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Background: Understanding the anatomy of the human cerebrum, cerebellum, and brainstem and their 3-dimensional (3D) relationships is critical for neurosurgery. Although 3D photogrammetric models of cadaver brains and 2-dimensional images of postmortem brain slices are available, neurosurgeons lack free access to 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem that can be simulated in both augmented reality (AR) and virtual reality (VR)., Objective: To create 3D models and AR/VR simulations from 2-dimensional images of cross-sectionally dissected cadaveric specimens of the cerebrum, cerebellum, and brainstem., Methods: The Klingler method was used to prepare 3 cadaveric specimens for dissection in the axial, sagittal, and coronal planes. A series of 3D models and AR/VR simulations were then created using 360° photogrammetry., Results: High-resolution 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem were obtained and used in creating AR/VR simulations. Eleven axial, 9 sagittal, and 7 coronal 3D models were created. The sections were planned to show important deep anatomic structures. These models can be freely rotated, projected onto any surface, viewed from all angles, and examined at various magnifications., Conclusion: To our knowledge, this detailed study is the first to combine up-to-date technologies (photogrammetry, AR, and VR) for high-resolution 3D visualization of the cross-sectional anatomy of the entire human cerebrum, cerebellum, and brainstem. The resulting 3D images are freely available for use by medical professionals and students for better comprehension of the 3D relationship of the deep and superficial brain anatomy., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background: Immersive anatomic environments offer an alternative when anatomic laboratory access is limited, but current three-dimensional (3D) renderings are not able to simulate the anatomic detail and surgical perspectives needed for microsurgical education., Objective: To perform a proof-of-concept study of a novel photogrammetry 3D reconstruction technique, converting high-definition (monoscopic) microsurgical images into a navigable, interactive, immersive anatomy simulation., Methods: Images were acquired from cadaveric dissections and from an open-access comprehensive online microsurgical anatomic image database. A pretrained neural network capable of depth estimation from a single image was used to create depth maps (pixelated images containing distance information that could be used for spatial reprojection and 3D rendering). Virtual reality (VR) experience was assessed using a VR headset, and augmented reality was assessed using a quick response code-based application and a tablet camera., Results: Significant correlation was found between processed image depth estimations and neuronavigation-defined coordinates at different levels of magnification. Immersive anatomic models were created from dissection images captured in the authors' laboratory and from images retrieved from the Rhoton Collection. Interactive visualization and magnification allowed multiple perspectives for an enhanced experience in VR. The quick response code offered a convenient method for importing anatomic models into the real world for rehearsal and for comparing other anatomic preparations side by side., Conclusion: This proof-of-concept study validated the use of machine learning to render 3D reconstructions from 2-dimensional microsurgical images through depth estimation. This spatial information can be used to develop convenient, realistic, and immersive anatomy image models., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: Large, destructive intracranial and extracranial lesions at the jugular foramen (JF) and anterior craniovertebral junction (CVJ) are among the most challenging lesions to resect., Objective: To compare the extreme lateral transodontoid approach (ELTOA) with the extreme medial endoscopic endonasal approach (EMEEA) to determine the most effective surgical approach to the JF and CVJ., Methods: Seven formalin-fixed cadaveric heads were dissected. Using neuronavigation, we quantitatively measured and compared the exposure of the intracranial and extracranial neurovascular structures, the drilled area of the clivus and the C1 vertebra, and the area of exposure of the brainstem., Results: The mean total drilled area of the clivus was greater with the EMEEA than with the ELTOA (1043.5 vs 909.4 mm 2 , P = .02). The EMEEA provided a longer exposure of the extracranial cranial nerves (CNs) IX, X, and XI compared with the ELTOA (cranial nerve [CN] IX: 18.8 vs 12.0 mm, P = .01; CN X: 19.2 vs 10.4 mm, P = .003; and CN XI, 18.1 vs 11.9 mm, P = .04). The EMEEA, compared with the ELTOA, provided a significantly greater area of exposure of the contralateral ventromedial medulla (289.5 vs 80.9 mm 2 , P < .001) and pons (237.5 vs 86.2 mm 2 , P = .005) but less area of exposure of the ipsilateral dorsolateral medulla (51.5 vs 205.8 mm 2 , P = .008)., Conclusion: The EMEEA and ELTOA provide optimal exposures to different aspects of the CVJ and JF. A combination of these approaches can compensate for their disadvantages and achieve significant exposure., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: Precise communication between neurosurgeons and pathologists is crucial for optimizing patient care, especially for intraoperative diagnoses. Confocal laser endomicroscopy (CLE) combined with a telepathology software platform (TSP) provides a novel venue for neurosurgeons and pathologists to review CLE images and converse intraoperatively in real-time., Objective: To describe the feasibility of integrating CLE and a TSP in the surgical workflow for real-time review of in vivo digital fluorescence tissue imaging in 3 patients with intracranial tumors., Methods: Although the neurosurgeon used the CLE probe to generate fluorescence images of histoarchitecture within the operative field that were displayed on monitors in the operating room, the pathologist simultaneously remotely viewed the CLE images. The neurosurgeon and pathologist discussed in real-time the histological structures of intraoperative imaging locations., Results: The neurosurgeon placed the CLE probe at various locations on and around the tumor, in the surgical resection bed, and on surrounding brain tissue with communication through the TSP. The neurosurgeon oriented the pathologist to the location of the CLE, and the pathologist and neurosurgeon discussed the CLE images in real-time. The TSP and CLE were integrated successfully and rapidly in the operating room in all 3 cases. No patient had perioperative complications., Conclusion: Two novel digital neurosurgical cellular imaging technologies were combined with intraoperative neurosurgeon-pathologist communication to guide the identification of abnormal histoarchitectural tissue features in real-time. CLE with the TSP may allow rapid decision-making during tumor resection that may hold significant advantages over the frozen section process and surgical workflow in general., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: M2-M2 end-to-end reimplantation that creates a middle communicating artery has recently been proposed as a reconstruction technique to treat complex aneurysms of the middle cerebral artery that are not amenable to clipping., Objective: To examine the surgical anatomy, define anatomic variables, and explore the feasibility of this bypass., Methods: Sixteen cadaver heads were prepared for bypass simulation. After the middle cerebral artery bifurcation was approached, the proximal insular (M2) segments and perforators were explored. To define the maximal distance between the M2 segments that allows the bypass to be performed, the M2 segments were mobilized and reimplanted in an end-to-end fashion., Results: Successful reimplantation was performed in all specimens. The mean maximal distance between the M2 segments to create the proposed reimplantation was 9.1 ± 3.2 mm. The mean vessel displacement was significantly greater for the superior (6.0 ± 2.3 mm) M2 segment than for the inferior (3.2 ± 1.4 mm) M2 segment (P < .001)., Conclusion: In this cadaveric study, the stumps of the M2 segments located at a distance of ≤9.1 mm could be approximated to create a feasible M2-M2 end-to-end anastomosis. Intraoperative inspection of the M2 segments and their perforators could allow further assessment of the feasibility of the procedure before final revascularization decisions are made., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: Both the pterional and supraorbital approaches have been proposed as optimal access corridors to deep and paramedian anatomy., Objective: To assess key intracranial structures accessed through the surgical approaches using the angle of attack (AOA) and the volume of surgical freedom (VSF) methodologies., Methods: Ten pterional and 10 supraorbital craniotomies were completed. Data points were measured using a neuronavigation system. A comparative analysis of the craniocaudal AOA, mediolateral AOA, and VSF of the ipsilateral paraclinoid internal carotid artery (ICA), terminal ICA, and anterior communicating artery (ACoA) complex was completed., Results: For the paraclinoid ICA, the pterional approach produced larger craniocaudal AOA, mediolateral AOA, and VSF than the supraorbital approach (28.06° vs 10.52°, 33.76° vs 23.95°, and 68.73 vs 22.59 mm3 normalized unit [NU], respectively; P < .001). The terminal ICA showed similar superiority of the pterional approach in all quantitative parameters (27.43° vs 11.65°, 30.62° vs 25.31°, and 57.41 vs 17.36 mm3 NU; P < .05). For the ACoA, there were statistically significant differences between the results obtained using the pterional and supraorbital approaches (18.45° vs 10.11°, 29.68° vs 21.01°, and 26.81 vs 16.53 mm3 NU; P < .005)., Conclusion: The pterional craniotomy was significantly superior in all instrument maneuverability parameters for approaching the ipsilateral paraclinoid ICA, terminal ICA, and ACoA. This global evaluation of 2-dimensional and 3-dimensional surgical freedom and instrument maneuverability by amalgamating the craniocaudal AOA, mediolateral AOA, and VSF produces a comprehensive assessment while generating spatially and anatomically accurate corridor models that provide improved visual depiction for preoperative planning and surgical decision-making., (Copyright © Congress of Neurological Surgeons 2021. All rights reserved.)

Background: Although the full transcavernous approach affords extensive mobilization of the oculomotor nerve (OMN) for exposure of the basilar apex and interpeduncular cistern region, this time-consuming procedure requires substantial dural dissection along the anterior middle cranial fossa., Objective: To quantify the extent to which limited middle fossa dural elevation affects the carotid-oculomotor window (C-OMW) surgical area during transcavernous exposure after OMN mobilization., Methods: Four cadaveric specimens were dissected bilaterally to study the C-OMW area afforded by the transcavernous exposure. Each specimen underwent full and limited transcavernous exposure and anterior clinoidectomy (1 procedure per side; 8 procedures). Limited exposure was defined as a dural elevation confined to the cavernous sinus. Full exposure included dural elevation over the gasserian ganglion, extending to the middle meningeal artery and lateral middle cranial fossa., Results: The C-OMW area achieved with the limited transcavernous exposure, compared with full transcavernous exposure, provided significantly less total area with OMN mobilization (22 ± 6 mm2 vs 52 ± 26 mm2, P = .03) and a smaller relative increase in area after OMN mobilization (11 ± 5 mm2 vs 36 ± 13 mm2, P = .03). The increase after OMN mobilization in the C-OMW area after OMN mobilization was 136% ± 119% with a limited exposure vs 334% ± 216% with a full exposure., Conclusion: In this anatomical study, the full transcavernous exposure significantly improved OMN mobilization and C-OMW area compared with a limited transcavernous exposure. If a transcavernous exposure is pursued, the difference in the carotid-oculomotor operative corridor area achieved with a limited vs full exposure should be considered., (Copyright © Congress of Neurological Surgeons 2021. All rights reserved.)

Background: Aneurysm clipping simulation models are needed to provide tactile feedback of biological vessels in a nonhazardous but surgically relevant environment., Objective: To describe a novel system of simulation models for aneurysm clipping training and assess its validity., Methods: Craniotomy models were fabricated to mimic actual tissues and movement restrictions experienced during actual surgery. Turkey wing vessels were used to create aneurysm models with patient-specific geometry. Three simulation models (middle cerebral artery aneurysm clipping via a pterional approach, anterior cerebral artery aneurysm clipping via an interhemispheric approach, and basilar artery aneurysm clipping via an orbitozygomatic pretemporal approach) were subjected to face, content, and construct validity assessments by experienced neurosurgeons (n = 8) and neurosurgery trainees (n = 8)., Results: Most participants scored the model as replicating actual aneurysm clipping well and scored the difficulty of clipping as being comparable to that of real surgery, confirming face validity. Most participants responded that the model could improve clip-applier-handling skills when working with patients, which confirms content validity. Experienced neurosurgeons performed significantly better than trainees on all 3 models based on subjective (P = .003) and objective (P < .01) ratings and on time to complete the task (P = .04), which confirms construct validity. Simulations were used to discuss clip application strategies and compare them to prototype clinical cases., Conclusion: This novel aneurysm clipping model can be used safely outside the wet laboratory; it has high face, content, and construct validity; and it can be an effective training tool for microneurosurgery training during aneurysm surgery courses., (© Congress of Neurological Surgeons 2021.)

Background: Interrupted and continuous suturing are 2 common techniques for microvascular anastomosis in cerebrovascular surgery. One of the technical complexities of interrupted suturing includes the risk of losing the needle in between interrupted sutures during knot tying, which may result in unnecessary movements and wasted time., Objective: To report a new needle parking technique for microvascular anastomosis that addresses a needle control problem during interrupted suturing., Methods: The needle parking technique involves puncturing both vessel walls at the site of the next provisional suture and leaving the needle parked in place while the knots at the first suture are being made. The thread is then cut, the needle is pulled through, and the process is repeated. Illustrative cases in which the needle parking technique was used are presented. We also compared time of anastomosis completion between the conventional interrupted, needle parking interrupted, and continuous suturing techniques during an in vitro study on standardized artificial vessels., Results: This technique is being used successfully by the senior author for various cerebrovascular bypass surgeries. The in vitro study demonstrated that the needle parking technique can be significantly faster than the conventional interrupted suturing technique and may be as fast as continuous suturing., Conclusion: Needle parking technique is a modification of conventional interrupted suturing and solves the problem of losing the needle during knot tying. This technique is simple, prevents unnecessary movements, and may result in a faster anastomosis time., (© Congress of Neurological Surgeons 2021.)

Background: An extended retrosigmoid approach can offer sufficient space for clip reconstruction of some high-riding posterior inferior cerebellar artery (PICA) aneurysms., Objective: To quantitatively investigate the glossopharyngo-cochlear triangle (GCT) and anatomic structures within it., Methods: Extended retrosigmoid craniotomies were performed on 10 sides of cadaveric heads, and the GCT was identified in each specimen. The length of the base and the area of the GCT were measured. The depth of the vertebrobasilar system and the abducens nerve to the GCT were measured. The proximal and distal exposable and controllable points on the vertebrobasilar system were identified. Two imaging-based patient selection algorithms are provided using the lengths from those points to the vertebral artery dural entry point and the superoinferior distances from those points to the inferior edge of the foramen magnum. Other factors related to accessibility via the GCT were investigated., Results: The mean (standard deviation [SD]) area of the GCT was 45.7 (12.55) mm2. The mean (SD) depth of the abducens nerve was 14.3 (1.42) mm. The mean (SD) superoinferior distances from the foramen magnum to those points were 23.1 (7.39), 24.7 (8.25), 30.0 (9.56), and 32.6 (7.79) mm, respectively. The lower segment of the vertebrobasilar system was more superficial in the setting of a high-lying vertebrobasilar junction (VBJ) than a low-lying VBJ., Conclusion: We describe the GCT in an extended retrosigmoid approach for high-riding PICA aneurysms and evaluate the spatial relationship of the neurovascular structures within it. Two potential algorithms are offered for preoperative patient selection., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Skull base epidermoid tumors, meningiomas, and schwannomas can be accessed by different techniques depending on the location and size of the lesion. Small lesions located anterior to the internal acoustic meatus (IAM) can be accessed via the subtemporal approach, and lesions located posterior to the IAM can be approached via retrosigmoid craniotomy. However, expansive lesions that are located anterior to the IAM and extend posteriorly toward the lower clivus can be accessed via the petrosal approach. The petrosal approach (presigmoid-retrolabyrinthine) is centered on the petrous ridge of the temporal bone and is mainly performed for intradural lesions located at the clivus and petroclivus junction area. Patients with intact hearing can benefit from this technique, as the labyrinth is untouched and yet the middle and posterior fossa compartments are connected. Additionally, extension of the lesion from the suprasellar area/cavernous sinus to the foramen magnum can be dissected and removed. There are variations of the petrosal approach, such as translabyrinthine, transotic, and transchoclear, with which hearing cannot be preserved, and the "transcrusal" approach, wherein posterior and superior semicircular canals are sacrificed yet hearing preserved. The endolymphatic duct is usually transected and not reapproximated. Neurotology input is always helpful when dealing with inner ear structures. This complex approach demands exhaustive practice with temporal bone dissection in a cadaver laboratory. Although this approach can be extended anteriorly, combination with an anterior petrosal approach permits more rostral exposure. In this video, we demonstrate the stepwise dissection of the posterior petrosal approach only, showing procedure nuances in a cadaver.1-8Used with permission from Barrow Neurological Institute, Phoenix, Arizona., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Hypoglossal-facial anastomosis (HFA) is a popular facial reanimation technique. Mobilizing the intratemporal segment of the facial nerve and using the post-descendens hypoglossal nerve (ie, the segment distal to the take-off of descendens hypoglossi) have been proposed to improve results. However, no anatomic study has verified the feasibility of this technique., Objective: To assess the anatomic feasibility of HFA and the structural compatibility between the 2 nerves when the intratemporal facial and post-descendens hypoglossal nerves are used., Methods: The facial and hypoglossal nerves were exposed bilaterally in 10 sides of 5 cadaveric heads. The feasibility of a side-to-end (ie, partial end-to-end) HFA with partial sectioning of the post-descendens hypoglossal nerve and the mobilized intratemporal facial nerve was assessed. The axonal count and cross-sectional area of the facial and hypoglossal nerves at the point of anastomosis were assessed., Results: The HFA was feasible in all specimens with a mean (standard deviation) 9.3 (5.5) mm of extra length on the facial nerve. The axonal counts and cross-sectional areas of the hypoglossal and facial nerves matched well. Considering the reduction in the facial nerve cross-sectional area after paralysis, the post-descendens hypoglossal nerve can provide adequate axonal count and area to accommodate the facial nerve stump., Conclusion: Using the post-descendens hypoglossal nerve for side-to-end anastomosis with the mobilized intratemporal facial nerve is anatomically feasible and provides adequate axonal count for facial reanimation. When compared with use of the pre-descendens hypoglossal nerve, this technique preserves C1 fibers and has a potential to reduce glottic complications., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Surgical exposure of the V1 segment of the vertebral artery (V1-VA) at the lower neck may be necessary to address intravascular (atherosclerotic) and extravascular (external compression by neoplastic or degenerative) pathologies. The adjacent anatomy at the lower cervical region is complex and relatively unfamiliar to neurosurgeons compared to that of upper cervical levels. High-quality cadaveric images simulating the surgical approach to V1-VA are important for learning the relevant anatomy., Objective: To provide a brief stepwise depiction of the exposure of the V1-VA using a cadaveric surgical simulation., Methods: A cadaveric surgical simulation was performed on the left side to expose the V1-VA using the retrojugular and interjugular carotid approaches. The important adjacent anatomic structures en route to the V1-VA were identified., Results: A stepwise photographic demonstration of the surgical exposure of the V1-VA is provided., Conclusion: Exposure of the V1-VA can be challenging and requires a clear anatomic understanding of the relevant anatomy. The present work attempts to facilitate this objective., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Meningeal branches originating from intradural arteries may be involved in several diseases such as meningeal tumors and arteriovenous lesions. These "pial-dural" arterial connections have been described for anterior cerebral, posterior cerebral, and cerebellar arteries. However, to the best of our knowledge, meningeal supply originating from the arterial plexus over the dorsolateral aspect of the medulla oblongata (dorsolateral medullary plexus [DLMP]) has not been described., Objective: To define the microsurgical anatomy of the meningeal branch of DLMP., Methods: A total of 20 cadaver heads (40 sides) underwent far-lateral craniotomy and the cerebellomedullary cisterns were explored to find the DLMP and any meningeal branches. Additionally, de-identified intraoperative images of 85 patients with vertebral artery (VA)/posterior inferior cerebellar artery aneurysms who had undergone far-lateral craniotomy were studied to find any meningeal branches of DLMP., Results: The meningeal branches of DLMP were identified in 4 cadavers/sides. These branches reached the region of jugular tubercle (JT) after crossing the accessory nerve. In 3 specimens, these branches were joined by a small twig from V4-VA before penetrating the dura. DLMP meningeal branches were found in 12 patients of the studied cohort (14%) with similar anatomical features as those found in the cadaveric study., Conclusion: DLMP may give rise to meningeal branches to the adjacent dura of JT. The actual prevalence of this anatomic variation is difficult to estimate using our data. However, when present, these branches may have important clinical implications, ie, diseases such as dural arteriovenous fistulas, pial arteriovenous malformations (AVMs), and meningeal-based tumors., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: The V3 segment of the vertebral artery (V3-VA) is at risk during various approaches to the craniovertebral junction. Several landmarks have been defined to identify V3-VA, but these landmarks are not routinely exposed during a retrosigmoid (RS) approach, where musculocutaneous dissection inferiorly towards the foramen magnum can threaten this arterial segment., Objective: To find a landmark that will identify the V3-VA during the RS approach, and analyze the inferior nuchal line (INL) as this novel landmark., Methods: The anatomic relationships between the INL and the V3-VA were assessed in 7 cadaveric heads through RS exposure in the lateral position., Results: The INL is an L-shaped bony ridge with horizontal (medial) and vertical (lateral) arms, with the vertical arm being more conspicuous in all specimens (INLV). The mean depths of the V3-VA relative to the medial and lateral ends of the INLV were (mean ± standard deviation) 24.9 ± 7.1 mm, and 8.3 ± 3.2 mm, respectively. In all specimens, the V3-VA was located inferior and anterior to the INLV., Conclusion: The INL provides an important landmark during RS approach that can protect the V3-VA from inadvertent injury or identify it for use in an interpositional bypass. The INLV identifies the region of the suboccipital triangle where the V3-VA is embedded. INLV is routinely seen during the RS approach, making it more relevant than other classic landmarks such as the transverse process of C1, C1 posterior arch, and the atlantomastoid line that are not exposed during the RS approach., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Styloidogenic jugular venous compression syndrome (SJVCS) is a rare cause of idiopathic intracranial hypertension (IIH)., Objective: To elucidate the pathophysiology and the hemodynamics of SJVCS., Methods: We conducted a retrospective review of medical records, clinical images, dynamic venography, and manometry for consecutive patients with SJVCS undergoing microsurgical decompression from April 2009 to October 2017. Patients with IIH with normal venography and manometry findings served as controls., Results: Data were analyzed for 10 patients with SJVCS who presented with headaches. Neck flexion exacerbated headaches in 7 patients. Eleven patients with IIH provided control data for normal intracranial venous pressure and styloid process anatomy. Patients with SJVCS had bilateral osseous compression of venous outflow. The styloid processes were significantly longer in patients with SJVCS than in those with IIH (mean [standard deviation (SD)] distance, 31.0 [10.6] vs 19.0 [14.1] mm; P < .01). The styloid process-C1 lateral tubercle distance was shorter in patients with SJVCS than in those with IIH (mean [SD] distance, 2.9 [1.0] vs 9.9 [2.8] mm; P < .01). Patients with SJVCS had significantly higher global venous pressure and a higher pressure gradient across the stenosis site than controls (mean [SD] pressure, 2.86 [2.61] vs 0.13 [1.09] cm H2O; P = .09). All 10 patients with SJVCS experienced venous pressure elevation during contralateral neck turning (mean [SD] pressure, 4.29 [2.50] cm H2O). All 10 patients with SJVCS underwent transcervical microsurgical decompression, and 9 experienced postoperative improvement or resolution of symptoms. One patient had transient postoperative dysphagia and facial drooping, and another patient reported jaw numbness., Conclusion: SJVCS is a novel clinical entity causing IIH. Patients should be evaluated with dynamic venography with manometry. Surgical decompression with removal of osseous overgrowth is an effective treatment in select patients., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background and Importance: Although posterior petrosal approaches are utilized less frequently in many practices today, they continue to provide distinct surgical advantages in carefully selected cases. Here, we report a case of a recurrent cerebellopontine angle (CPA) hemangioblastoma that had failed a prior, more conservative, surgical approach. We provide cadaveric dissections of variations of posterior petrosal approaches to illustrate the advantages of the selected approach., Clinical Presentation: A 70-yr-old female presented with a growing left CPA hemangioblastoma. The lesion had undergone a prior subtotal resection from a retrosigmoid approach and subsequent adjuvant radiation treatment. The patient had worsening left facial strength, progressive balance difficulty, and absent left auditory function. Preoperative angiogram demonstrated arterial blood supply from the left anterior inferior cerebellar artery (AICA) that was deemed unsafe for embolization due to significant arteriovenous shunting. A posterior petrosal transotic approach was performed in order to optimize the working angle to the anterior brainstem and afford the ability to occlude the vascular supply from AICA prior to surgical resection of the lesion., Conclusion: The posterior petrosal transotic approach offers an improved surgical working angle to the anterior brainstem compared to the translabyrinthine approach. This advantage can be particularly important with vascular tumors that receive blood supply anteriorly, as in this case from AICA, and can improve the safety of the resection., (Copyright © 2019 by the Congress of Neurological Surgeons.)

The transcavernous approach (TcA) is an extension of the pterional approach that widens access to the central and lateral skull base regions. Through working between the nerves and vascular structures within the cavernous sinus, the TcA enables enhanced exposure of areas and structures including but not limited to the retrosellar area, Meckel's cave, and the basilar trunk. When the basilar apex and retrosellar regions are targeted, the TcA offers a valuable solution to the problem of the restricted space between the neurovascular structures of the central skull base through opening and widening the 2 major triangles of the cavernous sinus roof: the clinoidal and oculomotor triangles. Mastery of this approach requires careful review of the anatomy and much time spent in the cadaver lab. Although many quantitative studies and illustrative papers exist on the technical nuances of the TcA to the basilar apex region, the TcA is still difficult to understand, learn, and undertake. This cadaveric surgical simulation attempts to facilitate this objective. Of note, we have demonstrated and discussed the specific variant of the TcA that aims to reach the basilar apex area, and this video does not include the full TcA that also involves complete exposure of the lateral aspect of the cavernous sinus and the Meckel's cave., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Posterior column osteotomy (PCO) is a powerful technique for correcting lordosis, but the surgical literature lacks objective evidence on preoperative predictors of achievable lordotic correction following PCO., Objective: To measure the correlation between disc geometry and achievable lordotic correction following Schwab grade 2 osteotomies and to describe geometric changes to disc space following lordotic correction., Methods: Schwab grade 2 osteotomies were performed from T1 to S1 in 5 cadavers. Lateral radiographs were taken before and after posterior column compression. Anterior disc height (ADH), middle disc height (MDH), posterior disc height (PDH), and lordotic angles were measured. The association between disc height and lordotic correction was analyzed using linear regression., Results: For all spinal levels (n = 79), PDH was most strongly correlated with lordotic correction (r = 0.72, P < .001). Regional subset analyses showed the strongest correlation between PDH and lordotic correction achievable within the lumbar spine (n = 22, r = 0.77, P < .001), followed by ADH for lower thoracic spine (n = 29, r = 0.65, P < .001) and PDH for upper thoracic spine (n = 28, r = 0.61, P = .001). Postcorrection analysis of disc heights revealed that as lordotic correction increases, the PDH decreases, and the ADH expands., Conclusion: PDH is a strong predictor of achievable lordotic correction following Schwab grade 2 osteotomies and compression of an intact disc space. In the lumbar spine, 50% of lordotic change is predictable using PDH alone. Further testing of our linear regression equation is planned for prospective clinical studies, and further testing of postcorrection disc space geometry is planned for future biomechanical and surgical technique studies., (Copyright © 2018 by the Congress of Neurological Surgeons.)

The external carotid artery (ECA) is a robust extracranial donor used for high-flow cerebrovascular bypass procedures. It is usually exposed through the anterior triangle of the neck and may be used to revascularize recipients in the anterior or upper posterior cerebral circulations. However, when a high-flow bypass to the posterior circulation is indicated, oftentimes the patient needs to be put in the prone position (or variants thereof). In such situations, accessing the ECA through the anterior triangle of the neck can be challenging. Therefore, using a technique that enables the surgeon to expose the ECA through a posterior approach could be helpful.1 Although we have not yet encountered a case requiring this type of exposure and bypass, this cadaveric surgical simulation video demonstrates the surgical technique of exposing the ECA through the posterior triangle of the neck (as a cadaveric video, no patient consent was necessary). Briefly, this technique involves an inferolateral extension of the muscular stage of the far-lateral approach and exposing the ECA through a plane developed between the parotid gland and the posterior belly of the digastric muscle. The technical details of this technique are described. Also, relevant anatomic information regarding the safety measures taken to protect adjacent neurovascular structures are discussed., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: Intracranial-intracranial and extracranial-intracranial bypass options for revascularization of deep cerebral recipients are limited and technically demanding., Objective: To assess the anatomical feasibility of using the temporopolar artery (TPA) for revascularization of the anterior cerebral artery (ACA), posterior cerebral artery (PCA), and superior cerebellar arteries (SCA)., Methods: Orbitozygomatic craniotomy was performed bilaterally on 8 cadaveric heads. The cisternal segment of the TPA was dissected. The TPA was cut at M3-M4 junction with its proximal and distal calibers and the length of the cisternal segment measured. Feasibility of the TPA-A1-ACA, TPA-A2-ACA, TPA-SCA, and TPA-PCA bypasses were assessed., Results: A total of 17 TPAs were identified in 16 specimens. The average distal TPA caliber was 1.0 ± 0.2 mm, and the average cisternal length was 37.5 ± 9.4 mm. TPA caliber was ≥ 1.0 mm in 12 specimens (70%). The TPA-A1-ACA bypass was feasible in all specimens, whereas the TPA reached the A2-ACA, SCA, and PCA in 94% of specimens (16/17). At the point of anastomosis, the average recipient caliber was 2.5 ± 0.5 mm for A1-ACA, and 2.3 ± 0.7 mm for A2-ACA. The calibers of the SCA and PCA at the anastomosis points were 2.0 ± 0.6 mm, and 2.7 ± 0.8 mm, respectively., Conclusion: The TPA-ACA, TPA-PCA, and TPA-SCA bypasses are anatomically feasible and may be used when the distal caliber of the TPA stump is optimal to provide adequate blood flow. This study lays foundations for clinical use of the TPA for ACA revascularization in well-selected cases., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: The side-to-side anastomosis is one of the difficult bypass configurations that may be used in various complex cerebral vascular and neoplastic cases. Few pure arterial models exist for practicing this bypass subtype., Objective: To provide an optimized side-to-side anastomosis training model using rat common carotid arteries (CCA)., Methods: Bilateral CCAs were exposed in the neck of 10 anesthetized Sprague-Dawley rats. The arteries were juxtaposed in parallel, using temporary aneurysm clips applied proximally and distally. CCA caliber and the length of CCA juxtaposition were measured. Side-to-side anastomosis was completed and ischemia time was recorded. Unintended complications were recorded for further analysis., Results: Anastomosis was completed successfully in all animals. The CCAs were approximated in all animals without any difficulty or undue tension. In 2 rats, death occurred prior to completion of anastomosis, which was attributed to injury to the external jugular vein during vessel exposure. Mean ischemia time was 35 min with an average of 22 sutures done to complete the anastomosis. The average CCA caliber was 1.1 ± 0.2 mm and the arteries could be juxtaposed for an average length of 10.2 ± 1.5 mm., Conclusion: Full exposure of the cervical segment of the CCAs enables tension-free approximation of adequate length of the vessel for a side-to-side anastomosis. Avoiding complications during exposure helps in prevention of animal death during the ischemia period., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: Arthrodesis is critical for achieving favorable outcomes in reconstructive spine surgery. Vascularized bone grafts (VBGs) have been successfully used to augment fusion rates in a variety of skeletal pathologies, and pedicled VBG has numerous advantages over free transfer VBG. Pedicled VBG has not previously been described for the posterior occipitocervicothoracic spine., Objective: To identify, describe, and assess potential donor sites for pedicled VBGs from occiput to T12 using a cadaver model and to describe important technical considerations for graft harvest and placement., Methods: A multidisciplinary team of plastic surgeons and neurosurgeons hypothesized that it is feasible to rotate a pedicled VBG from the occiput to T12 via a posterior approach. In 6 cadavers, 3 VBG donor sites were identified as anatomically feasible: occiput, scapula, and rib., Results: Split- and full-thickness occipital VBGs were mobilized on a semispinalis pedicle. Occipital VBGs could be mobilized from occiput to T1 and span up to 4 levels. Scapular VBGs were mobilized on a subscapular pedicle and could be mobilized from occiput to T7 and span up to 8 levels. Rib VBGs were mobilized on subcostal pedicles and could be mobilized from C6 to T12. Ribs T2 to T4 and T11 and T12 could cover 2 levels, and ribs T5 to T10 could cover 3 levels. The first rib was anatomically unsuitable as a VBG due to its primarily ventral course., Conclusion: Pedicled VBGs can feasibly be applied to posterior spinal arthrodesis from occiput to T12. Patients at high risk for nonunion may benefit from this strategy.

Background: The far-lateral transcondylar surgical approach is often used to clip vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms. The role of condyle resection during this approach is controversial., Objective: To evaluate patient outcomes in patients with VA-PICA aneurysms in whom drilling the occipital condyle was not necessary., Methods: Between May 2005 and December 2012, a total of 56 consecutive patients with incidental or ruptured VA-PICA aneurysms underwent surgery with a far-lateral approach without condylar resection. Clinical presentation, surgical reports, presurgery and postsurgery radiological examinations, and clinical follow-up reports were assessed. Anatomic aneurysm location was analyzed through angiography or computed tomography angiography. We compared postsurgical Glasgow Outcome Scale scores, modified Rankin Scale scores, and morbidity in 2 groups: those with aneurysms in the anterior medullary segment and those with aneurysms in the lateral medullary segment., Results: The predominant presentation was subarachnoid hemorrhage in 34 patients (60.7%). Most aneurysms (n = 27 [48.2%]) were located in the lateral medullary segment of the PICA, followed by the anterior medullary segment (n = 25 [44.6%]). Total aneurysm occlusion was achieved in 100% of patients, and bypass techniques were necessary in 3 patients (5.4%). Fifty-two patients (92.8%) had Glasgow Outcome Scale scores of 4 or 5 postsurgery., Conclusions: A far-lateral approach that leaves the occipital condyle intact is adequate for treating most patients with VA-PICA aneurysms., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: Carotid endarterectomy (CEA) is a common, well-developed surgical procedure. Although surgical simulation is gaining in importance for residency training, CEA practice opportunities for surgical residents are limited., Objective: To describe a new haptic CEA model., Methods: Six bovine placentas were used to create the model. Each placenta provided about 6 large arterial and venous bifurcations. In total, 36 large-vessel bifurcations were dissected and prepared for the CEA simulation. Bovine placenta vessels were arranged to simulate the common carotid artery (CCA), internal carotid artery (ICA), and external carotid artery (ECA). The diameters and wall thicknesses were measured and compared with human CCA, ICA, and ECA parameters., Results: All bovine placentas provided vessels suitable for modeling carotid artery bifurcations and CEA training. Mean ± SD diameters of simulated CCAs, ECAs, and ICAs were 11.2 ± 1.8, 4.3 ± 0.5, and 9.8 ± 3.0 mm, respectively, from nondilated veins and 8.7 ± 1.4, 4.4 ± 1.3, and 7.2 ± 1.7 mm, respectively, from nondilated arteries. Mean vessel wall thicknesses were 2.0 ± 0.6 mm for arteries and 1.4 ± 0.5 mm for veins. Placental vessel tissue had dimensions and handling characteristics similar to those of human carotid arteries. The CEA procedure and its subtasks, including vessel-tissue preparation and surgical skills performance, could be reproduced with high fidelity., Conclusion: A bovine placenta training model for CEA is inexpensive and readily available and closely resembles human carotid arteries. The model can provide a convenient and valuable simulation and practice addition for vascular surgery training.

Background: Acute spinal cord injury (SCI) is commonly treated by elevating the mean arterial pressure (MAP). Other potential interventions include cerebrospinal fluid drainage (CSFD)., Objective: To determine the efficacy of aggressive MAP elevation combined with intrathecal pressure (ITP) reduction; our primary objective was to improve spinal cord blood flow (SCBF) after SCI., Methods: All 15 pigs underwent laminectomy. Study groups included control (n = 3); SCI only (n = 3); SCI combined with MAP elevation (SCI + MAP) (n = 3); SCI combined with CSFD (SCI + CSFD) (n = 3); and SCI combined with both MAP elevation and CSFD (SCI + MAP + CSFD) (n = 3). SCBF was measured with laser Doppler flowmetry., Results: In the SCI group, SCBF decreased by 56% after SCI. MAP elevation after SCI resulted in a 34% decrease in SCBF, whereas CSFD resulted in a 59% decrease in SCBF. The combination of CSFD and MAP elevation resulted in a 24% increase in SCBF. The SCI + MAP group had an average ITP increase of 5.45 mm Hg after MAP elevation 1 hour after SCI and remained at that level throughout the experiment., Conclusion: Both MAP elevation alone and CSFD alone led to only short-term improvement of SCBF. The combination of MAP elevation and CSFD significantly and sustainably improved SCBF and spinal cord perfusion pressure. Although laser Doppler flowmetry can provide flow measurements to a tissue depth of only 1.5 mm, these results may represent pattern of blood flow changes in the entire spinal cord after injury.

Background: Microscopic and endoscopic transsphenoidal approaches to the sellar are well established. Surgical freedom is an important skull base principle that can be measured objectively and used to compare approaches., Objective: To compare the surgical freedom of 4 transsphenoidal approaches to the sella turcica to aid in surgical approach selection., Methods: Four transsphenoidal approaches to the sella were performed on 8 silicon-injected cadaveric heads. Surgical freedom was determined with stereotactic image guidance using previously established techniques. The results are presented as the area of surgical freedom and angular surgical freedom (angle of attack) in the axial and sagittal planes., Results: Mean total exposed area surgical freedom for the microscopic sublabial, endoscopic binostril, endoscopic uninostril, and microscopic endonasal approaches were 102 ± 13, 89 ± 6, 81 ± 4, and 69 ± 10 cm2, respectively. The endoscopic binostril approach had the greatest surgical freedom at the pituitary gland and ipsilateral and contralateral internal carotid arteries (25.7 ± 5.4, 28.0 ± 4.0, and 23.0 ± 3.0 cm2) compared with the microscopic sublabial (21.8 ± 3.5, 21.3 ± 2.4, and 19.5 ± 6.3 cm2), microscopic endonasal (14.2 ± 2.7, 14.1 ± 3.2, and 16.3 ± 4.0 cm2), and endoscopic uninostril (19.7 ± 4.8, 22.4 ± 2.3, and 19.5 ± 2.9 cm2) approaches. Axial angle of attack was greatest for the microscopic sublabial approach to the same targets (14.7 ± 1.3°, 11.0 ± 1.5°, and 11.8 ± 1.1°). For the sagittal angle of attack, the endoscopic binostril approach was superior for all 3 targets (16.6 ± 1.7°, 17.2 ± 0.70°, and 15.5 ± 1.2°)., Conclusion: Microscopic sublabial and endoscopic binostril approaches provided superior surgical freedom compared with the endonasal microscopic and uninostril endoscopic approaches. This work provides objective baseline values for the quantification and evaluation of future refinements in surgical technique or instrumentation.

Background: The management of basilar apex (BX) aneurysms remains problematic., Objective: We quantified the surgical exposure of the BX through the opticocarotid window (OCW) and the carotid-oculomotor window (COW), before and after mobilization of the internal carotid artery and division of the posterior communicating artery (PCoA)., Methods: Eleven silicone-injected cadaveric heads were dissected bilaterally. The surgical dissection was divided into 4 major steps: (1) supraorbital modified orbitozygomatic craniotomy, (2) mobilization of the internal carotid artery after drilling out the anterior clinoid process intradurally and cutting the distal dural ring, (3) drilling out the posterior clinoid process and dorsum sellae, and (4) dividing the PCoA from the posterior third portion of the vessel. A frameless navigation system was used to quantify the surgical exposure area of the BX through the OCW and COW., Results: The total surgical area increased significantly from steps 1 to 4 (P < .001) in both OCW and COW groups. Overall, there was a larger total surgical area obtained in the COW compared with the OCW (P = .010). ICA mobilization increased the surgical area for temporary (P < .001) and permanent (P < .003) clip application in both windows. The division of PCoA significantly increased the overall surgical area for permanent clip application (P < .003). Compared with the OCW, the COW had a significantly increased change in the area for permanent clip application in the low-lying group (P = .03)., Conclusion: When approaching the BX via the pterion route, the appropriate surgical step and window should be selected according to characteristics of the PCoA and height of the BX.

Background: Neurosurgery, a demanding specialty, involves many microsurgical procedures that require complex skills, including open surgical treatment of intracranial aneurysms. Simulation or practice models may be useful for acquiring these skills before trainees perform surgery on human patients., Objective: To describe a human placenta model for the creation and clipping of aneurysms., Methods: Placental vessels from 40 human placentas that were dimensionally comparable to the sizes of appropriate cerebral vessels were isolated to create aneurysms of different shapes. The placentas were then prepared for vascular microsurgery exercises. Sylvian fissure--like dissection technique and clipping of large- and small-necked aneurysms were practiced on human placentas with and without pulsatile flow. A surgical field designed to resemble a real craniotomy was reproduced in the model., Results: The human placenta has a plethora of vessels that are of the proper dimensions to allow the creation of aneurysms with dome and neck dimensions similar to those of human saccular and fusiform cerebral aneurysms. These anatomic scenarios allowed aneurysm inspection, manipulation, and clipping practice. Technical microsurgical procedures include simulation of sylvian fissure dissection, unruptured aneurysm clipping, ruptured aneurysm clipping, and wrapping; all were reproduced with high fidelity to the haptics of live human surgery. Skill-training exercises realistically reproduced aneurysm clipping., Conclusion: Human placenta provides an inexpensive, widely available, convenient biological tissue that can be used to create models of cerebral aneurysms of different morphologies. Neurosurgical trainees may benefit from the preoperative use of a realistic model to gain familiarity and practice with critical surgical techniques for treating aneurysms.

Background: One challenge when performing endoscopic endonasal approaches is the surgical conflict that occurs between the surgical instruments and endoscope in the crowded nasal corridor. This conflict decreases surgical freedom, increases surgeon frustration, and lengthens the learning curve for trainees., Objective: To evaluate the impact a malleable endoscope has on surgical freedom for endoscopic approaches to the parasellar region., Methods: Uninostril and binostril endoscopic transsphenoidal approaches to the pituitary gland and cavernous carotid arteries were performed on 8 silicon-injected, formalin-fixed cadaveric heads using both rigid and flexible 3-dimensional endoscopes. Surgical freedom to targets in the parasellar region was assessed using an established technique based on image guidance. Results are presented as 3 measurements: area of surgical freedom for a point target, area for the surgical field (cavernous carotids and sella), and angular surgical freedom (angle of attack)., Results: Point target surgical freedom, exposed area surgical freedom, and angle of attack were all significantly greater in approaches using the malleable endoscope compared with the rigid endoscope (P values .06 to <.001), with values varying between 17% and 28%. The improved surgical freedom noted with the malleable endoscope was due to the minimization of instrument-endoscope conflict at the back end (camera) and front end (tip) of the endoscope., Conclusion: This study demonstrates that application of a malleable endoscope to transsphenoidal approaches to the parasellar region decreases instrument-endoscope conflict and improves surgical freedom.

Background: Cranial nerve injury (CNI) is the most common neurological complication associated with carotid endarterectomy (CEA). Some authors postulate that the transverse skin incision leads to increased risk of CNI., Objective: We compared the incidence of CNI associated with the transverse and longitudinal skin incisions in a high-volume cerebrovascular center., Methods: We reviewed the charts of 226 consecutive patients who underwent CEAs between January 2007 and August 2009. Pre- and postoperative standardized neurological evaluations were performed by faculty neurologists and neurosurgeons., Results: One hundred sixty nine of 226 (75%) CEAs were performed with the use of a transverse incision. The longitudinal incision was generally reserved for patients with a high-riding carotid bifurcation. Mean patient age was 69 years (range, 45-91 years); 62% were men; 59% of patients were symptomatic and had high-grade stenosis (70%-99%). CNI occurred in 8 cases (3.5%): 5 (3%) in transverse and 3 (5.3%) with longitudinal incisions (P = .42). There were 2 marginal mandibular nerve injuries, 1 (0.6%) transverse and 1 longitudinal; 5 recurrent laryngeal nerve injuries, 4 transverse and 1 longitudinal; and 1 case of hypoglossal nerve injury associated with longitudinal incision. One hematoma was associated with CNI. All injuries were transient. Fourteen wound hematomas required surgical evacuation., Conclusion: The transverse skin incision for CEAs is not associated with an increased risk of CNI (P =.42). In this study, the incidence of CNI associated with the transverse incision was 3% (n = 5) vs 5% (n = 3) for longitudinal incisions. All CNIs were temporary.

Background: The proximal superior cerebellar artery (pSCA) is often considered a perforator-free area. Precise anatomical knowledge of this region clarifies the pathophysiology underlying posterior fossa ischemic syndromes and helps avoid treatment-related complications., Objective: To anatomically evaluate perforating branches arising from the pSCA and the upper basilar artery (BA)., Methods: Forty-four SCAs from 20 cadaveric heads were examined to determine patterns of the pSCA; its morphometry for medial and lateral branches; and frequency, number, diameter, distribution, and vascular territory of perforators arising from the pSCA and rostral BA., Results: SCA arose as a single trunk in 36 sides (90%): mean diameter at origin was 1.38 mm; mean length was 14.4 ± 7.9 mm. Ninety-nine pSCA perforator branches were present in 82% of specimens (mean, 2.3 ± 1.6; range, 0-7 perforators/side). Of these, 59% were direct, belonging to the interpeduncular group in 85% of cases; 28% were short circumflex, belonging to lateral and medial pontine group; and 13% were long circumflex, reaching the medullary perforation zone (basal cerebellar group). Median distance to the first perforator was 2.0 mm (range, 0.1-15 mm). There were 132 perforator branches in the last centimeter of the BA., Conclusion: The pSCA should not be regarded as a perforator-free area. Although the pSCA territories likely overlap with the posterior cerebral artery, BA, and anterior inferior cerebellar artery, the pSCA segment cannot be surgically manipulated with impunity.

During the 1930s, white matter tracts began to assume relevance for neurosurgery, especially after Cajal's work. In many reviews of white matter neurobiology, the seminal contributions of Josef Klingler (1888-1963) and their neurological applications have been overlooked. In 1934 at the University of Basel under Eugen Ludwig, Klingler developed a new method of dissection based on a freezing technique for brain tissue that eloquently revealed the white matter tracts. Klingler worked with anatomists, surgeons, and other scientists, and his models and dissections of white matter tracts remain arguably the most elegant ever created. He stressed 3-dimensional anatomic relationships and laid the foundation for defining mesial temporal, limbic, insular, and thalamic fiber and functional relationships and contributed to the potential of stereotactic neurosurgery. Around 1947, Klingler was part of a Swiss-German group that independently performed the first stereotactic thalamotomies, basing their targeting and logic on Klingler's white matter studies, describing various applications of stereotaxy and showing Klingler's work integrated into a craniocerebral topographic system for targeting with external localization of eloquent brain structures and stimulation of deep thalamic nuclei. Klingler's work has received renewed interest because it is applicable for correlating the results of the fiber-mapping paradigms from diffusion tensor imaging to actual anatomic evidence. Although others have described white matter tracts, none have had as much practical impact on neuroscience as Klinger's work. More importantly, Josef Klingler was an encouraging mentor, influencing neurosurgeons, neuroscientists, and brain imaging for more than three quarters of a century.

Background: The ability to diagnose brain tumors intraoperatively and identify tumor margins during resection could maximize resection and minimize morbidity. Advances in optical imaging enabled production of a handheld intraoperative confocal microscope., Objective: To present a feasibility analysis of the intraoperative confocal microscope for brain tumor resection., Methods: Thirty-three patients with brain tumor treated at Barrow Neurological Institute were examined. All patients received an intravenous bolus of sodium fluorescein before confocal imaging with the Optiscan FIVE 1 system probe. Optical biopsies were obtained within each tumor and along the tumor-brain interfaces. Corresponding pathologic specimens were then excised and processed. These data was compared by a neuropathologist to identify the concordance for tumor histology, grade, and margins., Results: Thirty-one of 33 lesions were tumors (93.9%) and 2 cases were identified as radiation necrosis (6.1%). Of the former, 25 (80.6%) were intra-axial and 6 (19.4%) were extra-axial. Intra-axial tumors were most commonly gliomas and metastases, while all extra-axial tumors were meningiomas. Among high-grade gliomas, vascular neoproliferation, as well as tumor margins, were identifiable using confocal imaging. Meningothelial and fibrous meningiomas were distinct on confocal microscopy--the latter featured spindle-shaped cells distinguishable from adjacent parenchyma. Other tumor histologies correlated well with standard neuropathology tissue preparations., Conclusion: Intraoperative confocal microscopy is a practicable technology for the resection of human brain tumors. Preliminary analysis demonstrates reliability for a variety of lesions in identifying tumor cells and the tumor-brain interface. Further refinement of this technology depends upon the approval of tumor-specific fluorescent contrast agents for human use.

Background: Sonic hedgehog (Shh) is a glycoprotein molecule that upregulates the transcription factor gli-1 and plays a critical role in the proliferation of endogenous neural precursor cells when directly injected into adult rodent spinal cords after injury., Objective: To use small-molecule agonists of the hedgehog pathway in an attempt to replicate these findings with intravenous administration., Methods: Forty Sprague-Dawley rats were randomly divided into 4 groups. Saline treatment control groups were divided into a contusion injury group and a noninjury sham group; Shh agonist treatment groups were divided into an injury group and a noninjury sham group. Shh agonist Ag11.1 was administered to the treatment groups and saline to the control groups. Injections were performed on days 1 and 4 after surgery. On day 14, 1 group was sacrificed, and injured spinal cord portions were removed for explant cultures. After 7 days in culture, specimens were fixed for immunostaining neural precursor cells, and cell counts were taken., Results: Histological analysis demonstrated cystic cavitary lesions with a rim of white-matter sparing in all specimens. In animals treated with hedgehog agonist for a contusion injury, a significant increase in the number of nestin- and musashi-1-positive neural precursor cells at the rim of the cavity was noted., Conclusion: There was a significant increase in the number of O4-positive oligodendrocyte precursors compared with uninjured controls and BrdU-positive cells, reproducing the findings of previous studies using direct Shh protein injection, which demonstrated spared white matter and increased recovery.

In a family of 7 siblings in Rio de Janeiro, Brazil, 2 of the most remarkable national personalities decided to follow different fields at the beginning of the 20th century. Their life's work would, however, intersect in at least 2 respects: the quest for innovation and a passion for sinuosity. The achievements of Paulo and Oscar Niemeyer are landmarks in the history of neurosurgery and architecture in Brazil. Among his many innovations in neurosurgery, Paulo Niemeyer first described the transventricular amygdalohippocampectomy in 1957 and introduced the operating microscope to neurosurgery in Brazil in 1971. His brother Oscar became a world-renowned representative of the modern architecture movement, sculpting graceful curves from concrete.

Background: Treating deep-seated cerebral lesions often requires retracting the brain. Retraction, however, causes clinically significant postoperative neurological deficits in 3% to 9% of intracranial cases., Objective: This pilot study used automated analysis of postoperative magnetic resonance images (MRIs) to determine whether brain retraction caused local anatomic changes to the cerebral neocortex and whether such changes represented sensitive markers for detecting brain retraction injury., Methods: Pre- and postoperative maps of whole-brain cortical thickness were generated from 3-dimensional MRIs of 6 patients who underwent selective amygdalohippocampectomy for temporal lobe epilepsy (5 left hemispheres, 1 right hemisphere). Mean cortical thickness was determined in the inferior temporal gyrus (ITG test), where a retractor was placed during surgery, and in 2 control gyri-the posterior portion of the inferior temporal gyrus (ITG control) and motor cortex control. Regions of cortical thinning were also compared with signs of retraction injury on early postoperative MRIs., Results: Postoperative maps of cortical thickness showed thinning in the inferior temporal gyrus where the retractor was placed in 5 patients. Postoperatively, mean cortical thickness declined from 4.1 +/- 0.4 mm to 2.9 +/- 0.9 mm in ITG test (P = .03) and was unchanged in the control regions. Anatomically, the region of neocortical thinning correlated with postoperative edema on MRIs obtained within 48 hours of surgery., Conclusion: Postoperative MRIs can be successfully interrogated for information on cortical thickness. Brain retraction is associated with chronic local thinning of the neocortex. This automated technique may be sensitive enough to detect regions at risk for functional impairment during craniotomy that cannot be easily detected on postoperative structural imaging.

Background: An alternative route must be used for atlantoaxial arthrodesis to avoid the risks of transoral route or when posterior approaches are contraindicated., Objective: To assess relevant quantitative anatomic parameters for C1-C2 anterolateral transarticular fixation and to demonstrate the nuances of an anterolateral approach to the upper cervical spine., Methods: Five cadaveric necks were dissected bilaterally to demonstrate anatomic landmarks and surgical technique. The C2 pars interarticularis was used as the entry for inserting screws toward the C1 lateral mass. Ten computed tomography scans were analyzed to quantify working area and optimal angles of approach., Results: The medial surface of sternocleidomastoid muscle was dissected extensively but not divided. The C2 transverse process was a landmark for guiding dissection posterior to the carotid sheath. In all specimens, the gray ramus communicans from the superior cervical ganglion to the C2 nerve was a landmark for locating the C2 pars. Slightly below that branch, the longus capitis muscle could be displaced medially to reach the C2 pars. The ideal angles for screw placement were 22.9 +/- 5.7 degrees medial to the sagittal plane and 25.3 +/- 7.4 degrees posterior to the coronal plane. The mean working area was 71.2 mm (range, 49-103 mm)., Conclusion: We propose a new anterolateral stabilization technique for atlantoaxial instability based on less traumatic dissection of the upper cervical region, different instrumentation, and guidance by reliable landmarks. For anterolateral transarticular C1-C2 screw fixation, the gray ramus communicans to the C2 nerve is a reliable landmark for locating the entry for a screw on the C2 pars.

Background: The rationale for choosing between the condylar fossa and transcondylar variations of the far-lateral approach requires understanding of the relationships between the occipital condyle, jugular tubercle, and hypoglossal canal., Objective: We examined the anatomic relationship of these 3 structures and analyzed the effect that changes in these relationships have on the surgical exposure and angle of attack for these 2 approaches., Methods: Anatomic measurements of 5 cadaveric heads from 3-dimensional computed tomographic scans were compared with direct measurements of the same specimens. The condylar fossa and transcondylar approach were performed sequentially in 8 of 10 sides. Surgical exposure and angle of attack were measured after each exposure., Results: The jugular tubercle (JT) angle (JTA) measures the angle formed by reference points on the condyle, hypoglossal canal, and JT. When the JT and occipital condyle are not prominent (JTA > 180 degrees ), the transcondylar approach does not significantly increase petroclival or brainstem exposure compared with the condylar fossa approach; however, it does significantly increase the angle of attack to the junction of the posterior inferior cerebellar and vertebral arteries and the surgical angle for the medial part of the JT (P < .05)., Conclusion: The condylar fossa and transcondylar approaches provide similar exposures of the petroclivus and brainstem when the JT and occipital condyle are not prominent (JTA > 180 degrees on 3-dimensional computed tomographic). However, for lesions below the hypoglossal canal, the transcondylar approach is preferred because it significantly increases the angle of attack.

Background: The transciliary supraorbital approach (TCSO) provides an anterior view for visualizing sellar, parasellar, and suprasellar structures. Whether an orbital osteotomy adds to this exposure has not been quantified., Objective: We quantitatively evaluated the TCSO and benefits of an additional orbital osteotomy for exposing common sites of anterior circulation aneurysms., Methods: Under image guidance, TCSO and orbital osteotomy were performed on 10 sides of 5 cadaver heads to quantify exposures of 4 surgical targets: (1) the junction of the anterior cerebral and anterior communicating arteries (ACoA); (2) the internal carotid artery (ICA) at the level of the posterior communicating artery (PCoA); (3) the bifurcation of the ICA; and (4) the middle cerebral artery (MCA) bifurcation. Horizontal and vertical angles of attack and surgical freedom for instrument manipulation were measured before and after the orbital rim and roof were removed., Results: An orbital osteotomy significantly increased surgical freedom to the ACoA (from 471.15 +/- 182.14 mm2 to 683.35 +/- 283.78 mm2, P = .021); PCoA (from 746.58 +/- 242.78 mm2 to 966.23 +/- 360.22 mm2, P = .007); ICA bifurcation (from 616.08 +/- 310.95 mm2 to 922.38 +/- 374.88 mm2, P = .002); and MCA bifurcation (from 1160.77 +/- 412.03 mm2 to 1597.71 +/- 733.18 mm2, P = .004). There were no significant differences in horizontal angles of attack. The vertical angles of attack were significantly greater after orbital osteotomy, principally with the ACoA and ICA bifurcation as targets., Conclusion: TCSO combined with orbital osteotomy improves exposure. Removing the orbital rim and roof increases the area for instrument use and improves the vertical angle of attack to common sites in the anterior circulation involving aneurysms.

Background: We compared the transsylvian transchoroidal (TSTC) approach with the lateral transtemporal (LTT) approach. Both approaches proceed through the choroidal fissure but through different incisions and along different trajectories., Methods: Four fixed, silicon-injected heads (8 sides) were used. Nine strategic anatomic points within the dissections were compared between the TSTC and LTT approaches in 7 other silicon-injected heads (14 sides). Neuronavigation was used to gather coordinates from selected points of both approaches to calculate surgical angles and distances to common targets., Results: The surgical angle of the TSTC approach for the inferior choroidal point was wider compared with the LTT approach (P < .05). The surgical angles for the P2a-P2p point were similar for both approaches. In the TSTC approach, the P2-P3 point angle was smaller than in the LTT approach (P < .05). The TSTC approach provided (except for the P2-P3 point) significantly shorter distances to all defined anatomic targets compared with the LTT approach. When the posterior cerebral artery was the target in the TSTC approach, the hippocampus was retracted 3 to 8 mm compared with 8 to 13 mm in the LTT approach., Conclusion: We quantitatively described anatomic features of the TSTC approach and compared them with the LTT approach. For approaching the mesial temporal region, the TSTC approach offers an adequate surgical angle and shorter or similar distances proximal to P2-P3 and requires less temporal lobe and hippocampal retraction than the LTT approach. Such information can help surgeons select the optimal approach to the mesial temporal lobe and its surrounding structures. The TSTC approach should be considered for lesions located in the medial temporal region.

Objective: The aim of this study was to describe quantitatively the properties of the posterolateral approaches and their combination., Methods: Six silicone-injected cadaveric heads were dissected bilaterally. Quantitative data were generated with the Optotrak 3020 system (Northern Digital, Waterloo, Canada) and Surgiscope (Elekta Instruments, Inc., Atlanta, GA), including key anatomic points on the skull base and brainstem. All parameters were measured after the basic retrosigmoid craniectomy and then after combination with a basic far-lateral extension. The clinical results of 20 patients who underwent a combined retrosigmoid and far-lateral approach were reviewed., Results: The change in accessibility to the lower clivus was greatest after the far-lateral extension (mean change, 43.62 +/- 10.98 mm2; P = .001). Accessibility to the constant landmarks, Meckel's cave, internal auditory meatus, and jugular foramen did not change significantly between the 2 approaches (P > .05). The greatest change in accessibility to soft tissue between the 2 approaches was to the lower brainstem (mean change, 33.88 +/- 5.25 mm2; P = .0001). Total removal was achieved in 75% of the cases. The average postoperative Glasgow Outcome Scale score of patients who underwent the combined retrosigmoid and far-lateral approach improved significantly, compared with the preoperative scores., Conclusion: The combination of the far-lateral and simple retrosigmoid approaches significantly increases the petroclival working area and access to the cranial nerves. However, risk of injury to neurovascular structures and time needed to extend the craniotomy must be weighed against the increased working area and angles of attack.

Objective: We introduce a technique for performing a selective amygdalohippocampectomy (AH) through a minisupraorbital approach., Methods: A minisupraorbital craniotomy and an anterior selective AH were performed in 8 cadaver heads (16 sides). The anatomic specimens were analyzed, and the extent of resection of the hippocampus and amygdala was evaluated. Surgically relevant measurements were performed using anatomic specimens. An image-guided system was used to document the extent of the anterior AH. Laboratory data were used to support the clinical application of the technique., Results: The anterior route allowed removal of the amygdala and hippocampus, as confirmed by anatomic assessment. The image-guided system and anatomic evaluation confirmed that the amygdala and hippocampus can be accessed and removed through this route. The mean distance between the anterior aspect of the uncus and the tip of the temporal horn was 17.0 +/- 4.6 mm; the mean distance from the head of the hippocampus to the posterior border of the cerebral peduncles was 26.0 +/- 3.2 mm. Clinical application resulted in satisfactory removal of the amygdala and hippocampus., Conclusion: The anterior route for selective AH is a logical and straightforward approach to the mesial temporal lobe. Compared with other variations, it is less invasive and destructive, especially in terms of the fibers of the optic pathway, temporal stem, and lateral temporal neocortex.

Objective: To compare the effectiveness of the telovelar approach with tonsillar manipulation for approaching the recesses of the fourth ventricle., Methods: A telovelar approach was performed in 8 injected cadaveric heads. Areas of exposure were measured for the superolateral and lateral recesses. Horizontal angles were evaluated by targeting the cerebral aqueduct and medial margin of the lateral recess. Quantitative comparisons were made between the telovelar dissections and various tonsillar manipulations., Results: Tonsillar retraction provided a comparable exposure of the superolateral recess with tonsillar resection (26.4 +/- 17.6 vs 25.2 +/- 12.5 mm2, respectively; P = .825). Tonsillar resection significantly increased exposure of the lateral recess compared with tonsillar retraction (31.1 +/- 13.3 vs 20.2 +/- 11.5 mm2, respectively; P = .002). Compared with tonsillar retraction, the horizontal angle to the lateral recess increased after either contralateral tonsillar retraction (22.7 +/- 4.8 vs 36.7 +/- 6.5 degrees) or tonsillar resection (22.7 +/- 4.8 vs 31.5 +/- 7.6 degrees; all adjusted P < .01). The horizontal angle to the cerebral aqueduct increased significantly with tonsillar resection compared with tonsillar retraction (17.6 +/- 2.3 vs 13.2 +/- 2.8 degrees; P < .001), Conclusion: Compared with tonsillar retraction, tonsillar resection provides a wider corridor to, and a larger area of exposure of, the cerebral aqueduct and lateral recess. Contralateral tonsillar retraction improves access to the lateral recess by widening the surgical view from the contralateral side.

Background: The callosomarginal artery (CMA), the main branch of the pericallosal artery, courses in or near the cingulate sulcus and gives rises to 2 or more major cortical branches. There is confusion about the artery best fitting the definition of "callosomarginal artery." Distal anterior cerebral artery aneurysms represent 1.5% to 9% of intracranial aneurysms, and most often occur at the origin of the CMA. The microsurgical anatomic features of the CMA, its relationship with the pericallosal artery, and clinical implications are presented., Methods: The origin, course, branching pattern, and diameter of the CMA and its branches and its relationship with the pericallosal artery were studied in 60 cerebral hemispheres, including cadaveric dissections and angiographic images., Results: The CMA was present in 93.3% of hemispheres studied and arose mainly from A3 (55.2%), a mean of 3.11 +/- 1.90 cm from the anterior communicating artery. The mean diameter of the CMA at its origin was 1.53 +/- 0.36 mm. The CMA ran 1.28 +/- 0.89 cm until its first branch, describing an anterior convex curve backward and upward (60.7%). An average of 3 lesser branches originated from the CMA. The most consistent branch was the posterior internal frontal artery (67.9%). The mean diameter of the CMA branches was 0.93 +/- 0.33 mm., Conclusion: These morphometric measurements can help neurosurgeons access lesions located in distal intracranial vessels. The vessel coursing the longest pathway in or near the cingulate sulcus and otherwise following Moscow's classic definition should be considered the CMA.

Objective: The supracerebellar infratentorial (SCIT) approach can be performed at the midline (median variant), lateral to the midline (paramedian variant), or at the level of the angle formed by the transverse and sigmoid sinuses (extreme lateral variant). We analyzed our experience with SCIT approaches for the surgical treatment of cavernous malformations of the brainstem (CMBs)., Methods: Demographic, clinical, radiologic, and surgical data from 45 patients (20 males and 25 females; mean age, 36.2 years) with CMBs surgically removed through SCIT approaches were reviewed retrospectively. Anatomic information was explored using cadaver head dissection., Results: Twenty-three lesions were in the midbrain, 3 were at the midbrain and extended to the thalamus, 9 were at the pontomesencephalic junction, and 10 were in the upper pons. All patients presented with hemorrhage. The median variant was used in 13 patients, the paramedian variant in 9, and the extreme lateral variant in 23. Intraoperatively, all CMBs were associated with a developmental venous anomaly. At last follow-up, 88% of the patients were the same or better. After a mean follow-up of 20 months, their mean Glasgow Outcome Scale score was 4.1., Conclusion: SCIT approaches provide excellent exposure to CMBs located at the posterior incisural space, not only in the midline but also in the posterolateral surface of the upper pons and midbrain. Careful preoperative planning and neuronavigational assistance are needed to determine the best angle of attack and trajectory for SCIT approaches. Refined microsurgical techniques are paramount to achieve safe surgical removal of CMBs with good outcomes.

Introduction: Recent developments in optical science and image processing have miniaturized the components required for confocal microscopy. Clinical confocal imaging applications have emerged, including assessment of colonic mucosal dysplasia during colonoscopy. We present our initial experience with handheld, miniaturized confocal imaging in a murine brain tumor model., Methods: Twelve C57/BL6 mice were implanted intracranially with 10(5) GL261 glioblastoma cells. The brains of 6 anesthetized mice each at 14 and 21 days after implantation were exposed surgically, and the brain surface was imaged using a handheld confocal probe affixed to a stereotactic frame. The probe was moved systematically over regions of normal and tumor-containing tissue. Intravenous fluorescein and topical acriflavine contrast agents were used. Biopsies were obtained at each imaging site beneath the probe and assessed histologically. Mice were killed after imaging., Results: Handheld confocal imaging produced exquisite images, well-correlated with corresponding histologic sections, of cellular shape and tissue architecture in murine brain infiltrated by glial neoplasm. Reproducible patterns of cortical vasculature, as well as normal gray and white matter, were identified. Imaging effectively distinguished between tumor and nontumor tissue, including infiltrative tumor margins. Margins were easily identified by observers without prior neuropathology training after minimum experience with the technology., Conclusion: Miniaturized handheld confocal imaging may assist neurosurgeons in detecting infiltrative brain tumor margins during surgery. It may help to avoid sampling error during biopsy of heterogeneous glial neoplasms, with the potential to supplement conventional intraoperative frozen section pathology. Clinical trials are warranted on the basis of these promising initial results.

Objective: Manganese (Mn(2+))-enhanced magnetic resonance imaging (MEMRI) is a potentially important tool for assessing neural tissue regeneration after spinal cord injury (SCI). We evaluated the relation between Mn(2+) and T1-weighted magnetic resonance (MR) signals in an SCI rat model., Methods: Rats were divided into 4 groups with or without SCI (T9-level transection) and with or without Mn(2+) injection. Two microliters of 0.2 mol/L MnCl(2) was injected into the lateral ventricles. Magnetic resonance imaging (MRI) was performed 60 hours after injection. Signal intensities at cervical, thoracic, and lumbar levels were measured and normalized to the intensity of perivertebral muscles. Spinal cord sections were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for total Mn(2+) content. The results of ICP-MS were compared with MR signal intensity., Results: T1-weighted MR signal intensity and ICP-MS-measured Mn(2+) were significantly decreased below the SCI injury site in Mn(2+)-injected groups with or without SCI, and were similar to intensity and Mn(2+) levels of noninjected animals. Signal intensity and Mn(2+) concentration tended to decrease from cervical to lumbar spinal levels in the control rats. ICP-MS data correlated with MRI results., Conclusion: The results confirmed Mn(2+) uptake in the spinal cord after intraventricular injection. T1-weighted MR signal intensity correlates with spinal Mn(2+) concentration as measured with ICP-MS. This work establishes the repeatability of MEMRI of the injured spinal cord and makes it possible to compare changes in axonal transport rates through the spinal cord after neuronal regeneration in vivo at different stages. MEMRI in animal models may improve understanding of the factors required to promote spinal cord regeneration.