Surgical Freedom Research Articles

Endoscopic Multiportal Approaches to Meckel's Cave: A Cadaveric Study and a Three-Dimensional Anatomical Video.

Objective This cadaveric study aims to illustrate the lateral transorbital (LTO), transantral transpterygoid (TATP), and endoscopic endonasal approaches (EEA) to Meckel's cave (MC), defining their surgical freedom, area of exposure, and advantages and limitations; thus, refining their respective indications. Design Cadaveric study. Setting The Anatomical Laboratory for Visuospatial Innovations in Otolaryngology and Neurosurgery (ALT-VISION) at the Ohio State University, Wexner Medical Center. Participants Bilateral dissections of five injected cadavers (10 sides). Main Outcome Measures Distance to targets, surgical freedom, and area of exposure provided by the EEA, TATP, and LTO approaches. Results The TATP approach provides superior surgical freedom to foramen rotundum (167.70 ± 29.762 mm). However, surgical freedom to foramen ovale was best when using the LTO approach (75.01 ± 15.773 mm). The EEA provides a superior exposure of the medial MC (mean area of 587.69 ± 38.59 mm 2 ). The LTO and TATP approaches provide equivalent access to the lateral MC (ranging from 468.90 ± 26.98 mm 2 for TATP to 650.11 ± 35.76 mm 2 for the LTO approach). Combining approaches increases the area of exposure significantly (1,237.79 ± 48.41 mm 2 and 1,056.59 ± 48.12 mm 2 for EEA and LTO vs. EEA and TATP). Conclusion This study thoroughly emphasizes the pros and cons of the aforementioned approaches. Each approach may be applied in selected cases as a single or as part of a combined technique. However, conventional approaches are still indicated according to extent and pathology. Level of Evidence : V.

Balloon dilatation versus CO2 laser surgery in subglottic stenosis, a retrospective analysis of therapeutic approaches

Background Subglottic stenosis (SGS) is a narrowing of the airway just below the vocal folds. The cause of SGS and the optimal care for these patients, have remained elusive. Endoscopic surgery of SGS using either balloon or CO2 laser is associated with recurrence. Aims and objectives Our aim is to compare surgery free intervals (SFI) between these two methods applied in two different timeframes. The knowledge gained from this project can support decision-making regarding surgical method choice. Material and methods Participants were retrospectively identified using medical records between 1999 – 2021. We used pre-defined broad inclusion criteria to identify cases using the International Classification of Disease (ICD-10). Primary outcome was surgery free intervals. Results 141 patients were identified, 63 met the criteria for SGS, and were included in the analysis. Results show no significant difference in SFI, comparing balloon dilatation and CO2 laser. Conclusion These findings demonstrate no detected difference in treatment intervals (SFI) when comparing these two commonly used surgical alternatives for SGS. Significance The outcome of this report supports surgical freedom of choice based on the surgeon’s experience and skill and ushes for further studies on patient experience regarding these two therapeutic approaches.

Comparison of the Endoscopic Endonasal Approach with the Endoscopic Supraorbital Keyhole Approach to the Tuberculum Sellae Region: A Quantitatively Cadaveric Study.

The endoscopic endonasal approach (EEA) and the endoscopic supraorbital keyhole approach (eSKA) provide minimally invasive access to tuberculum sellae (TS) tumors. Evaluation of the operating maneuverability is helpful for approach selection. Herein, we compared the two approaches and aimed to provide quantitative anatomic data for surgical decision-making in the management of TS lesions. Fifteen dissections were performed on five silicone-injected cadaveric heads. The EEA and eSKA (both right and left) were performed on each head. Surgical freedom and working angles in the axial and sagittal planes were calculated using the stereotactic navigation system in the selected six targets: the midpoint of the leading edge of the sphenoid sinus (leSS), the midpoint of the edge of the dorsum sellae (eDS), the ipsilateral medial opticocarotid recess (imOCR), the contralateral medial opticocarotid recess (cmOCR), the ipsilateral lateral opticocarotid recess (ilOCR), and the contralateral lateral opticocarotid recess (clOCR). The surgical freedom at the ilOCR and the axial working angles at the leSS, ilOCR, and imOCR (imOCR with excessive manipulation of the optic apparatus) were greater in the eSKA. The EEA provided greater surgical freedom and/or working angles at most targets than eSKA (the surgical freedom at the imOCR, cmOCR, clOCR, and eDS; the axial working angles at the cmOCR and clOCR; and the sagittal working angles at the leSS, imOCR, cmOCR, clOCR, and eDS). The EEA provides greater surgical freedom and working angles for paramedian lesions, whereas the eSKA provides better surgical maneuverability for lesions with lateral extension.

Cavernous Malformations: What They Have Taught Us.

Cavernous Malformations: What They Have Taught Us.

Endoscopic Approaches to the Paramedian Skull Base: An Anatomic Comparison of Contralateral Endonasal and Transmaxillary Strategies.

The expanded endoscopic endonasal approach (EEA) is limited laterally by the internal carotid artery (ICA). The EEA to the paramedian skull base often requires complex maneuvers such as dissection of the Eustachian tube (ET) and foramen lacerum (FL), and ICA manipulation. An endoscopic contralateral transmaxillary approach (CTMA) has the potential to provide adequate exposure of the paramedian skull base while bypassing manipulation of the aforementioned anatomic structures. To quantify and compare the surgical nuances of a CTMA and a contralateral EEA when approaching the paramedian skull base in cadaveric specimens. Five adult cadaveric heads were dissected bilaterally (10 sides) using a contralateral EEA and a CTMA to expose targets of interest at the paramedian skull base. For each target in both approaches, the surgical freedom, angle of attack, the corridor's "perspective angle," and "turning angle" to circumvent the ICA, ET, and FL were obtained. The CTMA achieved superior surgical freedom at all targets ( P < .05) except at the root entry point of cranial nerve XII. The CTMA provided superior vertical and horizontal angles of " attack " to the majority of targets of interest. Except when approaching the root entry point of cranial nerve XII, the CTMA " turning angle " around the ICA, ET, and FL were wider with CTMA for all targets. A CTMA complements the EEA to access the paramedian skull base. A CTMA may limit the need for complex maneuvers such as ICA mobilization and dissection of the ET and FL when approaching the paramedian skull base.

Improving the metric of surgical freedom in the laboratory based on a novel concept of volume.

In laboratory-based neuroanatomical studies, surgical freedom, the most important metric of instrument maneuverability, has been based on Heron's formula. Inaccuracies and limitations hinder this study design's applicability. A new methodology, volume of surgical freedom (VSF), may produce a more realistic qualitative and quantitative representation of a surgical corridor. Overall, 297 data set measurements assessing surgical freedom were completed for cadaveric brain neurosurgical approach dissections. Heron's formula and VSF were calculated specifically to different surgical anatomical targets. Quantitative accuracy and the results of an analysis of human error were compared. Heron's formula for irregularly shaped surgical corridors resulted in overestimation of the respective areas (minimum overestimation 31.3%). In 92% (188/204) of data sets reviewed for influence of offset, areas calculated on the basis of measured data points were larger than areas calculated on the basis of the translated best-fit plane points (mean [SD] overestimation of 2.14% [2.62%]). Variability in the probe length attributable to human error was small (mean [SD] calculated probe length 190.26 mm [5.57 mm]). VSF is an innovative concept that can develop a model of a surgical corridor producing better assessment and prediction of the ability to maneuver and manipulate surgical instruments. VSF corrects for deficits in Heron's method by generating the correct area for an irregular shape using the shoelace formula, adjusting the data points to account for offset, and attempting to correct for human error. VSF produces 3-dimensional models and, therefore, is a preferable standard for assessing surgical freedom.

Endoscopic Endonasal Accessibility and Maneuverability Around the Internal Carotid Artery from Distal Dural Ring to Foramen Lacerum: Cadaveric Study

Background: Expanded-endoscopic endonasal approaches (eEEA) to surgical targets around the internal carotid artery (ICA) remain inspiring and necessitate a special learning curve. Methods: Six formalin-fixed heads were dissected to study the 360° accessibility and manoeuvrability around ICAs from the distal dural ring (DDR) to the foramen lacerum (FL) on each side (n=12) via eEEA. The ICA course was divided into three segments: ICA in cavernous sinus (CS-ICA), paraclival-ICA and lacerum-ICA. Following total exposure of each ICA, the three-dimensional (3D= medial/lateral, superficial/deep and above/below) anatomical targets (n= 35) around each ICA were evaluated. The data were collected and analyzed. Results: Distinctively, we included 35 anatomical targets (pertinent to CS-ICA, paraclival-ICA and lacerum-ICA were 16, 10, and 9, respectively) in 360° around every ICA (n=12) from the DDR to FL. Although reasonable visual validation was possible for all targets, micro-dissections were safely achievable for 19 targets (54.3%) through full or limited surgical freedom in 73.7% and 26.3%, respectively. In the remaining 45.7%, the accessibility to targets was abandoned due to hazardous manipulation. The most unreachable targets were around the lacerum-ICA (55.6%) with extremely restricted maneuverability (75%). Though, favorable accessibility (60%) and full surgical freedom (100%) were around the paraclival-ICA. Conclusion: This study delivers a distinctive view to appreciate the degree of complexity and invasiveness in relation to the degree of surgical freedom around ICA via eEEA. Illustrating these details for skull base surgeons can lead them to tailor their approach. It delivers prospective feedback for our operative theatre.

Combined Transoral Exoscope and OARM-Assisted Approach for Craniovertebral Junction Surgery. New Trends in an Old-Fashioned Approach.

The introduction of recent innovations in the field of intraoperative imaging and neuronavigation, such as the O-arm StealthStation, allows for obtaining crucial intraoperative data by performing safer and controlled surgical procedures. As part of the improvement of surgical visual magnification and wide expansion of surgical corridors, the 3D 4 K exoscope (EX) has nowadays become an interesting and useful tool. The transoral approach (TOA) is the historical gold-standard direct microsurgical route to ventral craniovertebral junction (CVJ). We herein report our experience, consisting of ten cases via TOA concerning the simultaneous application of an O-arm with a StealthStation navigation system (Medtronic, Memphis, TN) and an imaging system, along with the 3D 4 K exoscopes in the TOA, for the treatment of CVJ pathologies. No intraoperative neurophysiological changes or postoperative infections occurred, but neurological improvement was evident in all the patients. A complete decompression and a stable instrumentation and fusion of the CVJ were accomplished in all cases at the maximum follow-up time. With EX, the role of the surgeon becomes self-sufficient with better individual surgical freedom compared to endoscopic surgery and excellent 3D vision and magnification. O-arms offer absolutely reliable intraoperative support for more-effective CVJ decompression. Nevertheless, with O-arm-assisted neuronavigation, it can be difficult to navigate C1 lateral masses and C2 isthmi, and converting 3D into 2D real-time navigation can be quite complicated. Finally, the combination of an EX with an O-arm appears more time-consuming compared to the old-fashion one.

Quantitative Comparative Analysis of the Endoscope-Assisted Expanded Retrosigmoid Approach and the Far-Lateral Approach to the Inframeatal Area: An Anatomic Study With Surgical Implications.

The inframeatal area (IFMA) is a complex anatomic region of the posterior cranial fossa. Given its deep-seated location, tumors involving the IFMA represent a surgical challenge. To objectively compare the endoscope-assisted expanded retrosigmoid approach (ERSA) and the far-lateral supracondylar transtubercular approach (FLTA) to address the IFMA. Anatomic dissections were performed on 5 cadaveric heads (10 sides). The ERSAs were performed before and after the FLTAs. The surgical exposure, surgical freedom, and angles of attack to the IFMA were measured and compared for each approach. In addition, 2 illustrative clinical cases are reported. Compared with FLTA, ERSA yielded a nonsignificantly smaller mean area of exposure, whereas FLTA provided a significantly larger mean area of surgical freedom, compared with ERSA ( P = .002). The mean horizontal and vertical angles of attack were significantly different between the approaches. In the vertical plane, FLTA yielded the broadest angle of attack at the root entry zone of the lower cranial nerves (CN; P < .004), whereas ERSA did so at the dural entry zone of CN VII/VIII ( P = .006). In the horizontal plane, FLTA achieved its broadest angle of attack at the root entry zone of the lower CNs ( P = 1.83) while ERSA at the dural entry zone of CN VII/VIII ( P = .37). ERSA and FLTA granted a comparable exposure with the IFMA. Although FLTA may afford a larger area of surgical freedom, ERSA may be a suitable alternative to approach the IFMA, particularly to reach the most medial and superior aspects of this region. Conversely, FLTA may facilitate access to more caudally targets.

Utilization of Navigation-Integrated, Mixed Reality Templates for Minimizing Invasiveness of Neurosurgical Procedures: A Case Series

BACKGROUND: The tenets of minimally invasive neurosurgery require small craniotomies that nevertheless afford sufficient surgical freedom to safely accomplish the operative goal. OBJECTIVE: To present a novel technique which couples surgical rehearsal in virtual reality (VR) with navigation-integrated, microscope-synchronized augmented reality (AR) to optimize minimally invasive openings. METHODS: A retrospective review of the senior author's early experience with this mixed reality (VR + AR) platform was conducted. Patient-specific VR models were rendered from standard computed tomography/MRI. Surgical rehearsal with these models created templates with the optimal opening, which were integrated with the AR system. In surgery, the templates were projected through a navigation-tracked microscope and appeared as AR objects onto the patient. The templates guided the planning of the incision and steps of the approach. RESULTS: Sixteen patients were included in this study, 11 women and 5 men (33-79 years; median: 59.5). Twelve operations were performed for mass lesions and 4 for microvascular decompression for trigeminal neuralgia. There were no intraoperative adverse events related to AR. For 15 patients (94%), the templates provided major advantage in optimizing the bony opening and guided the operation to the specific anatomic location chosen preoperatively. For 1 patient, the AR template guided the drilling away from the critical structures inside the temporal bone. In addition, 3-dimensional AR markers relieve the surgeon from ergonomically cumbersome monitor-based navigation (Video 1). CONCLUSION: This novel mixed reality platform combines surgical rehearsal in VR and navigation-integrated, microscope-synchronized overlay of AR templates to ensure that optimal exposure is efficiently obtained.

Novel Multiportal Approach to the Internal Auditory Canal for Hearing-Preserving Surgery: Feasibility Assessment in Dissections

State-of-the-art, minimally invasive endoscopic transcanal surgery of the internal auditory canal (IAC) sacrifices the cochlea with complete hearing loss. With a combination of the transcanal infracochlear and transmastoid retrolabyrinthine approaches, we aim to preserve hearing and enable minimally invasive surgical treatment of vestibular schwannoma. In this study, we investigate the anatomical indications and the feasibility of both approaches in dissections, in human whole head specimens. We operated whole head anatomical specimens with a four-handed technique, using the retrolabyrinthine approach as the main surgical corridor and the infracochlear approach for endoscopic visualization. We tested 4 different powered surgical systems. We collected intraoperative data on the size of the access windows, the surgical freedom, and the exposed area of the IAC. Finally, we evaluated the outcome in postoperative computed tomography scans. Six out of 14 sides were anatomically suitable and qualified for the surgery based on preoperative computed tomography. In all attempted sides, the IAC could be reached and opened, leaving the ossicular chain and the labyrinth intact. 51%-75% of the length and 22%-40% of the circumference of the IAC could be exposed. All tested instruments were beneficial at different stages of the surgery. The four-handed technique enabled good maneuverability of the instruments. The combined multiportal approach to the IAC is feasible with a good surgical exposure and full anatomical preservation of hearing. State-of-the-art surgical instruments in specimens with suitable anatomy are sufficient to perform this approach.

Extended endoscopic transorbital approach with superior-lateral orbital rim osteotomy: cadaveric feasibility study and clinical implications (SevEN-007).

The endoscopic transorbital approach (ETOA) has been developed, permitting a new surgical corridor. Due to the vertical limitation of the ETOA, some lesions of the anterior cranial fossa are difficult to access. The ETOA with superior-lateral orbital rim (SLOR) osteotomy can achieve surgical freedom of vertical as well as horizontal movement. The purpose of this study was to confirm the feasibility of the ETOA with SLOR osteotomy. Anatomical dissections were performed in 5 cadaveric heads with a neuroendoscope and neuronavigation system. ETOA with SLOR osteotomy was performed on one side of the head, and ETOA with lateral orbital rim (LOR) osteotomy was performed on the other side. After analysis of the results of the cadaveric study, the ETOA with SLOR osteotomy was applied in 6 clinical cases. The horizontal and vertical movement range through ETOA with SLOR osteotomy (43.8° ± 7.49° and 36.1° ± 3.32°, respectively) was improved over ETOA with LOR osteotomy (31.8° ± 5.49° and 23.3° ± 1.34°, respectively) (p < 0.01). Surgical freedom through ETOA with SLOR osteotomy (6025.1 ± 220.1 mm3) was increased relative to ETOA with LOR osteotomy (4191.3 ± 57.2 mm3) (p < 0.01); these values are expressed as the mean ± SD. Access levels of ETOA with SLOR osteotomy were comfortable, including anterior skull base lesion and superior orbital area. The view range of the endoscope for anterior skull base lesions was increased through ETOA with SLOR osteotomy. After SLOR osteotomy, the space for moving surgical instruments and the endoscope was widened. Anterior clinoidectomy could be achieved successfully using ETOA with SLOR osteotomy. The authors performed ETOA with SLOR osteotomy in 6 cases of brain tumor. In all 6 cases, complete removal of the tumor was successfully accomplished. In the 3 cases of anterior clinoidal meningioma, anterior clinoidectomy was performed easily and safely, and manipulation of the extended dural margin and origin dura mater was possible. There was no complication related to this approach. The authors evaluated the clinical feasibility of ETOA with SLOR osteotomy based on a cadaveric study. ETOA with SLOR osteotomy could be applied to more diverse disease groups that do not permit conventional ETOA or to cases in which surgical application is challenging. ETOA with SLOR osteotomy might serve as an opportunity to broaden the indication for the ETOA.

Pterional Approach: Technical Variations, Functional, and Cosmetic Outcome in a Series of 1000 Patients

INTRODUCTION Most of the versatility of the pterional approach depends on a series of variations progressively reported by several groups, but little emphasized over the years. The present study condenses the technical notes which the authors adopted in their practice to maximize the surgical freedom of the pterional approach, at once lessening the approach-related complication rate. METHODS Data of a series of patients who underwent a pterional approach between January 2011 and May 2021 were retrospectively reviewed focusing on the technical variations compared to the original Yaşargil’s description. The anatomical rationale, technique, and advantages were outlined and validated through the appraisal of functional and cosmetic complications. RESULTS 994 patients were reviewed. Head extension was avoided in the case of anterior clinoidectomy. A single double-layered galea-pericranium flap was used for duraplasty. The submuscular technique, with compulsive preservation of deep temporal fascia and deep temporal arteries, was preferred for temporalis muscle dissection. McCarty keyhole was never used, thus avoiding exposing the orbit if unnecessary. Widening of the superior orbital fissure and thinning of the orbital roof allowed to significantly increase the working area. The average follow-up was 7.2 years. The overall rate of functional and cosmetic complications was 2.1. DISCUSSION In the authors' experience, the gradual adoption of technical variations related to the patient's positioning, soft tissue dissection, bony work, dura opening, and reconstruction allowed to enhance the versatility of the pterional approach concurrently decreasing the risk of functional and cosmetic complications.

Pterional Approach: Technical Variations, Functional, and Cosmetic Outcome in a Series of 1000 Patients

INTRODUCTION&#x0D; Most of the versatility of the pterional approach depends on a series of variations progressively reported by several groups, but little emphasized over the years.&#x0D; The present study condenses the technical notes which the authors adopted in their practice to maximize the surgical freedom of the pterional approach, at once lessening the approach-related complication rate.&#x0D; METHODS &#x0D; Data of a series of patients who underwent a pterional approach between January 2011 and May 2021 were retrospectively reviewed focusing on the technical variations compared to the original Yaşargil’s description. The anatomical rationale, technique, and advantages were outlined and validated through the appraisal of functional and cosmetic complications. &#x0D; RESULTS&#x0D; 994 patients were reviewed. Head extension was avoided in the case of anterior clinoidectomy. A single double-layered galea-pericranium flap was used for duraplasty. The submuscular technique, with compulsive preservation of deep temporal fascia and deep temporal arteries, was preferred for temporalis muscle dissection. McCarty keyhole was never used, thus avoiding exposing the orbit if unnecessary. Widening of the superior orbital fissure and thinning of the orbital roof allowed to significantly increase the working area. The average follow-up was 7.2 years. The overall rate of functional and cosmetic complications was 2.1.&#x0D; DISCUSSION&#x0D; In the authors' experience, the gradual adoption of technical variations related to the patient's positioning, soft tissue dissection, bony work, dura opening, and reconstruction allowed to enhance the versatility of the pterional approach concurrently decreasing the risk of functional and cosmetic complications.

Endoscopic Endonasal Approach to the Pterygopalatine Fossa and Infratemporal Fossa: Comparison of the Prelacrimal and Denker's Corridors.

Both the endoscopic transnasal Denker's and prelacrimal approaches provide surgical access to the pterygopalatine fossa (PPF) and infratemporal fossa (ITF). This study compares the potential maximum exposure of the PPF and ITF and quantifies the difference in surgical freedom via endoscopic Denker's and prelacrimal approaches. Six cadaveric specimens (12 sides) were dissected using a prelacrimal approach on one side and an endoscopic Denker's approach on the contralateral side. The contents of the PPF and ITF were sequentially exposed. Surgical freedom for each corridor was subsequently calculated. This study confirms that both the prelacrimal and Denker's approaches provide adequate exposure of the PPF and ITF. The maximum exposure boundaries were similar for both approaches, including the middle cranial fossa superiorly, floor of the maxillary sinus inferiorly, zygomatic arch and temporomandibular joint laterally, and post-styloid space posteriorly. However, the data revealed a statistically significant difference (p < 0.05) regarding the surgical freedom of the prelacrimal (388.17 ± 32.86 mm2) and the endoscopic Denker's approaches (906.35 ± 38.38 mm2). When compared with an endoscopic Denker's approach, a prelacrimal approach seems to achieve a similar extent of exposure (ie, visualization) of the PPF and ITF. Nonetheless, the endoscopic Denker's approach offers superior surgical freedom; thus, it is preferred for the management of complex lesions which requires increased instrument maneuverability with a 3- or 4-handed technique.

Endoscope-controlled extended supraorbital keyhole approach through a modified eyebrow incision for a large dural-based solitary fibrous tumor of the frontal convexity: A technical note.

Background: The extended supraorbital approach through a modified eyebrow incision is a minimally invasive approach that has been recently described. It entails a lateral extension of the skin incision beyond the lateral end of the eyebrow and allows exposure of the proximal sylvian fissure with a superior degree of surgical freedom in the middle fossa and the parasellar region. In this technical note, we describe an endoscope-controlled extended supraorbital keyhole approach with modified eyebrow incision for excision of a large dural-based solitary fibrous tumor of the left frontal convexity.Methods: An endoscope-controlled extended supraorbital keyhole approach with modified eyebrow incision was performed to excise a large extra-axial mass attached to the dura of the left frontal convexity and extends from the superior temporal line up to the midline in a 34-year-old male patient presented with 1-year history of headache, dizziness, and blurred vision.Results: The patient had an uneventful postoperative course with gross total excision of the lesion and satisfying cosmetic appearance. Histopathological examination revealed a Grade 1 solitary fibrous tumor.Conclusion: We demonstrated the feasibility of the endoscope-controlled extended supraorbital keyhole approach through a modified eyebrow incision for excision of tumors that abut the inner table of the frontal calvarial bone, extend highly above the skull base level, or extend medially reaching the midline. The approach is very versatile and allows a great exposure for a category of lesions deemed not perfectly suitable for the classic supraorbital keyhole approach.

Endoscopic-assisted paramedian supracerebellar infratentorial approach to the posterior portion of the third ventricle: anatomical study and surgical cases.

To date, morphometrical data providing a systematic quantification of accessibility and operability parameters to the boundaries of the posterior portion of the third ventricle (PTV) when applying an endoscopic-assisted paramedian supracerebellar infratentorial approach (EPSIA) are lacking. We performed an anatomical study and complemented our findings with surgical cases. Eight EPSIAs towards the PTV were performed in cadaveric specimens. Optimal approach angles (OA), surgical freedom (SF) and operability indexes (Oi) to the PTV boundaries were assessed. Additionally, a 54-year-old man and 33-year-old woman were operated on PTV tumors applying the EPSIA. Sagittal OA to ventricle's roof and floor was 36±1.4° and 25.5±3.5° respectively, axial OA to the ipsilateral and contralateral ventricle's wall were 9.5±1.3° and 28.5±1.6°. SF was maximal on the contralateral wall (121.2±19.3mm2), followed by the roof (112.7±18.8mm2), floor (106.6±19.2mm2) and ipsilateral wall (94.1±15.7mm2). SF was significantly lower along the ipsilateral compared the contralateral wall (P<0.01) and roof (P<0.05). Facilitated surgical maneuvers with multiangled exposure were possible up to 8.5±1.07mm anterior to ventricle's entrance, whereas surgical maneuvers were possible but difficult up to 15.25±3.7mm. Visualization of more anterior was possible up to a distance of 27±2.9mm, but surgical maneuvers were barely feasible. EPSIA enabled successful resection of both PTV tumors and postoperative course was uneventful. EPSIA can be effective for approaching the PTV, enabling surgery along all boundaries, but especially on its roof and contralateral wall. In the not-enlarged ventricle, surgical maneuvers are feasible up to the level of the Monro foramen, becoming more limited anteriorly.

Cranio-Orbito-Zygomatic Approach: Core Techniques for Tailoring Target Exposure and Surgical Freedom.

Background: The cranio-orbito-zygomatic (COZ) approach is a workhorse of skull base surgery, and each of its steps has a precise effect on target exposure and surgical freedom. The present study overviews the key techniques for execution and tailoring of the COZ approach, focusing on the quantitative effects resulting from removal of the orbitozygomatic (OZ) bar, orbital rim, and zygomatic arch. Methods: A PRISMA-based literature review was performed on the PubMed/Medline and Web of Science databases using the main keywords associated with the COZ approach. Articles in English without temporal restriction were included. Eligibility was limited to neurosurgical relevance. Results: A total of 78 articles were selected. The range of variants of the COZ approach involves a one-piece, two-piece, and three-piece technique, with a decreasing level of complexity and risk of complications. The two-piece technique includes an OZ and orbitopterional variant. Superolateral orbitotomy expands the subfrontal and transsylvian corridors, increasing surgical freedom to the basal forebrain, hypothalamic region, interpeduncular fossa, and basilar apex. Zygomatic osteotomy shortens the working distance of the pretemporal and subtemporal routes. Conclusion: Subtraction of the OZ bar causes a tremendous increase in angular exposure of the subfrontal, transsylvian, pretemporal, and subtemporal perspectives avoiding brain retraction, allowing for multiangled trajectories, and shortening the working distance. The COZ approach can be tailored based on the location of the lesion, thus optimizing the target exposure and surgical freedom and decreasing the risk of complications.

Extradural anterior clinoidectomy versus endoscopic transplanum-transcavernous approach to the paraclinoid region: quantitative anatomical exposure analysis.

Transcranial anterior clinoidectomy is a conventional microsurgical approach for treatment of paraclinoid aneurysms. The endoscopic endonasal approach (EEA) is an alternative method for clipping intracranial aneurysms. No analysis has been conducted to anatomically compare approaches with respect to treating paraclinoid aneurysms. The surgical anatomical exposures of the paraclinoid region during transcranial extradural anterior clinoidectomy (EAC) and the endoscopic endonasal transplanum-cavernous approach (EETC) are described and quantitatively assessed. Seven cadaveric heads underwent EAC and EETC. Measurements included the area of exposure, volume of surgical freedom, angle of attack, ophthalmic artery (OphA) origin, and coronal exposure angle of the internal carotid artery (ICA). The EETC provided a larger area of exposure than the EAC (100.1±24.9 vs 76.1±12.9 mm2, p = 0.04). The EAC provided a higher volume of surgical freedom and greater angle of attack than the EETC in all neurovascular parameters, including the OphA, superior hypophyseal artery (SHA), distal ICA, and distal dural ring (all p < 0.001). The OphA origin was intradural in 85.7% and extradural in 14.3% of specimens. With regard to the coronal angle of exposure, the EAC exposed the OphA and SHA in the upper lateral quadrant (67.9±7.8° and 80.6±4.5°, respectively) and the distal ICA in the upper medial and upper lateral quadrants (92±7.5°). The EEA exposed the OphA, SHA, and distal ICA in the upper medial and lower medial quadrants (130.4±10.7°, 68.4±10.8°, and 58±11.4°, respectively). The EAC and EETC each offer specific advantages for paraclinoid region exposure. The EAC is appropriate for paraclinoid aneurysms that occur at the dorsolateral surface of the paraclinoid ICA. The EETC is an alternative approach for aneurysms that occur along medial surface of the paraclinoid ICA (e.g., carotid cave and SHA aneurysms). The EETC provides greater surgical exposure to the medial aspect of the paraclinoid ICA.

The mini-combined transpetrosal approach: an anatomical study and comparison with the combined transpetrosal approach.

The combined transpetrosal approach (CTPA) is a versatile technique suitable for challenging skull base pathologies. Despite the advantages provided by a wide surgical exposure, the soft tissue trauma, complex and time-consuming bony work, and cosmetic issues make it far from patient expectations. In this study, the authors describe a less invasive modification of the CTPA, the mini-combined transpetrosal approach (mini-CTPA), and perform a quantitative comparison between these two approaches. Five human specimens were used for this study. CTPA was performed on one side and mini-CTPA on the opposite side. The surgical freedom, petroclival and brainstem area of exposure, and maneuverability for 6 anatomical targets, provided by the CTPA and mini-CTPA, were calculated and statistically compared. The bony volumes corresponding to each anterior petrosectomy were also measured and compared. Three clinical cases with an operative video are also reported to illustrate the effectiveness of the approach. The question-mark skin incision done along the muscle attachments permits an optimal cosmetic result. Even though the limited incision, the smaller craniotomy, and the less extensive bone drilling of mini-CTPA provide a smaller area of surgical freedom, the areas of exposure of petroclival region and brainstem were not statistically different between the two approaches. The antero-posterior maneuverability for the oculomotor foramen (OF), Meckel's cave (MC) and the REZ of trigeminal nerve, and the supero-inferior maneuverability for OF, MC, Dorello's canal, and REZ of CN VII are significantly reduced by the smaller opening. The bony volume of anterior petrosectomy resulted similar among the approaches. The mini-CTPA is an interesting alternative to the CTPA, providing comparable surgical exposure both for petroclival region and for brainstem. Although the lesser soft tissue dissection and bony opening decrease the surgical maneuverability, the mini-CTPA may reduce surgical time, potential approach-related morbidities, and improve cosmetic and functional outcomes for the patients.