Presigmoid Approach Research Articles

Retrolabyrinthine approach to the lateral skull base: The value of preoperative temporal bone CT analysis

PurposeThe most used neurosurgical approach to reach cerebellar-pontine angle is the retrosigmoid route. This article describes the presigmoid approach which requires excellent knowledge of the labyrinthine block together with quantitative analysis of temporal bone CT. MethodsCT-based quantitative measurements were obtained in patients undergoing vestibular neurectomy with a presigmoid approach. Eighteen patients were enrolled, and five measures were taken: Trautmann’s area, the petro-clival angle, presigmoid dura length and its angle. The relationship between these measurements and hospitalization days, operating times, and complications was explored. ResultsThe posterior semicircilar canal (PSC)-sigmoid sinus (SS) distance, presigmoid dura- internal auditory canal (IAC)-PSC angle, and duration of surgery are predictors of complications. Specifically, a PSC-sigmoid sinus distance <11 mm, a dura presig-IAC-PSC angle <14 are associated with the highest risk of complications. ConclusionPreoperative temporal bone CT scan can guide the surgeon through the narrowest areas of the surgical approach. Trautmann’s triangle area and petro-clival angle reduction are challenging and can be faced with combined microscopic-endoscopic technique, and with optics angulation-rotation. The retrolabyrinthine approach can enable hearing preservation and minimal cerebellar retraction.

Endoscopic-Assisted Presigmoid Approach to the Internal Auditory Canal. A Feasibility Study.

The retrolabyrinthine (presigmoid) approach has been utilized in various skull base surgeries but has not been fully utilized in the management of internal auditory canal (IAC) lesions, such as vestibular schwannoma (VS). Microsurgical retrolabyrinthine approach provides limited visualization of the IAC, while endoscopic-assisted techniques allow for further lateral exposure with labyrinthine preservation. Traditional approaches to the IAC have the disadvantage of hearing sacrifice or retraction of brain tissue. With the introduction of endoscopic techniques and enhanced visualization, access to this region of complex anatomy is possible. Radiomorphometric and anatomical dissection was performed on two cadaveric temporal bones. High-resolution computed tomography was used to segment and delineate the volume of the IAC. Projected accessible IAC was compared to actual postdissection data with preservation of the posterior semicircular canal (PSCC) via the retrolabyrinthine corridor. While preserving the PSCC, the 0° and 30° endoscopes visualized 57.1% and 78.6% of the IAC for cadaver 1, and 64.0% and 76.0% of the IAC for cadaver 2, respectively. Sacrificing the PSCC, the 0° and 30° endoscopes provided visualization of 78.6% 85.7% of the IAC for cadaver 1, and 88.0% and 95.1% of the IAC for cadaver 2, respectively. Retrolabyrinthine approach to resection of VS is a potentially viable hearing-preserving alternative to traditional approaches. This approach provides access to the majority of the IAC, while angled endoscopes or sacrifice of the PSCC can provide additional access toward the fundus. Further studies are needed to determine the clinical feasibility of this approach.

Anatomical Study of the Supratentorial Extension for the Retrolabyrinthine Presigmoid Approaches

Supra-tentorial craniotomy represents the upper part of the combined trans-tentorial or the supra-infra-tentorial presigmoid approach. In this study, we provide qualitative and quantitative analyses for the supratentorial extension of the presigmoid retrolabyrinthine suprameatal approach (PRSA). The infratentorial PRSA followed by the supratentorial extension craniotomy with dividing and removal of the tentorial strip were performed on both sides of 5 injected human cadaver heads (n=10 sides). Quantitative analysis was performed for the surface area gained (surgical accessibility) by adding the supratentorial craniotomy. Qualitative analysis was performed for the parts of the brainstem, cranial nerves, and vascular structures that became accessible by adding the supratentorial craniotomy. The anatomical obstacles encountered in the added operative corridor were analyzed. The supratentorial extension of PRSA provides an increase in surgical accessibility of 102.65% as compared to the PRSA standalone. The mean surface area of the exposed brainstem is 197.98 (SD: 76.222) and 401.209 (SD: 123.96) for the infratentorial and the combined supra-infratentorial presigmoid approach, respectively. Exposure for parts of III, IV, and V cranial nerves is added after the extension, and the surface area of the outer craniotomy defect has increased by 60.32%. Parts of the basilar, anterior inferior cerebellar, and superior cerebellar arteries are accessible after the supratentorial extension. The supratentorial extension of PRSA allows access to the supra-trigeminal area of the pons and the lower part of the midbrain. Considering this surgical accessibility and exposure significantly assists in planning such complex approaches while targeting central skull base lesions.

Retrolabyrinthine approach to the lateral skull base: The value of preoperative temporal bone CT analysis

PurposeThe most used neurosurgical approach to reach cerebellar-pontine angle is the retrosigmoid route. This article describes the presigmoid approach which requires excellent knowledge of the labyrinthine block together with quantitative analysis of temporal bone CT. MethodsCT-based quantitative measurements were obtained in patients undergoing vestibular neurectomy with a presigmoid approach. Eighteen patients were enrolled, and five measures were taken: Trautmann’s area, the petro-clival angle, presigmoid dura length and its angle. The relationship between these measurements and hospitalization days, operating times, and complications was explored. ResultsThe posterior semicircilar canal (PSC)-sigmoid sinus (SS) distance, presigmoid dura- internal auditory canal (IAC)-PSC angle, and duration of surgery are predictors of complications. Specifically, a PSC-sigmoid sinus distance <11 mm, a dura presig-IAC-PSC angle <14 are associated with the highest risk of complications. ConclusionPreoperative temporal bone CT scan can guide the surgeon through the narrowest areas of the surgical approach. Trautmann’s triangle area and petro-clival angle reduction are challenging and can be faced with combined microscopic-endoscopic technique, and with optics angulation-rotation. The retrolabyrinthine approach can enable hearing preservation and minimal cerebellar retraction.

Combined presigmoid approach: A literature review.

The presigmoid approach represents the standard route to reach the petrous area anterior to the sigmoid sinus. Several lateral skull base approaches have been integrated into this approach for the purpose of widening the window, leading to variable combined approaches and variable terminology. Herein, the authors conducted a systematic review of the literature to simplify understanding of the potential combination of different approaches and their complications. PubMed, EMBASE and Web of Science databases were searched on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to include studies describing modifications of the presigmoid approach. We included 27 studies comprising 545 patients. Five combination types applied to the presigmoid approach were identified: Anterior petrosal (Kawase's) approach (Type-1), Supra-tentorial approach (Type-2), Infratemporal fossa approach (Type-3), retrosigmoid approach (Type-4), and Far-lateral suboccipital approach (Type-5). Type-1 combined approach was the commonest type (n = 204, 37.5%), followed by type-2 (n = 197, 36%), type-4 (n = 54, 9.9%), type-5 (n = 51, 9.4%), and type-3 (n = 39, 7.2%). Meningioma was the typical target lesion in all types except type 3, where it is solely used for paraganglioma. The petroclival region was the prevalent access location in all the types of combined presigmoid approaches (type-1, 92%; type-2, 95%; type-3, 100%; type-4, 59%; and type-5, 64%). The intraoperative lateral patient position was dominantly utilized in type-1, type-3, and type-5 approaches (65%, 100%, and 100%, respectively), while park-bench was the most common position in type-2 (36%) and type-4 (100%) approaches. Overall, all types exhibited good outcomes in the form of gross total resection of the lesion and the absence of surgical complications in the follow-up. Presigmoid approaches are becoming increasingly complex with the application and integration of the lateral skull base approaches, resulting in broadening the surgical field and easy access to the targeted lesions. The importance of designing a comprehensive nomenclature of the combined presigmoid approaches may add distinctive contributions to the growing knowledge of neurosurgery.

A proposed classification system for presigmoid approaches: a scoping review.

The "presigmoid corridor" covers a spectrum of approaches using the petrous temporal bone either as a target in treating intracanalicular lesions or as a route to access the internal auditory canal (IAC), jugular foramen, or brainstem. Complex presigmoid approaches have been continuously developed and refined over the years, leading to great heterogeneity in their definitions and descriptions. Owing to the common use of the presigmoid corridor in lateral skull base surgery, a simple anatomy-based and self-explanatory classification is needed to delineate the operative perspective of the different variants of the presigmoid route. Herein, the authors conducted a scoping review of the literature with the aim of proposing a classification system for presigmoid approaches. The PubMed, EMBASE, Scopus, and Web of Science databases were searched from inception to December 9, 2022, following the PRISMA Extension for Scoping Reviews guidelines to include clinical studies reporting the use of "stand-alone" presigmoid approaches. Findings were summarized based on the anatomical corridor, trajectory, and target lesions to classify the different variants of the presigmoid approach. Ninety-nine clinical studies were included for analysis, and the most common target lesions were vestibular schwannomas (60/99, 60.6%) and petroclival meningiomas (12/99, 12.1%). All approaches had a common entry pathway (i.e., mastoidectomy) but were differentiated into two main categories based on their relationship to the labyrinth: translabyrinthine or anterior corridor (80/99, 80.8%) and retrolabyrinthine or posterior corridor (20/99, 20.2%). The anterior corridor comprised 5 variations based on the extent of bone resection: 1) partial translabyrinthine (5/99, 5.1%), 2) transcrusal (2/99, 2.0%), 3) translabyrinthine proper (61/99, 61.6%), 4) transotic (5/99, 5.1%), and 5) transcochlear (17/99, 17.2%). The posterior corridor consisted of 4 variations based on the target area and trajectory in relation to the IAC: 6) retrolabyrinthine inframeatal (6/99, 6.1%), 7) retrolabyrinthine transmeatal (19/99, 19.2%), 8) retrolabyrinthine suprameatal (1/99, 1.0%), and 9) retrolabyrinthine trans-Trautman's triangle (2/99, 2.0%). Presigmoid approaches are becoming increasingly complex with the expansion of minimally invasive techniques. Descriptions of these approaches using the existing nomenclature can be imprecise or confusing. Therefore, the authors propose a comprehensive classification based on the operative anatomy that unequivocally describes presigmoid approaches simply, precisely, and efficiently.

Approach Selection Strategies for Repeat Resection of Brain Cavernous Malformations: Cohort Study.

Neurosurgical management of cerebral cavernous malformations (CMs) often benefits from using skull base approaches. Although many CMs are cured by resection, residual or recurrent disease may require repeat resection. To review approach selection strategies for reoperation of CMs to aid decision-making for repeat procedures. In this retrospective cohort study, a prospectively maintained single-surgeon registry was queried for patients with CMs who underwent repeat resection from January 1, 1997, to April 30, 2021. Of 854 consecutive patients, 68 (8%) underwent 2 operations; 40 had accessible data on both. In most reoperations (33/40 [83%]), the index approach was repeated. In most reoperations using the index approach (29/33 [88%]), that approach was deemed ideal (no equivalent or superior alternative), whereas in some (4/33 [12%]), the alternative approach was deemed unsafe because of conformation of the tract. Among patients with reoperations using an alternative approach (7/40 [18%]), 2 with index transsylvian approaches underwent bifrontal transcallosal approaches, 2 with index presigmoid approaches underwent extended retrosigmoid revisions, and 3 with index supracerebellar-infratentorial approaches underwent alternative supracerebellar-infratentorial trajectory revisions. Among patients with reoperations with an alternative approach considered or selected (11/40 [28%]), 8 of 11 patients had a different surgeon for the index resection than for the repeat resection. The extended retrosigmoid-based approaches were used most often for reoperations. Repeat resection of recurrent or residual CMs is a challenging neurosurgical niche at the intersection of cerebrovascular and skull base disciplines. Suboptimal index approaches may limit surgical options for repeat resection.

An alternative route for petroclival tumors: Without mastoidectomy and superior petrosal sinus ligation: A cadaveric study

Objective: Retrosigmoid approach and presigmoid approach and its derivatives including retrolabyrinthine, translabyrinthine, and transpetrosal approaches have long been used for reaching posterior and middle cranial fossa. In neurosurgery perspective, many types of tumors arise extradurally and surgical resection of these tumors is still challenging. We aimed to describe a modified way to approach posterior and middle fossa to contribute to the surgical management of petroclival tumors with posterior extension. Methods: Modified sigmoid approaches were performed bilaterally in 5 fresh adult cadaver heads. Results: In this approach, it was possible to reach the middle and posterior fossa with a single craniotomy. Temporal dura matter was dissected from the temporal bone with extradural gentle dissection. In addition, sigmoid sinus and superior petrosal sinus (SPS) were dissected off from the petrous bone meticulously. Subsequently, the posterolateral superior arcuate petrosectomy was performed with high-speed surgical drill extradurally by protecting the semicircular canal, labyrinthine channel, and cochlea. Dura matter was elevated for 1.5 cm with retractor above the mastoid bone. Dura was opened from an alternative area of Trautmann’s triangle. After having exposed and opened the dura, posterior fossa was reached at the level of 7.−8. cranial nerves. Conclusion: We described an alternative route which seems to be a feasible way to reach posterior and middle fossa without mastoidectomy and SPS ligation. Notably, this technique can be applicable to petroclival tumor surgery after more anatomic studies with cadaveric specimens.

Presigmoid approach preserving the superior petrosal sinus in a pontine cavernous malformation associated to abnormal venous drainage of the brainstem: how I do it.

The presigmoid approach classically includes the ligature and section of the superior petrosal sinus to get a wider visibility window to the antero-lateral brainstem surface. In some cases, the separation of this venous structure should not be performed. We present our experience getting safely to a pontine cavernous malformation through a conventional mastoidectomy presigmoid approach preserving an ingurgitated superior petrosal sinus because the association with an abnormal venous drainage of the brainstem. When sectioning the superior petrosal sinus in classical presigmoid approaches is contraindicated, its preservation could also offer good surgical corridors to get to small-medium anterior and lateral brainstem cavernous malformations.

Indication for a skull base approach in microvascular decompression for hemifacial spasm.

A thorough observation of the root exit zone (REZ) and secure transposition of the offending arteries is crucial for a successful microvascular decompression (MVD) for hemifacial spasm (HFS). Decompression procedures are not always feasible in a narrow operative field through a retrosigmoid approach. In such instances, extending the craniectomy laterally is useful in accomplishing the procedure safely. This study aims to introduce the benefits of a skull base approach in MVD for HFS. The skull base approach was performed in twenty-eight patients among 335 consecutive MVDs for HFS. The site of the neurovascular compression (NVC), the size of the flocculus, and the location of the sigmoid sinus are measured factors in the imaging studies. The indication for a skull base approach is evaluated and verified retrospectively in comparison with the conventional retrosigmoid approach. Operative outcomes and long-term results were analyzed retrospectively. The extended retrosigmoid approach was used for 27 patients and the retrolabyrinthine presigmoid approach was used in one patient. The measurement value including the site of NVC, the size of the flocculus, and the location of the sigmoid sinus represents well the indication of the skull base approach, which is significantly different from the conventional retrosigmoid approach. The skull base approach is useful for patients with medially located NVC, a large flocculus, or repeat MVD cases. The long-term result demonstrated favorable outcomes in patients with the skull base approach applied. Preoperative evaluation for lateral expansion of the craniectomy contributes to a safe and secure MVD.

The crux of helix curvature: A potential surface landmark for the anterior border of the sigmoid sinus in minimally invasive presigmoid approaches.

Surgical landmarks are widely used across all surgical specialties to assist surgeons in accurately estimating the deep anatomical structures. We describe the crus of helix curvature as a potential indicator for the anterior border of the sigmoid sinus (SS) in the setting of minimally invasive presigmoid approaches. Anatomy investigations were performed on injected cadaveric heads to identify consistent surface surgical landmarks estimating the curse of the SS. Presigmoid mastoid was noted in the center of the skin incision in 100% of the specimens. The crus of helix curvature was superimposed on the anterior border of the SS on 6 sides (60%). On the other four sides, the curvature lays within 5 mm of the anterior SS border (40%). For the minimally invasive presigmoid approaches, the "crus of helix curvature" can be used as a landmark for the anterior border of the SS, which can aid in the speed and safety of the procedure. The ease of use of this landmark makes it particularly convenient for physicians early in training.

Microsurgical endoscopy-assisted presigmoid retrolabyrinthine approach with mastoid bone drilling: an anatomical laboratory investigation.

This study aims to evaluate the applicability of the endoscopy-assisted presigmoid retrolabyrinthine approach, advantages, disadvantages, and the applicability of surgery with pre-op radiological parameters; identify important landmarks; and to reveal their relationships with important structures in the surgical field with objective data. Also, we aim to improve the surgical technique for increasing reachable anatomic structure. Mastoid drilling and endoscopy-assisted presigmoid retrolabyrinthine approach were performed and endoscopic instruments were used to obtain the three-dimensional pictures. Computed tomography images were evaluated to correlate to the anatomic data. In terms of pre-operative radiological evaluation of the applicability of the presigmoid approach were investigated with selected radiological parameters. The endoscopy-assisted presigmoid retrolabyrinthine approach applied to cadavers the relationship, distances between important anatomical landmarks, and anatomical structures in the surgical field recorded. The anatomical structures that could reach with the application of the procedure were recorded. The relationship between pre-operative measured radiological parameters and surgical results was evaluated with objective data. Additional combinations to improve this surgical method discussed and the results of our combination were recorded with photographs. Although the presigmoid retrolabyrinthine approach has facilitated with the assistance of endoscope, it has observed that there are still some difficulties, and it has been concluded that the radiological parameters are useful in evaluating the applicability of this surgery. It observed that this surgery can be performed more effectively with combinations.

Diagnosis and surgical outcomes in the management of petrous bone cholesteatoma

To evaluate the effectiveness of surgical treatment of patients with petrous bone cholesteatoma (PBC) depending on the localization of the pathological process. The analysis of surgical treatment using various surgical approaches and its results in 32 patients with PBC, depending on the type, localization in petrous bone and intraoperative findings, is presented. Patients with supralabirint PBC underwent extended atticoantromastoidotomy with tympanoplasty and mastoidoplasty with automaterials (n=19), labyrinthectomy (n=4), subtotal petrozectomy with labyrinthectomy and suturing of the external auditory meatus (EAM) (n=2). In infralabirint and infralabirint-apical PBC, a transotic approach was used with Rambo suturing of EAM (n=9). The pre-sigmoid approach was performed in 1 patient. With an extradural subtemporal approach, PBC of apical localization was removed in 1 case. After surgical treatment, hearing remained at the same level in 15 (47%) patients, 14 of them had deafness. In the early postoperative period, a temporary increase in bone conduction hearing thresholds by 10-20 dB was detected in 14 (44%) patients with their gradual recovery over 3 months. Deafness in the postoperative period developed in 3 (9%) patients after removal of supralabirint cholesteatoma. In the early postoperative period, 3 (9%) patients developed systemic dizziness, which was stopped after 3 months. In 25 (78%) patients, the function of the facial nerve in the early postoperative period remained at the same level, of which 14 (44%) were normal, and 11 (34%) had the same degree according to the House-Brackmann (HB) classification. Improvement of function by one degree of HB classification was observed in 4 (12.5%) patients on average 5 months after surgery. An adequate personalized choice of surgical treatment methods allowed mainly to preserve the function of hearing and facial nerve. In cases of deterioration of facial nerve function in the postoperative period, gradual improvement was observed for 3-10.5 months with further positive dynamics.

Abordaje presigmoideo transpetroso (petrosectomía parcial) combinado con abordaje subtemporal transtentorial para meningioma petroclival

Introduction: Petroclival meningiomas constitute 3 to 10% of meningiomas of the posterior fossa, they originate in the petroclival fissure, in the upper part of the clivus, petrosal apex, and medial to the trigeminal nerve. Resection of these tumors is a neurosurgical challenge. The combined partial petrosectomy approach associated with a sub-temporal approach is a technique described by various authors; however, its performance is considered highly complex. We report the case of a petroclival meningioma operated successfully in our hospital using a combined presigmoid and subtemporal transtentorial transpetrosal approach. Clinical case: 33-year-old female patient with a clinical picture of headache, nausea, and gait disturbance. Brain magnetic resonance imaging showed a large right petroclival tumor (4.2x3.9x3.8cm) that displaced the brainstem and secondary hydrocephalus. The hydrocephalus was treated with a ventricular peritoneal shunt. Then, the tumor was resected using a combined presigmoid and subtemporal transpetrosal approach, a technique that allowed adequate exposure of the tumor, achieving complete resection, without intraoperative complications. Postoperative evolution was favorable, with no sequelae. Conclusion: The combined presigmoid and transtentorial subtemporal transpetrous approach for petroclival meningiomas is an effective and feasible technique to perform in our environment. The support of technology such as Neuronavigation, the ultrasonic aspirator, intraoperative monitoring, and adequate experience in skull base surgery are fundamental factors for the success of this surgery. Keywords: Meningioma, Skull Base Neoplasms, Craniotomy, Neurosurgical Procedures. (Source: MeSH NLM)

Total Petrosectomy for the Total Resection of Sphenopetroclival Meningioma: 2-Dimensional Operative Video.

Sphenopetroclival meningioma is a most formidable meningioma. Many patients have few preoperative deficits and surgery has the potential of severe neurological complications. Surgical treatment is challenging due to brainstem compression, the involvement of multiple cranial nerves and cerebral vessels. Wide tumor exposure, multiple dissection axis, and short distance are paramount factors in the quest of achieving total removal of Simpson grade I, including the involved dura and bone. The posterior petrosal, transtentorial presigmoid approach offers a wide and shallow operative field.1-7 When the patient has hearing loss, extending the resection of the temporal bone provides unmatchable exposure facilitating safer and more complete tumor removal. This article demonstrates the removal of a sphenopetroclival meningioma through total petrosectomy with closing of the external auditory canal and preservation of the facial nerve in the Fallopian canal. A total resection of the tumor was achieved with long-term preservation of cranial nerve function. The surgical steps of total petrosectomy are shown, including the skin flap, combined middle and posterior fossa craniotomy, skeletonization of the sigmoid transverse sinus, radical mastoidectomy, dissection of the Fallopian canal, and drilling of the labyrinth, cochlea, and petrous apex for superb exposure.8 We demonstrate the intra-arachnoidal microsurgical dissection utilized for the radical resection of petroclival meningioma. This surgery performed in 1995 is a testament to the time-tested technique. The patient consented to the procedure and image use. Images at 1:33 and 3:57 © Ossama Al-Mefty, used with permission.

Hearing preservation/rehabilitation surgery for small vestibular schwannoma: preliminary experience with the presigmoid retrolabyrinthine approach

Background The presigmoid retrolabyrinthine approach (PRA) for small vestibular schwannoma (VS) has unique advantages. Combination with partial labyrinthectomy further makes up its defect of high demand for anatomy. Objective Aimed to describe our use of the PRA with partial labyrinthectomy in VS surgery. Methods We retrospectively analyzed 10 patients diagnosed with VS who underwent PRA between September 2017 and November 2020. Their perioperative data were analyzed. Results Six tumors were on the left and three were on the right. One case was due to neurofibromatosis type 2 with bilateral involvement and underwent internal auditory canal decompression by PRA without tumor removal; all other patients underwent total tumor resection. Four patients underwent cochlear implantation simultaneously because of hearing loss that was detected during surgery. Three patients underwent partial labyrinthectomy. Five patients achieved hearing preservation, and one experienced hearing improvement. One of the three patients who underwent partial labyrinthectomy maintained hearing. All patients’ pre- and postoperative facial nerve functions were House-Brackmann grade I. After a median follow-up time of 13 months, no tumors recurred. Conclusions PRA for small VS is a safe and effective surgery that can achieve facial nerve and hearing preservation. Combination with partial labyrinthectomy can also preserve hearing.

The Bonebridge active bone conduction system: a fast and safe technique for a middle fossa approach.

The transmastoid pre-sigmoid approach is always the preferred choice for implantation of the Bonebridge active bone conduction system in patients with a normal anatomy. When an anatomical variant exists or a previous surgery has been performed, a retrosigmoid approach or middle fossa approach can be performed. The preferred surgical technique for a middle fossa approach is described. A 14 mm drill head (Neuro Drill) was used to create the bed at the squamous portion of the temporal bone. Surgical time and complication rate were analysed. The surgical time was shorter than 30 minutes in all cases, and only 14 seconds were needed to create a 14 mm bone bed. No complications were observed during the follow-up period (6-45 months). Use of the Neuro Drill for the middle fossa approach is an easy technique. It significantly decreases the surgical time, without increasing the complication rate.

Occipital artery to upper posterior circulation bypass through the presigmoid approach in revascularization of the posterior circulation: An anatomical study

We describe a novel extracranial (EC)-to-intracranial (IC) bypass technique between the occipital artery and upper posterior circulation (UPC) for revascularization of the posterior circulation through the presigmoid approach. Five formalin-fixed human heads were examined to demonstrate the detailed anatomy of the occipital artery and UPC and illustrate the step-by-step bypass procedure. The occipital artery, a branch of the external carotid artery, can be anastomosed to the P2/P3 segment of the posterior cerebral artery and S1/S2 segments of the superior cerebellar artery as an alternative to EC bypass donor segments for treatment of affection requiring revascularization. Presigmoid approach for the anastomosis of the occipital artery to the UPC provides a shorter distance, due to resection of some bones.

Presigmoid Approach to Dumbbell Trigeminal Schwannoma.

This case is a 15-year-old male, presenting with headaches, right face, and arm numbness, and ataxia. MRI (magnetic resonance imaging) revealed a large right sided dumbbell shaped lesion, extending into the middle and posterior fossa with compression of the brainstem consistent with a trigeminal schwannoma. Treatment options here would be a retrosigmoid suprameatal approach or a lateral presigmoid approach. Given the tumor extension into multiple compartments, a presigmoid craniotomy, combining a middle fossa approach with anterior petrosectomy, and retrolabyrinthine approach with posterior petrosectomy were used to maximize the direct access corridor for resection. The petrous apex was already expanded and remodeled by the tumor. Nerve fascicles preservation technique is paramount to the functional preservation of the trigeminal nerve. The extent of resection should be weighed against the anatomical functional integrity of the nerve. Near total resection is considered if that means more nerve preservation. Postoperatively, the patient had a slight (House–Brackman grade II) facial droop, which resolved over days and developed right trigeminal hypesthesia at several weeks. This case is presented to demonstrate a combined petrosectomy technique for resection of lesions extending into both the middle and posterior cranial fossa with near total resection and trigeminal nerve preservation. The link to the video can be found at: https://youtu.be/kA9GyFhL1dg .

Transnasal Endoscopic and Lateral Approaches to the Clivus: A Quantitative Anatomic Study.

Transnasal endoscopic approaches to the clivus have been established recently. Comparative analyses with classic lateral approaches are limited. In this study, we compared transnasal endoscopic and lateral approaches to the clivus, quantifying the exposure and working volume of each approach in the anatomy laboratory. High-resolution computed tomography scans were performed on 5 injected specimens (10 sides). In each specimen, transnasal endoscopic approaches (i.e., paraseptal, transrostral, extended transrostral, transethmoidal, and extended transclival without and with intradural hypophysiopexy) and lateral approaches (i.e., retrosigmoid, far-lateral, presigmoid retrolabyrinthine and translabyrinthine) to the clivus were performed. An optic neuronavigation system and dedicated software (ApproachViewer; Guided Therapeutics Program, University Health Network, Toronto, Ontario, Canada) were used to quantify the working volume and exposed clival area of each approach. Statistical evaluation was performed with the Kruskal-Wallis test and Steel-Dwass-Critchlow-Fligner post hoc test. Endoscopic transnasal transclival approaches showed higher working volume and larger clival exposure compared with lateral approaches. Incremental volumetric values were evident for transnasal approaches; presigmoid approaches provided less working volume than retrosigmoid approaches. A transnasal transclival approach with hypophysiopexy provided significant exposure of the upper clivus (84.4%). The transrostral approach was the first transnasal approach providing satisfactory access to the midclivus (66%); retrosigmoid and far-lateral approaches provided exposure of approximately one half of the midclivus. The lower clivus was optimally exposed with endoscopic transclival approaches (83%), whereas access to this region was limited with lateral approaches. This quantitative anatomic study shows that endoscopic transnasal approaches to the clivus provide a larger working volume and wider exposure of the clivus compared with lateral approaches.