surgical field. RESULTS: We found that both modalities are suitable for this surgery and offer distinct qualities. The microscope enables faster magnification adjustment and continuous mouth switch-controlled focus adjustments. The advantages of the exoscope include the adaptation of color and contrast settings, and the surgeon can keep both hands in the surgical field while the camera pivots around its working field. CONCLUSION: The exoscope and operating microscope offer a similar high-quality visualization of, and smooth maneuvering within, the surgical field. The method of visualization and maneuvering is, however, very distinct. Therefore, a surgeon's acquaintance and experience with the specific features and how to optimally use them in surgery are of utmost importance. Further analyses of both systems are needed to evolve these tools.

Brainstem intraparenchymal schwannoma: A case report and literature review.

BACKGROUND: Intracranial intraparenchymal schwannomas (IS) are rare tumors that have mainly been described in case reports. Here, we report on a case of a brainstem IS and included a comprehensive literature review. CASE DESCRIPTION: A 74-year-old man presented with progressive gait disturbances. CT- and MRI-imaging revealed a contrast-enhancing mass accompanied by a cyst in the dorsolateral pons. Hemangioblastoma was suspected and surgery was advised. During surgery, gross total resection of a non-invasive tumor was performed. Postoperative recovery was uneventful. Based on histopathological examination, the intraparenchymal brainstem tumor was diagnosed as schwannoma. CONCLUSION: Our extensive review illustrates that ISs are benign tumors that most often present in relatively young patients. Malignant cases have been described but form an extremely rare entity. Preoperative diagnosis based on radiological features is difficult but should be considered when peritumoral edema, calcifications, and cysts are noted. In benign cases, gross total resection of the lesion is curative. To adequately select this treatment and adjust the surgical strategy accordingly, it is important to include IS in the preoperative differential diagnosis when the abovementioned radiological features are present.

Clinical outcome after microsurgical resection of intraventricular trigone meningiomas: a single-centre analysis of 20 years and literature overview.

BACKGROUND: Outcome and treatment-associated morbidity analysis of trigone meningioma surgery. METHODS: We retrospectively assessed 27 neurosurgically treated patients (median age 63 years, range 15-84) between 1999 and 2019. The median preoperative Karnofsky Performance Scale (KPS) was 80 (range 20-100), and the majority (78%) suffered from tumour-specific symptoms. The most frequent symptoms were aphasia (n = 6), visual field deficits (n = 5), and increased intracranial pressure (n = 5). The median tumour volume was 11.2 cm3 (range 3.9-220.5). The most common approaches were the transtemporal (n = 17) and transparietal routes (n = 5). RESULTS: At last follow-up (median follow-up 35 months, range 3-127), the median KPS was 90 (range 30-100); eleven (42%) patients had improved, nine (35%) were unchanged, six (23%) had worsened, and one was lost to follow-up. One year after surgery, 18/21 (86%) patients had retained an activity level similar or improved compared with preoperatively. No surgery-related mortality was recorded. Postoperative new neurological deficits were seen in 13 (48%) patients; eight suffered from permanent, most commonly motor deficits (n = 4), and five of transient deficits. Permanent new motor deficits improved in the majority of affected patients (3/4) over time. New deficits were more often seen for transtemporal (8/17) than transparietal approaches (1/5). Patients with postoperative permanent new deficits had a significantly worse KPS at last follow-up (p < 0.001). CONCLUSIONS: The transtemporal and transparietal approaches provide good access, but the latter might provide for a better risk profile. Patients show favourable outcome, but there is a considerable risk for new neurological deficits. This must be taken into consideration for oligosymptomatic patients.

Microsurgical removal of a misplaced intraspinal venous stent in a patient with inferior vena cava atresia.

Inferior vena cava atresia (IVCA) is a rare vascular condition that may be treated by venous stenting. The authors report on the microsurgical removal of an intraspinally misplaced stent causing nerve root compression and neurological deficits.A 42-year-old patient with IVCA and painful cutaneous collaterals had been scheduled for treatment by stenting of the iliocaval confluence and associated venous collaterals. Initial stenting of the right iliac vein was successful; however, during recanalization of the left paravertebral plexus, the stent entered the spinal canal via extraspinal-to-intraspinal venous collaterals. Because of the use of monoplanar angiography, the stent misplacement was not seen during the procedure. Postinterventionally, the patient experienced a foot elevation weakness (grade 1/5) as well as pain and hypesthesia corresponding to the L5 dermatome. Ultrasonography ruled out a lumbosacral plexus hematoma. CT angiography showed that a stent had entered the spinal canal through the left S1 neuroforamen causing nerve root compression. The intraspinal portion of the stent was removed piecemeal via a left-sided hemilaminectomy. Venous bleeding due to the patient's anticoagulation therapy, the stent's sharp mesh wire architecture, and the proximity to nerve roots complicated the surgery. Postoperatively, the foot elevation improved to grade 4/5.

Meditation music improved the quality of suturing in an experimental bypass procedure.

BACKGROUND: Neurosurgeons are vulnerable to additional noise in their natural operating environment. Noise exposure is associated with reduced cognitive function, inability to concentrate, and nervousness. Mediation music provides an opportunity to create a calmer environment which may reduce stress during surgery. METHODS: A pilot study was performed to find a suitable task, meditation music of surgeon's choice, and operation noise and to reach a certain level of training. For the main experiment, two neurosurgeons with different microsurgical experience used real operation noise and meditation music with delta waves as mediating music. Each surgeon performed 10 training bypasses (five with noise and five with music) with 16 stitches in each bypass. The total time to complete 16 stitches, a number of unachieved movements (N.U.Ms), length of thread consumed, and distribution of the stitches were quantified from the recorded videos and compared in both groups. RESULTS: A N.U.Ms were significantly reduced from 109 ± 38 with operation room (OR) noise to 38 ± 13 (p < 0.05) with meditating music in novice surgeon. Similar results were found in the experienced surgeon performing the same task [from 29 ± 6.94 to 14 ± 3.36 (p < 0.05)]. The total time utilized for the sixteen stitches was slightly improved (not significantly) in the novice surgeon and unchanged in the experienced surgeon. However, the thread length used for 16 stitches was significantly different with OR noise in comparison to meditating music in both surgeons. The distribution stitches showed a non-significant trend toward a uniform distribution with meditation music in both surgeons. CONCLUSIONS: Meditation music of surgeon's choice is a simple method that improved quality of bypass suturing in an experimental bypass procedure.

Preliminary experience with a digital robotic exoscope in cranial and spinal surgery: a review of the Synaptive Modus V system.

BACKGROUND: The microscope is the standard tool for microneurosurgery worldwide. However, the reduced illumination of the surgical field with the use of a conventional microscope during surgeries of deeply located pathologies remains unaddressed. Accordingly, different exoscope systems have recently been introduced in clinical practice. Here, we report our initial experience with the digital 2-dimensional Synaptive Modus V exoscope system in spinal and cranial surgery. METHODS: During a 2-week period between 27 September to 11 October 2018, we used the Synaptive Modus V exoscope system and performed eight neurosurgical procedures including spine (n = 4) and cranial procedures (n = 4). Visual quality, depth perception, complications, switching to microscope comfort level of the surgeon, and learning curve during surgery were evaluated. RESULTS: A total of eight procedures were performed, namely, vestibular schwannoma (n = 1), skull base meningioma (n = 1), olfactory groove meningioma (n = 1), tentorial meningioma (n = 1), anterior cervical discectomy (n = 1), cervical laminectomy (n = 1), and lumbar disc herniation (n = 2). The overall results were comparable to the operative microscope with better visual quality and greater comfort for the surgeon. CONCLUSION: The Synaptive Modus V system is a safe tool to perform common spinal surgeries and intracranial tumor resection. Image quality is better than a microscope but with slightly less depth perception. Vigorous training in the laboratory may be helpful before clinical use.

Bypass Surgery for Complex Internal Carotid Artery Aneurysms: 39 Consecutive Patients.

OBJECTIVE: Bypass surgery is a special technique used to treat complex internal carotid artery (ICA) aneurysms. The aim of this retrospective study is to provide a comprehensive description of treatment and outcome of complex ICA aneurysms at different ICA segments (cavernous, supraclinoid, ICA bifurcation) treated with bypass procedures. METHODS: We identified 39 consecutive patients with 41 complex ICA aneurysms that were treated with 44 bypass procedures between 1998 and 2016. We divided the aneurysms into 3 anatomic subgroups to review our treatment strategy. All the imaging studies and medical records were reviewed for relevant information. RESULTS: The aneurysm occlusion (n = 34, 83%) or flow modification (n = 5, 12%) was achieved in 39 aneurysms (95%). The long-term bypass patency rate was 68% (n = 30). Minor postoperative ischemia or hemorrhage was commonly seen (n = 20, 51%), but large-scale strokes were rare (n = 1, 3%). Preoperative dysfunction of extraocular muscles (cranial nerves III, IV, and VI) showed low-to-moderate improvement rates (20%-50%). Preoperative vision disturbance (cranial nerve II) improved seldom (22%). At the latest follow-up (mean; 51 months) 29 patients (74%) were independent (modified Rankin Scale ≤2). CONCLUSIONS: Bypass surgery for complex ICA aneurysms is a feasible treatment method with an acceptable risk profile. Patients should be informed of the uncertainty related to improvement of pretreatment cranial nerve dysfunctions.