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Purpose: Multiple hippocampal transection (MHT) is a surgical technique that offers adequate seizure control with minimal perioperative morbidity. However, there is little evidence available to guide neurosurgeons in selecting this technique for use in appropriate patients. This systematic review analyzes patient-level data associated with MHT for intractable epilepsy, focusing on postoperative seizure control and memory outcomes.Methods: The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant articles were identified from 3 databases (PubMed, Medline, Embase) up to August 1, 2021. Inclusion criteria were that the majority of patients had received a diagnosis of intractable epilepsy, the article was written in English, MHT was the primary procedure, and patient-level metadata were included.Results: Fifty-nine unique patients who underwent MHT were identified across 11 studies. Ten (17%) of 59 patients underwent MHT alone. Forty-three (75%) of 57 patients who had a follow-up 12 months or longer were seizure free at last follow-up. With respect to postoperative verbal memory retention, 9 of 38 (24%) patient test scores did not change, 14 (37%) decreased, and 16 (42%) increased. With respect to postoperative nonverbal memory retention, 12 of 38 (34%) patient test scores did not change, 13 (34%) decreased, and 13 (33%) increased.Conclusion: There are few reported patients analyzed after MHT. Although the neurocognitive benefits of MHT are unproven, this relatively novel technique has shown promise in the management of seizures in patients with intractable epilepsy. However, structured trials assessing MHT in isolation are warranted. [ABSTRACT FROM AUTHOR]

• The subtemporal without parahippocampal ressection approach is not suitable for approaching pulvinar lesions due to limited exposure and reduced angle of dissection. • For lesions restricted to the pulvinar surface, the occipital interhemispheric and subtemporal after parahippocampal ressection are adequate approaches. • For lesions extending to the lateral aspect of the pulvinar, the transchoroidal was the most adequate approach. • The supracerebellar-infratentorial approaches are recommended for lesions lying deep along the thalamus axis. To compare the area of exposure to the cisternal thalamus associated with four surgical techniques: supracerebellar-infratentorial (SCIT), occipital interhemispheric (OI), transchoroidal (TC) and subtemporal before and after parahippocampal resection (ST and STh, respectively). All approaches were performed on both sides of three heads. Qualitative anatomical analyses were performed to understand anatomical limits, advantages, and flaws of each technique. Quantitative analyses for multiple repeated dependent variables assessed significant differences between areas of exposure. Exposure area was significantly more extensive using TC and STh approaches compared to ST, OI, and SCIT. STh achieved a significantly wider exposure compared to ST. Regarding dissection angle, surrounding structures and limitations, ST approaches do not provide adequate exposure, nor alignment with the thalamic axis. The OI and STh may provide a better field of exposure, but without adequate alignment and challenging deeper dissections. TC provides better exposure of the cisternal pulvinar with access to lateral pulvinar at the atrium's anterior wall but is a transcortical route that disrupts non-pathological tissue. SCIT provides an adequate area of exposure with the possibility of alignment with the thalamus axis, thus allowing an easier dissection of deeper lesions. For lesions at the pulvinar surface, OI and STh are adequate. For lesions restricted to medial pulvinar and deep along the thalamus axis, SCIT approaches are recommended. Lesions extending to the lateral pulvinar and ventricular atrium are best removed through TC approaches. The ST approach was not suitable to the cisternal pulvinar due to its limited angular exposure. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme remains a therapeutic challenge. We offer a historical review of the outcomes of patients with glioblastoma from the earliest report of surgery for this lesion through the introduction of modern chemotherapeutics and aggressive approaches to tumor resection. We reviewed all major surgical series of patients with glioblastoma from the introduction of craniotomy for glioma (1884) to 2020. The earliest reported craniotomy for glioblastoma resulted in the patient's death less than a month after surgery. Improved intracranial pressure management resulted in improved outcomes, reducing early postoperative mortality from 50% to 6% in Harvey Cushing's series. In the first major surgical series (1912), the mean survival was 10.1 months. This figure did not improve until the introduction of radiotherapy in the 1950s, which doubled survival relative to those who had surgery alone. The most recent significant advance, chemotherapy with the alkylating agent temozolomide, extended survival by 2.5 months compared with surgery and radiotherapy alone (14.6 and 12.1 months, respectively). This protocol remains the standard regimen for newly diagnosed glioblastoma. The innovative treatments being investigated have yet to show a survival benefit. With advancements in localization, imaging, anesthesia, surgical technique, control of cerebral edema, and adjuvant therapies, outcomes in glioblastoma improved incrementally from Cushing's time until the introduction of magnetic resonance imaging enabled better degrees of resection in the 1990s. Modest improvements came with the advent of biomarker-driven targeted chemotherapy in the first decade of the current century. [ABSTRACT FROM AUTHOR]

Highlights • Opening the Sylvian fissure is a key technique in many neurosurgical procedures. • We have revisited the arachnoidal and vascular anatomy of the Sylvian fissure. • Techniques of opening Sylvian fissure are analyzed based on its functional anatomy. • A live rodent model is proposed for practicing Sylvian fissure opening. • Similarities between the model and the technique of Sylvian splitting are assessed. Abstract Opening the Sylvian fissure is an important technique in neurosurgery. Despite providing excellent anatomic fidelity, cadaveric and synthetic models lack real-time hemodynamics and coagulation physiology. We introduce a live rat aortoiliac model to practice the basic skills of Sylvian fissure splitting based on its arachnoidal microanatomy. Cadaveric dissections were carried out to assess the microanatomical relationships between the Sylvian fissure arachnoid and its contents, namely arteries (A), veins (V), and brain (B). Rat surgeries were performed to assess the similarities between separating aortoiliac arteries from adjacent veins and the various technical aspects of dissecting the Sylvian fissure. The Sylvian fissure could be divided into 3 compartments regarding the progressive steps of its dissection: (1) superficial opercular, (2) deep opercular, and (3) cisternal. The major arachnoidal connections that required division during dissection of each Sylvian compartment were as follows: B-V and V-V types in the superficial opercular; B-B and A-B types in the deep opercular; and A-B and A-A types in the cisternal compartments. Dissection techniques in the rat aortoiliac model correlated with key techniques in Sylvian fissure dissection. Despite lacking brain tissue, the rat aortoiliac arteries offer a model in which the arteries and veins with their investing connective tissues mimic the arachnoid-vessel interconnections in the Sylvian fissure. Therefore, using this model simulates the essential sub-techniques of splitting the Sylvian fissure. The rat model may be used to provide trainees with an opportunity to practice under the duress of the real-time hemodynamics and coagulation physiology. [ABSTRACT FROM AUTHOR]

The ambient cistern is an arachnoid complex that extends from the crural cistern to lateral border of cerebral colliculi. The subtemporal approach has been recognized as the best access to reach pathologies in the ambient cistern, however many disadvantages exist. The present work aims to analyze quantitatively the area of exposure provided by the subtemporal access. The objective is to evaluate if there are advantages of using the neuroendoscope in conventional subtemporal access when compared to the subtemporal access with resection of the parahippocampal gyrus. A subtemporal approach was performed in six brain hemispheres. Qualitative and quantitative analyses were made. The linear exposition of the vascular structures and the surgical exposure area were evaluated. The linear exposure to the posterior cerebral artery was 5.95 for subtemporal access (ST) and 13.6 for subtemporal access with resection of the parahippocampal gyrus (STh) (p = 0.019). The total exposure area was 104.8 mm 2 for ST and 210.5 for STh (p = 0.0001). Regarding endoscope assistance the medial area, ST was 81.0 mm 2 , and STend was 176.2 mm 2 (p = 0.038). For the total area of exposure, we obtained a value of 210.5 mm 2 for ST and a value of 391.3 mm 2 for STend (p = 0.041). In conventional subtemporal access, the use of the neuroendoscopes avoids the need for resection of the parahippocampal gyrus for better visualization of the ambient cistern structures. [ABSTRACT FROM AUTHOR]

We quantified the effects on anatomical cadaver dissection of a balloon-inflation tumor model positioned in the parasellar region and approached through an orbitozygomatic (OZ) craniotomy. A modified supraorbital OZ was performed bilaterally on 5 silicon-injected cadaver heads. Ten predetermined anatomical points assigned using a frameless stereotactic device were used to measure the working area of exposure, degree of surgical freedom, and horizontal and vertical angles of attack to specific target points before and after inflation of a balloon catheter mimicking a parasellar tumor. Balloon inflation displaced the central anatomical structures (pituitary stalk, lamina terminalis, anterior chiasm, and internal carotid artery [ICA]–posterior communicating artery and ICA-A1 junctions) by 14–51% (p ≤ .05). With tumor simulation, the vertical angle of attack increased by 67% (p < .01), while the area of exposure increased by 83% (p < .01) and surgical freedom increased by 58% (p < .01). This tumor model also significantly displaced central anatomical sella-associated structures. Compared to a normal anatomical configuration, the tumor simulation (balloon) opened surgical corridors (especially vertical) and acted as a natural retractor, widening the angle of access to the infundibular apex–hypothalamic junction. Although this model cannot exactly mimic a tumor mass in a patient, the effects of tumor compression and sequential displacement of important structures can be combined into and then assessed in a cadaveric neurosurgical anatomical scenario for training and research. [ABSTRACT FROM AUTHOR]

We describe a novel intracranial-to-intracranial bypass technique between the anterior temporal artery and the posterior cerebral artery for revascularization of the posterior circulation. Four formalin-fixed human heads were examined to demonstrate the detailed anatomy of the middle cerebral artery and the posterior cerebral artery, and to illustrate the step-by-step bypass procedure. The anterior temporal artery, a branch of the middle cerebral artery, can be anastomosed to the P2 segment of the posterior cerebral artery as an alternative to extracranial bypass donor segments for treatment of complex aneurysms requiring revascularization. The anastomosis of the anterior temporal artery as a pedicled donor to the posterior cerebral artery provides a shorter graft, due to its close anatomical position to the posterior cerebral artery, for posterior circulation revascularization. [ABSTRACT FROM AUTHOR]

• We present an efficient method for harvesting the OA via small incisions. • The harvested OA can be used as a donor artery for bypasses. • This technique uses fixed landmarks on the outer surface of the occipital bone. The occipital artery (OA) can be used as a donor artery in many types of bypasses; however, harvesting this artery in the depths of its course is challenging. In order to safely harvest the OA, a large hockey-stick-shaped incision is often used, even when only a retrosigmoid approach is needed for the intracranial procedure. In this article, we describe a detailed technique whereby the OA is harvested via a suboccipital subperiosteal-transperiosteal dissection technique. In this technique, the occipital groove is identified via a small linear incision. With the technique described, the OA can be localized and harvested effectively for bypass in the subsequent retrosigmoid approach. [ABSTRACT FROM AUTHOR]

The pterional approach was described in the 1970s and has become the most utilized cranial approach with many variations described, including the minipterional technique. Although described recently as an alternative to the pterional approach for anterior circulation aneurysms, to our knowledge a large series of cases using the minipterional approach in both ruptured and unruptured aneurysms has not been described. We present our clinical experience with the minipterional craniotomy in more than 100 ruptured and unruptured anterior circulation aneurysms. The results of 86 consecutive patients with 102 ruptured non-giant, anterior circulation aneurysms treated with early surgery utilizing the minipterional craniotomy were analyzed. Postoperative angiography was carried out in all cases. Outcome results were classified as excellent in 67 (77.9%), and good in seven (8.1%), while 16 (13.9%) patients died. The minipterional technique provides adequate surgical exposure and excellent outcomes for both ruptured and unruptured anterior circulation aneurysm clipping. It constitutes a safe and effective alternative to the pterional approach, with equivalent or potentially better aesthetic and functional outcomes. [ABSTRACT FROM AUTHOR]

We aimed to determine the clinical indications and surgical outcomes for thoracoscopic discectomy. Thoracic disc disease is a rare degenerative process. Thoracoscopic approaches serve to minimize tissue injury during the approach, but critics argue that this comes at the cost of surgical efficacy. Current reports in the literature are limited to small institutional patient series. We systematically identified all English language articles on thoracoscopic discectomy with at least two patients, published from 1994 to 2013 on MEDLINE, Science Direct, and Google Scholar. We analyzed 12 articles that met the inclusion criteria, five prospective and seven retrospective studies comprising 545 surgical patients. The overall complication rate was 24% (n = 129), with reported complications ranging from intercostal neuralgia (6.1%), atelectasis (2.8%), and pleural effusion (2.6%), to more severe complications such as pneumonia (0.8%), pneumothorax (1.3%), and venous thrombosis (0.2%). The average reported postoperative follow-up was 20.5 months. Complete resolution of symptoms was reported in 79% of patients, improvement with residual symptoms in 10.2%, no change in 9.6%, and worsening in 1.2%. The minimally invasive endoscopic approaches to the thoracic spine among selected patients demonstrate excellent clinical efficacy and acceptable complication rates, comparable to the open approaches. Disc herniations confined to a single level, with small or no calcifications, are ideal for such an approach, whereas patients with calcified discs adherent to the dura would benefit from an open approach. [ABSTRACT FROM AUTHOR]

Abstract: Sulforhodamine 101 (SR101) is a useful tool for immediate staining of astrocytes. We hypothesized that if the selectivity of SR101was maintained in astrocytoma cells, it could prove useful for glioma research. Cultured astrocytoma cells and acute slices from orthotopic human glioma (n=9) and lymphoma (n=6) xenografts were incubated with SR101 and imaged with confocal microscopy. A subset of slices (n=18) were counter-immunostained with glial fibrillary acidic protein and CD20 for stereological assessment of SR101 co-localization. SR101 differentiated astrocytic tumor cells from lymphoma cells. In acute slices, SR101 labeled 86.50% (±1.86; p <0.0001) of astrocytoma cells and 2.19% (±0.47; p <0.0001) of lymphoma cells. SR101-labeled astrocytoma cells had a distinct morphology when compared with in vivo astrocytes. Immediate imaging of human astrocytoma cells in vitro and in ex vivo rodent xenograft tissue labeled with SR101 can identify astrocytic tumor cells and help visualize the tumor margin. These features are useful in studying astrocytoma in the laboratory and may have clinical applications. [Copyright &y& Elsevier]

Objective: Current treatments for cerebral aneurysms are far from ideal. Platinum coils are prone to compaction, and currently used liquid embolics are delivered with angiotoxic agents. This work presents initial in vivo studies of a novel liquid-to-solid gelling polymer system (PPODA-QT), focusing on biocompatibility and effective delivery strategies. Methods: PPODA-QT was used to embolize surgically created lateral wall carotid artery aneurysms in swine using three delivery strategies. Group 1 aneurysms were completely filled with PPODA-QT (n = 5), group 2 aneurysms were subcompletely (80%–90%) filled (n = 3), and group 3 aneurysms underwent three-dimensional coil placement followed by polymer embolization (n = 3). The study was designed such that three animals per treatment group survived to 1 month. Results: The group 1 delivery strategy (100% filling) resulted in survival of 3/5 animals. This strategy led to aneurysm stretching, which resulted model failure in 2/5 animals. Group 2 aneurysms, although initially <100% filled with the polymer, displayed robust neointimal tissue coverage and complete obliteration after 1 month. Group 3 aneurysms showed less prominent neointimal tissue coverage as well as two instances where excess polymer was found in the parent vessel. The PPODA-QT material showed good biocompatibility with vascular tissue in all animals at 1 month. Conclusions: This small-scale pilot study highlighted first-time in vivo use of PPODA-QT as an embolic agent for aneurysm treatment. Filling aneurysms to 80% to 90% capacity proved to be a safe and effective delivery strategy, and PPODA-QT showed excellent biocompatibility. This study indicates that future investigation of PPODA-QT for aneurysm embolization is warranted, as it may prove to be a viable alternative to current embolic materials. [Copyright &y& Elsevier]

Abstract: Seven sides of cadaver heads were used to compare the surgical exposures provided by the mini-modified orbitozygomatic (MOz) and supra-orbital (SO) approaches. The Optotrak 3020 computerized tracking system (Northern Digital, Waterloo, ON, Canada) was utilized to evaluate the area of anatomical exposure defined by six points: (1) ipsilateral sphenoid ridge; (2) most distal point of the ipsilateral middle cerebral artery (MCA); (3) most distal point of the ipsilateral posterior cerebral artery (PCA); (4) most distal point of the contralateral PCA; (5) most distal point of the contralateral MCA; and (6) contralateral sphenoid ridge. Additionally, angles of approach for the ipsilateral MCA bifurcation, ipsilateral ICA bifurcation, basilar artery tip, contralateral MCA and ICA bifurcation and anterior communicating artery (AcomA) were evaluated, first for SO and then for MOz. An image guidance system was used to evaluate the limits of surgical exposure. No differences in the area of surgical exposure were noted (p >0.05). Vertical angles were significantly wider for the ipsilateral and contralateral ICA bifurcation, AcomA, contralateral MCA and basilar tip (p <0.05) for MOz. No differences in horizontal angles were observed between the approaches for the six targets (p >0.05). There were no differences in the limits of exposure. MOz affords no additional surgical working space. However, our results demonstrate systematically that vertical exposure is improved. The MOz should be performed while planning an approach to these regions and a wider exposure in the vertical axis is needed. [Copyright &y& Elsevier]

Abstract: Development of biomaterials that provide mechanical and molecular cues for wound healing and regeneration must meet several design parameters. In addition to high biocompatibility, biomaterials should possess suitable porosity as well as the ability to be chemically tailored to control parameters including biodegradability and bioactivity. These characteristics were studied in hyaluronan (HA), a natural polymer found in the body. HA was modified with thiol cross-linking sites to form a stable hydrogel scaffold to examine effects in in vitro cortical cell growth. HA with 20% and 44% thiolation was used to make gels at 0.5%, 0.75%, 1%, and 1.25% (w/v). Results indicate that the bioactivity of the HA after functionalization, as determined by degree of substitution (HA thiolation), has a greater effect on neurite outgrowth than does gel stiffness. The lower substituted HA (20%) promoted greater neurite growth as compared to the higher substituted HA (44%). [Copyright &y& Elsevier]

The contributions of Laurent Princeteau (1858–1932) to anatomy and to the establishment of neurosurgery have largely gone unrecognized, perhaps because he was educated and practiced in a French city other than Paris at a time when Paris was one of the chief centers of medicine in Europe. After completing a thesis describing an iliac artery anomaly and obtaining the distinguished agrégé teaching degree, Princeteau began his surgical career at the University of Bordeaux. Within 10 years, he became chef de clinique and one of the busiest surgeons in Saint-André Hospital, as well as head of the anatomy institute and professor of anatomy at the dental school. In 1891, he achieved the rank of surgeon. In the field of general anatomy, he was recognized for novel cadaveric preparations and vascular perfusion techniques. In the neurosciences, he made important contributions to the anatomy of the trigeminal nerve and trigeminal neuralgia. In 1898, Princeteau supervised a thesis that addressed contemporary surgical approaches to the trigeminal complex. In the course of this effort, he identified a bony prominence near the petrous apex (the retrogasserian tubercle) that helped to locate the gasserian ganglion. The surgical significance of the retrogasserian tubercle was quickly acknowledged in the European neurosurgical community and was noted in French textbooks of anatomy. Thierry de Martel, a founding member of the French neurosurgical School, named the tubercle after Princeteau. To the rest of the world, however, it remained almost unknown. [ABSTRACT FROM AUTHOR]

Surgical techniques to achieve complete resection of mesial–basal temporal tumors should be pursued by neurosurgical oncologists. We describe the anatomical subpial amygdalohippocampectomy (SpAH) technique for tumor resection. The key anatomical landmarks and critical steps of the SpAH technique were outlined and emphasized with medical illustrations and intraoperative photographs. The senior author's 90-day surgical outcomes with this approach were reviewed. Twenty-five patients (men, 17 [68%]; women, 8 [32%]; median [range] age, 59 [23–80] years) with temporal tumors involving the amygdalohippocampal region were included. SpAH was performed selectively in 8 [32%] patients, whereas 17 [68%] patients underwent SpAH in conjunction with an anterior temporal lobectomy due to tumor involvement of the anterolateral temporal cortex. The subpial resection of the amygdala protected the critical structures of the suprasellar cistern and sylvian fissure. Identifying the choroidal fissure as the superior-most aspect of hippocampal resection protected the optic tract and the thalamus. Subpial resection of the parahippocampal gyrus inferiorly protected the brainstem and critical structures of the ambient cistern. Tumors in the amygdalohippocampal region were anatomically and completely resected in all 25 patients. Of the 15 patients who presented with seizures, 13 (87%) were seizure-free at the 90-day postsurgical follow-up. Permanent neurologic deficits occurred in 3 patients (12%). The SpAH technique permits complete resection of mesial–basal temporal tumors with an acceptable morbidity profile. An in-depth understanding of temporal lobe anatomy combined with a refined microsurgical technique allows for reproducible resection of tumor in the amygdalohippocampal region while protecting critical neurovascular structures. [ABSTRACT FROM AUTHOR]

Multicompartmental lesions of the anterior craniovertebral junction require aggressive management. However, the lesions can be difficult to reach, and the surgical procedure is difficult to understand. The aim of this study was to create a procedural, stepwise microsurgical educational resource for junior trainees to learn the surgical anatomy of the extreme lateral transodontoid approach (ELTOA). Ten formalin-fixed, latex-injected cadaveric heads were dissected under an operative microscope. Dissections were performed under the supervision of a skull base fellowship–trained neurosurgeon who has advanced skull base experience. Key steps of the procedure were documented with a professional camera and a high-definition video system. A relevant clinical case example was reviewed to highlight the principles of the selected approach and its application. The clinical case example also describes a rare complication: a pseudoaneurysm of the vertebral artery. Key steps of the ELTOA include patient positioning, skin incision, superficial and deep muscle dissection, vertebral artery dissection and transposition, craniotomy, clivus drilling, odontoidectomy, and final extradural and intradural exposure. The ELTOA is a challenging approach, but it allows for significant access to the anterior craniovertebral junction, which increases the likelihood of gross total lesion resection. Given the complexity of the approach, substantial training in the dissection laboratory is required to develop the necessary anatomic knowledge and to minimize approach-related morbidity. [ABSTRACT FROM AUTHOR]

We performed a bibliometric analysis of studies reporting cases of brain and spinal arteriovenous malformations (AVMs). We retrieved the 100 most cited reports in brain and spinal AVM research from Scopus and assessed the citation count, journal of publication and its impact factor, year of publication, first author and corresponding authors and their h-index, country, institution, department, and study category. The median number of citations per article was 215. The Journal of Neurosurgery was the most prolific journal (39 reports and 12,069 citations), including 9 of the 10 most cited reports. Seventy reports (19,251 citations), including 8 of the 10 most cited, were from the United States. The Barrow Neurological Institute was the most cited institution (7 reports; 2792 citations), and the Mayo Clinic had the greatest number of reports (8 reports; 1994 citations). Most studies had been reported before 2000 (71 reports; 19,262 citations). The most discussed topics were treatment (40 studies; 9560 citations) and natural history and/or clinical features (37 studies; 9595 citations). Neurosurgery was the most prolific department (58 studies; 15,860 citations). Spetzler was the author with the highest number of articles (n = 7) and citations (n = 2792). Brain and spinal AVM research was centralized in the United States, has been mainly reported in specific neurosurgical journals, and has been more often related to treatment and natural history and/or clinical features. It is possible that high impact AVM research has been decreasing recently. Because the best approach to these pathological entities remains controversial, research stimulation within this field should be encouraged. [ABSTRACT FROM AUTHOR]

Objective Apparently similar intra-axial pontine lesions may demand distinct surgical approaches. Selecting the optimal approach reduces unnecessary manipulation of tracts and nuclei. This study aims to reveal a quantitative analysis of main surgical corridors dealing with intrinsic pontine pathology. Methods Six approaches were performed repeatedly in 10 cadaveric heads: 1) retrosigmoid, 2) retrolabyrinthine, 3) subtemporal transtentorial, 4) anterior petrosectomy, 5) combined petrosal approach, and 6) suboccipital telovelar. Six safe entry zones were studied: peritrigeminal, supratrigeminal, lateral pontine, supracollicular, infracollicular, and median sulcus of fourth ventricle. A neuronavigation device was used to collect 3-dimensional coordinates from fixed points over the edge of craniotomies and brainstem surface; 4 variables were studied: 1) angles of attack; 2) areas of exposure; 3) lengths of exposure; and 4) trajectories. Results The mean area of exposure generated by the retrosigmoid approach over the brainstem was 538.6 ± 161.0 mm2, whereas that yielded by the retrolabyrinthine was 475.0 ± 173.4 mm2. There were no significant differences between both when considering areas of exposure and angles. Adding a tentorial cut to the subtemporal approach exposed the superior part of the lateral surface of pons; the area of exposure increased a mean of 33% (P < 0.001). Conclusions In addition to producing similar areas and angles of attack, the retrolabyrinthine yields a more orthogonal trajectory to lateral pons than the retrosigmoid approach. Adding a tentorial cut and anterior petrosectomy significantly increased areas and lengths of exposure of a regular subtemporal approach. The combined approach significantly increased angles of attack to both the supratrigeminal and lateral pontine safe zones. Highlights • Quantitative data of the main surgical approaches to pons are provided. • No significant differences were found in areas produced by retrosigmoid and retrolabyrinthine. • Mean distance between origin of cranial nerves V and VII, approaching the lateral pontine zone, was 7.1 mm. • Dividing the tentorium produced a mean gain of 6.9 mm (P < 0.001) in vertical exposure. • The combined approach significantly increased angles to the supratrigeminal and lateral pontine zones. [ABSTRACT FROM AUTHOR]

Background Vascularized bone grafts (VBGs) are described as having superior osteogenicity, osteoconductivity, and osteoinductivity compared with other graft types and have been used in high-risk patients to augment arthrodesis. Pedicled VBGs are rotated on an intact vascular pedicle and therefore maintain all the benefits of VBGs but avoid many of the challenges and additional morbidity of free-tissue transfer. This study describes a novel surgical technique for rotating vascularized spinous process into the posterolateral space for augmenting arthrodesis in patients undergoing posterolateral fusion (PLF). Methods A technique is described for rotating the spinous process into the posterolateral space on an intact vascular pedicle of paraspinal muscle. Early clinical and radiographic outcomes are reported for 4 patients who have undergone this procedure. Results Four patients were treated with a single or 2-level PLF combined with posterior, anterior, or lateral interbody fusion and vascularized spinous process graft. Three-month postoperative computed tomography scans demonstrated a dislodged graft in 1 patient and successful arthrodesis in 3 patients. Additional operative time taken for graft harvest and implantation ranged from 22 minutes for the first patient to 6 minutes for the fourth patient. Conclusions Rotation of vascularized spinous process graft for augmentation of posterolateral arthrodesis in the lumbar spine is a potentially safe, effective surgical technique that results in successful arthrodesis in as little as 3 months but requires further study. This technique is expected to add little additional time or morbidity to the traditional lumbar PLF because it requires no separate incision or additional bone removal. [ABSTRACT FROM AUTHOR]

Objective Although endoscopic diskectomy is superior to microsurgical diskectomy in terms of incision size, postoperative pain, and cosmetic appeal, the effectiveness and indications for endoscopic versus microsurgical diskectomy remain active discussion topics. Because of the increasing incidence of diskectomies being performed in Russia, further assessment of these techniques is needed. We performed a comparative analysis of 1-year clinical results and complications of microsurgical, tubular-based interlaminar endoscopic, and endoscopically assisted microsurgical diskectomies for patients with herniated lumbar disks. Methods The patient cohort included 131 patients who were enrolled in a prospective, randomized controlled study and 617 patients for whom data were gathered retrospectively. The quality of life was assessed using the Oswestry Disability Index (version 2.1a) and pain severity was analyzed using the visual analog scale for pain preoperatively, at discharge, and at 3, 6, and 12 months postoperatively. Results Microsurgical, tubular-based endoscopic, and endoscopically assisted microsurgical diskectomies were all effective in relieving acute radicular symptoms. Recurrent disk herniation occurred more frequently after tubular-based endoscopic diskectomy than after the other approaches. Conclusions Our findings indicate that these 3 surgical techniques are highly effective and have similar clinical results at 1-year follow-up. Although this study points to differences in complications resulting from the 3 techniques, larger prospective studies are needed to more definitively assess possible surgical differences, complications, and outcomes. The endoscopically assisted diskectomy technique allows for minimally invasive surgery and offers enhanced visualization of the anatomy that is hidden from view in microscopic procedures. [ABSTRACT FROM AUTHOR]

Procedures performed along the skull base require technical prowess and a thorough knowledge of cranial anatomy to navigate the operative field. Anatomical triangles created by unique anatomical structures serve as landmarks to guide the surgeon during meticulous skull base procedures. The corridors rapidly orient the surgeon to the operative field and permit greater confidence regarding skull base position during dissection. A literature review was performed with use of the PubMed database and reference list searches from full-text reviewed articles, which resulted in the identification of 31 distinct anatomical triangles of the skull base. The 31 anatomical triangles are categorized into a corresponding cranial fossa or the extracranial subsection. The triangles described in the manuscript include junctional, interoptic, precommunicating, opticocarotid, supracarotid, parasellar, clinoidal, oculomotor, carotid-oculomotor, supratrochlear, infratrochlear, anteromedial, quadrangular, anterolateral, posteromedial, posterolateral, lateral, superior petrosal, oculomotor-tentorial, inferomedial, inferolateral, glossopharyngo-cochlear, vagoaccessory, suprahypoglossal, hypoglossal-hypoglossal, infrahypoglossal, parapetrosal, suprameatal, retromeatal, suboccipital, and the inferior suboccipital. The goal of this review is to create a comprehensive resource for existing skull base triangles that includes borders, contents, surgical applications, and illustrations to enhance awareness and inform microsurgical dissection. [ABSTRACT FROM AUTHOR]

Transcranial anterior petrosectomy (AP) is a classic approach; however, it is associated with adverse consequences. The endoscopic endonasal approach (EEA) has been developed as an alternative. We describe surgical techniques for AP and EEA and compare the anatomic exposures of each. Ten cadaveric heads (20 sides) were dissected. Specimens were divided into 4 groups: 1) AP, 2) EEA for medial petrosectomy (MP), 3) EEA for inferior petrosectomy (IP), and 4) EEA for inferomedial petrosectomy (IMP). Outcomes were areas of exposure, angles of attack to neurovascular structures, and bone resection volumes. AP had a greater area of exposure than did MP and IP (P = 0.30, P < 0.01) and had a higher angle of attack to the distal part of the facial nerve–vestibulocochlear nerve (cranial nerve [CN] VII/VIII) complex than did IP and IMP (P < 0.01). MP had a lower angle of attack than IMP to the midpons (P = 0.04) and to the anterior inferior cerebellar artery (P < 0.01). Compared with IMP, IP had a lower angle of attack to the proximal part of the CN VII/VIII complex (P < 0.01) and the flocculus (P < 0.01). The bone resection volume in AP was significantly less than that in MP, IP, and IMP (P < 0.01). AP and all EEA techniques had specific advantages for each specific area. We suggest AP for the ventrolateral pons and the anterior superior internal auditory canal, MP for the midline clivus, IP for the ventrolateral brainstem, and IMP to enhance the lateral corridor of the abducens nerve. [ABSTRACT FROM AUTHOR]

Although several commercially available sutureless anastomotic techniques are available, they are not routinely used in neurosurgery. We performed an in vivo flow analysis of end-to-end anastomosis using a microvascular coupler device in rats. We report our first clinical use of the microvascular anastomotic coupler. Bilateral rat common carotid arteries (CCAs) were exposed, and a microvascular coupler was used to perform 8 anastomoses. A microflow probe provided quantitative measurement of blood-flow volume. Flow augmentation was assessed with end-to-side anastomoses connecting the distal CCA to the jugular vein (JV). A patient with chronic dominant hemisphere atherosclerotic ischemic disease and progressive symptoms refractory to medical management underwent end-to-end cerebral artery bypass using the microvascular coupler. Mean preanastomosis flow in the rat CCA was 3.95 ± 0.45 mL/min; this flow was maintained at 3.99 ± 0.24 mL/min on final measurements 54–96 minutes postanastomosis. Total occlusion time for each rat CCA was 12–19 minutes. After end-to-side anastomosis, with proximal and distal JV patent, CCA flow increased 477% to 22.8 ± 3.70 mL/min (P = 0.04, proximal; P = 0.01, distal). After in vivo testing, we successfully used the coupler clinically in a superficial temporal artery–to–middle cerebral artery bypass for dominant hemisphere flow augmentation. In vivo quantitative flow analysis demonstrated no flow difference between an unaltered artery and artery with end-to-end anastomosis using a microvascular coupler in rats. A 1-mm coupled anastomosis achieved a 4-fold flow increase with low-resistance venous outflow in rats, simulating increased arterial demand. The coupler was successfully used for extracranial-to-intracranial bypass in a patient. [ABSTRACT FROM AUTHOR]

Various well-known people associated with the history of the presidency of the United States have experienced neurologic disease or injury, especially trauma to the head or spine. Nancy Reagan, however, as the wife of President Ronald Reagan and First Lady, would leave a significant and lasting mark on the progress of neurosurgical science and education. Recognized for endeavors against drug abuse, Alzheimer disease, and polio, her interest in neurosurgical research is less well known. Nancy's father Loyal Davis was a remarkable neurosurgeon and educator of extraordinary influence. When Barrow Neurological Institute (BNI) founder John Green experienced complications after an illness, Davis served as BNI director during 1966 − 1967. After Davis's death in 1982, Robert Spetzler, who had been a student of Davis at Northwestern University Medical School and was then BNI director, convinced Green, despite his misgivings, to support a neurosurgical laboratory recognizing Davis. In 1988, Nancy Reagan, then First Lady, dedicated the Loyal and Edith Davis Neurosurgical Research Laboratory. At the dedication, she remarked on her years growing up in the home of a pioneering neurosurgeon and remarked that "my father believed deeply in the importance of research to develop new methods for treating patients." Green and Spetzler's unified efforts honored the extraordinary career of Davis in a manner he would have appreciated, were supported by a First Lady with deep involvement in politics and philanthropy dedicated to promoting advances in medicine, and are part of neurosurgery's unique heritage. [ABSTRACT FROM AUTHOR]

The incorporation of perspective into art and science revolutionized the study of the brain. Beginning in about 1504, Leonardo da Vinci began to model the ventricles of the brain in three dimensions. A few years later, Andreus Vesalius illustrated radically novel brain dissections. Thomas Willis' work, Cerebri Anatome (1664), illustrated by Christopher Wren, remarkably showed the brain undersurface. Later, in the early 1800s, Charles Bell's accurate images of neural structures changed surgery. In the 1960s, Albert L. Rhoton Jr. (1932–2016) began to earn his place among the preeminent neuroanatomists by focusing his lens on microanatomy to harness a knowledge of microneurosurgery, master microneurologic anatomy, and use it to improve the care of his patients. Although his biography and works are well known, no analysis has been conducted to identify the progression, impact, and trends in the totality of his publications, and no study has assessed his work in a historical context compared with the contributions of other celebrated anatomists. We analyzed 414 of 508 works authored by Rhoton; these studies were analyzed according to subjects discussed, including anatomic region, surgical approaches, subjects covered, anatomic methods used, forms of multimedia, and subspecialty. Rhoton taught detailed neuroanatomy from a surgical perspective using meticulous techniques that evolved as the technical demands of neurosurgery advanced, inspiring students and contemporaries. His work aligns him with renowned figures in neuroanatomy, arguably establishing him historically as the most influential anatomist of the neurosurgical era. [ABSTRACT FROM AUTHOR]

Encephalocele is a common congenital malformation of the central nervous system; however, giant encephaloceles are rare. The use of folic acid supplementation and termination of pregnancies, which are prenatally diagnosed with encephaloceles and other congenital malformation of the central nervous system, has significantly reduced the occurrence of this type of congenital malformation, especially in developed countries. This was a retrospective review over a 5-year period from January 2006 to December 2010 at the Department of Neurosurgery, Regional Centre for Neurosurgery, Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria. The records of patients with giant encephalocele were retrieved from the case notes of patients who had excision and repair for encephalocele. Seventy-three patients had excision and repair of encephalocele over the study period. However, the records of only 50 patients were retrieved. Fourteen (28%) of the 50 whose records were retrieved had giant encephalocele. There were 4 male and 10 female patients (1:2.5). Thirteen (92.9%) had the lesion located in the occipital region, whereas in 1 patient (7.1%) the lesion was at the vertex. Three (21%) of the cases had microcephaly, 1 (7.1%) had macrocephaly, and 1 (7.1%) developed postoperative hydrocephalus. The average size of defect was 2.43 cm, and the size of the lesion ranged from 12 × 6 cm to 40 × 50 cm. The average maternal age was 20.3 years (n = 6), and the paternal age was 29 years (n = 4). Four out of 7 (57%) mothers had febrile illness in early pregnancy. Seven out of 10 patients (70%) did not have antenatal care. This condition is more common in children conceived during the period when farm products are yet to be harvested, and whose mothers did not attend antenatal care visits. It is recommended that mothers should be educated on the necessity of preconception folic acid. Implementation of a national strategy on food fortification is also advised. We recommend surgery after the first month of life to reduce poor early postoperative outcomes. In developing countries and centers with suboptimal pediatric intensive care units, surgical intervention is preferred after the first month of life with good temperature control, adequate fluid replacement following rupture of the sac, blood transfusion availability, and, only if necessary, complex cranial reconstruction. [ABSTRACT FROM AUTHOR]

Localization of the temporal horn of the lateral ventricle (TH) may be required during temporal lobe and ambient cistern surgery. Most available anatomic landmarks for TH localization are based on adjacent cortical landmarks that are inherently variable or subtle. This study aimed to localize the anterior tip of the TH relative to adjacent bony landmarks. The TH was exposed on 21 sides of 11 cadaveric heads via removal of the middle temporal gyrus. Two lines were defined: (1) a perpendicular line to the zygomatic arch projected from the anterior concavity of the posterior zygomatic root (line A), and (2) a parallel line passing through the anterosuperior corner of the external auditory canal (line B). Sagittal distances from lines A and B to a parallel line passing through the anterior recess of the TH (line H) were measured. Mean (standard deviation) distances from lines A and B to line H were 13.3 (2.5) mm and 11.9 (2.2) mm, respectively. Line H was at 53% (8%) of the line A–line B interval measured from line A. The best way to search for the TH was to start approximately 15 mm posterior to line A and progress posteriorly such that a more posteriorly located TH tip would not be missed. The zygomatic-meatal landmark is a reliable tool to localize TH during various approaches. It is independent from the approach trajectory. This landmark may be used as an ancillary tool in conjunction with other cortical landmarks and image guidance. [ABSTRACT FROM AUTHOR]

Edward Archibald, Professor of Surgery at McGill University (1904–1945), Montreal, Canada, was the foremost thoracic surgeon of his generation. Although instrumental in establishing the American Board of Surgery and in standardizing surgical training, he was also influential as a neurosurgeon. Archibald, an early member invited by Harvey Cushing to join the Society of Neurological Surgeons, helped establish neurosurgery as a distinct, specialized discipline. We review Archibald's contributions to the development of neurosurgery in light of his encyclopedic 1908 monograph, "Surgical Affections and Wounds of the Head," which we compare and contrast to the contemporary treatise by Cushing in the same year. Through his writings and correspondence with Wilder Penfield and Cushing, we also describe his role in the creation of the Montreal Neurological Institute. Primary archival sources addressing the professional relationship between Archibald and Cushing and between Archibald and Penfield were consulted. Archibald's personal acquaintance with the principal neurosurgeons of the day, his insight into their personalities, their prominence in the field, and their career paths played a critical role in influencing Penfield to consider relocating to Montreal from Columbia University, despite tempting offers from Boston and Philadelphia. However, it was Archibald's support and mentorship for the creation of an academic center that finally convinced Penfield to move to McGill University. As one of the most influential surgeons of the early 20th century and a founding figure of modern neurosurgery, Archibald is an important part of neurosurgery's legacy. [ABSTRACT FROM AUTHOR]

Mastery of the microsurgical anastomosis is an indispensable component of neurosurgical training. However, in many resource-limited countries, the training, materials, and equipment to obtain these surgical and decision making skills are severely lacking. This study aimed to compare different suturing techniques for microvascular anastomosis and to complete a comparative assessment of the performance of a young neurosurgeon when using the various techniques. We compared 3 end-to-end suturing techniques for microvascular anastomosis: interrupted suturing, continuous suturing, and a 2-octyl-cyanoacrylate–based lid technique using an umbilical artery model. We assessed the subjective difficulty of the suturing technique, the time needed to perform the procedure, and the flow rate and leakage of the vessel after each technique. This study was designed to use materials that would be available in developing countries. Surgical apparatus used, such as operating microscopes, were first-generation technology, and testing procedures were designed for neurosurgical residents in developing countries. The mean times to complete the anastomosis were 20.7 ± 7.7 minutes for the interrupted technique, 26.4 ± 7.7 minutes for the continuous technique, and 12.5 ± 2.5 minutes for the lid technique; these values were significantly different (P < 0.01). The differences among the 3 techniques in leakage and flow rates and subjective difficulty in performance were not significant. Suturing time was the only statistically significant difference among the 3 anastomotic techniques, with the lid technique apparently the quickest to perform. Such techniques can be designed to assess microsurgical abilities and help neurosurgery residents in developing countries improve their surgical skills and techniques. [ABSTRACT FROM AUTHOR]

For nearly 90 years, notions of the brain have been inextricably associated with a homunculus that has become embedded within medical education as the precise representation of rolandic cortical function. We sought to define the history, evolution, accuracy, and impact of this pictorial means of showing cortical representation. We mathematically defined the evolutionary accuracy of appropriate homunculi using image analysis techniques for all points defined by Penfield, Boldrey, Rasmussen, Jasper, and Erickson, calculating perpendicular distances and defining areas and distributions of rolandic and sylvian regions labeled for sensory and motor activity with comparison with all homunculi. Prerolandic sensory representation composed 13%–47% of total sensory area (mean, 29%); postrolandic motor representation composed 15%–65% of total motor area (mean, 31%). Discrepancy between cortical perpendicular length attributed to a particular function on 1937 diagrams was greater than that attributed on the 1950 homunculus (motor: mean, 74%; range, 63%–96%; sensory: mean, 66%; range, 17%–92%) (P < 0.05). The homunculus, if truly drawn according to cortical mapping evidence, could never have been recognized as near humanoid, yet it has attained epic educational and practical longevity. [ABSTRACT FROM AUTHOR]

An increasing body of literature describing use of high-fidelity surgical training models is challenging long-held dogma that cadavers provide the best medium for postgraduate surgical skills training. The purpose of this study was to describe a surgical skills course comprising entirely synthetic training models developed by resident and attending neurosurgeons and to evaluate their perceptions of the overall usefulness of this course and its usefulness compared with cadaveric courses. Ten high-fidelity neurosurgical training models were developed. A neurosurgical skills course for residents was structured to include 7 spinal and 3 cranial learning stations, each with its own model and assigned attending expert. Resident and attending neurosurgeons were asked to complete surveys on their overall impressions of the course and models and on workload comparisons between models and real cases. Student t tests were used for statistical comparisons. Survey responses were collected from 9 of 16 participating residents (56.3%) and 3 of 10 attending neurosurgeons (30.0%). Both groups believed that the course was very helpful overall to resident education. Respondents furthermore believed that the course was more helpful overall than cadaveric courses. Task load index testing showed no significant workload difference between models and real cases (P ≥ 0.17), except in temporal demand (P < 0.001). Resident and attending neurosurgeons subjectively believe that high-fidelity synthetic models were superior to cadavers as a surgical skills teaching platform. This study raises the question of whether cadavers should remain the gold standard for surgical skills courses. Expanded use of these teaching models and further study are warranted. [ABSTRACT FROM AUTHOR]

Rootlets of the lower cranial nerves create a web that limits microsurgical maneuverability in the cerebellomedullary cistern (CMC). The vagoaccessory triangle (VAT) and 2 triangles within it were defined to identify surgical routes to aneurysms of the posterior inferior cerebellar artery (PICA). Dividing the VAT into 2 triangles (suprahypoglossal [SHT] and infrahypoglossal [IHT]), although elegant, oversimplifies CMC anatomy. The triangle formed by the superior and inferior hypoglossal rootlets (hypoglossal–hypoglossal triangle [HHT]) needs consideration as well. Far-lateral craniotomy was performed on 10 cadaveric heads bilaterally. Areas of CMC triangles were calculated. Relationships between the PICA origin and the adjacent triangles were analyzed. Vertebral artery (VA) exposure and clipping lengths were recorded for each triangle. The area of SHT was almost twice those of IHT and HHT. The average VA depth relative to VAT increased significantly when moving distally from proximal VA (P < 0.001), but VA exposure and clipping lengths were not significantly different between triangles. IHT, HHT, and SHT defined VA subsegments (V 4i , V 4h , and V 4s), with PICA most commonly originating from V 4h. Based on our cadaveric measurements, the V 4 subsegments were identified with 76% accuracy in angiograms. Based on this study, VAT should be divided into 3 triangles, not 2. Splayed rootlets of cranial nerve XII and multiple outlet foramina create an important space different from the previously recognized SHT and IHT. These triangles provide corridors to vascular pathologies. V 4 subsegments may be approximated from imaging studies and may help with preoperative planning. [ABSTRACT FROM AUTHOR]

Background Double origin of the posterior inferior cerebellar artery is rare. It has important clinical implications especially in cases of aneurysms of the vertebral artery or the posterior inferior cerebellar artery. Several radiologic reports of this variant exist. However, no anatomic illustration of this rarity exists in the literature. This brief report provides the first anatomic illustration of this important variation of the vertebrobasilar system. Case Description A cadaveric specimen was prepared for dissection. A far lateral craniotomy was performed on the right side. While exploring the right cerebellomedullary cistern, 2 separate origins of the posterior inferior cerebellar artery were found from the vertebral artery as the caudal and rostral trunks that joined to form the distal posterior inferior cerebellar artery trunk at the tonsillomedullary segment. Microscopic and endoscopic illustrations are provided. Conclusions To the best of our knowledge, this is the first anatomic report on the double origin of the posterior inferior cerebellar artery. Cadaveric illustration of this variant helps with understanding its anatomic relationship with adjacent neurovascular structures of the cerebellomedullary cistern including the perforating arteries and the lower cranial nerves. [ABSTRACT FROM AUTHOR]

Objective To describe and compare surgical exposure through microsurgical cadaveric dissection of the intercollicular region afforded by the median, paramedian, and extreme-lateral supracerebellar infratentorial (SCIT) approaches. Methods Ten cadaveric heads were dissected using SCIT variant approaches. A neuronavigation system was used to determine tridimensional coordinates for the intercollicular zone in each route. The areas of surgical and angular exposure were evaluated and determined by software analysis for each specimen. Results The median surgical exposure was similar for the different craniotomies: 282.9 ± 72.4 mm2 for the median, 341.2 ± 71.2 mm2 for the paramedian, and 312.0 ± 79.3 mm2 for the extreme-lateral (P = 0.33). The vertical angular exposure to the center of the intercollicular safe entry zone was also similar between the approaches (P = 0.92). On the other hand, the horizontal angular exposure was significantly wider for the median approach (P < 0.001). Conclusions All the SCIT approaches warrant a safe route to the quadrigeminal plate. Among the different variants, the median approach had the smallest median surgical area exposure but presented superior results to access the intercollicular safe entry zone. [ABSTRACT FROM AUTHOR]

Objective The contralateral interhemispheric transprecuneus approach (CITP) and the supracerebellar transtentorial transcollateral sulcus approach (STTC) are 2 novel approaches to access the atrium of the lateral ventricle. We quantitatively compared the 2 approaches. Methods Both approaches were performed in 6 sides of fixed and color-injected cadaver heads. We predefined the 6 targets in the atrium for measurement and standardization of the approaches. Using a navigation system, we quantitatively measured the working distance, cortical transgression, angle of attack, area of exposure, and surgical freedom. Results The distances from the craniotomy edge to the posterior pole of the choroid plexus of the CITP (mean ± standard deviation, 67 ± 5.3 mm) and STTC (mean, 57 ± 4.0 mm) differed significantly (P < 0.01). Cortical transgression with the CITP (mean, 27 ± 2.8 mm) was significantly greater than that with the STTC (mean, 21 ± 6.7 mm; P = 0.03). The CITP showed a significantly wider rostrocaudal angle of attack than that with the STTC (P = 0.01). The STTC showed a significantly wider mediolateral angle (P < 0.01). No significant difference was found for surgical freedom of any target except for point E, for which the CITP was larger. The exposure area did not differ significantly between the 2 approaches (P = 0.07). Conclusions Both approaches were feasible for accessing the atrium. The STTC provided a shorter working distance and wider mediolateral angle, CITP provided a wider rostrocaudal angle of attack and better exposure and maneuverability to the anterior and superior atrium. In contrast, the STTC was more favorable for the inferior and posterior regions. Highlights • Two novel approaches (CITP and STTC) allow access to the lateral ventricle atrium. • Both approaches avoid transgression of the optic radiation. • Both approaches are feasible for atrial lesions (e.g., ependymomas, meningiomas). • STTC is most appropriate for the inferior posterior atrium and CITP, for superior anterior atrium. [ABSTRACT FROM AUTHOR]

Objective Although pterional craniotomy and its variants are the most used approaches in neurosurgery, few studies have evaluated their precise indications. We evaluate the pterional (PT), pretemporal (PreT), and orbitozygomatic (OZ) approaches through quantitative measurements of area, linear, and angular exposures of the major intracranial vascular structures. Methods Eight fresh, adult cadavers were operated with the PT, followed by the PreT, and ending with the OZ approach. The working area, angular exposure of vascular structures and linear exposure of the basilar artery were measured. Results The OZ approach presented a wider area (1301.3 ± 215.9 mm2) with an increase of 456.7 mm2 compared with the PT and of 167.4 mm2 to the PreT (P = 0.011). The extension from PT to PreT and OZ increases linear exposure of the basilar artery. When comparing the PreT and OZ, we found an increase in the horizontal and vertical angle to the bifurcation of the ipsilateral middle cerebral artery (P = 0.005 and P = 0.032, respectively), horizontal angle to the basilar artery tip (P = 0.02), and horizontal angle to the contralateral ICA bifurcation (P = 0.048). Conclusions The OZ approach offered notable surgical advantages compared with the traditional PT and PreT regarding to the area of exposure and linear exposure to basilar artery. Regarding angle of attack, the orbital rim and zygomatic arch removal provided quantitatively wider exposure and increased surgical freedom. A detailed anatomic study for each patient and surgeon experience must be considered for individualized surgical approach indication. Highlights • Few studies have evaluated the precise indications of different craniotomies. • We evaluate the pterional, pretemporal, and orbitozygomatic approaches. • The orbitozygomatic approach presented a wider working area. • The pretemporal approach showed similar angle to the anterior communicating artery. [ABSTRACT FROM AUTHOR]

Background Despite the latest developments in microsurgery, electrophysiological monitoring, and neuroimaging, the surgical management of intrinsic brainstem lesions remains challenging. Several safe entry points have been described to access the different surfaces of the brainstem. Knowledge of this entry zone anatomy is critical to performing a safe and less morbid approach. To access the anterior midbrain surface, a well-known entry point is the anterior mesencephalic (AM) zone. Our aim was to quantify surgical AM zone exposure through the orbitozygomatic (OZ) and subtemporal (ST) approaches. We also analyzed the angular exposure along the horizontal and vertical axis angles for the AM zone. Methods Ten cadaveric heads were dissected using the OZ and ST approaches for anterior midbrain surface exposure. A neuronavigation system was used to determine the 3-dimensional coordinates. The area of surgical exposure, angular exposure, and anatomical limits of each craniotomy were evaluated and determined using software analysis and compared for intersection areas and AM safe zone exposure. Results The median surgical exposure was 164.7 ± 43.6 mm2 for OZ and 369.8 ± 70.1 mm2 for ST (P = 0.001). The vertical angular exposure was 37.7° ± 9.92° for the OZ and 18.4° ± 2.8° for the ST opening (P < 0.001). The horizontal angular exposure to the AM zone was 37.9° ± 7.3° for the OZ and 47.0° ± 3.2° for the ST opening (P = 0.002). Conclusions Although the OZ craniotomy offers reduced surgical exposure, it provides a better trajectory to the AM zone compared with the ST approach. Highlights • To access the anterior midbrain surface, a well-known entry point is the AM zone. • When approaching the AM zone, the ST approach offers greater median surgical area exposure. • However, the OZ craniotomy provides a better trajectory to the AM zone. [ABSTRACT FROM AUTHOR]

Background The end-to-side anastomosis is 1 of the most common anastomosis configurations used in cerebrovascular surgery. Although several living practice models have been proposed for this technique, few involve purely arterial vessels. The purpose of the present study was to compare 2 arterial models using common carotid arteries (CCAs) and common iliac arteries (CIAs) in rats. Methods The CIAs and CCAs were exposed in 10 anesthetized rats, and their lengths and diameters were measured. Also, the mobilization extent of each vessel along its contralateral counterpart was measured after each artery had been transected at its proximal exposure point. We also studied the technical advantages and disadvantages of each model for practicing end-to-side anastomosis. Results The average diameters of the CCA and CIA were 1.1 and 1.3 mm, respectively. The average extent of mobilization along the contralateral vessel was 13.9 mm and 10.3 mm for CCA and CIA, respectively. The CCA model had the advantages of greater arterial redundancy (allowing completion of both suture lines extraluminally) and a minimal risk of venous injury. The main disadvantage of the CCA model was the risk of cerebral ischemia. The CIA model was not limited by the ischemic time and provided the technical challenge of microsurgical dissection of the common iliac vein from the CIA, although it had limited CIA redundancy. Conclusions Both CCA and CIA models could be efficiently used for practicing the end-to-side anastomosis technique. Each model provides the trainee with a specific set of advantages and disadvantages that could help with the optimal selection of the practice model according to trainee's skill level. Highlights • End-to-side anastomosis is a common bypass procedure in neurosurgery. • The training models for the end-to-side anastomosis have not been optimized. • We compared the rat carotid and iliac arteries as models for practicing end-to-side anastomosis. • The carotid model was more robust in vessel mobilization and ease of dissection. • The iliac model offered the advantage of theoretically limitless ischemia time. [ABSTRACT FROM AUTHOR]

Background The subtemporal and orbitozygomatic approaches are the most commonly used surgical approaches for the treatment of basilar artery apex (BAX) aneurysms. Relative advantages and disadvantages are generally reported based on surgeons' experience. This study was performed to provide a detailed comparison between the subtemporal and orbitozygomatic approaches based on cadaveric dissection analysis for the treatment of BAX aneurysms. Methods Subtemporal and orbitozygomatic approaches were performed on 5 cadaveric heads (10 sides), and the following variables were assessed and compared between the 2 approaches: 1) number of exposed perforators on P 1 -posterior cerebral arteries (PCA); 2) lengths of exposure and clipping for bilateral PCA, superior cerebellar arteries (SCA), and basilar trunk; 3) surgical area of exposure; and 4) surgical freedom at the BAX. Results Number of perforators exposed on P 1 -PCA was not different between the subtemporal and orbitozygomatic approaches. Exposure and clipping of ipsilateral SCA and PCA were superior using the subtemporal approach, and better for contralateral SCA and PCA using the orbitozygomatic approach, all reaching statistical significance. The orbitozygomatic approach provided greater exposure and clipping length for the proximal basilar trunk. Although the surgical area of exposure was similar between the 2 approaches, the overall surgical freedom was greater in the orbitozygomatic approach. Conclusions The orbitozygomatic approach provides a greater number of surgical corridors to the BAX and is superior regarding multiple surgically relevant anatomic parameters. Importantly, control over the basilar trunk and over the contralateral SCA and PCA (blind spots) is superior with the orbitozygomatic approach. Highlights • Subtemporal and orbitozygomatic approaches are mainly used for basilar apex aneurysms. • Few studies exist on objective comparisons of these approaches. • The present study focuses on a detailed comparative analysis between the approaches. • We have considered relevant surgical anatomic variables to carry out comparisons. • The orbitozygomatic approach provides a more robust exposure of basilar apex. [ABSTRACT FROM AUTHOR]

Background The greater auricular nerve (GAN) may be used as a nerve graft during neurosurgical procedures to repair damaged nerves. There is extensive literature on localization of the GAN at the posterior triangle of the neck, but objective information on localization of the GAN at the anterior triangle of the neck close to cranial neurosurgical fields is lacking. The aim of this study was to introduce simple and reliable landmarks to localize the GAN at the anterior triangle of the neck to facilitate its harvest during neurosurgical procedures. Methods The GAN was exposed bilaterally in 11 cadaveric specimens at the point of crossing the anterior border of the sternocleidomastoid muscle (anterior greater auricular point [AGA]). Distances from the AGA point to the angle of the mandible and the tip of the mastoid process were measured. Additionally, the location of the crossing point between the GAN and an imaginary line passing through the mastoid tip and the angle of the mandible (M-A line) was found relative to these bony landmarks. Results Mean (±SD) distances from the AGA point to the mastoid tip and the angle of the mandible were 29.1 ± 3.4 mm and 27.5 ± 4.5 mm, respectively. The GAN was always found to cross the M-A line in its middle third (mean 48.2% ± 6.9% from the mastoid tip). Conclusions The AGA point and the M-A line are reliable landmarks for locating the GAN at the anterior triangle of the neck and for helping neurosurgeons expose and harvest the GAN efficiently. Highlights • The GAN is frequently harvested for cranial nerve repair. • Harvesting the GAN at the anterior triangle of the neck is surgically important. • Landmarks for localizing the GAN at the anterior neck triangle are needed. • Reliable landmarks for locating the GAN are present in the anterior neck triangle. [ABSTRACT FROM AUTHOR]

Objective We describe and quantitatively assess minimally invasive keyhole retrosigmoid approaches targeted to the upper, middle, and lower cranial nerve (CN) complexes of the cerebellopontine angle (CPA). Methods Anatomic dissections were performed on 10 sides of 5 fixed, silicone-injected cadaver heads. Surgical views through various trajectories were assessed in endoscopic videos and 3-dimensional (3D) interactive virtual reality microscope views. Surgical freedom and angles of attack to the proximal and distal areas of CN complexes of the CPA were compared among upper and lower keyholes and conventional retrosigmoid craniotomy using neuronavigation. Results Compared with keyholes, the conventional approach had superior surgical freedom to most areas except for the distal CN V, the root of CN VII, and the root of CN IX, where differences were not significant. The conventional retrosigmoid approach provided a larger horizontal angle of attack than either the upper or lower keyholes for all selected areas; however, the vertical angles of attack were not different. Splitting the petrosal fissure resulted in a significant increase in the vertical angle of attack to the root zones of CNs V and VII but not to the distal areas of these nerves or CN IX. Illustrative cases of endoscope-assisted keyhole retrosigmoid approaches for the treatment of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia are presented. Conclusions Targeted keyhole retrosigmoid approaches require detailed understanding of the 3D anatomy of the CPA to create appropriate locations of corridors, including skin incisions and keyholes. Endoscope assistance complements the standard microsurgical technique by maximizing the visualization and identification of the delicate neurovascular structures. Highlights • Targeted keyhole retrosigmoid craniotomies to CPA nerves were assessed quantitatively. • Keyhole approach limits surgical freedom and requires precise planning of trajectory. • Three types of skin incision and keyhole positions were assessed for CPA nerves. • Endoscope assistance increases visualization of CPA structures in keyhole approaches. • Petrosal fissure splitting provides additional freedom compared with cerebellar retraction. [ABSTRACT FROM AUTHOR]

Objective To compare transcallosal-transchoroidal and transcallosal-subchoroidal approaches to the ipsilateral and contralateral edges of the floor of the third ventricle using quantitative analyses. Methods Five formalin-fixed cadaveric human heads (10 sides) were examined under the operating microscope. Quantitative measurements (area of surgical freedom and angle of attack) were obtained using 3-T magnetic resonance imaging and a StealthStation image guidance system. The limits of the surgical approaches were shown by touching a probe to 6 designated points on the floor of the third ventricle. Results The transchoroidal approach provided greater surgical freedom than the subchoroidal approach to access ipsilateral and contralateral middle landmarks at the edges of the floor of the third ventricle in both longitudinal and horizontal planes (P ≤ 0.03). No significant difference between the 2 approaches was found in accessing the anterior and posterior landmarks of the third ventricle in each plane. The surgical freedom to the contralateral anterior, middle, and posterior landmarks was greater than to the ipsilateral landmarks in both the transchoroidal and subchoroidal approaches. Conclusions The transcallosal-transchoroidal approach, compared with the transcallosal-subchoroidal approach, may provide better exposure and require less retraction for removal of ipsilateral or contralateral lesions located in the midbrain or hypothalamus and situated near the floor of the third ventricle. The contralateral transcallosal approach with either the transchoroidal or subchoroidal approach may provide good surgical freedom for removal of lesions located near the floor of the third ventricle, such as lesions in the midbrain. Highlights • Detailed anatomic knowledge is necessary for surgery of third ventricle lesions. • Vital structures must remain undamaged to preserve maximum neurologic function. • We compare transcallosal-transchoroidal and transcallosal-subchoroidal approaches. • Both approaches provide good surgical freedom to remove third ventricle lesions. [ABSTRACT FROM AUTHOR]