Occipital artery to vertebral artery bypass for treatment of bilateral vertebral artery occlusion with QMRA as an adjunct to diagnostic assessment.

PURPOSE: Stroke, the second leading cause of death globally, often involves ischemia in the vertebrobasilar territory. This condition is underexplored, despite significant morbidity and mortality risks. The purpose of this study is to present a case of occipital artery to V3 segment vertebral artery bypass, emphasizing the role of quantitative magnetic resonance angiography (qMRA) in assessing flow and guiding surgical intervention. METHODS: A 66-year-old man with bilateral vertebral artery occlusion presented acute symptoms. qMRA was employed to evaluate flow dynamics and determine the feasibility of a flow augmentation bypass surgery. The occipital artery to left vertebral artery bypass (OA-to-VA) was performed, utilizing an inverted hockey-stick incision and an antegrade inside-out technique. The patency of the bypass was confirmed using both Doppler probe and Indocyanine green. RESULTS: Postoperative assessments, including computed tomography angiography (CTA) and qMRA, demonstrated the patency of the bypass with improved flow in the basilar artery and left vertebral artery. The patient's condition remained stable postoperatively, with residual peripheral palsy of the left facial nerve. CONCLUSION: In conclusion, the presented case illustrates the efficacy of the OA-to-VA bypass in addressing symptomatic bilateral vertebral artery occlusion. The study underscores the pivotal role of qMRA in pre- and postoperative assessments, providing noninvasive flow quantification for diagnostic considerations and long-term follow-up in patients with vertebrobasilar insufficiency.

Water quality modeling-based assessment for the scope of wastewater treatment of the urban reach of River Yamuna at Delhi, India.

River water quality management is a tedious job as it comprises multiple variables. The River Yamuna, Delhi's urban reach, is highly contaminated with very low or zero freshwater flow during the non-monsoon periods. The river quality has been appraised for pre- and post-monsoon periods of 10 years of data collected from the Delhi Pollution Control Council (DPCC). A sharp declination of dissolved oxygen and acceleration of BOD have been observed after the outfalling of drain 1. The wastewater treatment plants data for 2020-2022 have been analyzed, and the removal efficiencies of BOD and COD were found between 65 and 94%. The BIOFORE technology has shown maximum removal efficiencies, around 94% and 89% for BOD and COD, respectively. The level of treatment has been evaluated by developing a water quality model with the existing QUAL2kw framework. Twelve strategies have been generated for four levels of treatment and three different flow conditions. The severely polluted reach of Yamuna has low self-purification capacity; flow augmentation has little effect on the existing load. Hence, the level of treatment required to increase. After the introduction of outfalling drain D13-D16, a sag of DO has been observed; to improve the DO concentration, external aeration is suggested before wastewater disposal into the river. The study is a novel effort to manage the river quality by developing scenarios, including the level of treatments and flow augmentation, and keeping up the desired DO concentration assigned for this river reach.

Moyamoya Disease-Standards and Advances in Revascularization Procedure and Peri-operative Management.

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with unknown etiology characterized by progressive stenosis at the terminal portion of the internal carotid artery and the abnormal vascular network formation at the base of the brain. Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a preferred surgical procedure for ischemic-onset MMD patients by improving cerebral blood flow. Recent evidence further indicates that flow-augmentation bypass has a potential role for preventing re-bleeding in hemorrhagic-onset MMD patients. Based on such cumulative evidence, there is a worldwide increase in the number of MMD patients undergoing bypass surgery, thus thorough understanding of the basic pathology of MMD including peri-operative hemodynamics is critical for avoiding surgical complications. The author sought to demonstrate the standard surgical procedure of STA-MCA bypass with indirect pial synangiosis for adult MMD patients and its pitfall in the early postoperative period, introducing the characteristic peri-operative hemodynamic condition of adult MMD after surgery, such as local cerebral hyperperfusion and intrinsic hemodynamic ischemia caused by watershed shift phenomenon.

Current Open Surgical Indications for Revascularization in Cerebral Ischemia.

Cerebral revascularization was pioneered half a century ago. Gradual improvements in microsurgical instrumentation and training in microsurgical techniques have allowed significant changes that improved outcomes in neurosurgery, extrapolating this knowledge to other neurosurgical diseases (brain tumor, aneurysms, and skull base tumor surgery). But the popularity of cerebral bypass procedures was followed by their decline, given the lack of clear benefit of bypass surgery in chronic cerebrovascular ischemia after the EC-IC bypass studies. Over the last couple of decades, the formidable advance of neuro-endovascular techniques for revascularization has lessened the need for application of open cerebral revascularization procedures, either for flow augmentation or flow replacement. However, there is still a select group of patients with chronic cerebral ischemia, for whom open cerebral revascularization with flow augmentation is the only treatment option available, and this will be the objective of our current review.

Microsurgical Treatment Strategy of Vertebral Artery Fusiform Aneurysm-From the Standpoint of Hemodynamic Integrity and Perforator Preservation.

During treatment of vertebral artery (VA) fusiform aneurysms, it is critical to preserve peripheral perforators and anterograde blood flow of the VA and to reduce hemodynamic load to the contralateral VA. Even in the era of endovascular treatment, there are still many benefits to using microsurgical treatments with appropriate clip application and preservation of the perforators around the aneurysm, in conjunction with various bypass techniques. The ideal microsurgical technique involves reconstructive clipping that obliterates the aneurysm but preserves anterograde blood flow of the VA, followed by isolation of the aneurysm and VA reconstruction. If these two methods are unavailable, proximal clipping of the aneurysm combined with flow-augmentation bypass to the distal branch can be considered as an alternative surgical management. We discuss the microsurgical treatment of unruptured VA fusiform aneurysms in our surgical cases on the basis of a review of the current literature.

Simultaneous Energy Generation and Flow Enhancement (Electroslippage Effect) in Polyelectrolyte Brush Functionalized Nanochannels.

Energy generation through nanofluidics is a topic of great nanotechnological relevance. Here, we conduct all-atom molecular dynamics (MD) simulations of the transport of water and ions in a pressure-driven flow in nanochannels grafted with charged polyelectrolyte (PE) brushes and discover the possibility of simultaneous electrokinetic energy generation and flow enhancement (henceforth denoted as the electroslippage effect). Such PE-brush-functionalized nanochannels have been recently shown to demonstrate an overscreening (OS) effect (characterized by the presence of a greater number of screening counterions within the PE brush layer than needed to screen the PE brush charges), a consequent presence of excess co-ions within the PE brush-free bulk, and a co-ion-driven electroosmotic (EOS) transport in the presence of small to moderate applied axial electric fields. In this study, however, we find that the streaming current, which represents the current generated by the flow-driven downstream advection of the charge imbalance present within the electric double layer (EDL) that screens the PE brush charges, is governed by the migration of the counterions. This stems from the fact that the highest contribution to the overall streaming current arises from the region near the PE brush-water interface (where there is an excess of counterions), while the brush-free bulk yields a hitherto unreported, but small, co-ion-dictated streaming current. This downstream advection of the charge imbalance (and the resultant counterion-driven streaming current) eventually leads to the development of an electric field (streaming electric field) in the direction that is opposite the direction of the counterion-driven streaming current. The streaming current and the streaming electric field interact to generate the electrokinetic energy. Equally important, this streaming electric field induces an EOS transport, which becomes co-ion-driven, due to the presence of excess co-ions in the brush-free bulk. For the case of nanochannels grafted with negatively charged PE brushes, the streaming electric field will be in a direction that is opposite that of the pressure-driven transport, and hence the co-ion (or anion) driven EOS flow will be in the same direction as the pressure-driven transport. On the other hand, for the case of nanochannels grafted with positively charged PE brushes, the streaming electric field will be in the same direction as the pressure-driven flow, and hence the co-ion (or cation) driven EOS flow, will again be in the same direction as the pressure-driven flow. Therefore, whenever there occurs a presence of the OS and the resulting co-ion-driven EOS transport in PE brush grafted nanochannels, regardless of the sign of the charges of the PE brushes, this EOS transport will always aid the pressure-driven transport and will cause the most fascinating increase in the net volume flow rate across the nanochannel cross section, which is the electroslippage effect.

Novel Software-Derived Workflow in Extracranial-Intracranial Bypass Surgery Validated by Transdural Indocyanine Green Videoangiography.

BACKGROUND: The introduction of image-guided methods to bypass surgery has resulted in optimized preoperative identification of the recipients and excellent patency rates. However, the recently presented methods have also been resource-consuming. In the present study, we have reported a cost-efficient planning workflow for extracranial-intracranial (EC-IC) revascularization combined with transdural indocyanine green videoangiography (tICG-VA). METHODS: We performed a retrospective review at a single tertiary referral center from 2011 to 2018. A novel software-derived workflow was applied for 25 of 92 bypass procedures during the study period. The precision and accuracy were assessed using tICG-VA identification of the cortical recipients and a comparison of the virtual and actual data. The data from a control group of 25 traditionally planned procedures were also matched. RESULTS: The intraoperative transfer time of the calculated coordinates averaged 0.8 minute (range, 0.4-1.9 minutes). The definitive recipients matched the targeted branches in 80%, and a neighboring branch was used in 16%. Our workflow led to a significant craniotomy size reduction in the study group compared with that in the control group (P = 0.005). tICG-VA was successfully applied in 19 cases. An average of 2 potential recipient arteries were identified transdurally, resulting in tailored durotomy and 3 craniotomy adjustments. Follow-up patency results were available for 49 bypass surgeries, comprising 54 grafts. The overall patency rate was 91% at a median follow-up period of 26 months. No significant difference was found in the patency rate between the study and control groups (P = 0.317). CONCLUSIONS: Our clinical results have validated the presented planning and surgical workflow and support the routine implementation of tICG-VA for recipient identification before durotomy.