Double-barrel STA-MCA bypass for cerebral revascularization: lessons learned from a 10-year experience.

OBJECTIVE: In select patients, extracranial-intracranial (EC-IC) bypass remains an important tool for cerebral revascularization. Traditionally, superficial temporal artery-middle cerebral artery (STA-MCA) bypass was performed using one limb of the STA only. In an attempt to augment flow and to direct flow to different ischemic areas of the brain, the authors adopted a "double-barrel" technique in which both branches of the STA are used to revascularize distinct MCA territories. METHODS: A series of consecutive double-barrel STA-MCA bypasses performed between 2010 and 2020 were reviewed. Each anastomosis was directed to augment flow to a territory most at risk based on preoperative perfusion studies, cerebral angiography, and intraoperative indocyanine green data. CT perfusion and CTA were routinely used to evaluate postoperative augmentation and graft patency. Patient perioperative outcomes, surgical complications, and modified Rankin Scale (mRS) scores at the last follow-up were reported. RESULTS: Forty-four patients (16 males, 28 females) successfully underwent double-barrel STA-MCA bypass on 54 cerebral hemispheres: 28 operations were for moyamoya disease, 23 for atherosclerotic disease refractory to medical therapy, 2 for complex cerebral aneurysms, and 1 for carotid occlusion as a sequela of cavernous meningioma growth. Ten patients underwent multiple operations, 9 of whom had moyamoya disease/syndrome, with the subsequent operation on the contralateral hemisphere. The average patient age at surgery was 45.1 years (range 14-73 years), with a mean follow-up time of 22.1 months. Intraoperative graft patency was confirmed in 100% of cases, and 101 (98.1%) of the 103 anastomoses with imaging follow-up were patent. Perfusion to the revascularized hemisphere was improved in 88.2% of cases. Perioperative ischemic and hemorrhagic complications occurred in 8 procedures (2 were asymptomatic), whereas remote ischemic and hemorrhagic events occurred in 7 cases. There was no mortality in the series, and the mean patient mRS scores were 1.72 at presentation and 1.15 at the last follow-up. CONCLUSIONS: The high rates of intraoperative and postoperative patency support the feasibility of dual-anastomosis STA-MCA bypass for revascularization. The perioperative complication rate is not significantly different from that of single-anastomosis bypass. The functional outcomes at follow-up and perfusion improvement postoperatively support the efficacy and safety of this method as a treatment strategy.

A Survey of Microsurgical Technique for Extracranial-to-Intracranial Bypass.

BACKGROUND: Extracranial-to-intracranial bypass surgery is a well-established technique that has been practiced for over 50 years. Since then, numerous technical variants have developed nationally and internationally. OBJECTIVE: Based on a survey, to collect information on cerebrovascular bypass surgeons and their background, surgical volume, and technical steps of extracranial-to-intracranial bypasses with focus on superficial temporal artery to middle cerebral artery (STA-MCA) bypass. METHODS: An electronic survey was distributed among bypass neurosurgeons. Responses were analyzed for national-international variations of STA-MCA bypass surgery techniques. The survey focused on the technical aspects of the surgery itself rather than patient selection or perioperative management. RESULTS: Survey responses were collected from 51 neurosurgeons performing cerebrovascular bypass, from 11 different countries across North America, Europe, and Asia. The largest age block was early-to mid-career (66.7% aged 36-50 years). Most participating surgeons (80.40%) performed less than 20 bypasses annually, whereas a select few surgeons (3) performed more than 50 annually. The most common bypass was STA-M4 MCA bypass with a linear incision (34%) over the parietal branch (44%) and choosing an MCA recipient based on diameter (61.2%). The interrupted anastomosis technique was most common (74%). CONCLUSIONS: The results of this electronic survey will help to identify common patterns in STA-MCA bypass surgery and will serve as a guide to other neurosurgeons to modify and improve their technique. Cerebrovascular bypass is still widely practiced, including by young neurosurgeons, who are actively learning from established masters who share their experience.

Association of Anterior Communicating Artery Aneurysms with Triplicate A2 Segment of the Anterior Cerebral Artery.

OBJECTIVE: Triplicate A2 segment of the anterior cerebral artery is a rare anatomical variant (1%-3% prevalence) that which is thought to result mainly from persistence of the embryonic median artery of the corpus callosum. We sought to determine whether the triple-A2 variant is specifically associated with anterior communicating artery (ACoA) aneurysm. METHODS: We reviewed 2-dimensional digital-subtraction angiography (2D-DSA) as well as 3-dimensional rotational angiography (3D-RA) images of 55 patients with ACoA aneurysms who presented for evaluation and treatment between 2009 and 2014 at our institution. The criteria for definitively obtaining an accurate accounting of all A2 segments was presence of adequate cross-filling across the ACoA on 2D-DSA or 3D-RA imaging, or ability to fuse left and right 3D-RA images. Patients whose imaging did not meet these criteria were excluded from further analysis. RESULTS: We obtained a definitive count of all A2 segments in 36 patients. Among these, 19 patients (5 with the triple-A2 variant) were treated surgically, and 17 patients (2 with the triple-A2 variant) were treated endovascularly. The triple-A2 variant was seen in 7 patients. The prevalence of triple-A2 variant among patients with ACoA aneurysm was 19.4%. Patients with ACoA aneurysms had a significantly higher prevalence of the triple-A2 variant compared with the general population (P < 0.00001). CONCLUSIONS: Compared with the normal population, patients with ACoA aneurysms deemed to require treatment have a significantly higher likelihood of having triplicate A2 segment. Knowledge of this anatomical variation is of critical importance in planning and executing endovascular and microsurgical treatment of ACoA aneurysms.

The Ultimate Skull Base Maneuver Does Not Involve Removing Bone: Quantifying the Benefits of the Interfascial Dissection.

Introduction Several adjunctive osteal skull base maneuvers have been proposed to increase surgical exposure of the anterolateral approach. However, one of the easiest methods does not involve bone: the interfascial temporalis muscle dissection. Methods Sequential dissections were performed bilaterally on five fixed silicone-injected cadaver heads. The amount of sphenoid drilling, scalp retraction, and brain retraction was standardized in all specimens. For each approach, surgical angles were measured for four deep targets: the tip of the anterior clinoid process, the internal carotid artery terminus, the origin of the posterior communicating artery, and the anterior communicating artery. Five surgical angles were measured for each target. Results There were increases on the order of 20% in the anteroposterior (AP)-mid, AP-lateral, and mediolateral-anterior angles for all deep targets with interfascial approach versus a myocutaneous flap. An orbitozygomatic osteotomy additionally increased almost all the angles, but incrementally less so. Conclusion An interfascial dissection increases the surgical exposure to a larger degree than additional osteotomies for several surgically relevant working angles. The addition of an orbitozygomatic osteotomy affords a particular benefit for the suprachiasmatic region. Increased adoption of interfascial mobilization or the temporalis muscle-an easily performed and low-risk maneuver-during anterolateral craniotomies may obviate the need for more involved skull base drilling.

Surgical Reconstruction to Allow Endovascular Access for Flow Diversion of Giant Cavernous Aneurysm: A Combined Approach.

Giant cavernous aneurysms of the internal carotid artery (ICA) are challenging lesions associated with high surgical morbidity. Prior to the past several years, these were treated by surgical reconstruction, proximal ligation, or stent-assisted coiling techniques. Flow diversion has become the standard of care for these lesions, providing a high rate of obliteration with a much better safety profile. However, flow diverters rely upon a navigable vasculature and, usually, a tri-axial support system. Cases in which such access is difficult require unique approaches to combine the strengths of both surgical and endovascular therapy. A woman with a giant cavernous ICA aneurysm and an ophthalmic artery aneurysm presented for treatment, but access was challenging due to cervical ICA tortuosity and pseudoaneurysms. We elected a staged, combined approach with surgical reconstruction of the cervical ICA followed by flow diverter placement for the intracranial aneurysms. Our case features an "outside-the-box" approach that synergistically applied both microsurgical and endovascular techniques to treat a challenging pathology. Classic microsurgical techniques remain important in cases that are refractory or not amenable to endovascular therapy alone.

Transcavernous Approach to the Basilar Apex: A Cadaveric Prosection.

The transcavernous approach to the basilar artery, as initially described by Dolenc, is one of the most common and elegant approaches to the region. It affords a generous working and viewing angle, but it can be technically challenging and requires attention to detail at each step. We investigate this approach in this report via a cadaveric prosection with a focus on the value of each of the component steps in improving surgical view and exposure. The transcavernous approach steps are divided into extradural stages: orbitozygomatic osteotomy (a modern adjunct to Dolenc's original description), drilling of the lesser sphenoid wing, and anterior clinoidectomy; and intradural stages: wide splitting of the Sylvian fissure, unroofing of the oculomotor and trochlear nerves, and posterior clinoidectomy. The surgical windows afforded by each step in the approach are illustrated using microscopic images taken during the cadaveric prosection of a donor who happened to harbor a basilar apex aneurysm. An illustrative case and artist illustrations are used to emphasize the relative value of each step of the transcavernous exposure.

Double-Barrel Superficial Temporal Artery-Middle Cerebral Artery Bypass: Can It Be Considered "High-Flow?"

BACKGROUND: Traditionally, superficial temporal artery-middle cerebral artery (STA-MCA) bypass uses one STA branch. Its augmentation of flow has classically been described as "low flow." In a double-barrel STA-MCA bypass, however, both branches of the STA are utilized. Here we hypothesize that this should not be considered "low flow." OBJECTIVE: To review quantitative flow data from our cases and investigate the impact of double-barrel STA-MCA bypass on total flow augmentation, and to assess whether double-barrel STA-MCA bypass might be useful in situations that traditionally demand more complex bypass strategies. METHODS: Intraoperative flow probe measurements from STA-MCA bypass cases were retrospectively tabulated and compared. Cut flow and bypass flow measurements were, respectively, taken before and after completion of anastomoses. The higher value was labeled best observed flow (BOF). RESULTS: We identified 21 STA-MCA bypass cases with available intraoperative flow probe measurements, of which 17 utilized double-barrel technique. Only 1 STA branch was available in 4 cases. Significantly higher average BOF was seen when utilizing 2 STA branches (69 vs 39 cc/min, P < .001). A majority (9/17) of double-barrel bypasses provided BOF ≥ 65 cc/min (120 cc/min maximum). The single branch bypass maximum BOF was 40 cc/min. CONCLUSION: Double-barrel bypass technique significantly enhances STA-MCA flow capacity and may be useful in situations in which a high-flow bypass is needed. The 2 efferent limbs allow flexibility in distributing flow across separate at-risk territories. The method compares favorably to other descriptions of high-flow bypass without the morbidity of graft harvest or an additional cervical incision.

Advanced cone-beam CT venous angiographic imaging.

OBJECTIVE The evaluation of the venous neurovasculature, especially the dural venous sinuses, is most often performed using MR or CT venography. For further assessment, diagnostic cerebral angiography may be performed. Three-dimensional rotational angiography (3D-RA) can be applied to the venous system, producing 3D rotational venography (3D-RV) and cross-sectional reconstructions, which function as an adjunct to traditional 2D digital subtraction angiography. METHODS After querying the database of Baylor St. Luke's Medical Center in Houston, Texas, the authors reviewed the radiological and clinical data of patients who underwent 3D-RV. This modality was performed based on standard techniques for 3D-RA, with the catheter placed in the internal carotid artery and a longer x-ray delay calculated based on time difference between the early arterial phase and the venous phase. RESULTS Of the 12 cases reviewed, 5 patients had neoplasms invading a venous sinus, 4 patients with idiopathic intracranial hypertension required evaluation of venous sinus stenosis, 2 patients had venous diverticula, and 1 patient had a posterior fossa arachnoid cyst. The x-ray delay ranged from 7 to 10 seconds. The 3D-RV was used both for diagnosis and in treatment planning. CONCLUSIONS Three-dimensional RV and associated cross-sectional reconstructions can be used to assess the cerebral venous vasculature in a manner distinct from established modalities. Three-dimensional RV can be performed with relative ease on widely available biplane equipment, and data can be processed using standard software packages. The authors present the protocol and technique used along with potential applications to venous sinus stenosis, venous diverticula, and tumors invading the venous sinuses.

Tourniquet parent artery occlusion after flow diversion.

BACKGROUND: The Pipeline Embolization Device (PED) is increasingly used for both on- and off-label purposes for treatment of intracranial aneurysms. The device gradually slows flow of blood into the aneurysm, but the high metal coverage of PED promotes endothelialization of the device. Occasionally, this leads to in-stent stenosis that is clinically well tolerated. We present a multi-institutional Pipeline series that includes three cases of gradual asymptomatic occlusion within the PED and parent vessel. METHODS: Institutional databases at each participating center were searched for patients treated with the PED. Patients with at least 50% stenosis or occlusion were selected and all relevant clinical and radiographic data were reviewed. RESULTS: A total of 326 cases performed by five neurointerventionalists across four institutions were reviewed. Among these there were three cases of complete occlusion and two cases of stenosis of more than 50%, for an occlusion rate of 0.9%. All patients were clinically asymptomatic. CONCLUSIONS: A gradual tourniquet-like occlusion can occur following placement of the PED, leading to vessel occlusion. This has been clinically well tolerated by patients in our series due to the formation of pial collaterals as the stenosis progresses, likely due to ischemic preconditioning. Small parent vessel, pre-existing stenosis, fusiform pathology, overlapping devices, and suboptimal antiplatelet therapy seem to be predisposing factors. Further experience and follow-up will allow us to characterize the risk factors and optimize post-procedural therapy for these patients.

Intraoperative Computed Tomography Angiography: A Novel Completion Imaging Modality for Carotid Endarterectomy.

BACKGROUND: Intraoperative computed tomography angiography (ICTA) is a novel completion imaging modality for carotid endarterectomy (CEA). No studies exist in the literature describing ICTA use in CEA. OBJECTIVE: To evaluate the feasibility and efficacy of ICTA as a method of immediately evaluating the technical results of CEA. METHODS: Twenty-three consecutive CEAs were performed by a single neurosurgeon over an 8-month period. Of this series, 12 utilized ICTA for completion imaging, 10 utilized duplex ultrasonography (US), and 1 utilized no intraoperative completion imaging. Electronic medical records were reviewed to assess demographics, CTA results, US results, and need for revisions. RESULTS: Patients included 13 men (62%) and 8 women (38%). All patients had symptomatic internal carotid artery stenosis. Polytetrafluoroethylene (PTFE) patch angioplasty was used in 16 cases (70%). Average operative times were comparable between cases that utilized CTA and US, 180 and 175 min, respectively. Major technical defects were identified in one of the 12 cases utilizing ICTA and none of the 10 cases utilizing intraoperative US. The technical defect was revised without subsequent neurological complication. One patient had a postoperative intracerebral hemorrhage requiring surgical evacuation. Fifteen patients were followed for up to 3 months with no postoperative stroke or transient ischemic attacks. CONCLUSION: ICTA is a potentially safe and effective completion imaging modality compared to traditional alternatives, enabling the identification of technical deficits intraoperatively. While no statistically significant difference in operative times were noted between intraoperative CTA and US use, numerous steps must be taken to maximize the efficiency of ICTA.

An Intraoperative Look at Failure of Flow Diversion: When Additional or Alternative Treatments Should Be Considered.

BACKGROUND: The pipeline embolization device (PED) is a flow-diverting stent that provides an additional treatment modality in the management of intracranial aneurysms. An aneurysm treated with a flow diverter is expected to involute over time, contrary to the immediate obliteration expected by surgical clipping or coiling. Yet, which aneurysms will respond to PED therapy and the time frame to expect full obliteration remain unclear. CASE DESCRIPTION: We report the unusual case of a 50-year-old woman with multiple (4 total) intracranial aneurysms who underwent multimodality treatment. Two aneurysms were treated with PEDs. Nine months later, the patient underwent a craniotomy for treatment of an additional aneurysm; at the time of surgery, one of the PED-treated aneurysms was noted to be clearly obliterated, and the other was visualized to be filling. The ophthalmic artery arose from the persistently filling aneurysm. The aneurysm was treated by clip ligation without incident. CONCLUSIONS: The rate of PED aneurysm obliteration increases with longer follow-up; however, the time frame for observing a persistently filling aneurysm before additional treatment is considered remains unknown. Some aneurysms may never close even after discontinuation of dual antiplatelet therapy. Ophthalmic artery aneurysms have been noted to fail treatment with PED based on the anatomic relationship of the aneurysm to the ophthalmic artery. This case provokes us to consider factors that may affect the latency to aneurysm obliteration, including aneurysm size, aneurysm morphology, patient gender, failure of previous aneurysm treatment, and duration of time from initial endovascular treatment.

Application of 4-Dimensional Digital Subtraction Angiography for Dural Arteriovenous Fistulas.

BACKGROUND: Three-dimensional reconstruction of digital subtraction angiography (3D-DSA) is a useful imaging modality for assessing complex cerebrovascular lesions. However, due to the importance of flow over time in certain vascular lesions, 3D-DSA is of less value as it lacks the temporal resolution. Dural arteriovenous fistulas (AVFs) are complex lesions in which an arteriovenous shunt exists between meningeal arteries and a dural venous sinus or cortical vein. Traditional 2D-DSA, especially with superselective injections of feeding arteries, is currently the gold standard for assessment, but overlapping of opacified vessels can complicate interpretation. A novel imaging technique, 4D-DSA, merges 3D reconstructions of multiple temporal series. It offers a unique perspective on complex cerebrovascular lesions and may offer several advantages in the assessment of dural AVF. METHODS: 4D-DSA images were acquired in 5 patients who presented with dural AVFs. All relevant clinical data, imaging, and procedural/operative reports were reviewed retrospectively. 4D-DSA images were reconstructed on a separate 3D workstation and compared to 2D and 3D-DSA images in an offline fashion. RESULTS: In all 5 cases, 4D-DSA proved to be useful in lesion assessment and treatment planning. This included observation (n = 2), microsurgery (n = 1), and endovascular embolization (n = 2). CONCLUSIONS: In the small series of patients in which it has been evaluated, 4D-DSA offers several advantages in assessing dural AVFs. The ability to see and manipulate feeding arteries in 3D combined with temporal resolution was useful in assessment and treatment planning. Continued experience with this imaging technique will be needed to identify its optimal use.

Two-color 3D-3D fusion of selective rotational cerebral angiograms: a novel approach to imaging in cerebrovascular neurosurgery.

BACKGROUND: Since its introduction, digital subtraction angiography has been considered the gold standard in diagnostic imaging for neurovascular disease. Modern post-processing techniques have made angiography even more informative to the cerebrovascular neurosurgeon or neurointerventionalist. Open neurosurgical procedures such as aneurysm clipping, extirpation of arteriovenous malformations, and extracranial-intracranial bypass remain important techniques in the armamentarium of a comprehensive cerebrovascular neurosurgeon. In-depth study of the anatomy of vascular pathology prior to and after surgery, often via selective cerebral angiography, is a critical component of surgical planning. However, when a vascular lesion or relevant anatomical region is perfused by two or more vascular territories, each selective angiographic imaging volume may provide an incomplete anatomical picture. METHODS: An institutional database was searched for cases in which the syngo Inspace 3D-3D fusion software was used and assisted in diagnosis and surgical management. RESULTS: In the six cases reviewed, the 3D-3D fusion imaging was crucial in understanding the anatomy of the vascular lesion and aided in surgical decision-making. The cases included two unique anterior communicating artery aneurysms, an arteriovenous malformation, an extracranial-intracranial bypass, and an angiographically negative subarachnoid hemorrhage. CONCLUSIONS: This is a novel strategy of combining two independently acquired selective cerebral angiography volumes to create a more accurate representation of the vascular anatomy. Given the increasing availability of the relevant image acquisition and processing technologies, we propose this strategy as a valuable adjunct in cerebrovascular procedures.

Cone-beam CT angiography (Dyna CT) for intraoperative localization of cerebral arteriovenous malformations.

BACKGROUND: Arteriovenous malformations (AVMs) of the brain are commonly treated in multimodality fashion, with endovascular embolization followed by surgical extirpation being one of the most effective strategies. Modern endovascular suites enable rotational angiography, also known as cone-beam CT angiography (CBCT-A), using the full capability of modern C-arm digital angiography systems. This imaging modality offers a superior image quality to current options such as digital subtraction angiography, MRI, or CT angiography. Preoperative planning can be greatly aided by the resolution of angioarchitecture seen in CBCT-A images. Furthermore, these images can be used for intraoperative neuronavigation when integrated with widely used frameless stereotactic systems. The utility and outcome of the use of CBCT-A for preoperative planning and intraoperative localization of AVMs was evaluated. METHODS: A retrospective review was performed of 16 patients in which CBCT-A was performed, including radiological review and all clinical data. RESULTS: CBCT-A was successfully employed in all cases including those with (n=9) and without (n=7) rupture. Complete resection confirmed by postoperative angiography was achieved in all cases. CONCLUSIONS: We present a novel application of CBCT-A in the treatment of AVMs, both for preoperative surgical planning and an intraoperative reference during neuronavigation.

Separating the wheat from the chaff: region of interest combined with metal artifact reduction for completion angiography following cerebral aneurysm treatment.

INTRODUCTION: Following complicated endovascular or microsurgical treatments, assessment of radiographic outcome can be challenging due to device resolution and metallic artifact. Two-dimensional and three-dimensional angiography can reveal information about flow and aneurysm obliteration, but may be limited by beam hardening, overlapping vessels, and image degradation in the region of metallic implants. In this study, we investigated the combination of a collimated volumetric imaging (volume of interest, VOI) protocol followed by metal artifact reduction (MAR) post-processing to evaluate the correct positioning of stents, flow diverters, coils, and clips while limiting the radiation dose to the patient. METHODS: 9 patients undergoing 10 procedures were included in our study. All patients underwent endovascular or surgical treatment of a cerebral aneurysm involving stents, flow diverting stents, coils, and/or clips followed by either immediate or early postoperative evaluation of our protocol. RESULTS: Image datasets corrected for metallic artifacts (VOI-MAR) were judged to be better-a statistically significant finding-than image datasets only corrected for field of view truncation (VOI alone). Qualitatively, images were more interpretable and informative with regards to device position and apposition to the vessel wall for those cases involving a pipeline, and with regards to encroachment on the parent artery and possible residual aneurysm, in all cases. CONCLUSIONS: VOI acquisition combined with MAR post-processing provides for accurate and informative evaluation of cerebral aneurysm treatment while limiting the radiation dose to patients.

The first North American use of the Pipeline Flex flow diverter.

Flow diversion for the management of intracranial aneurysms represents a paradigm shift in how aneurysms are managed. The Pipeline embolization device (PED) is, to date, the only flow diverter approved for use in the USA by the Food and Drug Administration. Limitations and complications with new treatment strategies are inevitable, and with the PED there have been reports of complications, most commonly with challenging deployments. Once deployment has been initiated, the device is 'one-way'; it can only be deployed further or removed. Yet, situations arise in which the ability to recapture or reposition the device would be advantageous. A second-generation Pipeline has been developed that addresses these concerns. We report the first use in North America of this second-generation Pipeline device: the Pipeline Flex. We discuss our rationale for using the device, our impressions of its operation, and the relevant literature concerning the current state of flow diversion.