Objectives: To investigate the computer graphics (CG) reconstruction methods as visualization tools for cerebrovascular surgery simulations and their possible clinical applications.

Methods: The following CG technologies were used to improve three-dimensional fusion images reconstructed from medical images: particle-based fluid simulation enabling blood flow analysis; rigging and mesh editing for virtual tissue deformation and fusion with CG of normal anatomy, machine learning technology for automatic tissue segmentation, mixed reality technology enabling fusion with physical space, and rendering with texturing and shading. Problems and contributions of the proposed CG methods in preoperative surgical simulation were assessed in 299 cases of cerebrovascular surgery.

Results: Blood flow analysis enabled using the proposed CG method contributed to the differentiation of abnormal vessels, arteries, and veins in cerebral arteriovenous malformations. Mixed reality technology has contributed to the identification of anatomical features within a complex surgical field. Virtual tissue deformation and fusion with CG of normal anatomy offered a more flexible preoperative assessment than 3D fusion images constructed from medical images alone. The modified rendering improved the visibility. On the other hand, neurosurgeons thought that the image processing required for the proposed CG method was complicated and challenging. Image processing is also time-consuming.

Conclusion: The proposed methods have the potential to be more useful than conventional medical images in preoperative assessment for cerebrovascular surgery, but technical issues remain to be addressed.

Patients with poor-grade subarachnoid hemorrhage have a very poor prognosis, especially those with cardiopulmonary arrest and/or bilateral dilated pupils. Therapeutic indications for patients with poor-grade subarachnoid hemorrhage vary depending on the institution; however, we perform clipping or coil embolization in these patients with very poor-grade subarachnoid hemorrhage if their vital signs are stable at the time of admission. In this study, we summarize the outcomes of 31 patients with poor-grade subarachnoid hemorrhage seen between January 2015 and April 2017. Among the 31 patients, 13 patients had cardiopulmonary arrest at the time of admission and/or prehospital, and 15 patients had bilateral dilated pupils. Among these 13 patients with cardiopulmonary arrest, seven patients underwent clipping or coil embolization because their vital signs could be stabilized. The functional outcomes of these seven patients were very poor: mRS 1 (1 patient), mRS 4 (1 patient), and mRS 5 (5 patients); however, all of these patients survived 30 days after the subarachnoid hemorrhage onset. Meanwhile, the other nine patients with unstable vital signs and who could therefore not undergo clipping or coil embolization died within 30 days after the subarachnoid hemorrhage onset.

In conclusion, although the functional outcomes of patients with poor grade subarachnoid hemorrhage and cardiopulmonary arrest were very poor, a minority of these patients had good functional outcomes.

Introduction: To evaluate the clinical outcomes and factors affecting the prognosis of giant aneurysms and to better establish the role of microsurgery with bypass in its management.

Materials and Methods: Forty-eight patients with surgically treated giant aneurysms were included in this study. A giant aneurysm is defined as an aneurysm with a maximum diameter of ≥25 mm. Poor outcomes were defined as modified Rankin scale scores of 3-6.

Results: The mean size of the aneurysms was 30.9 mm (range, 25.0-54.9 mm). In 38 (79.2%) patients, the aneurysms were completely occluded without residual aneurysms, eight (16.7%) patients had minor aneurysm remnants, and two (4.2%) had incomplete occlusion. Two (1.3%) patients with giant basilar artery trunk aneurysms died due to rupture of the treated aneurysm. Bypass surgery was combined with microsurgery in 45 (93.8%) patients. Perforating artery infarction was observed postoperatively in 18 (37.5%) patients, and poor outcomes were observed in 12 (25.0%) patients. Male sex (p=0.002; odds ratio [OR]: 10.000, [2.262-44.203]), perforating artery infarction (p=0.036; OR: 5.200, [1.277-21.181]), branches arising from the aneurysms (p=0.031; OR: 4.900, [1.219-19.689]), and location of the aneurysm (p=0.002) were significantly associated with poor outcomes.

Conclusion: Microsurgery with bypass is an acceptable treatment modality for several giant aneurysms. Infarction of the perforating artery remains an unsolved problem, for which additional surgical strategies are required.

Introduction: Single-photon emission computed tomography (SPECT) with acetazolamide challenge is useful in the prediction and assessment of post-carotid endarterectomy (CEA) or carotid stenting (CAS) cerebral hyperperfusion (CHP). However, serious adverse reactions to acetazolamide have been reported to date.

Purpose: The purpose of this study was to predict the CHP using computed tomography perfusion imaging (CTP).

Methods: SPECT with acetazolamide challenge and CTP, as a preoperative study, were used in 116 patients undergoing CEA or CAS from August 2015 to August 2018. Twenty-one patients were determined to be at risk of CHP by SPECT with acetazolamide challenge. After co-registration of the CTP and SPECT images, we assessed the relationship between the CTP parameters and SPECT findings in 21 patients regarded as having a high risk of CHP. CTP maps were assessed for cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time-to-peak (TTP), time-to-start (TTS), and time-to-drain (TTD).

Results: Increased CBV and delayed TTD and TTP were observed in all the 21 patients. Six of the 21 patients had a CHP. In these six patients, delayed MTT and delayed TTS were observed. The delay in MTT and TTS was strongly correlated with postoperative CHP (p ＜ 0.05).

Conclusion: Preoperative CTP may be useful for the prediction of cerebral hyperperfusion.

Here, we report two cases of unruptured right middle cerebral aneurysms in which intraoperative electrophysiological monitoring showed false-positive responses due to dural closure. Patient 1 was a 71-year-old woman in whom direct surgery was performed under electrophysiological monitoring using transcranial electrical stimulation (TES). Motor-evoked potentials (MEPs) were recorded from the bilateral upper extremities. The MEP amplitude decreased on the left side when the dura mater was closed. In contrast, the MEP obtained from the contralateral side showed no obvious decrease. Postoperative computed tomography images showed no ischemic lesions, and the patient was discharged without complications. Patient 2 was a 69-year-old woman in whom direct surgery was performed under electrophysiological monitoring. MEP was recorded from the left extremity. Although the MEPs were stable until dural closure, their amplitudes disappeared once the dura mater was completely closed. Postoperative radiological imaging showed no ischemic changes, and the patient was discharged without complications. MEPs may fluctuate during direct surgery due to many factors. Accordingly, the TES results can sometimes be confusing. We should be aware that a false-positive response may occur because of dural closure.

A 41-year-old woman with Moyamoya disease (MMD) who had undergone bilateral indirect bypass during childhood presented with intracerebral hemorrhage in the genu of the corpus callosum. Digital subtraction angiography (DSA) revealed an occluded right anterior cerebral artery (ACA) and a small aneurysm in the frontal lobe, which arose on an unusual collateral artery from the M3 portion of the right middle cerebral artery. Since the aneurysm was still present on day 15, we performed proximal clipping using the navigation-guided trans-sulcal approach. Superficial temporal artery (STA)-ACA bypass with an indirect procedure was also performed to prevent further aneurysmformation. The aneurysm disappeared on DSA, and the patient fully recovered without neurological deficits.

Aneurysm formation at this site is extremely rare. Single-stage proximal clipping and bypass surgery to reduce hemodynamic stress can be a potentially effective therapeutic strategy.

The treatment of large thrombosed basilar trunk aneurysms is challenging. We report a case of an aneurysm treated with multiple LVIS stent placement. A 64-year-old man with transient hemiplegia was found to have a large thrombosed basilar trunk aneurysm with compression of the brain stem by using magnetic resonance imaging (MRI) and digital subtraction angiography (DSA). Interventional radiology (IVR) was performed to prevent aneurysm rupture and the deterioration of the mass effect. Specifically, three LVIS stents were placed from the top of the basilar artery to the vertebral artery. As a result, the patient was asymptomatic in the year following the IVR. To conclude, multiple LVIS stent placement is a useful method for the treatment of large thrombosed basilar trunk aneurysms.

We describe a case in which intraoperative indocyanine green videoangiography (ICG-VA) enabled the detection of hyperemia in the brain adjacent to the nidus during cerebral arteriovenous malformation (AVM) surgery. A 43-year-old woman presented with paresis and sensory disturbance in her left upper extremity, which revealed a subcortical hematoma in the right parietal lobe due to a small ruptured AVM. Craniotomy was performed. During surgery, despite resection of the nidus, a persistent red draining vein was observed. ICG-VA demonstrated that the reddish blood flow was not from the residual nidus but from the adjacent brain, suggesting hyperemia. The procedure was completed without additional manipulation. The paresis was almost completely reversed, and the patient was discharged 2 weeks after surgery. Interestingly, the observed hyperemia after nidus resection corresponded to an area where the pial venous reflux from the draining vein was observed before the resection, and it is possible that chronic venous hypertension contributed to this post-resection hyperemia. During AVM surgery, ICG-VA may be useful in evaluating changes in blood flow not only in malformation but also in adjacent brain regions.

An optimal treatment strategy has not been established for acute ischemic stroke (AIS) caused by intracranial artery occlusion associated with severe stenosis of the cervical internal carotid artery (ICA), also known as a tandem lesion. Herein, we describe our experience with two cases of tandem lesions, including device selection and treatment strategy. A tandem lesion was observed on emergency angiography. In the subsequent revascularization procedure, carotid artery stenting (CAS) was first performed for the cervical lesion, after which the guiding catheter was passed through the stent and placed in the ICA. Both outcomes received a score of 1 on the modified Rankin Scale (mRS), which is considered to be good. The time to reperfusion was delayed by about 15 minutes due to the CAS procedure; however, the guiding catheter was able to pass the cervical lesion relatively safely. Consecutive and anterograde treatments for tandem lesions were effective in AIS.

A 51-year-old woman was brought to our hospital with a major complaint of headache. Computed tomography (CT) showed a right temporal subcortical hemorrhage. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) did not show any abnormalities. Laboratory evaluation on admission showed a severe iron deficiency anemia (IDA) due to myoma uteri. Therefore, the patient was admitted to our hospital, and a conservative treatment was administered to lower the blood pressure. However, 4 hours after admission, she became comatose, and CT revealed an increased hematoma size and signs of herniation. External decompression was performed and white thrombosis was observed in the superficial middle cerebral vein (SMCV). The patient was treated with heparin and warfarin, and she was discharged with only left spatial neglect on hospital day 119. IDA induces thrombopoiesis, which is thought to be associated with a hypercoagulable state and microcytosis causing reduced red cell deformability and increased viscosity. This situation induced cerebral venous thrombosis.

Keyhole craniotomy is a minimally invasive method for microsurgical clipping. We describe a simple and easy pterional keyhole craniotomy (PKC) technique for clipping using an electromagnetic navigation system (the AxiEM Electromagnetic StealthStation navigation system, Medtronic, Minneapolis, MN, USA). We used the freehand technique with the emitter throughout the procedure to avoid electromagnetic interference from the metallic surgical instruments, which serves as a potential disadvantage of the electromagnetic navigation system. Navigation-guided surgery enables accurate PKC and provides sufficient working space for complete and meticulous clipping. The electromagnetic navigation system setup and subsequent registration can be performed rapidly, does not require special instruments, and is available at all facilities that have an electromagnetic navigation system.