Use of a Monopolar Stimulator to Preserve the Frontotemporal Branches of the Facial Nerve During a Pterional Approach: 2-Dimensional Operative Video.

Preservation of the frontotemporal branches of the facial nerve is essential to obtain good cosmetic outcomes after anterolateral cranial base approaches.1,2 Since the description of the interfacial dissection, most nerve injuries are due to retraction of the nerve fibers and not direct transection.3-5 In this video, we showcase the use of a monopolar stimulator to guide the placement of hook retractors and assess no undue retraction is applied to the nerve fibers during a pterional craniotomy. This simple tool can help in preserving frontalis function after anterolateral skull base craniotomies. Institutional review board approval was not required; the patient consented to the procedure and to the publication of his/her image.

Endoscopic Endonasal Approach to the Ventral Petroclival Fissure: Anatomical Findings and Surgical Techniques.

Objective The endoscopic endonasal approach has emerged as an excellent option for the treatment of lesions involving the petroclival fissure (PCF). Here, we investigate the surgical anatomy of the ventral PCF and its application in endoscopic endonasal surgery. Methods Sixteen head specimens were used to investigate the anatomical features of PCF and relevant technical nuances in translacerum, extreme medial, and contralateral transmaxillary (CTM) approaches. Two representative endoscopic endonasal surgeries involving the PCF were selected to illustrate the clinical application. Results From the endoscopic endonasal view, the ventral PCF is presented as a lazy L sign, which is divided into two distinct segments: (1) upper (or petrosphenoidal) segment, which extends vertically from the foramen lacerum inferiorly to the junction of the petrosal process of sphenoid bone and petrous apex superiorly, and (2) lower (or petroclival) segment, which extends inferolaterally from the foramen lacerum to the ventral jugular foramen. Approaching both segments of the ventral PCF first requires full exposure of the foramen lacerum, followed either by exposure of the anterior wall of cavernous sinus and paraclival internal carotid artery for upper segment access, or transection of pterygosphenoidal fissure and Eustachian tube mobilization for lower segment access. Combined with a CTM approach, the lateral extension of the surgical access can be improved for both upper and lower segment PCF approaches. Conclusion This study provides a detailed investigation of the microsurgical anatomy of the ventral part of PCF, relevant surgical approaches, and technical nuances that may facilitate its safe exposure intraoperatively.

Adequate control of seizures in a case of lead migration and neuromodulation of the posterior Sylvian junction: A case report.

Background: This report aims to describe the neuromodulation effect on seizure control in a patient with a left hippocampal migrated electrode to the Posterior Sylvian Junction (PSJ) during a follow-up of 17 years. Case Description: We report a case of a female patient with drug-resistant epilepsy who initiated at seven years old and underwent a stereotactic frame-based insertion of a left hippocampal electrode for deep brain stimulation (DBS). Posterior migration of the electrode was identified at PSJ by postoperative magnetic resonance imaging one month after surgery. A consistent seizure reduction (Engel IC) was obtained with 2v-120 uS-145 Hz, contacts 0-3 negative, casing positive DBS parameters and maintained to this day. Patient data were collected from electronic medical records preceded by obtaining an informed consent for research and publication purposes. Stimulation parameter adjustments were confirmed with the digital records of the local device provider (Medtronic). Results: PSJ is a connectivity confluence point of white matter pathways in the posterior quadrant of the hemispheres. White mater DBS could be considered for research as a potential complementary target for neuromodulation of refractory epilepsy.

Delimitation of the risk area of the vertebral artery during the paramedian suboccipital approach.

OBJECTIVE: The V3 segment of the vertebral artery (V3-VA) is at risk during diverse approaches to the craniovertebral junction. Our objective is to present a system of anatomic and topographic landmarks to identify the V3-VA during the paramedian suboccipital approach (PMSOA) with the help of minimal or basic tools. MATERIAL AND METHODS: The first was a retrospective analysis of the angiotomography (CTA) of 50 patients over 18-years old, and 9 anatomical dissections. A series of lines were defined between the different bony landmarks. Within this lines the risk area of the vertebral artery (RAsV3-VA) and the risk point of the vertebral artery (RPsV3-VA) were defined. The second stage was a prospective study, where the previously defined measurements were carried out by using neuronavigation in 10 patients (20 sides) operated with the PMSO approach in order to confirm the presence of the V3 segment in the RAsV3-VA and RPsV3-VA. RESULTS: In the first stage, the V3 segment was found in the middle third of the X line in 96,6% of the cases. The distance between the inion and the UCP (percentile 5) was 20 mm and to the LCP (percentile 95) was 40 mm. In the range between the UCP and the LCP, in the middle third of the inion-mastoid line (RAsV3-VA), we found 90% of the V3-VA. The measurements taken during the second stage revealed that the artery was in the middle third of the X line in 97% of the cases. 85% of the patients presented the total of the V3s-VA on the RAsV3-VA and in 85% there was a direct relationship with the V3 segment and the RPV3s-VA. CONCLUSION: We propose an easy-to-implement system to delimit the risk area of the V3-VA during the PMSOA. We believe that these landmarks provide a practical, reliable, costless and useful tool that could decrease the risk of lesion of the V3-VA during this approach without the need of using.

Probabilistic coverage of the frontal aslant tract in young adults: Insights into individual variability, lateralization, and language functions.

The frontal aslant tract (FAT) is a crucial neural pathway of language and speech, but little is known about its connectivity and segmentation differences across populations. In this study, we investigate the probabilistic coverage of the FAT in a large sample of 1065 young adults. Our primary goal was to reveal individual variability and lateralization of FAT and its structure-function correlations in language processing. The study utilized diffusion MRI data from 1065 subjects obtained from the Human Connectome Project. Automated tractography using DSI Studio software was employed to map white matter bundles, and the results were examined to study the population variation of the FAT. Additionally, anatomical dissections were performed to validate the fiber tracking results. The tract-to-region connectome, based on Human Connectome Project-MMP parcellations, was utilized to provide population probability of the tract-to-region connections. Our results showed that the left anterior FAT exhibited the most substantial individual differences, particularly in the superior and middle frontal gyrus, with greater variability in the superior than the inferior region. Furthermore, we found left lateralization in FAT, with a greater difference in coverage in the inferior and posterior portions. Additionally, our analysis revealed a significant positive correlation between the left FAT inferior coverage area and the performance on the oral reading recognition (p = .016) and picture vocabulary (p = .0026) tests. In comparison, fractional anisotropy of the right FAT exhibited marginal significance in its correlation (p = .056) with Picture Vocabulary Test. Our findings, combined with the connectivity patterns of the FAT, allowed us to segment its structure into anterior and posterior segments. We found significant variability in FAT coverage among individuals, with left lateralization observed in both macroscopic shape measures and microscopic diffusion metrics. Our findings also suggested a potential link between the size of the left FAT's inferior coverage area and language function tests. These results enhance our understanding of the FAT's role in brain connectivity and its potential implications for language and executive functions.

The Temporoparietal Fascia Flap Transposition Technique for Ventral Skull Base Reconstruction: Anatomic Analysis and Surgical Application.

BACKGROUND AND OBJECTIVES: The temporoparietal fascia (TPF) flap is an alternative for revision endoscopic skull base reconstruction in the absence of the nasoseptal flap, and we aimed to investigate the anatomy and surgical application of TPF flap transposition in endoscopic endonasal surgery. METHODS: Six lightly embalmed postmortem human heads and 30 computed tomography angiography imaging scans were used to analyze the anatomic features of the TPF flap transposition technique. Three cases selected from a 512 endoscopic endonasal cases database were presented for the clinical application of the TPF flap. RESULTS: The TPF flap, composed by the deepest 3 scalp layers (galea aponeurotica, loose areolar connective tissue, and pericranium), can be harvested and then transposed through the infratemporal-maxillary-pterygoid tunnel to the ventral skull base. The superficial temporal artery as its feeding artery, gives frontal and parietal branches with similar diameter (1.5 ± 0.3 mm) at its bifurcation. The typical bifurcation was present in 50 sides (83.3%), with single (frontal) branch in 5 sides (8.3%), single (parietal) branch in 2 sides (3.3%), and multiple branches (>2) in 3 sides (5%). The transposed TPF flap was divided into 3 parts according to its anatomic location: (1) infratemporal part with an area of 19.5 ± 2.5 cm2, (2) maxillary part with an area of 23.7 ± 2.8 cm2, and (3) skull base part with an area of 44.2 ± 4 cm2. Compared with the nasoseptal flap, nasal floor flap, inferior turbinate flap, and extended septal flap, the coverage area of the skull base part of the TPF flap was significantly larger than any of them (P < .0001). CONCLUSION: The TPF flap technique is an effective alternative for endoscopic endonasal skull base reconstruction. The TPF flap could successfully cover large skull base defects through the infratemporal-maxillary-pterygoid tunnel.

Comparative Analysis of Surgical Working Corridors for Meckel Cave Trigeminal Schwannomas: A Quantitative Anatomic Study.

BACKGROUND AND OBJECTIVES: Volumetric analysis of the working corridors of the interdural approach to the Meckel cave may lead to a selection of routes which are anatomically more advantageous for trigeminal schwannoma resection. The herein-reported anatomic study quantitively compares the infratrochlear (IT) transcavernous, anteromedial (AM), and anterolateral (AL) corridors, highlighting their feasibility, indications, advantages, and limitations. METHODS: Anatomic boundaries and depth of Meckel cave, porus trigeminus, IT transcavernous, AM, and AL corridors were identified in 20 formalin-fixed latex-injected cadaveric heads and were subsequently measured. The corridor areas and volumes were derived accordingly. Each opening angle was also calculated. Angles and volumes were compared using analysis of variance. Statistical significance was set at a P -value <.05. RESULTS: The IT transcavernous corridor volume was greater than that of the AM and AL. The opening angle of the AM middle fossa triangle was wider than the other 2. CONCLUSION: The IT corridor can be advantageous for Meckel cave schwannomas invading the cavernous sinus and those with a notable extension into the posterior fossa because the transcavernous approach maximizes the working space into the retrosellar area. The AM middle fossa corridor is strategic in schwannomas confined to the Meckel cave with a minor extension into the posterior fossa. It raises the chance of total resection with a single approach involving the porus trigeminus opening.

Resection of corticotroph microadenomas invading the medial wall of the cavernous sinus in two cases of a primary and recurrent case of Cushing's disease.

Emerging evidence from multiple highly specialized groups continues to support a role for resection of the medial wall of the cavernous sinus when it is invaded by functional pituitary adenomas, to offer durable biochemical remission. The authors present two cases of Cushing's disease that underscore the power of this surgical technique in achieving remission in microadenomas that ectopically present in the cavernous sinus or have invaded the medial wall of the sinus. This video demonstrates key steps in the safe removal of the medial wall of the cavernous sinus and successful resection of tumor burden in the cavernous sinus for sustained postoperative remission. The video can be found here: https://stream.cadmore.media/r10.3171/2023.4.FOCVID2323.

Endoscopic Endonasal Transtuberculum Approach for Pediatric Tuberoinfundibular Craniopharyngioma: 2-Dimensional Operative Video.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: The endoscopic endonasal transtuberculum approach grants access to suprasellar and retrochiasmatic lesions with hypothalamic involvement. Here, we present a case of a 13-year-old boy with a history of stunted growth, decreased vision, headaches, and low energy with a tuberoinfundibular craniopharyngioma. The patient consented to the procedure. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: Evaluation of the sphenoid sinus pneumatization, internal carotid artery disposition, presence of clinoidal rings, variations of the infrachiasmatic corridor (optic chiasm location, height of dorsum sella), and location of the pituitary stalk are crucial for surgical strategy. ESSENTIALS STEPS OF THE PROCEDURE: Harvesting of nasoseptal flap and access to the sphenoid sinus; drilling the sella, tuberculum, and chiasmatic sulcus up to the limbus sphenoidalis and laterally exposing the clinoidal carotid artery segment; wide dural opening to the level of distal rings inferolaterally and falciform ligaments superolaterally; identification and coagulation of superior hypophyseal branches providing tumor supply; intracapsular dissection and debulking and subpial sharp dissection at the hypothalamic tumor interface to achieve complete removal; and reconstruction with inlay collagen, fascia lata, and nasoseptal flap. PITFALLS/AVOIDANCE OF COMPLICATIONS: Preservation of the superior hypophyseal arteries and stalk is essential for preventing pituitary dysfunction. Preoperative reckoning of hypothalamic invasion and identification of adequate interface aids in avoiding complications. To reduce CSF leak risk, multilayer reconstruction was performed and lumbar drain placed postoperatively. VARIANTS AND INDICATIONS FOR THEIR USE: For retroclival extension, intradural pituitary transposition should be considered to expand the corridor; in patients with preoperative hypopituitarism, pituitary sacrifice is most effective to increase retroclival access.

The Pterygosphenoidal Triangle: Surgical Anatomy and Case Series in Endoscopic Endonasal Skull Base Surgery.

BACKGROUND: Safe exposure of the lacerum segment of the carotid artery remains a challenge in endoscopic endonasal surgery. OBJECTIVE: To introduce the pterygosphenoidal triangle as a novel and reliable landmark for facilitating access to the foramen lacerum. METHODS: Fifteen colored silicone-injected anatomic specimens were dissected using an endoscopic endonasal approach to the foramen lacerum region in a stepwise manner. Twelve dried skulls were studied and 30 high-resolution computed tomography scans were analyzed to measure the borders and angles of the pterygosphenoidal triangle. Surgical cases incorporating the foramen lacerum exposure between July 2018 and December 2021 were reviewed to provide surgical outcomes of the proposed surgical technique. RESULTS: The pterygosphenoidal triangle is delineated by the pterygosphenoidal fissure medially and the vidian nerve laterally. The palatovaginal artery is located at the base of the triangle anteriorly, while the apex is formed by the pterygoid tubercle posteriorly, which leads to the anterior wall of the foramen lacerum and lacerum internal carotid artery. In the reviewed surgical cases, 39 patients underwent 46 foramen lacerum approaches for resection of pituitary adenoma (12 patients), meningioma (6 patients), chondrosarcoma (5 patients), chordoma (5 patients), or other lesions (11 patients). There were no carotid injuries or ischemic events. Near-total resection was achieved in 33 (85%) of 39 patients (gross-total in 20 [51%]). CONCLUSION: This study details the pterygosphenoidal triangle as a novel and practical anatomic surgical landmark for safe and effective exposure of the foramen lacerum in endoscopic endonasal surgery.

Reappraisal of the anatomy of the frontotemporal branches of the facial nerve.

OBJECTIVE: The anatomy of the temporal branches of the facial nerve (FN) has been widely described in the neurosurgical literature because of its relevance in anterolateral approaches to the skull base and implication in frontalis palsies from these approaches. In this study, the authors attempted to describe the anatomy of the temporal branches of the FN and identify whether there are any FN branches that cross the interfascial space of the superficial and deep leaflets of the temporalis fascia. METHODS: The surgical anatomy of the temporal branches of the FN was studied bilaterally in 5 embalmed heads (n = 10 extracranial FNs). Exquisite dissections were performed to preserve the relationships of the branches of the FN and their relationship to the surrounding fascia of the temporalis muscle, the interfascial fat pad, the surrounding nerve branches, and their final terminal endpoints near the frontalis and temporalis muscles. The authors correlated their findings intraoperatively with 6 consecutive patients with interfascial dissection in which neuromonitoring was performed to stimulate the FN and associated twigs that were observed to be interfascial in 2 of them. RESULTS: The temporal branches of the FN stay predominantly superficial to the superficial leaflet of the temporal fascia in the loose areolar tissue near the superficial fat pad. As they course over the frontotemporal region, they give off a twig that anastomoses with the zygomaticotemporal branch of the trigeminal nerve, which crosses the superficial layer of the temporalis muscle, spanning the interfascial fat pad, and then pierces the deep temporalis fascial layer. This anatomy was observed in 10 of the 10 FNs dissected. Intraoperatively, stimulation of this interfascial segment yielded no facial muscle response up to 1 mA in any of the patients. CONCLUSIONS: The temporal branch of the FN gives off a twig that anastomoses with the zygomaticotemporal nerve, which crosses the superficial and deep leaflets of the temporal fascia. Interfascial surgical techniques aimed at protecting the frontalis branch of the FN are safe in their efforts to protect against frontalis palsy with no clinical sequelae when executed properly.

Refining the Anatomy of Percutaneous Trigeminal Rhizotomy: A Cadaveric, Radiological, and Surgical Study.

BACKGROUND: Percutaneous trigeminal rhizotomy (PTR) is a widely used procedure for trigeminal neuralgia. However, comprehensive analyses that combine anatomic, radiological, and surgical considerations are rare. OBJECTIVE: To present high-quality anatomic dissections and radiological studies that highlight the technical nuances of this procedure. METHODS: Six silicon-injected postmortem heads underwent PTR. The surgical corridors were dissected, and the neurovascular relationships were studied. In addition, 20 dried human skulls and 50 computed tomography angiography and MRI scans were collected to study the anatomic relationships for a customized puncture corridor. RESULTS: The PTR corridor was divided into 3 segments: the buccal segment (length, 34.76 ± 7.20 mm), the inferior temporal fossa segment (length, 42.06 ± 6.92 mm), and the Meckel cave segment (length, 24.75 ± 3.34 mm). The puncture sagittal (α) and axial (ß) angles measured in this study were 38.32° ± 4.62° and 19.13° ± 2.82°, respectively. The precondylar reference line coincided with the foramen ovale in 75% of the computed tomography angiography scans, and the postcondylar line coincided with the carotid canal in 70% of the computed tomography angiography scans; these lines serve as the intraoperative landmarks for PTR. The ovale-carotid-pterygoid triangle, delineated by drawing a line from the foramen ovale to the carotid canal and the lateral pterygoid plate, is a distinguished landmark to use for avoiding neurovascular injury during fluoroscopy. CONCLUSION: Knowledge of the anatomic and radiological features of PTR is essential for a successful surgery, and a customized technical flow is a safe and effective way to access the foramen ovale.

Frontotemporal-Orbitozygomatic Approach and Its Variants: Technical Nuances and Video Illustration.

The frontotemporal-orbitozygomatic (FTOz) approach is an extension of the traditional pterional approach. It provides the neurosurgeon with a wide access to the skull base with minimal or no brain retraction needed; it also offers a panoramic view that enables various trajectories toward the anterior, middle, and central cranial fossae as well as the upper segment of the posterior cranial fossa. Intracranial lesions that can be addressed using the FTOz approach include large medial sphenoid wing and spheno-orbital meningiomas; suprasellar and parasellar tumors; lesions of the orbital apex, interpeduncular cistern, third ventricle, and upper paraclival regions; and anterior communicating artery and basilar-tip aneurysms. In this article, we discuss the advantages and disadvantages of the FTOz approach and describe related technical nuances and common pitfalls. Our goal was to provide an up-to-date report of this time-tested surgical approach using original high-quality dissections, 3-dimensional models, and 2-dimensional 4K videos to serve as a reliable and practical educational resource for neurosurgery trainees and junior neurosurgeons. A case example is also provided to show the 1-piece orbitozygomatic approach.

Combined transpetrosal approach for giant petroclival meningioma: 2-dimensional operative video.

Petroclival meningiomas are extremally challenging lesions due to their deep location and close relation to critical neurovascular structures. Several approaches have been described to achieve gross-total resection with low morbidity and mortality. In this 2-dimensional operative video, the authors show a simultaneous combined transpetrosal approach. The patient is a 44-year-old woman with an 8-month history of gait imbalance with evidence of a giant petroclival meningioma on neuroimaging. She underwent a combined middle fossa approach with anterior petrosectomy and retrosigmoid/retrolabyrinthine approach to achieve gross-total tumor resection. The postoperative course was characterized by trigeminal neuralgia, and neuroimaging showed gross-total resection of the tumor. The video can be found here: https://stream.cadmore.media/r10.3171/2022.1.FOCVID21248.

Endoscopic Anatomy of the Zygomatic Nerve: Implications for the Endoscopic Transmaxillary Approach.

Introduction Understanding the anatomic features of the zygomatic nerve is critical for performing the endoscopic transmaxillary approach properly. Injury to the zygomatic nerve can result in facial numbness and corneal problems. Objective To evaluate the surgical anatomy of the zygomatic nerve and its segments from an endoscopic endonasal perspective for clinical implications of performing the endoscopic transmaxillary approach. Methods The origin, course, length, and segments of the zygomatic nerve were studied in four specimens from an endonasal perspective. Results The zygomatic nerve arises 4.1 ± 1.7 mm from the foramen rotundum of the maxillary nerve in the superolateral pterygopalatine fossa (PPF). According to its anatomic region in endonasal endoscopic surgery, we divided the zygomatic nerve into two segments: the PPF segment, from origin to the point of entry under Muller's muscle, which runs superolaterally to the inferior orbital fissure (IOF) (length, 4.6 ± 1.3 mm), and the IOF segment, starting at the entry point in Muller's muscle and terminating at the exit point in the IOF, which travels between Muller's muscle and the great wing of the sphenoid bone (length, 19.6 ± 3.6 mm). In the transmaxillary approach, the zygomatic nerve is a critical landmark in the superolateral PPF. Conclusion The zygomatic nerve travels in the PPF and the IOF; better visualization and preservation of this nerve during endonasal endoscopic surgery are crucial for successful outcomes.

Intracranial Breakthrough Through Cavernous Sinus Compartments: Anatomic Study and Implications for Pituitary Adenoma Surgery.

BACKGROUND: Pituitary adenomas (PAs) with cavernous sinus (CS) invasion can extend into the intradural space by breaking through the CS walls. OBJECTIVE: To elaborate on the potential breakthrough route through CS compartments for invasive PAs and describe relevant surgical anatomy and technical nuances, with an aim to improve resection rates. METHODS: Twelve colored silicon-injected human head specimens were used for endonasal and transcranial dissection of the CS walls; ligaments, dural folds, and cranial nerves on each compartment were inspected. Two illustrative cases of invasive PA are also presented. RESULTS: The potential breakthrough routes through the CS compartments had unique anatomic features. The superior compartment breakthrough was delimited by the anterior petroclinoidal ligament laterally, posterior petroclinoidal ligament posteriorly, and interclinoidal ligament medially; tumor extended into the parapeduncular space with an intimate spatial relationship with the oculomotor nerve and posterior communicating artery. The lateral compartment breakthrough was limited by the anterior petroclinoidal ligament superiorly and ophthalmic nerve inferiorly; tumor extended into the middle fossa, displacing the trochlear nerve and inferolateral trunk to reach the medial temporal lobe. The posterior compartment breakthrough delineated by the Gruber ligament, petrosal process of the sphenoid bone, and petrous apex inferiorly, posterior petroclinoidal ligament superiorly, and dorsum sellae medially; tumor displaced or encased the abducens nerve and inferior hypophyseal artery and compressed the cerebral peduncle. CONCLUSION: The superior lateral and posterior components of the CS are potential routes for invasion by PAs. Better identification of CS breakthrough patterns is crucial for achieving higher gross total resection and remission rates.