Olivary body exposure through far lateral and lower retrosigmoid approaches. Comparative analysis of the exposed surface and angle of attack

OBJECTIVES

Throughout neurosurgical history, the treatment of intrinsic lesions located in the brainstem has been subject of much controversy. The brainstem is the anatomical structure of the central nervous system (CNS) that presents the highest concentration of nuclei and fibers, and its simple manipulation can lead to significant morbidity and mortality. Once one of the safe entry points at the medulla oblongata has been established, we wanted to evaluate the safest approach to the olivary body (the most used safe entry zone on the anterolateral surface of the medulla oblongata). The proposed objective was to evaluate the working channel from the surface of each of the far lateral and retrosigmoid approaches to the olivary body: distances, angles of attack and channel content.

MATERIAL AND METHODS

To complete this work, a total of 10 heads injected with red/blue silicone were used. A total of 40 approaches were made in the 10 heads used (20 retrosigmoid and 20 far lateral). After completing the anatomical study and obtaining the data referring to all the approaches performed, it was decided to expand the sample of this research study by using 30 high-definition magnetic resonance imaging of anonymous patients without cranial or cerebral pathology. The reference points used were the same ones defined in the anatomical study. After defining the working channels in each of the approaches, the working distances, angle of attack, exposed surface, and the number of neurovascular structures present in the central trajectory were analyzed.

RESULTS

The distances to the cranial and medial region of the olivary body were 52.71 mm (SD 3.59) from the retrosigmoid approach and 27.94 mm (SD 3.99) from the far lateral; to the most basal region of the olivary body, the distances were 49.93 (SD 3.72) from the retrosigmoid approach and 18.1 mm (SD 2.5) from the far lateral. The angle of attack to the caudal region was 19.44° (SD 1.3) for the retrosigmoid approach and 50.97° (SD 8.01) for the far lateral approach; the angle of attack to the cranial region was 20.3° (SD 1.22) for the retrosigmoid and 39.9° (SD 5.12) for the far lateral. Regarding neurovascular structures, the probability of finding an arterial structure is higher for the lateral far, whereas a neural structure will be more likely from a retrosigmoid approach.

CONCLUSIONS

As conclusions of this work, we can say that far lateral approach presents more favorable conditions for the microsurgical treatment of intrinsic bulbar and bulbomedullary lesions approached through the caudal half of the olivary body. In those cases of bulbar and pontine-bulbar lesions approached through the cranial half of the olivary body, the retrosigmoid approach can be considered for selected cases.

How I do it: hearing preservation in large vestibular schwannomas using vestibular nerve fiber preservation technique

BACKGROUND

To improve hearing function after resection of large vestibular schwannomas, we describe a strategy of vestibular-nerve-fiber preservation. Anatomical considerations and stepwise dissection are described.

METHOD

Steps include locating the vestibular nerve at the brainstem and identifying a dissection plane between nerve fibers and tumor capsule. Using this plane to mobilize and resect tumor reduced manipulation and maintained vascularity of underlying cochlear and facial nerves.

CONCLUSION

Preservation of hearing function is feasible in large vestibular schwannomas with vestibular-nerve-fiber preservation. Reducing manipulation and ischemic injury of underlying cochlear and facial nerves thereby helped facilitate hearing preservation, even in large tumors.

Intraoperative ultrasonography in microsurgical resection of vestibular schwannomas via retrosigmoid approach: surgical technique and proof-of-concept illustrative case series

PURPOSE

Intraoperative ultrasonography (ioUS) is an established tool for the real-time intraoperative orientation and resection control in intra-axial oncological neurosurgery. Conversely, reports about its implementation in the resection of vestibular schwannomas (VS) are scarce. The aim of this study is to describe the role of ioUS in microsurgical resection of VS.

METHODS

ioUS (Craniotomy Transducer N13C5, BK5000, B Freq 8 MHz, BK Medical, Burlington, MA, USA) is integrated into the surgical workflow according to a 4-step protocol (transdural preresection, intradural debulking control, intradural resection control, transdural postclosure). Illustrative cases of patients undergoing VS resection through a retrosigmoid approach with the use of ioUS are showed to illustrate advantages and pitfalls of the technique.

RESULTS

ioUS allows clear transdural identification of the VS and its relationships with surgically relevant structures of the posterior fossa and of the cerebellopontine cistern prior to dural opening. Intradural ioUS reliably estimates the extent of tumor debulking, thereby helping in the choice of the right moment to start peripheral preparation and in the optimization of the extent of resection in those cases where subtotal resection is the ultimate goal of surgery. Transdural postclosure ioUS accurately depicts surgical situs.

CONCLUSION

ioUS is a cost-effective, safe, and easy-to-use intraoperative adjunctive tool that can provide a significant assistance during VS surgery. It can potentially improve patient safety and reduce complication rates. Its efficacy on clinical outcomes, operative time, and complication rate should be validated in further studies.

Intraoperative venous congestion and brainstem venous hemorrhagic infarction during retrosigmoid for acoustic neuroma

Venous hemorrhagic infarction is rare but can occur during acoustic neuroma resection [1-5]. We present the case of a 27-year-old male with 1.5 years of progressive headaches, tinnitus, imbalance and hearing loss. Imaging revealed a left Koos 4 acoustic neuroma. The patient underwent a retrosigmoid approach for resection. During surgery, a vein of significant size within the capsule of the tumor was encountered and was necessary to take to proceed with resection. After coagulation of the vein, intraoperative venous congestion with cerebellar edema and hemorrhagic infarction ensued, requiring resection of a portion of the cerebellum. Given the hemorrhagic nature of the tumor, continuing tumor resection was necessary to prevent postoperative hemorrhage. This was carried out until hemostasis was achieved. 85 % resection was achieved, leaving a residual against the brainstem and cisternal course of the facial nerve. Postoperatively, the patient required 5 weeks hospitalization followed by 1 month of rehabilitation. At discharge to rehabilitation, patient had trach, PEG, left House-Brackmann 5 facial weakness, left sided deafness, and right upper extremity hemiparesis (1/5). At 7 months follow up, he continued to have left House-Brackmann 5 facial weakness and left sided deafness but trach and PEG had been removed and strength had improved to 5/5. We demonstrate in this video the unfortunate and rare occurrence of intraoperative venous hemorrhagic infarction during acoustic neuroma resection - particularly for large tumors in young patients - and discuss its etiology and surgical steps that are necessary to partially remedy its devastating impact on the patient. The patient consented to the procedure and participating in this surgical video.

Keyhole retrosigmoid approach for resection of a petro-tentorial meningioma causing trigeminal neuralgia

Meningiomas involving the tentorium, comprising 3-6 % of all intracranial meningiomas, pose a great challenge for surgical excision due to their proximity to the deep neurovascular structures and complex anatomic boundries [1]. Depending on certain tumor characteristics and other anatomical findings, surgeons may attempt to tackle these lesions through a middle fossa, retrosigmoid or a single or multiple stage combination of approaches [2]. Here, we present a case of a 72-year-old male with severe left sided facial pain secondary to a homogenously enhancing mass arising in the left petro-tentorial junction, causing significant compression of the trigeminal nerve. After failing pharmacological therapy, the patient consented to surgical resection and decompression of the trigeminal nerve via a key hole retrosigmoid approach. This approach provided adequate exposure of the tumor and surrounding neurovascular structures, enabling safe microsurgical removal of the lesion while minimizing the amount of tissue disruption. Due to the small surgical foot print of the approach, the patient was able to be discharge quickly from the hospital with minimal post-surgical pain. We describe the key surgical steps and reconstruction technique.

Retrosigmoid Approach for Sporadic Vestibular Schwannoma: Patient Selection, Technical Pearls, and Hearing Results

The retrosigmoid corridor provides the most broadly applied approach for resection of sporadic vestibular schwannoma. It may be utilized for any size tumor and for patients with intact hearing with the intention of hearing preservation. For larger tumors, the skull base surgeon must weigh the benefits the retrosigmoid approach against those of the translabyrinthine route. For smaller tumors where hearing preservation is a goal, the retrosigmoid approach is contrasted to the middle fossa route. Hearing preservation is most likely for patients with small and medially located intracanalicular tumors with minimal extension into the cerebellopontine angle, and excellent preoperative hearing.

Delayed Facial Nerve Paralysis After Vestibular Schwannoma Resection

OBJECTIVE

To report the long-term outcome of delayed facial nerve paralysis (DFNP) after surgical resection of vestibular schwannoma and evaluate the influence of various factors on the prognosis of facial nerve function.

METHODS

Of 265 patients who underwent surgical excision of VS through a retrosigmoid approach between April 2019 and October 2021, 15 (5.7%) developed DFNP and were retrospectively studied. Preoperative and postoperative data were collected and analyzed.

RESULTS

The mean age of patients with DFNP was 42.6 years (range, 27-63 years), and 11 (73.3%) were male. Tumor size ranged from 12 to 37 mm (mean 24 mm) in largest dimension. All patients had normal (House-Brackmann [HB] I) facial nerve function preoperatively. Immediate postoperative facial nerve function was HB I in 12 patients (80%) and HB II in 3 patients (20%). The mean severity of DFNP onset was HB 4.7 (range, HB III-V). The average day of onset was postoperative day 12.6 (range, day 5-28). At 1-year follow-up, 12 patients (80%) were HB I, 1 patient (6.7%) was HB III, and 2 patients (13.3%) were HB IV. All patients who were HB III and IV at the last follow-up had immediate postoperative facial nerve function of HB II.

CONCLUSIONS

Most patients who develop DFNP have a favorable prognosis. However, a small proportion of patients with deteriorated facial nerve function immediately after surgery have poor long-term outcomes, despite confirmation of their facial nerve integrity anatomically and by electrical stimulation.

Microsurgical resection of a right dumbbell-shaped jugular foramen schwannoma through a modified retrosigmoid infra-jugular approach: how I do it

BACKGROUND

Surgical treatment of dumbbell jugular foramen schwannomas can be challenging. The main goals of surgery are maximal resection with preservation of function and overall patient quality of life.

METHODS

In this paper, we present a step-by-step technical description of a microsurgical resection of dumbbell-shaped JF schwannoma using a modified retrosigmoid infra-jugular approach.

CONCLUSION

The modified retrosigmoid infra-jugular is a safe and suitable approach in selected cases. This technique, however, must be limited only to those tumors with minimal extension into the jugular foramen.

Introducing the Posterior Condylar Emissary Vein as an Effective Surgical Landmark for Optimizing the Standard Retrosigmoid Approach: An Anatomo-Imaging Study

OBJECTIVE

There is a lack of definite anatomical landmarks for the inferior extension of the standard retrosigmoid approach. In this study, we evaluated whether the posterior condylar emissary vein (PCEV) can be used as an intraoperative landmark for optimizing the surgical corridor.

METHODS

We performed the standard retrosigmoid approach on 5 formalin-fixed and latex-injected cadaveric specimens and measured the distance between the PCEV near its bony canal and the vertebral artery (VA). In addition, vascular reconstructions of thin-sliced preoperative computed tomography (CT) scans were studied in 40 patients and the relationship between these 2 vessels was evaluated. An illustrative case is also included.

RESULTS

The PCEV was consistently identified on both sides of cadaveric specimens and in 87.5% and 82.5% of the left and right sides of the included CT scans, respectively. The average distance between the part of the PCEV near its osseous canal and the VA was measured to be between 8.4 mm and 8.6 mm in the specimens and between 9.2 mm and 9.3 mm in the CT scans. This distance offers a safe and effective plane of dissection during the standard retrosigmoid approach and allows easy access to the foramen magnum.

CONCLUSIONS

The PCEV near its bony canal proved to be an easy, straightforward, safe, and effective operative landmark with which the surgeon can extend the soft tissue dissection and bony exposure towards the foramen magnum. This maneuver provides ample access to the cisterna magna for cerebrospinal fluid drainage and increases visibility and surgical maneuverability to the entire cerebellopontine angle.

Microsurgical Treatment of a Petrotentorial Dural Arteriovenous Fistula: The Vein, the Whole Vein, and Nothing but the Vein: 2-Dimensional Operative Video

Dural arteriovenous fistulas (dAVFs) consist of abnormal anastomoses between 1 or multiple meningeal arteries to meningeal veins, venous sinuses, or subarachnoid veins.1 dAVFs account for 10% to 15% of all intracranial arteriovenous lesions.2 dAVFs can be challenging to treat with various approaches that include microsurgical ligation, endovascular embolization (transarterial or transvenous), and stereotactic radiosurgery. All these treatments share the common goal of disconnecting the draining vein from the fistulous point. We present a case of a 43-yr-old male who presented with progressive headaches and was found to have an incidental Zipfel type 3A3 right petrotentorial dAVF on catheter angiography. The patient underwent a right retrosigmoid craniotomy and clipping of 2 separate venous outflows. The case illustrates the principle that multiple venous outflows can exist in dAVF and a thorough analysis of the venous phase of the angiogram as well as corresponding inspection of the fistula at the time of surgical exploration is a necessity to avoid partial obliteration. The patient remained neurologically intact postoperatively and had complete resolution of his fistula on postoperative angiography. We review the neuroimaging, operative video, and technical nuances and provide a short literature review on the topic.4 The patient gave informed consent for the procedure and verbal consent for this publication. The patient consented to the publication of their image.

Microsurgical Resection of Intracanalicular Vestibular Schwannoma via Retrosigmoid Approach: 3-Dimensional Operative Video

Vestibular schwannomas are a multifaceted group of tumors that can present with different sizes and involvement of critical neurovascular structures.^1-6 While operating on these tumors, a critical goal is postoperative preservation of facial nerve function and hearing. We present the case of a 66-year-old male with a history of severe left-sided tinnitus and progressive hearing loss (Video 1). Preoperative imaging depicted a lesion highly suggestive of an intracanalicular vestibular schwannoma. Due to worsening of symptoms and after thoughtful discussion with the patient, microsurgical resection was indicated under constant neurophysiologic monitoring. A retrosigmoid approach was employed, and the posterior wall of the internal auditory canal was opened, allowing exposure of tumor and its total resection. Postoperative imaging demonstrated complete tumor resection. The patient's symptoms improve, and there were no new neurologic deficits on follow-up. Anatomical images were a Courtesy of the Rhoton Collection, American Association of Neurological Surgeons (AANS)/Neurosurgical Research and Education Foundation (NREF).

Endoscope-assisted microsurgical retrosigmoid approach to the lateral posterior fossa: Cadaveric model and a review of literature

Background:

The advancement of endoscopic techniques in the past decade has improved the surgical management of cerebellopontine angle (CPA) tumors. Endoscope-assisted microsurgery improves the ability to evaluate the extent of resection, achieve safe tumor resection and reduce the risk of surgery-related morbidity.

Methods:

In this study, we used a cadaveric model to demonstrate a step by step endoscope-assisted microsurgery of the retrosigmoid approach to the lateral posterior fossa.

Results:

Retrosigmoid craniotomies were performed on four latex-injected cadaver heads (eight CPAs). Microsurgical exposures were performed to identify neurovascular structures in each segment. 0° and 30° rigid endoscope lenses were subsequently introduced into each corridor and views were compared in this manner. The endoscopic images were compared with the standard microscopic views to determine the degree of visualization with each technique. In each case, better visualization was provided by both the 0° and 30° endoscope lenses. Endoscopic views frequently clarified neurovascular relationships in obscured anatomic regions.

Conclusion:

Endoscope-assisted microsurgery could allow better visualization of various regions of the posterior fossa. Surgical planning for posterior fossa lesions should include consideration of this combined approach.

Microsurgical Resection of a Pontine Cavernoma Using an Expanded Retrosigmoid Corridor: 2-Dimensional Operative Video

Cavernous malformations that have not previously bled have been reported to have an annual bleeding rate of 0.6% per year.1 Those with prior hemorrhage have been reported to have rebleeding rates of up to 4.5%.1 Additionally, infratentorial location, young age, and female gender have been associated with increased risk.1 We present the case of a 26-yr-old female who initially presented to an outside institution with left-sided weakness. She improved following her initial bleeding event and presented to us for further management. A large, cavernous malformation in the right pons was identified on imaging. The patient underwent a right expanded retrosigmoid craniotomy with splitting of the horizontal cerebellar fissure to completely remove the lesion. The expanded retrosigmoid craniotomy allows for an enhanced view of the medial pontine region and can be utilized for appropriately selected brainstem cavernous malformations. The case presentation, surgical anatomy, operative nuances, and postoperative course and outcome are reviewed. The patient gave verbal consent for participating in the procedure and surgical video. The patient also consented to the publication of her image.

The Vascularized Occipital Fascial Flap (OFF): A Novel Reconstructive Technique for Posterior Fossa Surgery

BACKGROUND

Posterior fossa surgery is particularly prone to cerebrospinal fluid (CSF) leakage. Several methods have been introduced to address and/or prevent this complication. However, to the best of our knowledge, the use of a vascularized fascial flap based on the occipital artery for the purpose of reconstruction has not been reported. We introduce the occipital fascial flap (OFF) for reconstruction of a craniectomy defect after the retrosigmoid approach.

METHODS

A 57-year-old woman with a large cerebellar metastasis underwent gross total resection of the mass followed by reconstruction of the craniectomy defect using OFF.

RESULTS

Postoperative imaging showed flap viability and no CSF leak occurred during follow-up.

CONCLUSIONS

We report the first use of OFF for reconstruction of a craniectomy defect in a retrosigmoid approach. The vascularized fascial flap in posterior fossa surgery is a potentially helpful technique to reduce the risk of CSF leak in high-risk patients.

Retrosigmoid Transtentorial Resection of a Petroclival Meningioma: 2-Dimensional Operative Video

In this video, we aimed to demonstrate retrosigmoid-transtentorial resection of a 4.5 × 4 × 4.5 cm3 left-sided petroclival meningioma compressing the brainstem in a 62-yr-old male who presented with decreased hearing on the left and imbalance.  The patient was placed in park-bench position and a left-sided suboccipital craniotomy was performed. The mass was severely compressing the brainstem as well as the cranial nerves V, VI, VII, and VIII while IV was encased by the tumor. The circumferential dissection of the tumor was facilitated while the surgical corridor and exposure were enlarged by incising the tentorium. Uneventfully, the meningioma was resected in piecemeal fashion as it was not coming out easily with the ultrasonic aspirator. All relevant cranial nerves and adjacent vascular structures were protected. Early postoperative CT scan demonstrated changes due to the surgery and resolution of the compression on the brainstem. The patient made excellent recovery and he was discharged home on postoperative day 4 safely.  Petroclival meningiomas are one of the most challenging tumors for neurosurgeons due to their close proximity to the vascular structures, cranial nerves as well as the brainstem. The retrosigmoid approach provides a direct route during microsurgical resection of these tumors. By incising the tentorium, the corridor can be widened while addressing the supratentorial portion of the tumor with relative ease.

How I do it: retrosigmoid intradural inframeatal petrosectomy

BACKGROUND

Lesions infiltrating the petrous temporal bone are some of the most complex to treat surgically. Many approaches have been developed in order to address these lesions, including endoscopic endonasal, anterior petrosectomy, posterior petrosectomy, and retrosigmoid.

METHOD

We describe in a stepwise fashion the surgical steps of the retrosigmoid intradural inframeatal petrosectomy.

CONCLUSION

The retrosigmoid intradural inframeatal petrosectomy may afford satisfactory exposure with limited drilling and minimal disruption of perilesional anatomical structures. It can provide excellent surgical results, especially for soft tumors, while minimizing surgical morbidity.

[Assessment of computed tomographic angiographysinus development combined with occipitalbone marks for the location of transverse sigmoid sinus junction]

Objective: To introduce and evaluate a technique to precisely localize the transverse-sigmoid sinus junction (TSSJ) in retrosigmoid craniotomy. Methods: This was a single-center prospective randomized controlled study. Sixty-three patients, 29 male and 34 female, who would undergo retrosigmoid craniotomy admitted to Department of Neurosurgery, the First Affiliated Hospital of Xinjiang Medical Universityfrom March to October 2019 were enrolled in the study and were divided into trial group and control group according to the computer-generated random numbers. Preoperative venous computed tomographic angiography (CTA) combined with 3-dimensional computed tomography computed tomography (3D CT) was randomly given to the patients(n=32). Asterion was used for identification of the TSSJ in the controls (n=31). The main outcome measures as postoperative complications and relevant intraoperative indicators were compared. Results: Incision length, craniotomy time, bone window sizein trial group were shorter or smaller than those of the controls, as(6.8±0.5) cm vs (8.0±1.5) cm, (37±8) min vs (45±15) min, (8.7±1.2) cm(2) vs (10.2±2.4) cm(2) respectively, with statistical significance (all P<0.05). No statistical significance was found in bleeding amount, incidence of sinus injury and cerebrospinal fluid leakage. While incidence of neck pain was lower in case group (15.63% vs 38.71%; P=0.04) and the remission time of incisional pain in case group was shorter [(6±1) d vs (9±2) d; P=0.01]. Conclusion: While the technique is used, the center of the keyhole should be located at transitional place of the lateral part of the occipitomastoid suture, the retromastoid ridge and the superior nuchal line. Compared with the traditional craniotomy method marked by asterion, it has great advantages in reducing incidence of postoperative complications, craniotomy time, and the remission time of incisional pain.

Comparison of translabyrinthine and retrosigmoid approach for treating vestibular schwannoma: A meta-analysis

BACKGROUND

To date, the literature directly comparing the translabyrinthine approach and retrosigmoid approach in the operation of patients with vestibular schwannoma was limited. We aimed to evaluate postoperative complications between translabyrinthine approach and retrosigmoid approach for treating vestibular schwannoma patients.

MATERIAL AND METHOD

Potential publications were selected from PubMed, Web of Science and Cochrane Library. Gray relevant studies were manually searched. We set the searching time spanning from the creation date of electronic engines to February 2020. STATA version 12.0 was exerted to process the pooled data.

RESULTS

A total of 9 literature included in the study, involving 2429 patients, hails from the Germany, USA, Canada, Italy, and France. Of these 2429 patients with vestibular schwannoma, there were 1628 cases from the translabyrinthine approach group versus 801 cases from the retrosigmoid approach group. The results demonstrated that the translabyrinthine approach group was associated with a lower rate of tinnitus (OR = 2.687; 95 %CI, 1.167-6.191; P = 0.02) and cranial nerve deficit (OR = 2.946; 95 %CI, 1.562-5.557; P = 0.001). And the translabyrinthine approach group was associated with a higher total resection rate (OR = 0.246; 95 %CI (0.071-0.848); P = 0.026). However, no statistic differences were found in the incidence of the near total (OR = 0.751; P = 0.351), subtotal resection (OR = 3.664; P = 0.109), postoperative facial nerve dysfunctions (OR, 0.763; P = 0.626), postoperative meningitis (OR = 2.7; P = 0.279), cerebrospinal fluid leak (OR = 1.225; P = 0.777), postoperative headache (OR = 1.412; P = 0.339), ophthalmic complications (OR = 0.87; P = 0.59), and vascular complications (OR = 2.501; P = 0.139).

CONCLUSION

Based on current evidence, the translabyrinthine approach was associated with a higher rate of total resection and a lower rate of the tinnitus and cranial nerve deficit. But the risk of cranial nerve deficit was clearly affected by the preoperative status. And a translabyrintine approach could imply a complete sensorineural hearing loss, which contribute to the lower rate of postoperative tinnitus. Consequently, more evidence-based researches are needed to supplement this opinion.

Retrosigmoid Clip Anterior Inferior Cerebellar Artery Aneurysm: 2-Dimensional Operative Video

Aneurysms of the anterior inferior cerebellar artery (AICA) are rare and require a considerate approach to facilitate successful and safe clipping. Surgical approaches vary and are dependent on the relation of the aneurysm to the internal acoustic meatus. An anterior approach should be considered for lesions medial to the meatus. Lesions adjacent to the meatus can be approached via a retrosigmoid or translabyrinthine approach. Lesions lateral to the meatus can be approached via a retrosigmoid or far lateral approach. This patient had a previously ruptured AICA aneurysm in the meatal region for which a retrosigmoid approach was selected. The approach involved locating the AICA distally and tracking it proximally to the origin off the basilar artery. A clip was applied across the aneurysm neck to facilitate occlusion while preserving parent vessel flow. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Postcraniectomy pain: comparison between 2 incisions for the retrosigmoid approach. Prospective randomized study

BACKGROUND

Suboccipital lateral approach is a common practice in neurosurgery to expose the region of the cerebellopontine angle. Postcraniectomy headache (PCH) is one of the most frequent complications that diminish the quality of life of patients.

OBJECTIVE

To compare postcraniectomy pain in patients operated on for vestibular neurinomas by a suboccipital lateral approach by 2 different incisions.

MATERIAL AND METHODS

Prospective randomized research study. Follow-up of patients operated for vestibular neurinomas between July 2017 and May 2019 (n=40) by the same surgeon. One group received the classical linear incision (n=20) and another group the alternative incision in an inverted "U" (modified Dandy) (n=20). Pain intensity was evaluated by numerical scale. A minimum follow-up of 3 months was carried out. The impact on quality of life was measured by the SF-36 questionnaire short version both before and after surgery.

RESULTS

The average age was 46.1 years. The overall PCH index was 27.5% (n=11) of the patients. The incidence of pain in the group that received the classical incision (A) was 20% (n=4) and in group B was 35% (n=7).

CONCLUSIONS

We found a higher rate of post-craniectomy headache in patients who underwent a "modified Dandy" incision. These are preliminary data of an undergoing study and we hope to obtain more representative information in the future. We recommend interdisciplinary follow up for the integral treatment of PCH.

Dural venous sinus thrombosis after cerebellopontine angle surgery: Should it be treated?

INTRODUCTION

Dural venous sinus thrombosis is an uncommon, but significant sequela that may occur after resection of a cerebellopontine angle lesion. The natural history and management of this pathology has not been sufficiently studied.

METHODS

All operative cases for cerebellopontine angle lesions performed in our local institution dating from 1 January 2005 to 30 June 2018 were retrospectively reviewed to identify patients who developed new post-operative dural venous sinus thrombosis. Patients who developed a significantly narrowed sinus without intrinsic thrombus were also identified. Progression of sinus thrombosis through time was followed, with comparisons made between complications amongst patients with and without a compromised sinus.

RESULTS

Of the 126 patients, 20 were found to have new sinus thrombosis, with another 16 developing a critically narrowed sinus without intrinsic thrombus. These cases are significantly associated with translabyrinthine resection of acoustic schwannoma. 4 patients amongst the thrombosed group were commenced on additional therapeutic anticoagulation or antiplatelets, whilst the rest were observed. Based on available follow up imaging, 10/17 patients had significantly improved sinus thrombosis on serial imaging, including 8/14 amongst those not given additional anticoagulation. Patients with a compromised sinus demonstrated a higher rate of cerebrospinal fluid leak requiring blindsac procedures. When involving a dominant sinus, there is also an association of an increased requirement for permanent CSF diversion.

CONCLUSION

Therapeutic anticoagulation should be considered for symptomatic post-operative dural venous sinus thrombosis or if it involves a dominant sinus. Further prospective studies are warranted to better elucidate the risk-benefit justification of treatment for postoperative sinus thrombosis.

Comparison between retrosigmoid and translabyrinthine approaches for large vestibular schwannoma: focus on cerebellar injury and morbidities

This study aimed to compare the surgical outcomes and morbidities of retrosigmoid and translabyrinthine approaches for large vestibular schwannoma (VS), with a focus on cerebellar injury and morbidities. Eighty-six consecutive patients with large VS, with a maximal extrameatal diameter > 3.0 cm, were reviewed between August 2010 and September 2018. The surgical outcomes, operating time, volume change of perioperative cerebellar edema, and inpatient rehabilitation related to cerebellar morbidities were compared between the two approaches. In total, 53 and 33 patients underwent the retrosigmoid and translabyrinthine approaches, respectively. The median follow-up time was 34.5 months. Surgical outcomes, including the extent of resection, tumor recurrence, and facial nerve preservation, showed no significant differences between the two groups. Patients who underwent the retrosigmoid approach showed a marginal trend for postoperative lower cranial nerve (LCN) dysfunction (P = 0.068). Although the approaching procedure time was longer in the translabyrinthine group, the tumor resection time was significantly longer in the retrosigmoid group (P = 0.001). The median change in the volume of the perioperative cerebellar edema was significantly larger in the retrosigmoid group (P < 0.001) and significantly related to the retrosigmoid approach, solid VS, and tumor resection time. Most cerebellar and LCN deficits were transient; however, the patients in the retrosigmoid group underwent inpatient rehabilitation more than those in the translabyrinthine group (P = 0.018). Both surgical approaches show equivalent surgical outcomes. Notably, the translabyrinthine approach for large VS has advantages in that it reduces cerebellar injury and related morbidities.

Two-Operator Endoscopic Resection of Left Cerebellopontine Angle Epidermoid

Intracranial epidermoid cysts are developmental central nervous system abnormalities that arise from erroneous ectodermal inclusion during neural tube closure. Epidermoids are relatively common, representing 1% of all intracranial masses, and are particularly predominant in the cerebellopontine angle (CPA), where they are the third most prevalent diagnosis after schwannomas and meningiomas. Although small, asymptomatic, or incidental lesions may be safely observed, in the presence of symptomatic mass effect, epidermoid cysts typically require surgical resection. As shown in Video 1, we demonstrate the operating room setup and endoscopic resection of a left CPA epidermoid cyst through a retrosigmoid craniotomy. By use of a 2-surgeon 4-hands technique, the mass was dissected from the surrounding neurovascular structures, and a gross total removal was achieved with no postoperative neurologic deficits. Our video highlights the critical nuances pertinent to the fully endoscopic resection technique, with special attention to the relative restrictions of a small working corridor parallel to the tentorium and the petrous bone.

A modified park bench position: the "Dormeuse" position

BACKGROUND

Because of the restricted volume of the cisternal space, proper patient positioning on the operating table is of utmost importance during surgery by retrosigmoid approaches. Three positions are commonly used: supine, with the head rotated to the side contralateral to the lesion; the semi-sitting position; and the park bench position. Each position has advantages and disadvantages, and the surgeon should choose the one best suited to the individual patient and the pathology to be treated.

METHODS

We describe a modified park bench position that we call the Dormeuse position.

CONCLUSION

The Dormeuse position guarantees decrease in the posterior fossa pressure and allows optimal neural and vascular manipulation and control of any aspect of the cerebellopontine angle.

Morbidity Rate of the Retrosigmoid versus Translabyrinthine Approach for Vestibular Schwannoma Resection

Background and Objectives

Controversy related to the choice of surgical approach for vestibular schwannoma (VS) resection remains. Whether the retrosigmoid (RS) or translabyrinthine (TL) approach should be performed is a matter of debate. In the context of a lack of clear evidence favoring one approach, we conducted a retrospective study to compare the morbidity rate of both surgical approaches.

Subjects and Methods

168 patients underwent surgical treatment (2007-2013) for VS at our tertiary care center. There were no exclusion criteria. Patients were separated into two groups according to the surgical approach: TL group and RS group. Signs and symptoms including ataxia, headache, tinnitus, vertigo and cranial nerve injuries were recorded pre- and postoperatively. Surgical complications were analyzed. Perioperative facial nerve function was measured according to House-Brackmann grading system.

Results

Tumor resection was similar in both groups. Facial paresis was significantly greater in RS group patients preoperatively, in the immediate postoperative period and at one year follow-up (p<0.05). A constant difference was found between both groups at all three periods (p=0.016). The evolution of proportion was not found to be different between both groups (p=0.942), revealing a similar rate of surgically related facial paresis. Higher rate of ataxic gait (p=0.019), tinnitus (p=0.039) and cranial nerve injuries (p=0.016) was found in RS group patients. The incidence of headache, vertigo, vascular complications, cerebrospinal fluid leak and meningitis was similar in both groups. No reported mortality in this series.

Conclusions

Both approaches seem similar in terms of resection efficacy. However, according to our analysis, the TL approach is less morbid. Thus, for VS in which hearing preservation is not considered, TL approach is preferable.

Retrosigmoid Transtentorial Approach: Technical Nuances and Quantification of Benefit From Tentorial Incision

OBJECTIVE

The transtentorial extension of the retrosigmoid approach allows for improved visualization of the brainstem and petroclival region. This approach is an important tool in the skull base surgeon's armamentarium for pathologies involving the petroclival region. It has been shown that the addition of tentorial transection improves the exposed surface area of the brainstem. However, no data have been reported regarding the depth of the additional anterior and medial exposure. The goal of the present study was to describe the additional depth of exposure gained by performing tentorial transection. This information allows surgeons to preoperatively estimate the amount of operative exposure gained by this technique.

METHODS

Five preserved cadaveric heads were dissected using frameless image guidance. A standard retrosigmoid craniotomy was performed, followed by tentorial transection. The boundaries of the surgical exposure and depth of the surgical field were compared before and after tentorial transection.

RESULTS

After transection, we found a 20.1-mm increase in anterior exposure (P < 0.01) and a 13-mm increase in medial exposure (P < 0.01). No significant difference was found in the extent of the superior (P = 0.32) or lateral (P = 0.07) exposure. The surgical working distance increased significantly from 68.8 to 90.3 mm (P < 0.01).

CONCLUSIONS

When performing retrosigmoid craniotomy, the addition of tentorial transection allows for a significant increase in anterior and medial exposure with no significant increase in superior or lateral exposure.

Postoperative headache following treatment of vestibular schwannoma: A literature review

Vestibular schwannoma (VS) is a brain tumour arising from Schwann cells that is typically closely associated with the vestibulocochlear nerve. Post-operative headaches (POH) are a potentially common complication of surgery for VS. Greatly differing rates of POH have previously been reported, particularly with different surgical approaches. The aim of this review is to identify and summarise the available peer-reviewed evidence on rates of POH following operative (or radiosurgery) treatment for VS, in addition to information about the treatment and prognosis of POH in these patients. A systematic search was conducted of Pubmed, Medline, Scopus and EMBASE in April 2017 using the medical subject headings (acoustic neuroma OR vestibular schwannoma) AND headache. Eligibility determination and data extraction were performed in duplicate with standardised forms. POH is common following surgery for VS. Differing rates of POH have been reported with different management approaches, patient age and tumour size. There are relatively few studies that have directly compared the rates of POH with different surgical approaches. The retrosigmoid approach with craniotomy appears to have lower rates of POH than when the retrosigmoid approach is performed with craniectomy. Patients under the age of 65 and with tumours <1.5 cm in size appear to have a higher risk of POH. The most commonly documented management of POH involves simple analgesia, although the majority of patients report this treatment is of only minimal benefit. Further prospective studies comparing rates of POH following different surgical approaches and radiosurgery are required.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Hydroxyapatite bone cement for suboccipital retrosigmoid cranioplasty: A single institution case series

OBJECTIVE

To report rates of cerebrospinal fluid leak, wound infection, and other complications after repair of retrosigmoid craniotomy with hydroxyapatite bone cement.

METHODS

Retrospective case review at tertiary referral center of patients who underwent retrosigmoid craniotomy from 2013 to 2016 with hydroxyapatite cement cranioplasty.

OUTCOME MEASURES

Presence of absence of cerebrospinal fluid leak, wound infection, and other complications.

RESULTS

Twenty cases of retrosigmoid craniotomy repaired with hydroxyapatite cement were identified. Median length of follow up was 9.8months. No cases of cerebrospinal fluid leak were identified. One patient developed a wound infection which was thought to be related to a chronic inflammatory response to the implanted dural substitute. No other major complications were noted.

CONCLUSIONS

A method and case series of suboccipital retrosigmoid cranioplasty using hydroxyapatite cement and a are reported. Hydroxyapatite cement cranioplasty is a safe and effective technique for repair of retrosigmoid craniotomy defects.

Endoscopic-Assisted Posterior Intradural Petrous Apicectomy in Petroclival Meningiomas: A Clinical Series and Assessment of Perioperative Morbidity

OBJECTIVE

To describe the clinical feasibility and outcome of the endoscopic-assisted posterior intradural petrous apicectomy approach (PIPA) for petroclival meningiomas extending into the supratentorial space.

METHODS

From 2005-2013, 29 patients with a petroclival meningioma underwent tumor removal through a PIPA approach. The approach consists of a retrosigmoid approach, intradural anterior resection of the petrous apex and microsurgical removal of the tumor, followed by endoscopic-assisted visualization and removal of tumor parts in the middle fossa or anterior to the brainstem.

RESULTS

Patients consisted of 7 men and 22 women; the mean age of patients was 52.7 years. In 24 patients, surgery was performed with the patient in a semisitting position; in 5 patients, surgery was performed with the patient in a supine position. A total resection was achieved in 19 patients (66%). A Karnofsky performance scale score >60% was recorded in 27 patients (93%), with surgical complications that involved a cerebrospinal fluid leak in 3 patients, bleeding in the surgical cavity in 2 patients, and pneumocephalus in 1 patient. The most frequent postoperative neurologic deficit was facial palsy (34%), which disappeared or improved consistently in all but 1 patient, who required a cranial nerve VII-cranial nerve XII anastomosis.

CONCLUSIONS

For petroclival meningiomas extending into the middle fossa, the endoscopic-assisted PIPA approach is safe and straightforward. The principal advantages of the PIPA approach are familiarity with the retrosigmoid route; the absence of temporal lobe retraction; and early control of the cranial nerves, vessels, and brainstem. However, careful patient selection regarding tumor extension is fundamental to obtaining optimal outcomes.

Glycerol rhizotomy via a retrosigmoid approach as an alternative treatment for trigeminal neuralgia

OBJECTIVES

Trigeminal neuralgia is a sensory nerve disorder characterized by lancinating pain and treated most commonly with carbamazepine, rhizotomy treatment, or open surgical management with microvascular decompression. We describe a novel technique to complement surgical treatment for trigeminal neuralgia via direct injection of the trigeminal nerve with glycerin in the cisternal portion of the nerve.

PATIENTS AND METHODS

We performed a retrospective analysis of patients who received standard microvascular decompression and injection of glycerin to the inferior third of the cisternal portion of the nerve anterior to the root entry zone with lack of a compressive vessel on MRI as the primary indication. Fourteen patients were identified and demographic information, post-operative course and complications were recorded.

RESULTS

There were eleven females and three males with an average age at time of surgery of 54.8 years. 100% of patients reported that their trigeminal pain was significantly improved following surgical intervention. Four out of fourteen patients reported a 50-80% decrease from the pre-surgery baseline pain at one month and three month follow up. One patient developed a CSF leak, and no surgical site infections or motor deficits were observed.

CONCLUSION

Intra-operative glycerin rhizotomy in conjunction with microvascular decompression can be used to safely treat patients suffering from trigeminal neuralgia.

Retrosigmoid implantation of an active bone conduction stimulator in a patient with chronic otitis media

Percutaneous bone conduction implants are widely used in patients with conductive and mixed hearing loss with no benefit from conventional air conduction hearing aids. These devices have several complications including skin reaction, wound infection, growth of skin over the abutment, and implant extrusion. We describe a case of a transcutaneous bone conduction implantation (Bonebridge, Med-el) in a patient with conductive hearing loss due to chronic otitis media. Surgical planification was performed with the software 3D slicer 4.1. According to this program, the implant transductor was positioned in the retrosigmoid area. Aided thresholds demonstrate a significant benefit, with an improvement from 68dB to 25dB. Speech discrimination scores improved 35dB. The patient is very happy and uses her device daily. The Bonebridge implant is a promising transcutaneous bone conduction implant for patients with conductive hearing loss. Retrosigmoid implantation may be useful in cases with mastoid pathology or previous surgery.