Extended Retrosigmoid Approach Research Articles

Microsurgical Treatment of Intracranial Dural Arteriovenous Fistulas: A Collaborative Investigation From the Multicenter Consortium for Dural Arteriovenous Fistula Outcomes Research.

First-line therapy for most intracranial dural arteriovenous fistulas (dAVFs) is endovascular embolization, but some require microsurgical ligation due to limited endovascular accessibility, anticipated lower cure rates, or unacceptable risk profiles. We investigated the most common surgically treated dAVF locations and the approaches and outcomes of each. The Consortium for Dural Arteriovenous Fistula Outcomes Research database was retrospectively reviewed. Patients who underwent dAVF microsurgical ligation were included. Patient demographics, angiographic information, surgical details, and postoperative outcomes were collected. The 5 most common surgically treated dAVF locations were analyzed about used surgical approaches and postoperative outcomes. Univariate analyses were performed with statistical significance set at a threshold of P < .05. In total, 248 patients in the Consortium for Dural Arteriovenous Fistula Outcomes Research database met inclusion criteria. The 5 most common surgically treated dAVF locations were tentorial, anterior cranial fossa (ACF), transverse-sigmoid sinus (TSS), convexity/superior sagittal sinus (SSS), and torcular. Most tentorial dAVFs were approached using a suboccipital, lateral supracerebellar infratentorial approach (39.3%); extended retrosigmoid approach (ERS) (25%); or posterior subtemporal approach (19.6%). All ACF dAVFs used a subfrontal approach; 5.3% also included an anterior interhemispheric approach. Most TSS dAVFs were ligated via ERS (31.3%) or subtemporal (31.3%) approaches. All convexity/SSS dAVFs used an interhemispheric approach. All torcular dAVFs used the suboccipital, lateral supracerebellar infratentorial approach, with 10.5% undergoing simultaneous ERS craniotomy. Angiographic occlusion rates after microsurgery were 85.5%, 100%, 75.8%, 79.2%, and 73.7% for tentorial, ACF, TSS, convexity/SSS, and torcular dAVFs, respectively (P = .02); the permanent neurological complication rates were 1.8%, 2.6%, 9.1%, 0%, and 0% (P = .31). There were no statistically significant differences in development of complications (P = .08) or Modified Rankin Scale at the last follow-up (P = .11) by fistula location. Although endovascular embolization is the first-line treatment for most intracranial dAVFs, surgical ligation is an important alternative. ACF and tentorial fistulas particularly demonstrate high rates of postoperative obliteration.

Microsurgical resection of a large petroclival meningioma through an extended retrosigmoid approach: how I do it.

Petroclival meningiomas are challenging tumors. Several skull base approaches have been proposed in the last decades, with variable rates of postoperative morbidity and extent of resection. We herein reported the step-by-step microsurgical resection of a large petroclival meningioma through an extended retrosigmoid approach. Detailed surgical technique has been accompanied by a 2D operative video. The extended retrosigmoid approach allowed for a safe gross total resection of the tumor, as confirmed by the postoperative MRI. The patient did not experience any new postoperative deficit, despite a transient diplopia, and was discharged on postoperative day 7.

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.

In Reply: The Glossopharyngo-Cochlear Triangle-Part II: Case Series Highlighting the Clinical Application to High-Riding Posterior Inferior Cerebellar Artery Aneurysms Exposed Through the Extended Retrosigmoid Approach.

To the Editor: We thank the authors1 of this letter for their comments and insights. We hope this 2-part study successfully described the elucidation and execution of a patient-specific, microsurgical approach using the glossopharyngo-cochlear triangle (GCT) to treat a select subset of posterior inferior cerebellar artery (PICA) aneurysms.2,3 We wholeheartedly agree that 2-part studies—in which part I3 provides an in-depth discussion of the microsurgical anatomy and results of cadaveric dissections and part II2 highlights the clinical utility and the nuances of “real-world” surgical application of the anatomic principles—are “indispensable prerequisite(s).”1 We thank the editorial board of Operative Neurosurgery for continuing to publish and support these important endeavors. We believe that combining these 2 distinct studies into a single manuscript would have truncated and obscured the salient points of both studies, potentially diluting the significance and limiting the educational value and clinical applicability of the findings. Innovation in cerebrovascular and skull base microneurosurgery is driven by applying honed microsurgical techniques and skills to novel clinical scenarios, resulting in improvements in surgical outcomes and patient care. This innovation can be accomplished only by the continued enhancement of our knowledge of microsurgical anatomy; commitment to laboratory dissection, where we can continue to expand our armamentarium and safely push the limits of what is possible; and critical evaluation of our surgical and clinical outcomes. It is through spending time in the anatomy laboratory that we developed the microsurgical skills necessary to safely and efficaciously treat challenging lesions, such as distal PICA aneurysms, despite their proximity to delicate neurovascular structures and their location in deep surgical corridors. We welcome the idea that novel microsurgical approaches may provide an even more efficacious route or technique for treating these challenging lesions; if these new approaches could somehow obviate the need to manipulate the neighboring cranial nerves, all the better. We agree with the authors that such approaches can be devised, and their application critically evaluated, only by 2-part studies such as these. This point further highlights the importance of anatomic laboratory dissections, which are critical to neurosurgical education during residency and fellowship training and beyond. With regard to the definition of a “high-riding PICA aneurysm,” we found a measurement greater than 23 mm above the foramen magnum to be the most straightforward clinically applicable measurement.2,3 However, this is just one of many anatomic clues that can guide approach selection and patient-specific surgical intervention. In our clinical manuscript, in addition to reporting increased distance of the aneurysm from the foramen magnum, we reported how the distances from the internal auditory canal (IAC) and jugular foramen (JF) to the aneurysm differed significantly between typical and high-riding PICA aneurysms.2 High-riding PICA aneurysms had a mean distance below the IAC of 3.7 mm (range 0-6.8 mm) and a mean distance above the JF of 8.2 mm (range 6.9-9.4 mm). In contrast, the control group of typical PICA aneurysms had a mean distance below the IAC of 11.6 mm (range 7.0-18.0 mm) and a mean distance above the JF of 1.9 mm (range −7.3 to 7.3 mm). Identifying an aneurysm's location relative to these anatomic landmarks and using these results as a reference can guide surgical approach planning. These additional measurements can also assist in scenarios where the angle of gantry of the computed tomography angiography prevents direct measurement of distance in a single image slice. An additional solution to this issue can be to measure the distance on consecutive image slices (as was done in the illustrative case described in part I of our study).3 Although measuring on multiple slices may have a minor effect on the calculated distances, it is unlikely that this possible submillimetric difference would drastically affect approach selection. Importantly, much like our philosophy on anatomic triangles used to guide subarachnoid dissection, these measurement guidelines are meant to help predict approach corridors and are not intended to be rigid barriers. We agree that an operative video highlighting this technique would be of clinical interest and would clarify the nuances of the surgical approach and patient selection. Indeed, at the time of this response, we have a narrated video submitted for review, which we hope the authors of this letter and others will find interesting and clinically beneficial.4 Again, we would like to thank the authors1 of this letter for their comments and their thoughtful response. Funding This study did not receive any funding or financial support. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

Study of comparative surgical exposure to the petroclival region using patient-specific, petroclival meningioma virtual reality models.

Despite advancement of surgical techniques, the attachments of petroclival meningiomas near the central clival depression (CCD) remain difficult to visualize. With existing methods, the amount of tumor near the CCD that is inaccessible through various approaches cannot be compared. Tumors distort the brainstem, changing the size of the operative corridor for some but not all approaches; therefore, using cadavers with normal posterior fossae makes it impossible to compare different approaches to the tumor. The authors used virtual reality (VR) models created from the imaging data of patients to compare various surgical approaches that have otherwise been incomparable in previous studies. CT and MRI data obtained in 15 patients with petroclival meningiomas were used to create anatomically accurate 3D VR models. For each model, various surgical approaches were performed, and the surgical freedom to 6 targets of the regions were measured. Furthermore, portions of the tumor that were visually blocked by the brainstem or bony structures were segmented and recorded as blinded volumes for comparison. The extended retrosigmoid approach generated excellent exposure of the petroclival region, but for most specimens, there was inaccessible tumor volume adjacent to the brainstem (mean 641.3 mm3, SE 161.8). In contrast, the brainstem sides of the tumors were well-visualized by all the transpetrosal approaches. The blinded volume of the tumor was largest for the retrolabyrinthine approach, and this was statistically significant compared with all other approaches (mean 2381.3 mm3, SE 185.4). The authors performed a novel laboratory study by using patient CT and MRI data to generate 3D virtual models to compare surgical approaches. Since it is impossible to perform various approaches in separate surgeries in patients for comparison, VR represents a viable alternative for such comparative investigations.

Posterior Petrous Meningioma Fed by a Branch of the Persistent Trigeminal Artery Terminating in the Anterior Inferior Cerebellar Artery

Persistent trigeminal artery (PTA) is the most common persistent carotid-basilar fetal anastomosis and terminates extremely rarely directly in the dominant hemispheric branch of the anterior inferior cerebellar artery (AICA). We present a case of a branch of this PTA variant (Saltzman type 3b) demonstrated as the feeding artery of a large posterior petrous meningioma, which was confirmed under direct vision during surgery through the extended retrosigmoid approach. Meticulous dissection from the tumor surface provided early identification of the feeding branch from the PTA and its bifurcation at the attachment of the posterior petrous surface adjacent to the jugular foramen enabled preservation of the terminal cortical branch of the cerebellar hemisphere. Meningioma in the posterior cranial fossa may recruit substantial supply from branches of the PTA terminating in the AICA. This PTA variant should be recognized during surgical resection of posterior fossa neoplasms to prevent ischemic complication of the AICA territory.

The Glossopharyngo-Cochlear Triangle-Part I: Quantitative Anatomic Analysis of High-Riding Posterior Inferior Cerebellar Artery Aneurysms Exposed Through the Extended Retrosigmoid Approach.

An extended retrosigmoid approach can offer sufficient space for clip reconstruction of some high-riding posterior inferior cerebellar artery (PICA) aneurysms. To quantitatively investigate the glossopharyngo-cochlear triangle (GCT) and anatomic structures within it. Extended retrosigmoid craniotomies were performed on 10 sides of cadaveric heads, and the GCT was identified in each specimen. The length of the base and the area of the GCT were measured. The depth of the vertebrobasilar system and the abducens nerve to the GCT were measured. The proximal and distal exposable and controllable points on the vertebrobasilar system were identified. Two imaging-based patient selection algorithms are provided using the lengths from those points to the vertebral artery dural entry point and the superoinferior distances from those points to the inferior edge of the foramen magnum. Other factors related to accessibility via the GCT were investigated. The mean (standard deviation [SD]) area of the GCT was 45.7 (12.55) mm2. The mean (SD) depth of the abducens nerve was 14.3 (1.42) mm. The mean (SD) superoinferior distances from the foramen magnum to those points were 23.1 (7.39), 24.7 (8.25), 30.0 (9.56), and 32.6 (7.79) mm, respectively. The lower segment of the vertebrobasilar system was more superficial in the setting of a high-lying vertebrobasilar junction (VBJ) than a low-lying VBJ. We describe the GCT in an extended retrosigmoid approach for high-riding PICA aneurysms and evaluate the spatial relationship of the neurovascular structures within it. Two potential algorithms are offered for preoperative patient selection.

An a3-Anterior Inferior Cerebellar Artery to p3-Posterior Inferior Cerebellar Artery Bypass With Thrombectomy and Trapping of an Anterior Inferior Cerebellar Artery Aneurysm: 3-Dimensional Operative Video.

In situ bypasses to the anterior inferior cerebellar artery (AICA) are unusual because, with only one artery in the cerebellopontine angle (CPA), no natural intracranial donors parallel its course. In rare cases, the posterior inferior cerebellar artery (PICA) may have the tortuosity or redundancy to be mobilized to the AICA to serve as a donor. This video demonstrates this p3 PICA-to-a3 AICA in situ side-to-side bypass. A 75-yr-old woman presented with ataxia and hemiparesis from a large thrombotic right AICA aneurysm compressing the brainstem. Strategy consisted of bypass, trapping, and brainstem decompression. Written informed consent for surgery was obtained from the patient. A hockey-stick incision was made to harvest the occipital artery as a backup donor, but its diminutive caliber precluded its use. The bypass was performed through an extended retrosigmoid craniotomy. The aneurysm was trapped completely and thrombectomized to relieve the pontine mass effect. Indocyanine green videoangiography confirmed patency of the bypass, retrograde filling of the AICA to supply pontine perforators, and no residual aneurysmal filling. This unusual in situ bypass is possible when redundancy of the AICA and PICA allow their approximation in the CPA. The anastomosis is performed lateral to the lower cranial nerves in a relatively open and superficial plane. The extended retrosigmoid approach provides adequate exposure for both the bypass and aneurysm trapping. In situ AICA-PICA bypass enables anterograde and retrograde AICA revascularization with side-to-side anastomosis. The occipital artery-to-AICA bypass and the V3 vertebral artery-to-AICA interpositional bypass are alternatives when intracranial anatomy is unfavorable for this in situ bypass.1-6 Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Microsurgical resection of an enlarging lateral pontomedullary cavernous malformation.

The extended retrosigmoid approach provides an excellent corridor to the lateral aspect of the pontomedullary junction (PMJ).1,2 This video demonstrates a microsurgical resection of a progressive enlarging cavernous malformation (CM) of the PMJ. The patient is a 33-year-old woman with progressive symptoms, including right facial droop, left hemianesthesia, diplopia, and nystagmus. The patient underwent a right extended retrosigmoid approach with intraoperative neuronavigation and neuromonitoring. Lower cranial nerve dissection allowed access to the lateral PMJ. A longitudinal corticotomy was performed above the glossopharyngeal. The CM was removed in a piecemeal fashion. Postoperative MRI confirmed gross-total resection and the patient remained neurologically stable.The video can be found here: https://youtu.be/K_TtiTo1RsQ.

Extended Retrosigmoid Approach for the Resection of a Pontomedullary Junction Cavernous Malformation.

Objectives To describe an extended retrosigmoid approach for the resection of a cavernoma involving the ponto-medullary junction, with emphasis on the microsurgical anatomy and technique. Design A retrosigmoid craniotomy is performed in the lateral decubitus position and the sigmoid sinus exposed. After opening the dura, sutures are placed medial to the sinus to allow its gentle mobilization. Cerebrospinal fluid (CSF) is drained from the cisterna magna, and cerebellopontine cistern, and dynamic retraction is used over the cerebellum. Subarachnoid dissection of the cerebellopontine angle gives access to cranial nerves IX/X, VII/VIII, and VI. Inspection of the pontomedullary junction medial to the facial nerve reveals hemosiderin staining in that region. A small pial opening is made, exposing the hemorrhagic cavity. The cavernous malformation is then identified, dissected circumferentially, and resected. Photographs of the region are borrowed from Dr Rhoton's laboratory to illustrate the microsurgical anatomy. Participants The senior author performed the surgery. The video was edited by Drs. J.B. and V.N. Outcome Measures Outcome was assessed with extent of resection and postoperative neurological function. Results A gross total resection of the lesion was achieved. The patient did not develop any postoperative deficits. Conclusion Understanding the microsurgical anatomy of the cerebellopontine angle and meticulous microneurosurgical technique are necessary to achieve a complete resection of a brainstem cavernoma. The extended retrosigmoid approach provides an adequate corridor to the pontomedullary junction. The link to the video can be found at: https://youtu.be/FIKixWJT75w .

Reconstruction of anterior inferior cerebellar artery by occipital artery through extended retrosigmoid approach

Objective To explore the feasibility of occipital artery(OA) to anterior inferior cerebellar artery (AICA) through the extended retrosigmoid approach, also perform a systemic microanatomical study of OA and AICA with the exposure of extended retrosigmoid approach, find the easy way to perform the procedure. Methods From September, 2016 to January, 2017, 5 adult cadaveric heads injected with colored latex (total 10 sides) were performed the extended retrosigmoid approach, and measured the caliber of distal occipital artery (OA), the final length of the OA harvest, the reliable landmark of the OA harvest, and the distance from the flocculonodular segment of anterior inferior cerebellar artery (AICA) to the OA, the diameter of AICA flocculonodular segment branch. Whole procedure of OA to IACA bypass also be performed. Statistical analysis was performed. Results By the extended retrosigmoid approach, AICA flocculonodular segment could be easily exposure, the average diameter was 1.2 mm, the OA branch could be harvested in average was (72.3±3.3)mm in length from the occipital sulcus, and the average distance between occipital sulcus and AICA flocculonodular segment was (47.6±1.9)mm. The bypass procedure also could be performed through the proper corridor. Conclusion The Extended retrosigmoid approach is a safe and efficient way to perform the OA-AICA bypass procedure, and the procedure is easier to be performed than other surgical approaches. Key words: Occipital artery; Anterior inferior cerebellar artery; OA-AICA bypass; Extended-retrosigmoid approach; Applied anatomy

Extended Retrosigmoid Approach for Cerebellopontine Angle Meningiomas: Operative Technique and Results-A Series of 28 Patients.

Background The purpose of this article is to describe our approach, surgical strategies, and results for resection of meningiomas located at cerebellopontine angle (CPA). Methods We retrospectively identified 28 patients with CPA meningiomas operated by the extended retrosigmoid approach. This approach incorporates a generous mastoidectomy and the sigmoid sinus exposure. Results The mean age was 33.8 years, with a follow-up of 12.5 years. Gross total removal (GTR) was achieved in 22 (78.5%) patients with low surgical mortality, acceptable morbidity, and recurrence rate of 7.1% (2 patients). Conclusion The extended retrosigmoid approach enhances the exposure of the CPA and posterior fossa cisterns and increases the surgical angle of maneuverability. This approach provides adequate access even to extensive CPA meningiomas, enabling, in most of cases, GTR to be safe and effective. The extended retrosigmoid approach used in this group of patients is an alternative to more extensive cranial base approaches.

Surgical Strategy for Dermoid and Epidermoid Tumors of the Posterior Fossa - Experience with 21 Patients

Objective The aim of this paper is to describe our surgical strategy and technique and to identify the best management for posterior fossa dermoid and epidermoid tumors (PFDETs). Methods We retrospectively identified 21 consecutive patients (11 males and 10 females), with a mean age of 33.2 years, a mean follow-up of 6.1 years, and pathologically confirmed PFDETs. Total 17 patients were submitted to the extended retrosigmoid approach. This approach incorporates transverse sigmoid sinus exposure and a generous mastoidectomy. Results Gross total tumor removal was achieved in 16 (76.1%) cases, with no surgical mortality and a recurrence rate of 9.5%. Conclusions The surgical strategies used in this group of patients enabled the total removal of most tumors without surgical mortality and with minimal morbidity and recurrence rates. The extended retrosigmoid approach used is an alternative path regarding cranial base approaches. This approach is quick, simple and safe, and decreases the retraction of the cerebellum.

A Comparison of Cerebellar Retraction Pressures in Posterior Fossa Surgery: Extended Retrosigmoid versus Traditional Retrosigmoid Approach

Background The retrosigmoid approach is broadly applicable to many posterior fossa procedures. However, cerebellar retraction is often necessary for lesions in the cerebellopontine angle, which can lead to complications. An extended retrosigmoid approach skeletonizes the sigmoid sinus and allows a wider corridor with less retraction. This study investigated the differences in retraction pressure between the retrosigmoid and extended retrosigmoid approach in a cadaveric model. Methods Anatomic dissection of 2 cadaveric heads was performed for comparison of surgical approaches. Bilateral measurements were obtained on each head, providing 4 sets of data. Retrosigmoid craniotomy was first performed with recording of retraction pressure necessary for 1.5-cm exposure. The exposure was then expanded to an extended retrosigmoid approach, and retraction pressures were recorded. Results Mean retraction pressure in cadaver 1 for retrosigmoid and extended retrosigmoid approaches was 20.25 ± 5.9 mm Hg and 10.25 ± 3.8 mm Hg, respectively; in cadaver 2, values were 11.75 ± 3.1 mm Hg and 4.75 ± 1.8 mm Hg, respectively. This corresponded to a mean relative reduction in retraction pressure of 49.4% in cadaver 1 and 59.6% in cadaver 2 by using the extended retrosigmoid approach. Retraction pressures were also significantly less (P Conclusions The extended retrosigmoid approach gains better visualization with reduced brain retraction. In our study, cerebellar retraction pressures were greatly reduced when using the extended retrosigmoid approach in a cadaveric model.

Surgical Exposure Gained in an Extended Retrosigmoid Approach to the Cerebellopontine Angle Compared to the Traditional Retrosigmoid Approach.

Retrosigmoid approach to the posterior fossa has been a popular and dependable approach for accessing the cerebellopontine angle (CPA) and petroclival region. Although this approach is commonly used, it requires cerebellar retraction and has limitations when the lesion is located ventral to the brainstem. The aim was to quantify the angle of view provided by extended retrosigmoid approach in comparison to the traditional approach. A secondary objective was to identify a strategic initial burr hole site for craniotomy. Ten adult human cadaver heads (20 sides) were used. First, traditional retrosigmoid approach was performed and the angle of exposure was measured on cranial computerized tomography (CT). Following, extended retrosigmoid approach was performed with mastoid bone drilling and reflection of venous sinuses. Angle of exposure was measured on CT. Two measurements of both approaches were compared. Mean angle of view for the traditional retrosigmoid approach (31.4° ± 4.1°) was significantly smaller than that of the extended approach (46.0° ± 4.7°) (p < 0.001). Site of strategic burr hole was 5 mm below and 15 mm lateral to the asterion was defined. Extended retrosigmoid approach offers neurosurgeons approximately 50% larger angle of view and shorter working distance than the traditional approach provides. This modification permits better access to the CPA and ventral brain stem without cerebellar retraction.

Retrosigmoid craniotomy for clipping of two vertebrobasilar junction aneurysms

In this operative video, we demonstrate the approach to a 10-mm distal left vertebral artery and proximal basilar artery blister aneurysm in a 62-year-old male presenting with subarachnoid hemorrhage. He initially underwent clipping of the ruptured ACoA aneurysm and two incidental right MCA aneurysms. Ten days later, the posterior circulation aneurysms were clipped through an extended retrosigmoid approach, working between cranial nerves 9-11 inferiorly and 7-8 superiorly. The vertebral artery was accessible from its dural entry site to the vertebrobasilar junction with the rostral limit of the exposure at the level of the tentorium. He underwent uneventful clipping of all aneurysms without postoperative morbidity. The video can be found here: http://youtu.be/PaZM7ecBCB0 .

An endoscopic-assisted technique for retrosellar access during the extended retrosigmoid approach: a cadaveric feasibility study and quantitative analysis of retrosellar working area

The retrosigmoid approach has been advocated for certain petroclival tumors but provides limited access to any retrosellar extension of tumor, necessitating a two-stage operation. Our purpose was to demonstrate preliminary feasibility of an endoscopic-assisted technique to provide retrosellar access during the extended retrosigmoid approach and compare microscopic and endoscopic retrosellar working area. Standard retrosigmoid craniectomy and partial petrosectomy respecting inner ear structures were performed on six embalmed cadaveric heads. Two balloons were inflated to simulate a 15 mm petroclival tumor. Retrosellar clival and brainstem working area and ipsilateral oculomotor nerve and posterior cerebral artery (PCA) working distance were measured using the endoscope and microscope. Artificial tumors were implanted and resected using the endoscopic-assisted technique to assess feasibility. The endoscope provided significantly greater mean working area/distance on the clivus (201.6 vs 114.8 mm(2), p < 0.01), brainstem (223.5 vs 121.2 mm(2), p < 0.01), ipsilateral oculomotor nerve (10.8 vs 6.4 mm, p < 0.01), and ipsilateral PCA (13.7 vs 8.9 mm, p = 0.01). Petrous dissection to create a 10 × 10 mm working channel and artificial tumor resection was feasible in all dissections. The superior petrosal vein required ligation in 9 (75%) cases. Air cells were exposed in 1 (8%) case. The described endoscopic-assisted technique can provide retrosellar access during the extended retrosigmoid approach to access petroclival tumors with retrosellar extension. Risks include superior petrosal vein sacrifice, bleeding that can impair visualization, injury to the trigeminal nerve during endoscopic insertion/manipulation or injury to the brainstem while working in the medial limits of exposure. Further work is necessary to determine clinical feasibility, safety, and efficacy.

Critical remarks on the proposed “extended retrosigmoid approach”

Critical remarks on the proposed “extended retrosigmoid approach”

Surgical management of large posterior petrous meningiomas through extended retrosigmoid approach

Objective To evaluate extended retrosigmoid approach for surgery on large posterior petrous meningiomas. Methods During 5 - year period between 2004 and 2009, sixteen patients with large posterior petrous meningiomas were treateded through extended retrosigmoid approach. The maximum diameters of tumors were all more than 4 cm. The petrous bone erosion by lesions was found in 4 cases. The sigmoid sinus and the transverse sinus were thoroughly exposed after bone removal including mastoid and occipital bones. The sigmoid sinus was pulled anteriorly and the transverse sinus upward in order to widen the opening into the infratentorial space and the posterior surface of the petrous bone. Results Gross total resection of the tumors were achieved in 15 cases, subtotal resection in 1 case. There was no perioperative death. The symptoms disappeared or improved after surgery in 15 patients. There was a patient with irreversible hemifacial palsy. Cerebrospinal fluid rhinorrhea was found in one case. There was no tumor recurrence in all cases confirmed by MRI scanning during the follow - up period ( 3 to 60 months).Conclusion The extended retrosigmoid approach provides early devascularization of the tumor from its dural attachment to petrous pyramid, enhances surgical exposure and increases the complete tumor resection rate. Key words: Meningioma; Microsurgery; Skull base; Operative approach

Extended retrosigmoid approach for surgery of large petroclival meningiomas

Objective To evaluate the extended retrosigmoid approach for surgery of large petroclival meningiomas. Methods We retrospectively analyzed our experience in 6 patients with large petroclival meningiomas treated by extended retrosigmoid approach. The maximum diameter of tumors ranged from 3.4 to 6. 7 cm （ mean, 4. 5 cm）. The sigmoid sinus and the transverse sinus were thoroughly exposed with the bone removal including mastoid and occipital bones. The stay sutures of the dura flaps were performed to pull the sigmoid sinus anteriorly and the transverse sinus upward to widen the opening into the infratentorial space and the posterior surface of the petrous bone. Results Gross total resection of the tumors was achieved in 3 cases, subtotal resection in 2 cases and partial resection in 1 case. No patients died. The neurological deficits improvement was found in 1 case, unchanged in 3 cases, and 2 patients were found to have new cranial nerves palsy. There was no CSF leakage and infections after operations. There was no tumor recurrence or growth by MRI scanning during the follow-up period of 6 to 58 months in all patients. Conclusion The extended retrosigmoid approach can enhance the surgical exposure, enlarge the operative view, cut the blood supply of tumor earlier, and avoid the excessive retraction on cerebellum, as well as facilitate the protection of these vital cranial nerves and vessels around brain stem. Key words: Meningioma ; Microsurgery ; Skull base ; Operative approach