The Utility of a "Second-Look" Debridement Following Endonasal Skull Base Surgery in the Pediatric Population.

Background Sinonasal debridement is typically performed in the weeks following endonasal skull base surgery (ESBS). In the pediatric population, this second-look procedure may require general anesthesia; however, there is currently little evidence assessing the benefit of this practice. Methods This was a multicenter retrospective study of pediatric patients (age <18 years) undergoing a planned second-look debridement under general anesthesia following ESBS. Intraoperative findings, interventions performed, and perioperative complications were reviewed. Multivariate regression analysis was performed to identify associations between intraoperative findings and clinical factors. Results We reviewed 69 cases of second-look debridements (age mean 8.6 ± 4.2 years, range: 2-18 years), occurring a mean of 18.3 ± 10.3 days following ESBS. All abnormal findings were noted in patients age ≤12 years. Synechiae were noted in 8.7% of cases, bacterial rhinosinusitis in 2.9%, and failed reconstruction with cerebrospinal fluid leak in 4.5% (two cases of flap malposition and one case of flap necrosis). All failed reconstructions were noted following expanded endonasal cases for craniopharyngioma, and in each case, a revision reconstruction was performed during the second-look surgery. Synechiae were not significantly associated with younger age, revision cases, or cases with reconstructive flaps. There were no perioperative complications. Conclusion Second-look debridement under general anesthesia may be useful in the identification and intervention of sinonasal pathology following endoscopic skull base surgery, particularly in children ≤12 years old or those with pedicled flap reconstructions. Larger controlled studies are warranted to validate this practice and refine indications and timing of this second procedure.

Supramarginal resection of skull base chordomas: proof of concept and preliminary outcomes.

OBJECTIVE: The mainstay of treatment for skull base chordoma (SBC) is maximal safe resection followed by radiotherapy. However, even after gross-total resection (GTR), the recurrence rate is high due to microscopic disease in the resection margins. Therefore, supramarginal resection (SMR) could be beneficial, as has been shown for sacral chordoma. The paradigm of postoperative radiation therapy for every patient has also begun to change, as molecular profiling has shown variability in the risk of recurrence. The aim of this study was to present the concept of SMR applied to SBC, along with an individualized decision for postoperative radiation therapy. METHODS: This is a retrospective analysis of all SBCs operated on by the senior author between 2018 and 2023. SMR was defined as negative histological margins of bone and/or dura mater, along with evidence of bone resection beyond the tumor margins in the craniocaudal and lateral planes on postoperative imaging. Tumors were classified into 3 molecular recurrence risk groups (group A, low risk; group B, intermediate risk; and group C, high risk). Postoperative radiation therapy was indicated in group C tumors, in group B chordomas without SMR, or in cases of patient preference. RESULTS: Twenty-two cases of SBC fulfilled the inclusion criteria. SMR was achieved in 12 (55%) cases, with a mean (range) amount of bone resection beyond the tumor margins of 10 (2-20) mm (+40%) in the craniocaudal axis and 6 (1-15) mm (+31%) in the lateral plane. GTR and near-total resection were each achieved in 5 (23%) cases. Three (19%) tumors were classified as group A, 12 (75%) as group B, and 1 (6%) as group C. Although nonsignificant due to the small sample size, the trends showed that patients in the SMR group had smaller tumor volumes (13.9 vs 19.6 cm3, p = 0.35), fewer previous treatments (33% vs 60% of patients, p = 0.39), and less use of postoperative radiotherapy (25% vs 60%, p = 0.19) compared to patients in the non-SMR group. There were no significant differences in postoperative CSF leak (0% vs 10%, p = 0.45), persistent cranial nerve palsy (8% vs 20%, p = 0.57), and tumor recurrence (8% vs 10%, p = 0.99; mean follow-up 15 months) rates between the SMR and non-SMR groups. CONCLUSIONS: In select cases, SMR of SBC appears to be feasible and safe. Larger cohorts and longer follow-up evaluations are necessary to explore the benefit of SMR and individualized postoperative radiation therapy on progression-free survival.

Endoscopic endonasal pituitary sacrifice for select tumors with retrochiasmatic and/or retrosellar extension: surgical anatomy, operative technique, and case series.

OBJECTIVE: Tumors located in the retrochiasmatic region with extension to the third ventricle might be difficult to access when the pituitary-chiasmatic corridor is narrow. Similarly, tumor extension into the interpeduncular and retrosellar space poses a major surgical challenge. Pituitary transposition techniques have been developed to gain additional access. However, when preoperative pituitary function is already impaired or the risk of postoperative panhypopituitarism (PH) is considered to be particularly high, removal of the pituitary gland (PG) might be the preferred option to increase the working corridor. The aim of this study was to describe the relevant surgical anatomy, operative steps, and clinical experience with the endoscopic endonasal pituitary sacrifice (EEPS) and transsellar approach. METHODS: This study comprised anatomical dissections to highlight the relevant surgical steps and a retrospective case series reporting clinical characteristics, indications, and outcomes of patients who underwent EEPS. The surgical technique is as follows: both lateral opticocarotid recesses are exposed laterally, the limbus sphenoidale superiorly, and the sellar floor inferiorly. After opening the dura, the PG is detached circumferentially and mobilized off the medial walls of the cavernous sinuses. The descending branches of the superior hypophyseal artery are coagulated, and the stalk is transected. After removal of the PG, drilling of the dorsum sellae and bilateral posterior clinoidectomies are performed to gain access to the hypothalamic region, interpeduncular, and prepontine cisterns. RESULTS: From 2018 to 2023, 11 patients underwent EEPS. The cohort comprised mostly tuberoinfundibular craniopharyngiomas (n = 8, 73%). Seven (64%) patients had partial or complete anterior PG dysfunction preoperatively, while 4 (36%) had preoperative diabetes insipidus. Because of the specific tumor configuration, the chance of preserving endocrine function was estimated to be very low in patients with intact function. The main reasons for pituitary sacrifice were impaired visibility and surgical accessibility to the retrochiasmatic and retrosellar spaces. Gross-total tumor resection was achieved in 10 (91%) patients and near-total resection in 1 (9%) patient. Two (18%) patients experienced a postoperative CSF leak, requiring surgical revision. CONCLUSIONS: When preoperative pituitary function is already impaired or the risk for postoperative PH is considered particularly high, the EEPS and transsellar approach appears to be a feasible surgical option to improve visibility and accessibility to the retrochiasmatic hypothalamic and retrosellar spaces, thus increasing tumor resectability.

Multicenter Registry of Adenomas of the Pituitary and Related Disorders: Initial Description of Cushing Disease Cohort, Surgical Outcomes, and Surgeon Characteristics.

BACKGROUND AND OBJECTIVES: To address the lack of a multicenter pituitary surgery research consortium in the United States, we established the Registry of Adenomas of the Pituitary and Related Disorders (RAPID). The goals of RAPID are to examine surgical outcomes, improve patient care, disseminate best practices, and facilitate multicenter surgery research at scale. Our initial focus is Cushing disease (CD). This study aims to describe the current RAPID patient cohort, explore surgical outcomes, and lay the foundation for future studies addressing the limitations of previous studies. METHODS: Prospectively and retrospectively obtained data from participating sites were aggregated using a cloud-based registry and analyzed retrospectively. Standard preoperative variables and outcome measures included length of stay, unplanned readmission, and remission. RESULTS: By July 2023, 528 patients with CD had been treated by 26 neurosurgeons with varying levels of experience at 9 academic pituitary centers. No surgeon treated more than 81 of 528 (15.3%) patients. The mean ± SD patient age was 43.8 ± 13.9 years, and most patients were female (82.2%, 433/527). The mean tumor diameter was 0.8 ± 2.7 cm. Most patients (76.6%, 354/462) had no prior treatment. The most common pathology was corticotroph tumor (76.8%, 381/496). The mean length of stay was 3.8 ± 2.5 days. The most common discharge destination was home (97.2%, 513/528). Two patients (0.4%, 2/528) died perioperatively. A total of 57 patients (11.0%, 57/519) required an unplanned hospital readmission within 90 days of surgery. The median actuarial disease-free survival after index surgery was 8.5 years. CONCLUSION: This study examined an evolving multicenter collaboration on patient outcomes after surgery for CD. Our results provide novel insights on surgical outcomes not possible in prior single-center studies or with national administrative data sets. This collaboration will power future studies to better advance the standard of care for patients with CD.

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.

The RAPID Consortium: A Platform for Clinical and Translational Pituitary Tumor Research.

Objectives Pituitary tumor treatment is hampered by the relative rarity of the disease, absence of a multicenter collaborative platform, and limited translational-clinical research partnerships. Prior studies offer limited insight into the formation of a multicenter consortium. Design The authors describe the establishment of a multicenter research initiative, Registry of Adenomas of the Pituitary and Related Disorders (RAPID), to encourage quality improvement and research, promote scholarship, and apply innovative solutions in outcomes research. Methods The challenges encountered during the formation of other research registries were reviewed with those lessons applied to the development of RAPID. Setting/Participants RAPID was formed by 11 academic U.S. pituitary centers. Results A Steering Committee, bylaws, data coordination center, and leadership team have been established. Clinical modules with standardized data fields for nonfunctioning adenoma, prolactinoma, acromegaly, Cushing's disease, craniopharyngioma, and Rathke's cleft cyst were created using a Health Insurance Portability and Accountability Act-compliant cloud-based platform. Currently, RAPID has received institutional review board approval at all centers, compiled retrospective data and agreements from most centers, and begun prospective data collection at one site. Existing institutional databases are being mapped to one central repository. Conclusion The RAPID consortium has laid the foundation for a multicenter collaboration to facilitate pituitary tumor and surgical research. We sought to share our experiences so that other groups also contemplating this approach may benefit. Future studies may include outcomes benchmarking, clinically annotated biobank tissue, multicenter outcomes studies, prospective intervention studies, translational research, and health economics studies focused on value-based care questions.

Nerve to the zygomaticus major muscle: An anatomical study and surgical application to smile reconstruction.

Smile reconstruction using the branches that supply the zygomaticus major muscle as a motor source is an established procedure in facial reanimation surgery for facial paralysis. However, the anatomy of the nerve to the muscle remains unclear. Therefore, we herein examined the topographical anatomy of the nerve to the zygomaticus major muscle to obtain more detailed information on donor nerve anatomy. Preserved cadaver dissection was performed under a microscope on 13 hemifaces of 8 specimens. The branches that innervate the zygomaticus major muscle and their peripheral routes medial to the muscle were traced and examined. A median of four (ranges 2-4) branches innervated the zygomaticus major muscle. The proximal two branches (near the muscle origin) arose from the zygomatic branch, the second of which was the major branch. The distal branches (near the oral commissure) arose from the buccal branch or zygomaticobuccal plexus. The vertical distance from the caudal margin of the zygomatic arch to the major branch intersecting point was 19 ± 4.0 mm, while the horizontal distance parallel to the Frankfort plane was 29 ± 5.2 mm. The proximal two branches innervating the zygomaticus major muscle were detected in the majority of specimens. The anatomical findings obtained herein on the nerve to the zygomaticus major muscle will allow for more reliable donor selection in facial reanimation surgery.

Eustachian tube dysfunction symptoms after endonasal skull base surgery.

KEY POINTS: ETD symptoms are present in 16% patients with underlying skull base pathology. Preoperative ETD symptoms improve following surgical treatment of skull base pathology. ETD symptoms may worsen in patients with central, posterior, or malignant skull base pathology.

Intraoperative augmented reality fiber tractography complements cortical and subcortical mapping.

Augmented reality (AR) has been found to be advantageous in enhancing visualization of complex neuroanatomy intraoperatively and in neurosurgical education. Another key tool that allows neurosurgeons to have enhanced visualization, namely of white matter tracts, is diffusion tensor imaging (DTI) that is processed with high-definition fiber tractography (HDFT). There remains an enduring challenge in the structural-functional correlation of white matter tracts that centers on the difficulty in clearly assigning function to any given fiber tract when evaluating them through separated as opposed to integrated modalities. Combining the technologies of AR with fiber tractography shows promise in helping to fill in this gap between structural-functional correlation of white matter tracts. This novel study demonstrates through a series of three cases of awake craniotomies for glioma resections a technique that allows the first and most direct evidence of fiber tract stimulation and assignment of function or deficit in vivo through the intraoperative, real-time fusion of electrical cortical stimulation, AR, and HDFT. This novel technique has qualitatively shown to be helpful in guiding intraoperative decision making on extent of resection of gliomas. Future studies could focus on larger, prospective cohorts of glioma patients who undergo this methodology and further correlate the post-operative imaging results to patient functional outcomes.

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.

An Algorithm for the Use of Free Tissue Graft Reconstruction in the Endoscopic Endonasal Approach for Pituitary Tumors.

OBJECTIVE: To identify factors associated with successful use of free tissue grafting versus vascularized reconstruction after resection of pituitary tumors. METHODS: A retrospective chart review of 2 tertiary academic medical centers over 3.5 years was conducted. Variables assessed included age, sex, body mass index, pathology, extent of surgical exposure, cavernous sinus or suprasellar extension, intraoperative cerebrospinal fluid (CSF) leak, grade of leak, previous radiation, and previous surgery. Reconstructive techniques were divided into no reconstruction, free tissue grafts, and vascularized flaps. RESULTS: A total of 485 patients were included. Free grafts were used in 299/485 cases (61.6%) and were more commonly used with smaller approaches (P < 0.001). Larger exposure size and CSF leak grades 2 and 3 were associated with vascularized flap use (P < 0.001 and P = 0.012, respectively). Using multivariate regression, type of reconstruction could be predicted by increasing extent of approach, intraoperative CSF leak grade, and suprasellar extension (odds ratio [OR], 2.014, P < 0.001, 95% confidence interval [CI], 1.335-3.039; OR, 1.636, P = 0.025, 95% CI, 1.064-2.517; OR, 1.975, P < 0.001, 95% CI, 1.554-2.510, respectively). Postoperative CSF leak occurred in 9 of 173 patients (5.2%) with intraoperative leak and was not associated with any factors on analysis. CONCLUSIONS: We propose an algorithm whereby grade 1 CSF leaks in sellar and parasellar resections can be successfully reconstructed with a free graft. Vascularized flaps may be reserved for grade 2 or 3 intraoperative CSF leaks, extended approaches, or tumors with suprasellar extension.

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.

Cytodifferentiation of pituitary tumors influences pathogenesis and cavernous sinus invasion.

OBJECTIVE: Pituitary tumors (PTs) continue to present unique challenges given their proximity to the cavernous sinus, whereby invasive behavior can limit the extent of resection and surgical outcome, especially in functional tumors. The aim of this study was to elucidate patterns of cavernoinvasive behavior by PT subtype. METHODS: A total of 169 consecutive first-time surgeries for PTs were analyzed; 45% of the tumors were functional. There were 64 pituitary transcription factor-1 (PIT-1)-expressing, 62 steroidogenic factor-1 (SF-1)-expressing, 38 T-box transcription factor (TPIT)-expressing, and 5 nonstaining PTs. The gold standard for cavernous sinus invasion (CSI) was based on histopathological examination of the cavernous sinus medial wall and intraoperative exploration. RESULTS: Cavernous sinus disease was present in 33% of patients. Of the Knosp grade 3 and 4 tumors, 12 (19%) expressed PIT-1, 7 (11%) expressed SF-1, 8 (21%) expressed TPIT, and 2 (40%), were nonstaining (p = 0.36). PIT-1 tumors had a significantly higher predilection for CSI: 53% versus 24% and 18% for TPIT and SF-1 tumors, respectively (OR 6.08, 95% CI 2.86-13.55; p < 0.001). Microscopic CSI-defined as Knosp grade 0-2 tumors with confirmed invasion-was present in 44% of PIT-1 tumors compared with 7% and 13% of TPIT and SF-1 tumors, respectively (OR 11.72, 95% CI 4.35-35.50; p < 0.001). Using the transcavernous approach to excise cavernous sinus disease, surgical biochemical remission rates for patients with acromegaly, prolactinoma, and Cushing disease were 88%, 87%, and 100%, respectively. The granule density of PIT-1 tumors and corticotroph functional status did not influence CSI. CONCLUSIONS: The likelihood of CSI differed by transcription factor expression; PIT-1-expressing tumors had a higher predilection for invading the cavernous sinus, particularly microscopically, compared with the other tumor subtypes. This elucidates a unique cavernoinvasive behavior absent in cells from other lineages. Innovative surgical techniques, however, can mitigate tumor behavior and achieve robust, reproducible biochemical remission and gross-total resection rates. These findings can have considerable implications on the surgical management and study of PT biology and behavior.

A simple technique for generating 3D endoscopic images.

Background: Most neurosurgical photographs are limited to two-dimensional (2D), in this sense, most teaching and learning of neuroanatomical structures occur without an appreciation of depth. The objective of this article is to describe a simple technique for obtaining right and left 2D endoscopic images with manual angulation of the optic. Methods: The implementation of a three-dimensional (3D) endoscopic image technique is reported. We first describe the background and core principles related to the methods employed. Photographs are taken demonstrating the principles and also during an endoscopic endonasal approach, illustrating the technique. Later, we divide our process into two sections containing explanations, illustrations, and descriptions. Results: The results of taking a photograph with an endoscope and its assembly to a 3D image has been divided into two parts: Photo acquisition and image processing. Conclusion: We conclude that the proposed method is successful in producing 3D endoscopic images.

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.

Subtemporal Approach and Its Infratentorial Extension: Review and a Comparative Analysis of Different Techniques.

Introduction Surgical resection of lesions occupying the incisural space is challenging. In a comparative fashion, we aimed to describe the anatomy and surgical approaches to the tentorial incisura and to the rostral brainstem via the intradural subtemporal approach and its infratentorial extensions. Methods Six fresh human head specimens (12 sides) were prepared for the microscopic dissection of the tentorial incisura using the intradural subtemporal approach and its infratentorial extensions. Endoscope was used to examine the anatomy of the region inadequately exposed with the microscope. Image-guided navigation was used to confirm bony structures visualized around the petrous apex. Results Standard subtemporal approach provides surgical access to the supratentorial brainstem above the pontomesencephalic sulcus and to the lateral surface of the cerebral peduncle. The linear or triangular tentorial divisions can provide access to the infratentorial space below the pontomesencephalic sulcus. The triangular tentorial flap in comparison with the linear incision obstructs the exposure of anterior incisural space and of the prepontine cistern. Visualization of the brainstem below the trigeminal nerve can be achieved by the anterior petrosectomy. Conclusion Infratentorial extension of the intradural subtemporal approach is technically demanding due to critical neurovascular structures and a relatively narrow corridor. In-depth anatomical knowledge is essential for the selection of the appropriate operative approach and safe surgical resections of lesions.