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Background and Objectives: The abducens nerve (CN VI) is vulnerable to injury during endoscopic endonasal transcavernous surgery. In this study, the authors aimed to develop the surgical anatomic landmark and explore the relationship between the sympathetic nerves (SNs) around the internal carotid artery (ICA) and CN VI within the cavernous sinus (CS)., Methods: The relationship and patterns between the SNs and CN VI were investigated in 15 cadaveric specimens. The intraoperative examples of anatomic landmark were presented., Results: There were SNs around the ICA running into the CN VI, classified into ascending SNs and accessory sympathetic branches. The ascending SNs were divided into 3 types: (1) Type I had a single ascending SN. There were 2 subtypes of Type I (Type IA [17/30, 56.7%] was defined as a single ascending branch that ran into the CN VI, and Type IB [4/30, 13.3%] was defined as a single ascending branch with a terminal bifurcation before merging into the CN VI or lateral CS wall), (2) Type II (7/30, 23.3%) was defined as 2 ascending branches that ran into the CN VI and the lateral CS wall, and (3) Type III (2/30, 6.7%) was defined as 3 ascending branches that ran into the CN VIs and the lateral wall of the CS. The accessory branches of the SNs were defined by sympathetic branches from the posterior genu or horizontal ICA and found in 6/30 sides (20%)., Conclusion: The authors propose a classification of the relationship between paraclival ICA SNs and the CN VI within the CS, as approached during endoscopic endonasal surgery. The consistent relationship of the ascending SN and CN VI within the CS provides a reliable anatomic landmark during the endonasal approach to the CS., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Background and Objective: Conventional protocols for inferior petrosal sinus sampling (IPSS) during the workup of hypercortisolemia require adrenocorticotrophic hormone (ACTH) measurement at multiple time points with corticotropic-releasing hormone (CRH) used as a stimulator. Modernized evidence-based protocols must also reflect the increased utilization of desmopressin (DDAVP) for ACTH stimulation as the manufacturing shortage of traditionally used CRH continues. We model the diagnostic accuracy and potential economic savings of DDAVP utilization and reduced time point sampling., Methods: A single-institution, retrospective review of patients undergoing IPSS between 2007 and 2021 was performed. A computational search for the minimal set of time points which preserves conventional diagnostic accuracy was performed by testing all 1 through 5-point combinations generated using a binomial expansion. Economic savings were modeled using a publicly available hospital chargemaster., Results: A total of 50 patients qualified for inclusion, 47 of whom were diagnosed with Cushing disease and 3 with ectopic Cushing syndrome. Single-point diagnostic accuracy for DDAVP-stimulated tests was 71.4%-92.9%, and seven 2-point combinations (5-25 procedural minutes) were found, which preserved conventional diagnostic accuracy. Single-point accuracy for CRH-stimulated tests was 67.9%-89.3%, and two 2-point combinations ( t = -15, t = +2 and t = -15, t = +10) preserved accuracy. For every time point removed, the cost of ACTH laboratory tests was reduced by $507 from $3042 for 6-point IPSS). The shortest and most economical stimulator and time point combination that preserved conventional accuracy was DDAVP sampling at t = 0 and t = +5 or t = +2 and t = +5 minutes, which cost $2028 total compared with the most expensive 6-point IPSS option with CRH ($6392)., Conclusion: DDAVP is a cost-efficient and effective alternative to CRH during IPSS. Our results encourage prospective evaluation of potentially fewer sampling time points in the interest of time and cost efficiency balanced with preserved accuracy., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Indications Corridor and Limits of Exposure: Endoscopic endonasal far-medial approach provides an effective and safe corridor to access the parasagittal structures of the lower clivus such as the medial jugular tubercle (JT) and occipital condyle (OC) for lesions that displace neurovascular structures laterally., Anatomic Essentials Need for Preoperative Planning and Assessment: Parapharyngeal internal carotid arteries (ICAs) run posterolateral to the eustachian tubes and lateral to the OC. The supracondylar groove is a superficial landmark for the hypoglossal canal, which divides the lateral extension of clivus into the JT and OC., Essential Steps of the Procedure: Typically, approach starts with opening of the sphenoid sinus to localize the paraclival ICA. An "inverted U" rhinopharyngeal (RP) flap exposing the supracondylar groove and lower clivus. Doppler and navigation can confirm the course of the ICA. Drilling is started in the midline in the lower clivus and extended laterally to expose the hypoglossal canal, JT, and OC., Pitfalls/avoidance of Complications: Neurovascular injuries can be avoided by using intraoperative Doppler and nerve stimulator. Multilayer reconstruction with vascularized nasoseptal (NSF) and RP flaps minimize postoperative cerebrospinal fluid leak., Variants and Indications for Their Use: The contralateral transmaxillary approach provides an increased angle of access behind foramen lacerum and the petrous ICA.The endoscopic endonasal far-medial approach can be used for a variety of pathologies, including petroclival or JT meningiomas, chordomas and chondrosarcomas, and hypoglossal schwannomas, inferiorly extending cholesterol granulomas and even rare, ventral posterior inferior cerebellar artery aneurysms.The patients consented to the procedure., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background and Objectives: Triangular corridors have been used as reliable surgical entry points for open transcranial approaches to the petrous apex (PA) and petroclival region (PCR). The endoscopic endonasal approaches have grown rapidly in the last decade, and the indications have advanced. The knowledge of accurate and reliable anatomic landmarks through endoscopic endonasal route is essential and remain to be established. The purpose of this study was to describe the feasibility and surgical exposure of the anteromedial petrous (Gardner's) triangle as a novel corridor to the PA and PCR., Methods: Five anatomic specimens were dissected. The PA and PCR were accessed through endoscopic endonasal approaches and contralateral transmaxillary approach. The limits of the anteromedial petrous (Gardner's) triangle were identified and dissected and associated measurements performed., Results: The dissection was divided into 6 steps. The limits of the anteromedial petrous (Gardner's) triangle were identified and defined by the paraclival internal carotid artery anterolaterally, the abducens nerve posteromedially, and the petroclival synchondrosis inferiorly. Three lines were established following the limits of the triangle. The mean distance of the anterolateral limit was 10.03 mm (SD = 0.94), of the posteromedial limit was 20.06 mm (SD = 2.90), and of the inferior limit was 17.99 mm (SD = 2.99). The mean area was 87.56 mm 2 (SD = 20.06). The 3 anatomic landmarks with a critical role to safely define the triangle were the pterygosphenoidal fissure, the petrosal process of the sphenoid bone, and the petroclival synchondrosis., Conclusion: The anteromedial (Gardner's) triangle is a well-defined bone corridor which provides access to the entire petrous bone and petroclival junction through endoscopic endonasal route. Regardless of the anatomic variations or tumor location, the landmarks of the abducens nerve, paraclival internal carotid artery, and petroclival synchondrosis are key for understanding lateral access to tumors extending from the clivus., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background: There is controversy over the choice of optimal approach for olfactory groove meningiomas (OGM). The endoscopic endonasal approach (EEA) is one of the most recently described corridors, which provides direct access to the tumor base., Objective: To detail the evolution of the endoscopic endonasal technique over the past 2 decades and demonstrate the impact of this evolution on patient outcomes., Methods: This is a retrospective study based on a prospectively maintained database of consecutive cases of OGM operated on at our institution via EEA. For analysis, the whole cohort has been divided into 3 equal "eras" according to the time period during which the surgery happened, creating early, middle, and contemporary groups., Results: Seventy-five patients were included, 25 in each group. The rate of postoperative cerebrospinal fluid leak significantly decreased over time (28%, 32%, and 8% in the early, middle, and contemporary groups, respectively, P = .020). The rate of postoperative encephalomalacia was significantly lower in more recent groups (24%, 16%, and 0% in the early, middle, and contemporary groups, respectively, P = .029), as was the time to resolution of postoperative brain edema (103.9 months, 87.3 months, and 16.8 months in the early, middle, and contemporary groups, respectively, P = .020)., Conclusion: The endoscopic endonasal approach for OGM significantly evolved over time, achieving lower cerebrospinal fluid leak rates while providing a high rate of Simpson grade 1 resection. Technical improvements minimized the frontal lobe impact. Current data support EEA as a safe and effective corridor to treat OGM., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: Chiari I malformations secondary to other causes represent a small subset of presenting symptomatic cases. Typically, the primary cause of the malformation is addressed first and results in resolution of the malformation and symptoms. However, in some cases, a patient may present with both a primary Chiari I malformation and another unrelated neurosurgical lesions., Objective: To present a unique case in which resection of a ventral tumor allowed for spontaneous resolution of a simultaneously noted dorsal Chiari I malformation., Methods: Pertinent data, including presenting symptoms, hospital course, surgical notes, preoperative images, and postoperative images, were collected using the electronic medical record., Results: We present a case of a 46-yr-old man with a Chiari I malformation in conjunction with a ventral cranio-cervical junction chordoma. Endoscopic endonasal resection of the chordoma and ventral foramen magnum decompression resulted in radiographic resolution of the Chiari malformation and resolution of his symptoms. Our report represents a rare case of ventral foramen magnum decompression as a treatment for Chiari I malformation., Conclusion: It is felt that the chordoma mass effect was not the source of the Chiari I malformation. Thus, both ventral and dorsal decompressions of the posterior fossa may be considered for Chiari I decompression in select circumstances., (© Congress of Neurological Surgeons 2021.)

The authors present a 3D surgical video of a direct occipital to angular artery bypass for cerebral revascularization in the setting of Post-irradiation middle cerebral artery stenosis and symptomatic hypoperfusion. The case refers to a 50-yr-old woman with a history of an unresectable residual skull base meningioma, previously approached through a left frontotemporal craniotomy, and treated with radiation 5 yr prior to presentation. She now presented with right-sided limb shaking transient ischemic attacks and aphasia, along with evidence of left middle cerebral artery territory ischemia. Her symptoms were progressive, despite extensive external carotid collateral blood supply through the prior craniotomy. The video analyzes the surgical steps of the procedure, emphasizing multiple surgical pearls. After positioning, an incision is designed to expose the full course of the occipital artery. After dissection of the donor vessel, a craniotomy is performed to expose the distal sylvian fissure. The donor and recipient vessels are prepared, and the anastomosis is performed with interrupted sutures given the sub-millimeter diameter of the recipient vessel (suture used: 10-0 Ethilon BV75-3 Taper, Ethicon, Johnson & Johnson). Every step of the closure is modified to avoid any constriction of the donor vessel. The patient tolerated the procedure well, and multiple modalities, both intra- and post operatively confirmed patency of, and robust flow within the bypass. No identifying patient information is included. However, the patient's consent was obtained for this publication., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: Many studies have explored molecular markers of carotid plaque development and vulnerability to rupture, usually having examined whole carotid plaques. However, there are regional differences in plaque morphology and known shear-related mechanisms in areas surrounding the lipid core., Objective: To determine whether there are regional differences in protein expression along the long axis of the carotid plaque and how that might produce gaps in our understanding of the carotid plaque molecular signature., Methods: Levels of 7 inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10, IL-12 p70, IFN-γ, and TNF-α) and caspase-3 were analyzed in prebifurcation, bifurcation, and postbifurcation segments of internal carotid plaques surgically removed from symptomatic and asymptomatic patients. Expression profiles of miRNAs and mRNAs were determined with microarrays for the rupture-prone postbifurcation segment for comparison with published whole plaque results., Results: Expression levels of all proteins examined, except IL-10, were lowest in the prebifurcation segment and significantly higher in the postbifurcation segment. Patient group differences in protein expression were observed for the prebifurcation segment; however, no significant differences were observed in the postbifurcation segment between symptomatic and asymptomatic patients. Expression profiles from postbifurcation carotid plaques identified 4 novel high priority miRNAs differentially expressed between patient groups (miR-214, miR-484, miR-942, and miR-1287) and 3 high-confidence miRNA:mRNA targets, including miR-214:APOD, miR-484:DACH1, and miR-942:GPR56., Conclusion: The results demonstrate regional differences in protein expression for the first time and show that focus on the rupture-prone postbifurcation region leads to prioritization for further study of novel miRNA gene regulation mechanisms., (Copyright © 2018 by the Congress of Neurological Surgeons.)

Background: Pharmacological prophylaxis for venous thromboembolism (VTE) in the neurosurgical population is still a matter of debate, as the risk-to-benefit ratio is not well defined., Objective: To further evaluate the risk-to-benefit ratio of VTE prophylaxis (VTEP) for all neurosurgical procedures., Methods: A prospective evaluation was performed after the initiation of a VTEP protocol for 11 436 patients undergoing neurosurgical procedures over 24 mo. Unless a bleeding complication was present, 5000 international units of subcutaneous heparin every 8 h was ordered on postoperative day (POD) 1 for spine, POD2 for cranial, and by POD4 for subdural, intracerebral, and epidural hematoma cases. Incidence of VTE and any subsequent bleeding complications were noted., Results: A total of 70 VTEs (0.6% overall) were documented (28 deep vein thrombosis, 42 pulmonary embnolism). The highest rates of VTE were associated with deformity (6.7%); open cerebrovascular (6.5%); subdural, intracerebral, and epidural hematoma (3.2%); spinal trauma (2.4%); and craniotomy for tumor (1.6%) cases. Seven cases of deep vein thrombosis progressed to pulmonary embolisms, and 66 of 70 VTEs occurred while on pharmacological VTEP. Fifty-four bleeding complications occurred on or after POD2 following initiation of VTEP. These bleeding complications consisted of any new clinically or radiographically observed hemorrhages. Twenty-eight of the 54 delayed bleeding complications required operative intervention with 1 mortality. Forty-five patients were on anticoagulation when the initial bleeding event occurred. Overall, an estimated 0.5% incidence of delayed bleeding complications was noted with 99.4% of patients within the study cohort remaining VTE free., Conclusion: This VTEP protocol was determined to afford a good risk-to-benefit ratio for a wide variety of neurosurgical procedures.

Background: The endoscopic endonasal approach (EEA) has been proposed as a potential alternative for ventral brainstem lesions. The surgical anatomy, feasibility, and limitations of the EEA for intrinsic brainstem lesions are still poorly understood., Objective: To describe the surgical planning, anatomy, and technique of an intrinsic pontine glioma operated via EEA., Methods: Six-human brainstems were prepared for white matter microdissection. Ten healthy subjects were studied with high-definition fiber tractography (HDFT). A 56-yr-old female with right-hemiparesis underwent EEA for an exophytic pontine glioma. Pre- and postoperative HDFTs were implemented., Results: The corticospinal tracts (CSTs) are the most eloquent fibers in the ventral brainstem. At the pons, CSTs run between the pontine nuclei and the middle cerebellar peduncle (MCP). At the lower medulla, the pyramidal decussation leaves no room for safe ventral access. In our illustrative case, preoperative HDFT showed left-CST displaced posteromedially and partially disrupted, right-CST posteriorly displaced, and MCP severely disrupted. A transclival exposure was performed achieving a complete resection of the exophytic component with residual intra-axial tumor. Immediately postop, patient developed new left-side abducens nerve palsy and worse right-hemiparesis. Ten days postop, her strength returned to baseline. HDFT showed preservation and trajectory restoration of the CSTs., Conclusion: The EEA provides direct access to the ventral brainstem, overcoming the limitations of lateral approaches. For intrinsic pathology, HDFT helps choosing the most appropriate surgical route/boundaries for safer resection. Further experience is needed to determine the indications and limitations of this approach that should be performed by neurosurgeons with high-level expertise in EEA.

Background: Despite abundant published support of patch angioplasty during carotid endarterectomy (CEA), primary closure is still widely used. The reasons underlying the persistence of primary closure are not quite evident in the literature., Objective: To present our experience with primary closure in CEA, and provide a rationale for its persistent wide use., Methods: Medical records of all patients undergoing CEA by the senior author (R.F.) were retrospectively reviewed. Follow-up was supplemented with a telephone interview and completion of a structured questionnaire. A review of the current literature was performed., Results: From 1998 to 2010, the senior author performed 111 CEAs. Average cross-clamp time was 33 ± 11 minutes. Postoperative complications included 1 non-ST-elevation myocardial infarction and 2 strokes. No deaths, cranial-nerve deficits, or acute reocclusions were observed. After a mean follow-up of 64.6 months (7170.6 case-months), there were 3 contralateral strokes and 7 deaths. There were no ipsilateral strokes or restenoses >50%. Follow-up medication compliance was 94.6% for antiplatelet agents and 91.9% for statins. The outcomes of the current study were comparable to those of the available trials comparing patch angioplasty with primary closure. A careful evaluation of the literature revealed a number of reasons potentially explaining the persistent use of patch angioplasty., Conclusion: In conjunction with contemporary medical management, primary closure during CEA may yield results comparable or superior to patch angioplasty. Advantages of primary closure include shorter cross-clamp times and elimination of graft-specific complications.