Relationship between tumor location, size, and WHO grade in meningioma.

OBJECTIVE Prior studies have investigated preoperative risk factors for meningioma; however, no association has been shown between meningioma tumor size and tumor grade. The objective of this study was to investigate the relationship between tumor size and grade in a large single-center study of patients undergoing meningioma resection. METHODS A retrospective chart review of patients undergoing meningioma resection at the University of California, San Francisco, between 1985 and 2015 was performed. Patients with incomplete information, spinal meningiomas, multiple meningiomas, or WHO grade III meningiomas were excluded. The largest tumor dimension was used as a surrogate for tumor size. Univariate and multivariate logistic regression models were used to investigate the relationship between tumor grade and tumor size. A recursive partitioning analysis was performed to identify groups at higher risk for atypical (WHO grade II) meningioma. RESULTS Of the 1113 patients identified, 905 (81%) had a WHO grade I tumor and in 208 (19%) the tumors were WHO grade II. The median largest tumor dimension was 3.6 cm (range 0.2-13 cm). Tumors were distributed as follows: skull base (n = 573, 51%), convexity/falx/parasagittal (n = 431, 39%), and other (n = 109, 10%). On univariate regression, larger tumor size (p < 0.001), convexity/falx/parasagittal location (p < 0.001), and male sex (p < 0.001) were significant predictors of WHO grade II pathology. After controlling for interactions, multivariate regression found male sex (OR 1.74, 95% CI 1.25-2.43), size 3-6 cm (OR 1.69, 95% CI 1.08-2.66), size > 6 cm (OR 3.01, 95% CI 1.53-5.94), and convexity/falx/parasagittal location (OR 1.83, 95% CI 1.19-2.82) to be significantly associated with WHO grade II. Recursive partitioning analysis identified male patients with tumors > 3 cm as a high-risk group (32%) for WHO grade II meningioma. CONCLUSIONS Larger tumor size is associated with a greater likelihood of a meningioma being WHO grade II, independent of tumor location and male sex, which are known risk factors.

Broadening vestibular migraine diagnostic criteria: A prospective cohort study on vestibular migraine subtypes.

BACKGROUND: Current Bárány Society criteria for vestibular migraine (VM) include only episodic symptoms. Anecdotal observations suggest that some patients have episodic forms and others have chronic forms of VM, with interplay and evolution of both subtypes over time. OBJECTIVE: To better understand VM subtypes and evaluate a more inclusive diagnostic schema. METHODS: Four VM groups were studied: definite episodic (dVM), probable episodic (pVM), definite chronic (dCVM), and probable chronic (pCVM). Chronic VM was defined as having more than 15 dizzy days per month. Sociodemographic and clinical characteristics were analyzed, along with Dizziness Handicap Inventory (DHI) and Vestibular Migraine Patient Assessment Tool and Handicap Inventory (VM-PATHI) scores. RESULTS: 54 adults with a mean age of 47.0 years (SD 13.7) were enrolled. 10 met criteria for dVM, 11 pVM, 22 dCVM, and 11 pCVM. Overall, there were strong similarities in clinical characteristics between dVM, pVM, dCVM, and pCVM. Compared to subjects with episodic VM, those with chronic VM had a higher average number of VM triggers (8.7 vs. 6.4, P = 0.019), including motion (93.9% vs. 66.7%, P = 0.009), scrolling on a screen (78.8% vs. 47.6%, P = 0.018), skipped meal (57.6% vs. 23.8%, P = 0.015), and air travel (57.6% vs. 23.8%, P = 0.015). They also had higher symptom severity (DHI = 53.3, P = 0.194) and burden of disease (VM-PATHI = 48.2, P = 0.030) scores. CONCLUSIONS: Many patients do not meet current Bárány Society criteria for VM based on their duration of vestibular symptoms. Yet, these patients with chronic VM endorse several indistinguishable symptoms from those who do meet criteria. A more inclusive diagnostic schema should be adopted where patients with vestibular symptoms shorter than 5 minutes or longer than 72 hours are also recognized as having VM.

Dizziness After Traumatic Brain Injury: A Prospective TRACK-TBI Analysis of Risk Factors, Quality of Life, and Neurocognitive Effects.

OBJECTIVE: To determine the longitudinal incidence of dizziness and its association with demographic factors, neurocognitive effects, functionality, and quality of life. STUDY DESIGN: Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) is a prospective, longitudinal cohort study in which TBI patients were assessed at the emergency department and 2-week, 3-month, 6-month, and 12-month follow-up via telephone and/or in-person visits. SETTING: Multicenter study in emergency departments of 18 academic medical centers in the United States. PATIENTS: A total of 1,514 patients 17 years or older with a diagnosis of TBI, injury occurrence within 24 hours of admission, fluency in English or Spanish, and completed Rivermead Post-Concussion Symptoms Questionnaire (RPQ) at 12 months were enrolled between February 2014 and August 2018. MAIN OUTCOME MEASURE: RPQ, Short Form-12 Version 2, Wechsler Adult Intelligence Scale IV, Trail Making Test, Patient Health Questionnaire-9, PROMIS-PAIN, and Glasgow Outcome Scale-Extended Revised. The primary outcome measure was a self-report of "feelings of dizziness" on RPQ at 12 months post-TBI. RESULTS: Of the 1,514 participants, 1,002 (66%) were male and 512 (34%) were female. The mean age was 41.6 (SD, 17.4) years. At 12 months, 26% experienced dizziness, with 9% experiencing moderate or severe dizziness. Dizziness was strongly associated with headache (odds ratio [OR], 3.45; 95% confidence interval [CI], 2.92-4.07; p < 0.001), nausea (OR, 4.43; 95% CI, 3.45-5.69; p < 0.001), worse hearing (OR, 3.57; 95% CI, 2.64-4.82; p < 0.001), noise sensitivity (OR, 3.02; 95% CI, 2.54-3.59; p < 0.001), and light sensitivity (OR, 3.51; 95% CI, 2.91-4.23; p < 0.001). In multivariable regression models, participants with severe dizziness demonstrated lower performance compared with those without new or worse dizziness on the Wechsler Adult Intelligence Scale IV (-6.64; p < 0.001), Trail Making Test part A (7.90; p = 0.003) and part B (19.77; p = 0.028), and Short Form-12 physical (-13.60; p < 0.001) and mental health (-11.17; p < 0.001), after controlling for age, sex, education, and TBI severity. CONCLUSION: Dizziness is common among TBI patients and relates to quality of life and neurocognitive performance.

Episodic versus Chronic Dizziness: An Analysis of Predictive Factors.

OBJECTIVES: To elucidate differences in demographic and clinical characteristics between patients with episodic and chronic dizziness. METHODS: A cross-sectional, observational study of 217 adults referred for dizziness at 1 tertiary center was undertaken. Subjects were split into a chronic dizziness group (>15 dizzy days per month) and an episodic dizziness group (<15 dizzy days per month). RESULTS: 217 adults (average age, 53.7 years; 56.7% female) participated. One-third (n = 74) met criteria for chronic dizziness. Dizziness handicap inventory (DHI) scores were significantly higher in those with chronic dizziness compared to those with episodic dizziness (53.9 vs 40.7; P < .001). Comorbid depression and anxiety were more prevalent in those with chronic dizziness (44.6% and 47.3% vs 37.8% and 35.7%, respectively; P > .05). Abnormal vestibular testing and abnormal imaging studies did not differ significantly between the 2 groups. Ménière's disease and BPPV were significantly more common among those with episodic dizziness, while the prevalence of vestibular migraine did not differ according to chronicity of symptoms. A multivariate regression that included age, sex, DHI, history of anxiety and/or depression, associated symptoms, and dizziness triggers was able to account for 15% of the variance in the chronicity of dizziness (pseudo-R2 = 0.15; P < .001). CONCLUSIONS: Those who suffer from chronic dizziness have significantly higher DHI and high comorbid rates of depression and anxiety than those with episodic dizziness. Our findings show that factors other than diagnosis alone are important in the chronification of dizziness, an observation that could help improve on multimodal treatment options for this group of patients.

Constructing an Individualized Middle Cerebral Artery Model Using 3D Printing and Hydrogel for Bypass Training.

The importance and complexity of cerebral bypass surgery (CBS) highlight the necessity for intense and dedicated training. Several available training models are yet to satisfy this need. In this technical note, we share the steps to construct a digital imaging and communications in medicine (DICOM)-based middle cerebral artery (MCA) model that is anatomically accurate, resembles handling properties of living tissue, and enables trainers to observe the cerebrovascular anatomy, improve and maintain microsurgical dexterity, and train in the essential steps of CBS. The internal and external molds were created from the geometry of DICOM-based MCA using Fusion 360 software (Autodesk, San Rafael, USA). They were then three-dimension (3D) printed using a polylactic acid filament. The 15% w/v solution of polyvinyl alcohol (PVA) was prepared and injected between the molds. Using five freeze-thaw cycles the solution was converted to tissue-mimicking cryo-gel. The model was then placed in a chloroform bath until the internal mold dissolved. To evaluate the accuracy of the MCA model, selected characteristics were measured and compared with the MCA mesh. The DICOM-based MCA model was produced using 3D printing that was available in the lab and the overall cost was less than $5 per model. The external mold required six and a half hours to be 3D printed, while the internal mold only required 23 minutes. Overall, the time required to 3D print the DICOM-based MCA model was just short of seven hours. The greatest statistically significant difference between the virtual MCA model and the DICOM-based MCA model was found in the length of the pre-bifurcation part of the M1 segment and the total length of the superior bifurcation trunk of M1 and superior branch of M2. The smallest statistically significant difference was found at the diameter of the inferior post-bifurcation trunk of the M1 segment and the diameter at the origin of the artery. This technical report aims to show the construction of a CBS training system involving the DICOM-based MCA model that demonstrates the shape of the vascular tree, resembles the handling/suturing properties of living tissue, and helps set up a homemade training station. We believe that our DICOM-based MCA model can serve as a valuable resource for CBS training throughout the world due to its cost-effectiveness and straightforward construction steps. Moreover, once the DICOM-based MCA model is used with our training station, it may offer an option for trainers to gain and maintain CBS skills despite limitations on time, cost, and space. This work was presented in February 2019 at the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Cerebrovascular Section Annual Meeting held in Honolulu, Hawaii.

Far-Lateral Transcondylar Approach to a Right Cervicomedullary Dural Arteriovenous Fistula of the Posterior Fossa.

Objectives Dural arteriovenous fistulas (DAVFs) at the cervicomedullary junction are uncommon and often accompanied by subarachnoid hemorrhage (SAH). We aim to illustrate in detail the microsurgical procedure for treating a DAVF located at the cervicomedullary junction. Design We present a two-dimensional operative video that includes clinical history, preoperative imaging, surgical strategy, still images with labels, clinical course, and postoperative imaging. Setting The microsurgery was performed at an academic medical center. Participant The patient is a 55-year-old female who presented with SAH, acute onset headache, nausea, and vomiting. Angiography demonstrated right vertebral artery vasospasm and a persistent arteriovenous shunt at the cervicomedullary junction supplied by small perforating arteries of the right vertebrobasilar junction ( Fig. 1 ). Main Outcome Measures The patient was placed in the park-bench position with the head turned to the contralateral side. A hockey stick incision was made, followed by a right-side far-lateral transcondylar approach. Indocynanine green videoangiography was performed to help identify the areas of arteriovenous shunting. Multiple clips were placed to interrupt vessels that corresponded to arterial feeders at the level of the C1 and C2 nerve root sleeves ( Fig. 2 ). The dura was closed in a water tight fashion and the posterior fossa was reconstructed with a titanium mesh. Results Postoperative imaging showed no evidence of continued arteriovenous shunting. The patient was discharged in good clinical condition with an uneventful postoperative course. Conclusion A deep understanding of the microsurgical vascular anatomy is necessary for successful occlusion of a cervicomedullary DAVF. The link to the video can be found at: https://youtu.be/-LfOcNB05BY .

Anatomy of petrous face.

The anatomy of the petrous face of the temporal bone, also known as the petrous pyramid, should be carefully examined to understand the location of, blood supply to, and venous drainage of meningiomas in this area (42%-59% of posterior fossa meningiomas). The petrous face is located in the skull base between the sphenoid and occipital bones. It consists of a base that joins the mastoid laterally and an apex that extends anteromedially to form the foramen lacerum. The anatomy can be divided into three surfaces: anterior/superior, posterior, and inferior. The anterior/superior surface is a continuation of the posteromedial portion of the middle cranial fossa with boundaries extending from the arcuate eminence to the petrous apex. The posterior surface is a continuation of the front part of the posterior cranial fossa with the internal auditory meatus at its center. The inferior surface contains foramina that transmit important vessels and cranial nerves. The vascular anatomy of the petrous face is also described, including branches of the carotid artery and vertebrobasilar systems. It is imperative to understand potential anastomotic routes between extracranial and intracranial arteries, as well as arterial supply to cranial nerves, to facilitate preoperative transarterial embolization of meningiomas and avoid neurologic complications during surgery.

Vestibular Migraine Following Radiosurgery for Vestibular Schwannoma.

Vestibular schwannoma (VS) is associated with dizziness and vertigo during all stages of treatment. This report describes a patient who presented with a one-year history of intermittent motion sickness, dizziness, headache, imbalance, and nausea. MRI showed a right-side VS in the cerebellopontine angle and internal auditory canal. The patient elected to undergo Gamma Knife radiosurgery for treatment. Within two to three months, she continued to experience recurring dizziness, vertigo, neck stiffness, and head pressure. She was referred for neurotology evaluation, which led to a diagnosis of vestibular migraine (VM). Her vestibular reflexes were intact. Subsequently, she was treated with diet modification and low-dose venlafaxine. She reported dramatically improved dizziness and vertigo symptoms at six-month follow-up. VM is a very common cause of dizziness that should always be included in the differential diagnosis, even in VS patients.

Comparative Analysis of Pterional, Supraorbital, Extended Supraorbital, and Transtubercular-Transplanum Approaches for Exposing the Anterior Communicating Artery Complex: A Cadaveric Study.

OBJECTIVE: We aimed to quantify and compare surgical exposure and freedom at the anterior communicating artery (ACoA) complex using pterional (PT), supraorbital (SO), extended supraorbital withorbital osteotomy (SOO), and endonasal endoscopic transtubercular-transplanum (EEATT) approaches. METHODS: Right-sided PT, SO, SOO, and EEATT approaches were performed using 10 cadaveric heads. Surgical exposure and freedom (horizontal and vertical attack angle) at the ACoA complex were measured. The farthest clipping distance from ACoA to A1 (precommunicating segment of the anterior cerebral artery)/A2 (postcommunicating segment of the anterior cerebral artery) was also quantified. RESULTS: There was a significantly greater exposure length of right A1 in the PT approach (12.20 ± 2.48 mm) compared with the EEATT approach (9.52 ± 2.09 mm; P = 0.029). Among the 4 approaches, EEATT provided the shortest clipping distance for right A1 (6.56 ± 1.33 mm; P = 0.001) and the longest clipping distance for right A2 (3.36 ± 1.24 mm; P = 0.003). SO, SOO, and PT approaches (2.9 ± 0.9) had more observations on perforators from ACoA than did the EEATT approach (2.0 ± 0.66; P = 0.029). The EEATT approach (50.90 ± 17.45 mm2) provided better exposure of the superior part of the ACoA complex compared with the SO approach (29.37 ± 17.27 mm2; P = 0.05). PT and SOO approaches provided the greatest horizontal (36.88° ± 5.85°) and vertical (19.37° ± 4.70°) attack angle, respectively. CONCLUSIONS: The SO, SOO, and PT approaches provided a better hemilateral view of the ACoA complex and similar surgical exposure, whereas the EEATT approach offered greater exposure in the upper part of the ACoA complex, with relatively limited exposure of perforators from ACoA and surgical freedom. The EEATT approach can play a role in exposure of lesion involving the ACoA complex.

Comparative analysis of surgical exposure and freedom between the subtonsillar, endoscope-assisted subtonsillar, and far-lateral approaches to the lower clivus: A cadaveric study.

The far-lateral (FL)approach is a classic technique for skull base surgeries involving the lower clivus (LC).Recently, a modified suboccipital midline approach known as the subtonsillar (ST) approach, along with the endoscope-assisted subtonsillar (EST) approach, has been described as a minimally invasive technique to treat LC lesions. However, there is no quantitative study on comparing these approaches together for reaching LC. We aimed to compare surgical exposure and freedom provided by ST, EST, and FL approaches for various targets at LC. These approaches were performed on each side of five cadaveric specimens (total 10 sides), and relevant parameters were quantified and compared using a repeated measures ANOVA test. FL approach yielded the greatest surgical area (237.8 ± 56.0 mm2) and exposure, including lengths of glossopharyngeal nerve (16.2 ± 1.9 mm), hypoglossal nerve (11.4 ± 2.4 mm), vertebral artery (23.9 ± 3.3 mm), followed by EST and ST approaches. For surgical freedom, FL approach provided the greatest angle of attack (90.0 ± 14.0° at jugular foramen, 95.1 ± 15.8° at hypoglossal canal, 83.4 ± 31.4° at bifurcation point of posterior inferior cerebellar artery and vertebral artery). Our systematic comparison suggests that EST approach, compared to ST approach, can significantly increase surgical exposure to the medial side of LC, but FL approach still provides the greatest surgical exposure and freedom at LC. Despite the limitations of a cadaveric study, our quantitative data can update the literature on currently available surgical techniques for reaching LC and better inform preoperative planning in this area. Further studies should be performed to evaluate these approaches in clinical practice.

Replicating Skull Base Anatomy With 3D Technologies: A Comparative Study Using 3D-scanned and 3D-printed Models of the Temporal Bone.

HYPOTHESIS: 3D technologies, including structured light scanning (SLS), microcomputed tomography (micro-CT), and 3D printing, are valuable tools for reconstructing temporal bone (TB) models with high anatomical fidelity and cost-efficiency. BACKGROUND: Operations involving TB require intimate knowledge of neuroanatomical structures-a demand that is currently met through dissection of limited cadaveric resources. We aimed to document the volumetric reconstruction of TB models using 3D technologies and quantitatively assess their anatomical fidelity. METHODS: In the primary analysis, 14 anatomical characteristics of right-side TB from 10 dry skulls were measured. Each skull was 3D-scanned using SLS to generate virtual models, which were measured using mesh processing software. Metrics were analyzed using mean absolute differences and one-sample t tests with Bonferroni correction. In the secondary analysis, an individualized right-side TB specimen (TBi) was 3D-scanned using SLS and micro-CT, and 3D-printed on a stereolithography printer. Measurements of each virtual and 3D-printed model were compared to measurements of TBi. RESULTS: Significant differences between the physical skulls and virtual models were observed for 11 of 14 parameters (p < 0.0036), with the greatest mean difference in the length of petrous ridge (2.85 mm) and smallest difference in the diameter of stylomastoid foramen (0.67 mm). In the secondary analysis, greater mean differences were observed between TBi and virtual models than between TBi and 3D-printed models. CONCLUSION: For the first time, our study provides quantitative measurements of TB anatomy to demonstrate that 3D technologies can facilitate individualized and highly accurate reconstructions of TB, which may benefit anatomy education, clinical training, and preoperative planning.

Immersive Surgical Anatomy of the Pterional Approach.

The pterional approach (PA) is a versatile anterolateral neurosurgical technique that enables access to reach different structures contained in the cranial fossae. It is essential for neurosurgical practice to dominate and be familiarized with its multilayer anatomy. Recent advances in three-dimensional (3D) technology can be combined with dissections to better understand the spatial relationships between anatomical landmarks and neurovascular structures that are encountered during the surgical procedure. The present study aims to create a stereoscopic collection of volumetric models (VM) obtained from cadaveric dissections that depict the relevant anatomy and surgical techniques of the PA. Five embalmed heads and two dry skulls were used to record and simulate the PA. Relevant steps and anatomy of the PA were recorded using 3D scanning technology (e.g. photogrammetry, structured light scanner) to construct high-resolution VM. Stereoscopic images, videos, and VM were generated to demonstrate major anatomical landmarks for PA. Modifications of the standard PA, including the mini-pterional and two-part pterional approaches, were also described. The PA was divided into seven major steps: positioning, incision of the skin, dissection of skin flap, dissection of temporal fascia, craniotomy, drilling of basal structures, and dural opening. Emphasis was placed on preserving the temporal branches of the facial nerve and carefully dissecting the temporalis muscle. The interactive models presented in this article allow for clear visualization of the surgical anatomy and windows in 360-degrees and VR. This new modality of recording neuroanatomical dissections renders a closer look at every nuance of the topography experienced by our team in the laboratory. By accurately depicting essential landmarks, stereoscopy and VM can be valuable resources for anatomical education and surgical planning.

Immersive Surgical Anatomy of the Frontotemporal-Orbitozygomatic Approach.

The frontotemporal-orbitozygomatic (FTOZ) approach is widely used for accessing anterolateral lesions in skull base surgery. Many studies have described the technique and quantified the surgical exposure and freedom provided by the FTOZ approach. However, few studies have provided a detailed analysis of the technique and surgical landmarks using three-dimensional (3D) models. In this study, we aimed to create a collection of volumetric models (VMs) and stereoscopic media on the step-by-step surgical technique of the FTOZ approach using cadaveric dissections. The FTOZ approach was divided into eight major steps: positioning, incision of the skin, dissection of scalp flap, mobilization of the temporalis muscle, dissection of periorbita, craniotomy, drilling of basal structures, and dural opening. The MacCarty keyhole and inferior orbital fissure are major surgical landmarks that were referenced for the six bony cuts. Photogrammetry and structured light scanning were used to construct high-resolution VMs. We illustrated the two-piece FTOZ craniotomy, followed by the one-piece and three-piece FTOZ craniotomies. Stereoscopic images, videos, and VMs were produced for each step of the surgical procedure. In addition, the mini-orbitozygomatic (MOz) and orbitopterional (OPt) approaches were considered and described as possible alternatives to the FTOZ approach. Recent advances in 3D technology can be implemented in neurosurgical practice to further enhance our spatial understanding of neurovascular structures. Surgical approaches should be carefully selected and tailored according to the patient's unique pathology and needs.

Characterization of Anatomical Landmarks for Exposing the Internal Carotid Artery in the Infratemporal Fossa Through an Endoscopic Transmasticator Approach: A Morphometric Cadaveric Study.

BACKGROUND: The Eustachian tube and sphenoid spine have been previously described as landmarks for endonasal surgical identification of the most distal segment of the parapharyngeal internal carotid artery (PhICA). However, the intervening space between the sphenoid spine and PhICA allows for error during exposure of the artery. In the present study, we have characterized endoscopic endonasal transmasticator exposure of the PhICA using the sphenoid spine, vaginal process of the tympanic bone, and the "tympanic crest" as useful anatomical landmarks. METHODS: Endonasal dissection was performed in 13 embalmed latex-injected cadaveric specimens. Two open lateral dissections and osteologic analysis of 10 dry skulls were also performed. RESULTS: A novel and palpable bony landmark, the inferomedial edge of the tympanic bone, referred to as the tympanic crest, was identified, leading from the sphenoid spine to the lateral carotid canal. Additionally, the vaginal process of the tympanic bone, viewed endoscopically, was a guide to the PhICA. The sphenoid spine was bifurcate in 20% of the skulls, with an average length of 5.98 mm (range, 3.9-8.2 mm), width of 5.81 mm (range, 3.0-10.6 mm), and distance to the carotid canal of 4.48 mm (range, 2.5-6.1 mm). CONCLUSION: The sphenoid spine and pericarotid space has variable anatomy. Using an endoscopic transmasticator approach to the infratemporal fossa, we found that the closest landmarks leading to the PhICA were the tympanic crest, sphenoid spine, and vaginal process of the tympanic bone.

Construction of Neuroanatomical Volumetric Models Using 3-Dimensional Scanning Techniques: Technical Note and Applications.

BACKGROUND: Visuospatial features of neuroanatomy are likely the most difficult concepts to learn in anatomy. Three-dimensional (3D) modalities have gradually begun to supplement traditional 2-dimensionanl representations of dissections and illustrations. We have introduced and described the workflow of 2 innovative methods-photogrammetry (PGM) and structured light scanning (SLS)-which have typically been used for reverse-engineering applications. In the present study, we have described a novel application of SLS and PGM that could enhance medical education and operative planning in neurosurgery. METHODS: We have described the workflow of SLS and PGM for creating volumetric models (VMs) of neuroanatomical dissections, including the requisite equipment and software. We have also provided step-by-step procedures on how users can postprocess and refine these images according to their specifications. Finally, we applied both methods to 3 dissected hemispheres to demonstrate the quality of the VMs and their applications. RESULTS: Both methods yielded VMs with suitable clarity and structural integrity for anatomical education, surgical illustration, and procedural simulation. CONCLUSIONS: The application of 3D computer graphics to neurosurgical applications has shown great promise. SLS and PGM can facilitate the construction of VMs with high accuracy and quality that can be used and shared in a variety of 3D platforms. Similarly, the technical demands are not high; thus, it is plausible that neurosurgeons could become quickly proficient and enlist their use in education and surgical planning. Although SLS is preferable in settings in which high accuracy is required, PGM is a viable alternative with a short learning curve.

Acquisition of Volumetric Models of Skull Base Anatomy Using Endoscopic Endonasal Approaches: 3D Scanning of Deep Corridors Via Photogrammetry.

OBJECTIVE: In this study we aim to evaluate the feasibility of creating volumetric models of highly intricate skull-base anatomy-previously not amenable to volumetric reconstruction-using endoscopic endonasal approaches. METHODS: Ten human cadaveric heads were dissected through the nasal corridor to expose anterior, middle, and posterior cranial fossi structures and the pterygopalatine and infratemporal fossi. A rigid endoscope with a 30° lens was used to capture the images. Subsequently, a photogrammetry software was used to align, smooth, and texturize the images into a complete 3-dimensional model. RESULTS: An average of 174 photographs were used to construct each model (n = 10). In the end, we achieved high-definition stereoscopic volumetric models of the nasal corridor; paranasal fossae; and anterior, middle and posterior fossae structures that preserved structural integrity. Strategic points of interests were labeled and animated for educational use. CONCLUSIONS: Endoscopic volumetric models represent a new way to depict the anatomy of the skull base; their use with 3-dimensional technologies could potentially improve the visuospatial understanding of narrow surgical corridors for education and surgical-planning purposes.

Clipping of High-Risk Dural Arteriovenous Fistula of the Posterior Fossa: 3-Dimensional Operative Video.

Dural arteriovenous fistulas (DAVFs) represent 10%-15% of all intracranial arteriovenous malformations.1 DAVFs located in the posterior cranial fossa are rare and often present with intracranial hemorrhage and myelopathy.2 Arterial supply could be provided by the meningeal branches of the vertebral artery and external and internal carotid arteries.3 A 68-year-old man presented with progressive lower-extremity weakness (Video 1). Magnetic resonance imaging revealed a patchy longitudinal cord signal abnormality extending from the cervicomedullary junction to C7. A tentorial DAVF supplied by the right posterior meningeal artery with drainage via dorsal and ventral perimedullary veins was identified on angiography. According to the Cognard classification, the patient's DAVF was determined to be high risk as a type V lesion with spinal venous drainage and progressive myelopathy.4 The fistula was embolized with 50% ethanol resulting in near-complete occlusion. However, follow-up angiography revealed a persistent arteriovenous shunt and slightly worsening symptoms for the patient. He underwent a sitting supracerebellar approach with a torcular craniotomy for successful clip ligation of the dural arteriovenous fistula. The patient was discharged with improvements in lower-extremity strength and no residual arteriovenous shunting in postoperative imaging.

Supracerebellar Approach to Radiation-Induced Giant Capillary Telangiectasia Within Juvenile Pilocytic Astrocytoma of Upper Brainstem.

Radiation-induced telangiectasia of the central nervous system has been described predominantly in children, with up to 20% of patients affected after 3-41 years of radiotherapy.1,2 We present the case of a 45-year-old male with a pontine pilocytic astrocytoma treated with standard-dose radiation for 6 weeks in 1993. He developed a 3-cm multicystic, hemorrhagic brainstem lesion but was asymptomatic. The lesion caused severe brainstem mass effect, compatible with cavernous malformation or capillary telangiectasia.3 It has been reported that cavernomas and capillary telangiectasias share a similar pathologic process.4,5 The patient was surgically treated with a supracerebellar infratentorial approach to diagnose the hemorrhagic component of the lesion and ensure there was no transformation of the pilocytic astrocytoma (Video 1). He was placed in a gravity-dependent supine position with the head flexed and turned to allow for natural relaxation of the cerebellum via gravity-a technique we previously described.6 Surgical treatment proceeded with a left suboccipital craniotomy to decompress the cyst and facilitate removal of the intraaxial lesion. We took care to avoid injuring the fourth and fifth cranial nerves and branches of the superior cerebellar artery. No further lesional tissue was seen in the resection cavity. Interestingly, the final pathologic diagnosis indicated a mix of both pilocytic astrocytoma and radiation-induced capillary telangiectasia. From the surgeon's perspective, capillary telangiectasias appear similar to cavernous malformations on gross inspection, so pathologic confirmation is essential. Postoperative imaging demonstrated total resection of the lesion. The patient was discharged on postoperative day 3 with no neurologic deficit.

Comparative Analysis of the Subtonsillar, Far-Lateral, Extreme-Lateral, and Endoscopic Far-Medial Approaches to the Lower Clivus: An Anatomical Cadaver Study.

BACKGROUND: The lower clivus (LC) is one of the most difficult areas to access in neurosurgery. Several microsurgical approaches to the LC have been reported, including the subtonsillar, far-lateral (FL), extreme-lateral (EL), and endoscopic far-medial (Endo-FM). However, no consensus has been reached regarding the optimal approach. We aimed to quantify and compare the surgical exposure and freedom (angle of attack) for various targets at the LC using these 4 surgical approaches. METHODS: The subtonsillar, FL, EL, and Endo-FM approaches were performed on 5 cadaveric specimens (total 10 sides). Surgical exposure and freedom were measured using the neuronavigation system. RESULTS: At the LC, the Endo-FM approach provided the greatest area of exposure (459.3 ± 82.2 mm2). For surgical freedom, the EL approach provided the greatest angle of attack at the jugular foramen (98.1° ± 9.2°) and hypoglossal canal (128.8° ± 26.1°). The Endo-FM was the only approach that provided access to the midline of the LC in all specimens. However, the surgical freedom at the midline (20.9° ± 2.4° at the level of the jugular foramen; 24.2° ± 2.9° at the level of hypoglossal canal) was limited by its deep surgical corridor (104.3 ± 11.2 mm) compared with the EL and FL approaches. CONCLUSION: The Endo-FM approach provided the greatest surgical freedom at the ventral aspect but the least freedom at the lateral aspect. The EL approach provided maximal values for most parameters among the open approaches; however, the craniotomy with the EL approach was the most complicated. Our quantitative results could guide neurosurgeons in preoperative planning for LC lesions, including awareness of the maximum exposure limits and the advantages and disadvantages of each surgical approach.

Revascularization of the Anterior Inferior Cerebellar Artery Using Extracranial and Intracranial Donors: A Morphometric Cadaveric Study.

INTRODUCTION: Anterior inferior cerebellar artery (AICA) aneurysms are rare, accounting for 0.2%-1.3% of all intracranial aneurysms. The standard treatment is often endovascular embolization or neck clipping; however, sacrifice of the parent vessel is sometimes necessary. Addition of revascularization procedures is a subject of controversy. The occipital artery (OA) has been used as a donor for bypass, but recently there has been a trend toward intracranial-intracranial approaches. The posterior inferior cerebellar artery (PICA)-AICA side-to-side bypass may serve as a safe alternative. OBJECTIVE: To characterize the PICA-AICA side-to-side bypass and the OA-AICA end-to-side bypass and review the literature relevant to AICA revascularization. METHODS: We performed a far-lateral approach on 12 cadaveric specimens and analyzed the regional anatomy. On this basis, we performed either an OA-AICA or a PICA-AICA bypass and took morphometric measurements relevant to the technique. RESULTS: PICA-AICA bypass was successful in 6/12 specimens. The length of the flocculopeduncular segment was 42.6 ± 15.8 mm in the specimens in which the bypass was feasible and 26.2 ± 7.2 mm in those in which the bypass was not feasible (P = 0.04). Mean distance between AICA and PICA was 5.3 ± 4 mm in the specimens in which side-to-side bypass was feasible and 11.6 ± 4.2 mm in the specimens in which it was not (P = 0.02). OA-AICA end-to-side bypass was feasible in all the specimens (75% in the flocculopeduncular segment; 25% in the cortical segment). CONCLUSIONS: This is the first cadaveric study analyzing the PICA-AICA side-to-side bypass for AICA revascularization. Our analyses provide evidence for the feasibility of this bypass and document the anatomic variations that may indicate its use.