Anatomic Feasibility of a Superficial Temporal Artery to Distal Anterior Cerebral Artery Bypass With a Parietal Branch Interposition Graft: The Superficial Temporal Artery Telescope Bypass.

BACKGROUND AND OBJECTIVES: Revascularizing the postcommunicating segment of the anterior cerebral artery (ACA) using extracranial donor sites requires long interposition grafts. The superficial temporal artery (STA) is frequently used for extracranial-intracranial ACA revascularization. However, the length of either STA branch is not sufficient to reach the ACA with a proper caliber match, so an interposition graft is required. The aim of this study was to evaluate a bypass that uses the 2 main branches of the STA to reach the A3 (pericallosal) segment of the ACA. METHODS: The frontal and parietal branches of the STA were dissected from 10 cadaveric specimens. The middle internal frontal artery (MIFA) was exposed through an anterior interhemispheric approach. An interposition graft technique was applied using the parietal branch of the STA (pSTA) to connect the frontal branch of the STA (fSTA) with the MIFA. The bypass code is fSTA (E-Ec) pSTA + pSTA (E-Sc) MIFA. Measurements of length and caliber were taken at the anastomotic sites for the distal branches of the STA and the MIFA. RESULTS: The mean (SD) diameter of the MIFA measured 1.4 (0.2) mm, similar to the calibers of the frontal and parietal branches of the STA. The mean (SD) length of the end-to-side STA-MIFA bypass was 145.5 (7.4) mm, and the mean (SD) length of the donor-graft construct measured 204.2 (27.9) mm. This bypass design resulted in a surplus donor graft length of 38%. CONCLUSION: Using the pSTA as an interposition graft proved to be a successful technique for creating an STA-MIFA bypass, yielding excess donor graft length that facilitated an unstrained bypass construct. This approach offers several advantages, including a single skin incision, ample graft length, caliber compatibility, and a straightforward technical execution.

Placement of an intrasaccular flow diverter in an intracranial sidewall aneurysm using the Bendit articulating microcatheter.

Intrasaccular flow diversion is a new endovascular option for managing unruptured intracranial aneurysms.1-6 However, catheter ejection can occur during placement of an intrasaccular flow diverter, especially in tortuous vasculature that creates unfavorable angles between the aneurysm neck and the parent vessel.5 The Bendit steerable microcatheter (Bendit Technologies, Petah Tikva, Israel) can dynamically change its tip angle and may mitigate these placement concerns.7-9 Here, we report the placement of an intrasaccular flow diverter for the treatment of an unruptured internal carotid artery sidewall aneurysm at an unfavorable neck angle using the Bendit microcatheter (video 1). The Bendit was navigated around the 180° turn of the carotid siphon and held a stable position during device delivery. The device was sequentially deployed as the Bendit was progressively straightened and was successfully placed within the aneurysm. No neurological complications were experienced and the patient was asymptomatic on follow-up 3 months later.neurintsurg;jnis-2023-020529v1/V1F1V1Video 1Placement of an intrasaccular flow diverter in an intracranial sidewall aneurysm using the Bendit articulating microcatheter.

Transcranioplasty Ultrasonography Through a Sonolucent Prosthesis: A Review of Feasibility, Safety, and Benefits.

Data on the effectiveness of transcranioplasty ultrasonography through sonolucent cranioplasty (SC) are new and heterogeneous. We performed the first systematic literature review on SC. Ovid Embase, Ovid Medline, and Web of Science Core Collection were systematically searched and published full text articles detailing new use of SC for the purpose of neuroimaging were critically appraised and extracted. Of 16 eligible studies, 6 reported preclinical research and 12 reported clinical experiences encompassing 189 total patients with SC. The cohort age ranged from teens to 80s and was 60% (113/189) female. Sonolucent materials in clinical use are clear PMMA (polymethylmethacrylate), opaque PMMA, polyetheretherketone, and polyolefin. Overall indications included hydrocephalus (20%, 37/189), tumor (15%, 29/189), posterior fossa decompression (14%, 26/189), traumatic brain injury (11%, 20/189), bypass (27%, 52/189), intracerebral hemorrhage (4%, 7/189), ischemic stroke (3%, 5/189), aneurysm and subarachnoid hemorrhage (3%, 5/189), subdural hematoma (2%, 4/189), and vasculitis and other bone revisions (2%, 4/189). Complications described in the entire cohort included revision or delayed scalp healing (3%, 6/189), wound infection (3%, 5/189), epidural hematoma (2%, 3/189), cerebrospinal fluid leaks (1%, 2/189), new seizure (1%, 2/189), and oncologic relapse with subsequent prosthesis removal (<1%, 1/189). Most studies utilized linear or phased array ultrasound transducers at 3-12 MHz. Sources of artifact on sonographic imaging included prosthesis curvature, pneumocephalus, plating system, and dural sealant. Reported findings were mainly qualitative. We, therefore, suggest that future studies should collect quantitative measurement data during transcranioplasty ultrasonography to validate imaging techniques.

Racial and Ethnical Diversity Within the Neurosurgery Resident and Faculty Workforce in the United States.

BACKGROUND: Promoting workplace diversity leads to a variety of benefits related to a broader range of perspectives and insights. Underrepresented in medicine (URiM), including African Americans, Latinx, and Natives (Americans/Alaskan/Hawaiians/Pacific Islanders), are currently accounting for approximately 40% of the US population. OBJECTIVE: To establish a snapshot of current URiM representation within academic neurosurgery (NS) programs and trends within NS residency. METHODS: All 115 NS residencies and academic programs accredited by the Accreditation Council for Graduate Medical Education in 2020 were included in this study. The National Residency Matching Program database was reviewed from 2011 to 2020 to analyze URiM representation trends over time within the NS resident workforce. The academic rank, academic and clinical title(s), subspecialty, sex, and race of URiM NS faculty (NSF) were obtained from publicly available data. RESULTS: The Black and Latinx NS resident workforce currently accounts for 4.8% and 5.8% of the total workforce, respectively. URiM NSF are present in 71% of the Accreditation Council for Graduate Medical Education-accredited NS programs and account for 8% (148 of 1776) of the workforce. Black and Latinx women comprise 10% of URiM NSF. Latinx NSFs are the majority within the URiM cohort for both men and women. URiM comprise 5% of all department chairs. All are men. Spine (26%), tumor (26%), and trauma (17%) were the top 3 subspecialties among URiM NSF. CONCLUSION: NS has evolved, expanded, and diversified in numerous directions, including race and gender representation. Our data show that ample opportunities remain to improve URiM representation within NS.

Arachnoid and dural reflections.

The dura mater is the major gateway for accessing most extra-axial lesions and all intra-axial lesions of the central nervous system. It provides a protective barrier against external trauma, infections, and the spread of malignant cells. Knowledge of the anatomical details of dural reflections around various corners of the skull bases provides the neurosurgeon with confidence during transdural approaches. Such knowledge is indispensable for protection of neurovascular structures in the vicinity of these dural reflections. The same concept is applicable to arachnoid folds and reflections during intradural excursions to expose intra- and extra-axial lesions of the brain. Without a detailed understanding of arachnoid membranes and cisterns, the neurosurgeon cannot confidently navigate the deep corridors of the skull base while safely protecting neurovascular structures. This chapter covers the surgical anatomy of dural and arachnoid reflections applicable to microneurosurgical approaches to various regions of the skull base.

Venous anatomy of the supratentorial compartment.

The cerebral venous drainage system in humans has several unique characteristics that set it apart from its arterial counterpart. The intracranial drainage system can be broadly divided into supra- and infratentorial components. The supratentorial venous drainage is further subclassified into superficial and deep systems, each with a unique set of features. A thorough knowledge of the normal and variant venous drainage pathways is important to understand the different pathologic processes involving the venous vasculature, to identify and anticipate the different venous channels encountered during surgery and also to predict the possible sequelae of intentional or inadvertent venous sacrifice during surgery. This chapter summarizes the anatomic and radiologic characteristics of the venous supply of the supratentorial compartment of the brain, reviews its general characteristics, sheds light on the different classifications and nomenclature used for its descriptions, and briefly discusses its embryologic development.

Microsurgical Clipping Techniques and Outcomes for Paraclinoid Internal Carotid Artery Aneurysms.

BACKGROUND: Microsurgical clipping of paraclinoid aneurysms presents unique technical challenges because of the anatomical complexity of the paraclinoid region. OBJECTIVE: To analyze microsurgical clipping techniques, complications, and outcomes associated with paraclinoid aneurysms, with a focus on clip selection and clipping technique according to aneurysm location. METHODS: From 1997 to 2016, 231 unruptured paraclinoid aneurysms from 216 patients were treated using microsurgical clipping. We retrospectively reviewed patient records to analyze clinical outcomes. RESULTS: A total of 80 aneurysms (34.6%) were treated with simple clipping. Among them, fenestrated clips were used with superior hypophyseal artery (SHA) aneurysms, but curved clips were used with most other aneurysms. A total of 151 aneurysms (65.6%) were treated using multiple clips, including tandem clipping for ophthalmic artery (OphA) aneurysms, tandem angled-fenestrated clipping for SHA and ventral carotid aneurysms, stacked clipping for dorsal carotid aneurysms, and various techniques for clinoidal segment/carotid cave aneurysms. Postoperative angiography was performed in 214 aneurysms (92.6%), and complete obliteration was confirmed in 195 aneurysms (91.1%). Using the modified Rankin Scale (mRS), overall functional outcome was good (mRS 0-2) in 99.6% of patients, although 30 cases (13.0%) showed new postoperative visual deficits. CONCLUSION: Surgical clipping of paraclinoid aneurysms is an excellent treatment modality with good clinical outcomes and acceptable complication rates, particularly in centers with large experience in the microsurgical management of cerebrovascular disorders. Appropriate clip selection and clipping techniques are required to perform complete and safe clipping.

An Anatomic Feasibility Study for Revascularization of the Ophthalmic Artery, Part I: Intracanalicular Segment.

BACKGROUND: The anatomico-functional complexity of the ophthalmic segment aneurysms is attributable to the presence of critical neurovascular structures in the surgical field. Surgical clipping of the ophthalmic artery (OpA) aneurysms can result in postoperative visual deficit due to the complexity of the aneurysm, vasospasm, or optic nerve manipulation. In this study, we aimed to characterize the feasibility of an intracanalicular OpA (iOpA) revascularization with 2 donor vessels: an intracranial-intracranial (IC-IC) bypass using the anterior temporal artery (ATA) and an extracranial-intracranial (EC-IC) bypass using the superficial temporal artery (STA). We further discuss their potential role in "unclippable" OpA aneurysms. METHODS: Twenty cadaveric specimens were used to evaluate the operative exposure of the intradural and intracanalicular OpA segments using an extradural-intradural intracanalicular approach. The arterial caliber and length at the anastomotic sites and required donor artery lengths were measured. The feasibility of the bypass using both donors was assessed. RESULTS: The average length of the intradural and intracanalicular segment of the OpA was 9.5 ± 1.6 mm. The mean caliber of the iOpA was 1.5 ± 0.2 mm. The mean ATA length required for an ATA-OpA anastomosis was 26.7 ± 8.9 mm, with a mean caliber of 1.0 ± 0.1 mm. The mean length of STA required for the bypass was 89.9 ± 9.7 mm, with a mean caliber of 1.92 ± 0.4 mm. CONCLUSIONS: This study confirms the feasibility of iOpA revascularization using IC-IC and EC-IC bypasses. These techniques could potentially be used for prophylactic or therapeutic neuroprotection from retinal ischemic injury while treating complex OpA aneurysms, infiltrative tumors, or intraoperative arterial injuries.

An Anatomical Feasibility Study for Revascularization of the Ophthalmic Artery. Part II: Intraorbital Segment.

INTRODUCTION: Distal ophthalmic artery (OpA) aneurysms are a rare subset of vascular lesions with lack of optimal treatment. The management of these aneurysms may require complete occlusion of the parent vessel, carrying a risk of permanent visual impairment due to individual variations of extracranial collateral flow to the intraorbital ophthalmic artery (iOpA). OBJECTIVE: To test the feasibility of a superficial temporal artery (STA) to iOpA bypass to prevent acute ischemic retinal injury. Two different transorbital corridors (superomedial and posterolateral approaches) for this bypass were evaluated. METHODS: Each approach was carried out in 10 specimens each (n = 20). The corridors were compared to achieve the optimal exposure of the iOpA until the central retinal artery origin was visualized. An end-to-end anastomosis was performed from STA-to-iOpA. The arterial caliber and length at the anastomotic sites, required donor artery length, and intraorbital surgical area were measured. RESULTS: STA-iOpA bypasses were performed in all specimens. For the posterolateral transorbital approach, the mean caliber of STA was 1.8 ± 0.2 mm, and that of iOpA was 1.7 ± 0.5 mm. The required STA graft length was 78.3 ± 1 mm with lateral iOpA transposition of 8.2 ± 1.1 mm. For the superomedial approach, the average STA length required for an intraorbital bypass was 130.8 ± 14.0 mm. The mean calibers of iOpA and STA were 1.5 ± 0.1 mm and 1.5 ± 0.1 mm, respectively. CONCLUSIONS: This study demonstrates the feasibility of a novel revascularization technique of the iOpA using 2 different transorbital approaches. These techniques can be used in the management of intraorbital lesions such as OpA aneurysms, tumoral infiltrations, or intraoperative injuries.

Double-Barrel Extracranial-Intracranial Bypass and Trapping of Dolichoectatic Middle Cerebral Artery Aneurysms: 3-Dimensional Operative Video.

A dolichoectatic intracranial vessel with multiple fusiform aneurysms on the same vessel segment is rare, and usually managed with a bypass with aneurysm trapping. This video demonstrates trapping and a double-barrel superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass to treat two fusiform aneurysms in a left dolichoectatic superior MCA trunk. A 46-year-old man with AIDS presented with aphasia and hemiparesis. IRB approval and patient consent were obtained. Both STA branches (frontal and parietal) were harvested. After widely splitting the sylvian fissure from its proximal portion to the angular gyrus, the two fusiform aneurysms on the superior MCA trunk were identified in the insular recess and the circular sulcus. The outflow artery from each aneurysm was identified and prepared for the bypass. The STA was transected, and both limbs were brought down into the fissure. After trapping the distal aneurysm, an end-to-end anastomosis of the parietal STA branch to the M2 MCA was performed. Thereafter, a second bypass was performed in an end-to-side fashion to an M2 branch from the base of the first aneurysm. The second aneurysm was then trapped. Indocyanine green angiography confirmed the patency of both bypasses. Complete aneurysm occlusion and bypass patency were also confirmed with postoperative angiography. The patient recovered from his pre-operative neurological deficits. This case demonstrates the efficacy of double-barrel STA-MCA bypass in combination with aneurysm trapping in a patient with a complex dolichoectatic superior MCA trunk aneurysm. It also highlights the advantage of using end-to-end anastomosis for deep recipients with limited access.

Minimally Invasive Exposure of the Maxillary Artery at the Anteromedial Infratemporal Fossa.

BACKGROUND: The maxillary artery (MA) has been described as a reliable donor for extracranial-intracranial high-flow bypass. Existing techniques to harvest MA require brain retraction and drilling of the middle fossa (with or without a zygomatic osteotomy), carrying the potential risks of venous bleeding, injury to the branches of the maxillary or mandibular nerves, muscular transection, or temporomandibular junction disorders. OBJECTIVE: To describe a novel technique to expose the MA without bony drilling and with minimal impact to surrounding structures. METHODS: A conventional curvilinear incision was performed in 10 cadaveric specimens, prior to elevating the scalp to expose the zygomatic root and lateral orbital rim. The sphenozygomatic suture was followed to the anterolateral edge of the inferior orbital fissure (IOF) to locate and harvest the pterygoid segment of the MA. Topographic anatomy was assessed using surrounding landmarks and 3D Cartesian coordinates to define the surgical area. The number of visible MA branches and their lengths were recorded. RESULTS: The MA was successfully exposed in all specimens. This approach allowed 6 branches of MA to be exposed. The average length of exposure was 23.3 ± 8.3 mm and the average surgical area was 2.8 ± 0.9 cm2. The IOF was 11.5 ± 4.2 mm from the MA. CONCLUSION: Our technique provides landmarks to identify the distal pterygoid segment of MA as a donor for extracranial-intracranial bypasses without the need for additional craniectomies. Clear anatomical landmarks, including the sphenozygomatic suture, anterolateral edge of IOF, infraorbital artery, and the pterygomaxillary fissure defined a trajectory to efficiently localize the MA with minimal risk to surrounding structures.

Macrovascular Decompression of Facial Nerve With Anteromedial Transposition of a Dolichoectatic Vertebral Artery: 3-Dimensional Operative Video.

Most cranial nerve compression syndromes (ie, trigeminal neuralgia and hemifacial spasm) are caused by small arteries impinging on a nerve and are relieved by microvascular decompression. Rarely, cranial nerve compression syndromes can be caused by large artery impingement and can be relieved by macrovascular decompression. When present, this compression often occurs in association with degenerative atherosclerosis in the vertebral arteries (VA) and basilar artery. Conservative treatment is recommended for mild forms, but surgical transposition of the VA away from the root entry zone (REZ) can be considered. This video demonstrates macrovascular decompression of a dolichoectatic VA in a 74-yr-old female with refractory left hemifacial spasm. After obtaining IRB approval, patient consent was sought for the procedure. With the patient in three-quarter-prone position, a far-lateral craniotomy was performed. The dentate ligament was cut to free the VA, and the suprahypoglossal portion of the vagoaccessory triangle was widened. VA compressed the REZ of the facial nerve, but was mobilized anteromedially off the REZ. A muslin sling was wrapped around the VA and its tail brought down to the clival dura, which was punctured with a 19-gauge needle and enlarged with a dissector. The sling was pulled anteromedially to this puncture site and secured to the dura with an aneurysm clip, relieving the REZ of all compression. The patient tolerated the procedure with mild, transient hoarseness and her hemifacial spasm resolved completely. This case demonstrates the macrovascular decompression technique with anteromedial transposition of the vertebrobasilar artery, which can also be used for trigeminal neuralgia.

Left Transsylvian-Transinsular Approach for Radiation-Induced Cavernous Malformation: 3-Dimensional Operative Video.

De novo cavernous malformation (CM) formation after radiation therapy for brain tumors is well known, but CM formation adjacent to a radiosurgically treated arteriovenous malformation (AVM) is rare.1 This video demonstrates the microsurgical resection of a de novo CM adjacent to a previously treated high-grade AVM and clipping of a middle cerebral artery (MCA) aneurysm. A 70-yr-old male with history of radiosurgery for AVM presented with aphasia and confusion. Preoperative angiography showed complete occlusion of the AVM. MRI showed multiple cystic lesions suspicious for radiation-induced necrosis and CM. IRB approval and patient consent was obtained. A pterional craniotomy was performed with transsylvian exposure of the insula. The radiated feeding arteries were followed to the occluded AVM nidus. A CM was noted deep to this candelabra of the MCA vessels, which were mobilized to access and resect the CM. A small incision was made in this insular cortex underneath the malformation circumferentially freeing it of adhesions. The sclerotic AVM nidus was circumferentially dissected and removed en bloc. Thorough exploration of the resection cavity revealed no residual CM or AVM nidus. Attention was then turned to the M2-MCA bifurcation aneurysm, which was occluded with a straight clip. Postoperative imaging confirmed complete CM resection. The patient recovered from his aphasia. This case demonstrates the management of a radiation-induced de novo CM following treatment of a high-grade AVM. Radiographic follow-up for radiosurgically treated AVM is needed to rule out long-term complications. Bleeding from a de novo CM mimics bleeding from residual AVM nidus, requiring careful angiographic evaluation.

A mini-open transspinous approach for resection of intramedullary spinal cavernous malformations.

BACKGROUND AND IMPORTANCE: Advances in minimally invasive (MIS) and mini-open surgical approaches have led to reductions in perioperative morbidity without compromising rates of resection of non-degenerative intradural spinal pathologies. Whether these approaches may be adapted for the surgical resection for intramedullary vascular malformations - such as cavernous malformations (CMs) - has yet to be reported. The authors describe a mini-open transspinous approach to resect a ruptured intramedullary CM of the conus medullaris. CLINICAL PRESENTATION: A 28-year-old man presented with sudden onset of bilateral lower extremity weakness, urinary retention and saddle anesthesia. Magnetic resonance imaging demonstrated a ruptured CM within the conus medullaris with pronounced extralesional hemorrhage. A mini-open transspinous approach with an expandable tubular retractor was successfully applied to facilitate microsurgical resection of the CM and evacuation of the associated hematoma. The patient made a good neurologic recovery, and postoperative imaging confirmed a gross total resection of the CM. CONCLUSION: A mini-open transspinous approach utilizing an expandable tubular retractor offers feasible less invasive alternative to provide dorsal midline access for the microsurgical resection of intramedullary spinal CMs. Larger case series or future randomized prospective trials are warranted to fully explore suitability of MIS techniques for the surgical management of intradural spinal cord vascular pathologies - such as CMs.

Contralateral Transfalcine Versus Ipsilateral Anterior Interhemispheric Approach for Midline Arteriovenous Malformations: Surgical and Anatomical Assessment.

BACKGROUND: The contralateral anterior interhemispheric approach (CAIA) is considered to provide surgical advantages to access deep midline lesions: wider working angle, gravity enhanced dissection and retraction, more efficient lighting, and ergonomics. Our team has previously published on the merits of using a contralateral trajectory for medial frontoparietal arteriovenous malformations (AVMs) compared with the conventional anterior interhemispheric approach (IAIA). In this article, we compare the IAIA and CAIA for the resection of medial frontoparietal AVMs using quantitative surgical and anatomical analysis. METHODS: Two models were designed mimicking the most common features of midline AVMs. The CAIA and IAIA were performed bilaterally in 10 specimens. Variables to compare technical feasibility (surgical window [SW] and surgical freedom [SF], target exposure, and angle of attack) were independently assessed using stereotactic navigation. The average SW, SF, and angle of attack were compared with the Student t test. Significance threshold was set at 0.05. RESULTS: The CITA and IAIA were similar in terms of SW, target exposure, and SF in the superior aspect of the AVM. In the depth of the interhemispheric fissure, the CAIA was significantly superior to IAIA in both AVM models: 77% wider AA for the inferior aspect of the AVM (P < 0.01) and greater SF for the draining vein (54%, P = 0.01), ipsilateral (98%, P = 0.02), and contralateral ACA (117%, P < 0.01). CONCLUSIONS: This study suggests technical superiority of the CAIA for the resection of deep midline AVMs. No objective difference was noted in the superficial areas of our models, denoting that IAIA is a safer choice for superficial AVMs. Our results set the foundation for further clinical analysis comparing both approaches.

Internal Maxillary Artery to Anterior Circulation Bypass with Local Interposition Grafts Using a Minimally Invasive Approach: Surgical Anatomy and Technical Feasibility.

BACKGROUND: The internal maxillary artery (IMA) is a reliable donor for extracranial-intracranial high-flow bypasses. However, previously described landmarks and techniques to harvest the IMA are complex and confusing and require extensive bone drilling, carrying significant neurovascular risk. The objective of our study was to describe a minimally invasive technique for exposing the IMA and to assess the feasibility of using the IMA as a donor for anterior-circulation recipient vessels using 2 different local interposition vessels. METHODS: Via a minimally invasive technique, the IMA was harvested in 10 cadaveric specimens and a pterional craniotomy was performed. Two interposition grafts-the superficial temporal artery (STA) and middle temporal artery-were evaluated individually. Transsylvian exposure of the second segment of middle cerebral artery (M2), the supraclinoid internal carotid artery, and the proximal postcommunicating anterior cerebral artery segment was completed. Relevant vessel calibers and graft lengths were measured for each bypass model. RESULTS: The mean caliber of the IMA was 2.7 ± 0.5 mm. Of all 3 recipients, the shortest graft length was seen in the IMA-STA-M2 bypass, measuring 42.0 ± 8.4 mm. There was a good caliber match between the M2 (2.4 ± 0.4 mm) and STA (2.3 ± 0.4 mm) at the anastomotic site. The harvested middle temporal artery was sufficient in length in only 30% cases, with a mean distal caliber of 2.0 ± 0.7 mm. CONCLUSIONS: This study confirmed the technical feasibility of IMA as a donor for an extracranial-intracranial bypass to the second segment of the anterior cerebral artery, M2, and the supraclinoid internal carotid artery. However, IMA-STA-M2 was observed to be the most suitable bypass model.