Neuroendoscopic surgery for brainstem hemorrhage: Technical notes and preliminary clinical results.

BACKGROUND: Brainstem hemorrhage accounts for a relatively small proportion of spontaneous intracerebral hemorrhages (∼10 %) but tends to occur earlier in life and has poorer prognosis. Numerous studies support the therapeutic potential of minimally invasive hematoma evacuation for intracerebral hemorrhage; however, there have been few assessments of the benefits for brainstem hemorrhage. METHODS: We evaluated the safety and efficacy of a minimally invasive approach under neuroendoscopic guidance with pneumatic arm fixation for removing the hematoma in severe brainstem hemorrhage patients. 14 patients diagnosed with primary brainstem hemorrhage and treated by neuroendoscopy-assisted evacuation at Suzhou Ninth Hospital affiliated to Soochow University were included in the study. Relevant clinical and prognostic date were collected and analyzed. RESULTS: Hematoma volume ranged from 8 to 13 mL according to preoperative CT, while GCS at admission ranged from 4 to 6. The average operative time was 157 min and average intraoperative blood loss was 86 mL. All patients achieved satisfactory hematoma evacuation (over 90 %) according to immediate postoperative CT. Postoperative intensive care unit stay averaged 9.5 days and respiratory support averaged 7.5 days. 11 patients required tracheotomy due to pulmonary infection and absence of pharyngeal reflexes. 9 patients achieved satisfactory functional recovery (GOS score of 4 and 3), while 5 remained in a vegetative state (GOS score of 2). CONCLUSION: Neuroendoscopy provides excellent direct visualization of brainstem hematomas for safe and reliable evacuation. Patients with a new PPH score of 2 or 3 are more likely to benefit from surgical treatment. Large-scale studies are required to identify patients most likely to benefit from this technique.

AB087. Rectosigmoid approach for cerebellopontine angle tumors: what have we learned so far?

BACKGROUND: The cerebellopontine angle (CPA) is a multifaceted triangular region bordered by the brainstem medially, the cerebellum superiorly and posteriorly, and the temporal bone laterally. Tumors located in the CPA comprise 5% to 10% of all intracranial neoplasms, with vestibular schwannomas being the most prevalent, followed by meningiomas and epidermoid tumors. Various surgical approaches exist for removing these lesions, which consistently present challenges for neurosurgeons in effectively managing them. This study presents a case of a CPA tumor successfully treated via the retrosigmoid approach, followed by an assessment of the approach's efficacy and surgical outcomes. METHODS: A comprehensive literature search was conducted using electronic databases, including PubMed, ScienceDirect, and Google Scholar, to gather studies on surgically managed CPA tumors. In addition to reviewing the literature, we present a case study of a patient with CPA tumor who underwent surgery using the retrosigmoid approach. RESULTS: The literature review revealed that the retrosigmoid approach emerged as a commonly utilized technique, particularly for tumors in the CPA region. Analysis of the collected data indicated that the retrosigmoid approach offers several advantages, including excellent exposure of the CPA, minimal brain retraction, and reduced risk of injury to critical neurovascular structures. Moreover, studies consistently reported favorable surgical outcomes, with low rates of morbidity and mortality associated with this approach. In our case study, we successfully employed the retrosigmoid approach to resect a CPA tumor in a patient presenting with typical symptoms of spasticity in all four extremities and progressive hearing loss. CONCLUSIONS: In conclusion, the retrosigmoid approach remains a valuable surgical technique for the management of CPA tumors. This approach enhances the exposure of the CPA and increases the surgical angle of maneuverability. In most literature, the retrosigmoid approach provides adequate access that is safe and effective, with a low rate of postoperative complications. However, further prospective studies and comparative analyses are warranted to validate these findings and refine surgical techniques for optimizing patient outcomes.

Functional outcomes after retrosigmoid approach to the cerebellopontine angle: Observations from a single-center experience of over 13 years.

Introduction: Accessing the posterior base of the skull is complex because of the vital neurovascular structures in the area. However, the retrosigmoid approach (RSA) offers a solution to this challenge. Research question: To analyze surgical outcome of RSA. Material and methods: This study involved a retrospective review of patient charts from a single center, focusing on the surgical procedure and outcomes following the operation. Results: The study included 517 patients suffering from conditions like vestibular schwannomas (VS), metastatic cancers, and trigeminal neuralgia. The most frequent symptoms reported were balance disorders (42.7%), hearing loss (36.5%), walking difficulties (21.2%), headaches (18.9%), facial pain (17.1%), issues with trigeminal nerve function (14.1%), cerebellar dysfunction (13.5%), and facial nerve paralysis (10.2%). The rate of complications stood at 21.1%, with 11.3% of patients needing revision surgery. The median score on the Clavien-Dindo scale was 2, and the rate of mortality related to surgery was 1.0%. Permanent symptom improvement was seen in 72.1% of cases. Temporary new deficits occurred in 43.2% of patients, with facial nerve paralysis being the most common (14.1%). No significant correlation was found between the size of the craniotomy and the extent of tumor resection (p = 0.155), except in the case of VS (p = 0.041). Larger craniotomy sizes were associated with higher rates of complications (p = 0.016), especially CSF leaks (p = 0.006). Complications significantly affected the likelihood and number of new deficits (p < 0.001 for both), particularly postoperative bleeding (p = 0.019, p = 0.001), CSF leaks (p = 0.026, p = 0.039), and hydrocephalus (p = 0.050, p = 0.007). Conclusions: The potential for complications related to the surgical approach cannot be overlooked. The size of the tumor should not dictate larger surgical approaches due to the associated increase in postoperative complications; a tailored approach that considers the precise tumor location and pathology is crucial for optimizing postoperative outcomes.

Free bone flap reconstruction in retrosigmoid approach for microvascular decompression: a comparative cohort study.

Titanium plates and screws are common material used for rigid bone flap fixation after retrosigmoid craniotomy such as microvascular decompression (MVD). We conducted this study to evaluate outcomes of the free bone flap cranioplasty without fixation in MVD and compared its postoperative complication rate with routine methods. We retrospectively reviewed all patients who underwent MVD at our institution from May 2017 to August 2022. Patients were divided into two groups according to whether the bone flap was fixed or not. Follow-ups periods spanned 6-28 months after the operation. Of 189 patients who underwent MVDs via retrosigmoid approach, 79 cases (42%) had their bone flaps replaced without titanium fixation after craniotomies (< 3 cm x 3 cm). Compared to fixed bone flap group, free bone flap group had shorter operative time (105.56 ± 15.87 min vs. 113.72 ± 17.80 min, P = 0.001), less in-patient costs (¥23059.66 ± 4488.54 vs. ¥27714.82 ± 2705.74, P < 0.001), and less proportion of postoperative headache and incisional pain (43.0% vs. 60.9%, P = 0.015). One case of incisional cerebrospinal fluid leak happened in free bone flap group while one case of incisional infection happened in fixed bone flap group. No statistical difference in bone flap displacement, duration of postoperative hospital stays or complication rate was found between the two groups. Nineteen patients in free bone flap group received long-term CT follow-up and all were proved to have good skull union. This study proves that free bone flap cranioplasty in MVD without titanium plate fixation can shorten the operation time and reduce hospitalization expenditure without increasing complication rates.

Vestibular schwannoma microneurosurgery in patients over 70: a single institution experience and proposal of a treatment algorithm.

BACKGROUND: Elderly patients with vestibular schwannoma (VS) are commonly observed. OBJECT: Retrospective analysis of 25 patients aging ≥ 70 operated on in our neurosurgical department for unilateral VS. The purpose of our study is to propose an algorithm for the treatment of VS in elderly patients. METHODS: American Society of Anesthesiology (ASA) Grade I-II patients and Grade III with life-threatening tumors were enrolled. Karnofsky Performance Status Scale (KPS) was used for evalutation of the quality of life. The House-Brackmann (HB) scale for facial nerve (FN) outcome was used. Tumor size was categorized according to Koos' classification. A retrosigmoid approach was used in all cases, except one in which a translabyrinthine approach was performed. Surgical removal graduation: total (GTR), near total (NTR > 95%), subtotal (STR > 90%). The clinical and radiological follow-up period was set first at six months and then at one year after surgery. FN results evaluation was performed at one year, categorized according to House-Brackmann grades I-VI. RESULTS: Mean age: 74,4 years (70-83); 28% ASA I, 56% ASA II, 16% ASA III. Mean tumor size: 2,7 cm (1,5-4,2 cm). GTR/NTR: 68%, STR 32%. Mortality was zero. At last follow-up (one year after surgery) FN results were: HBI 81%, HBII 9.5%, HBIII 9.5%; HB IV 0%. Only 4 patients had preoperative HB IV, of whom one improved from HB IV to HB III. Transient complications occurred only in large VS. Re-growth of residue after STR was observed in 3 cases, treated with SRS in 2 cases and observed in 1. CONCLUSIONS: An algorithm of treatment of vestibular schwannoma in the elderly is proposed. In particular, in patients in general good conditions, age does not appear to be a major contraindication for microsurgery of VS. FN results at last follow-up are satisfactory and the complication rates are acceptable.

[Our approach to the treatment of vestibular schwannomas with arachnoid dissection of the facial nerve]. / Nash podkhod k lecheniyu vestibulyarnykh shvannom s primeneniem metodiki arakhnoidal'noi dissektsii litsevogo nerva.

Preserving the function of the facial nerve is extremely important in surgery for vestibular schwannomas. Two methods of arachnoid dissection are described for resection of vestibular schwannoma via retrosigmoid approach (from the brain stem and internal auditory canal). OBJECTIVE: To evaluate the results of arachnoid dissection of the facial nerve from internal auditory canal when resecting the vestibular schwannoma. MATERIAL AND METHODS: We analyzed 61 patients with vestibular schwannomas. Patients were divided into 2 groups depending on surgical technique. We estimated facial nerve function before and after surgery, preoperative dimension of vestibular schwannoma and extent of resection. The influence of various factors on extent of resection and postoperative facial nerve function was studied. RESULTS: Vestibular schwannoma resection from the brain stem was performed in 30 patients, arachnoid dissection - in 31 patients. There was no significant between-group difference. Gross total resection was performed in 78.7% of cases. Both techniques demonstrated similar results regarding extent of resection. Arachnoid dissection showed the advantage regarding facial nerve function immediately after surgery (p=0.012) and 6 months later (p<0.001). Normal facial nerve function in 6 months after arachnoid dissection was observed in 80.7% of patients. Preoperative dimension of tumor influenced facial nerve function in addition to technique of resection (p=0.001). CONCLUSION: We identified the factors influencing facial nerve function after resection of vestibular schwannoma. Surgical technique was the most significant factor. These data expand and popularize arachnoid dissection in surgery of vestibular schwannomas.

Graftless Primary Dural Closure Following Retrosigmoid Approach: Doing More With less.

INTRODUCTION: Achieving watertight dural closure without grafts via the retrosigmoid approach can be challenging, contributing to a significant rate of postoperative cerebrospinal fluid (CSF) leaks. This study describes a dural incision technique for achieving primary dural closure without grafts following the retrosigmoid approach and presents clinical data from the authors' experience. METHODS: Clinical and surgical data of 227 patients who underwent the dural incision technique following the retrosigmoid approach for various pathologies were retrospectively reviewed. To achieve no-graft watertight dural closure, the dural incision involves 2 critical steps: a 1 cm transverse incision of the dura parallel to the foramen magnum to drain CSF from the cisterna magna, and a vertical linear opening of the retrosigmoid dura. Dural incisions were closed watertight with vicryl 4/0 running sutures, without the use of grafts, fibrin glue, hemostatic overlays, or dural substitutes. Pre- or postoperative lumbar drainage was not employed. RESULTS: Primary watertight dural closure was successfully achieved in all patients without the use of grafts or duraplasty. The average duration of dura closure was 17.7 minutes. During an average follow-up period of 49.3 months, there were no instances of CSF leaks or meningitis. CONCLUSIONS: In the authors' preliminary experience, the linear dural incision described herein was effective for achieving a no-graft, watertight primary dural closure in the retrosigmoid approach, with no CSF leaks or meningitis in our series. Validation of these preliminary data in a larger patient cohort is necessary.

Clinical, Anatomical, and Histological Features of the Rhomboid Lip and Considerations for Surgery Using a Retrosigmoid Approach: A Retrospective Study.

OBJECTIVE: The rhomboid lip is a neural tissue encountered during cerebellopontine angle surgery, with differing shape and extent among individuals. This study aimed to investigate the variation of rhomboid lips during posterior fossa surgery. METHODS: In this retrospective study, we examined posterior cranial fossa surgeries performed using a retrosigmoid approach. Rhomboid lips were classified according to thickness, extent, and appearance, with some subjected to histological analysis. T2-weighted magnetic resonance imaging of rhomboid lips was conducted. RESULTS: Among 304 surgeries, rhomboid lips were observed in 75 patients who underwent schwannoma or meningioma resection, facial spasm-related neurovascular decompression, and other surgeries (37, 2, 32, and 4 patients, respectively). Rhomboid lips were categorized based on apparent thickness: thin membranous type, resembling an arachnoid membrane, and thick parenchymal type. Rhomboid lip extension was classified by position relative to the choroid plexus: nonextension, lateral extension, and jugular foramen (41, 22, and 12 patients, respectively). Veins were observed on the rhomboid lip surface in 37 cases. The rhomboid lip was visible in only 1 case (parenchymal jugular foramen type) on magnetic resonance imaging. Histologically, the rhomboid lip comprised an ependymal cell layer, a glial layer, and connecting tissue. The glial layer thickness determined the rhomboid lip thickness, which was greater in the parenchymal type than in the membrane type. In 42 patients, the rhomboid lip was dissected with no complications observed. CONCLUSIONS: Morphological classification of the rhomboid lip and understanding of its anatomical details contribute to safe surgical field development for neurosurgeons.

A novel theory for rapid localization of the transverse-sigmoid sinus junction and "keyhole" in the retrosigmoid keyhole approach: micro-anatomical study, technique nuances, and clinical application.

To determine a rapid and accurate method for locating the keypoint and "keyhole" in the suboccipital retrosigmoid keyhole approach. (1) Twelve adult skull specimens were selected to locate the anatomical landmarks on the external surface of the skull.The line between the infraorbital margin and superior margin of the external acoustic meatus was named the baseline. A coordinate system was established using the baseline and its perpendicular line through the top point of diagastric groove.The perpendicular distance (x), and the horizontal distance (y) between the central point of the "keyhole" and the top point of the digastric groove in that coordinate system were measured. The method was applied to fresh cadaveric specimens and 53 clinical cases to evaluate its application value. (1) x and y were 14.20 ± 2.63 mm and 6.54 ± 1.83 mm, respectively (left) and 14.95 ± 2.53 mm and 6.65 ± 1.61 mm, respectively (right). There was no significant difference between the left and right sides of the skull (P > 0.05). (2) The operative area was satisfactorily exposed in the fresh cadaveric specimens, and no venous sinus injury was observed. (3) In clinical practice, drilling did not cause injury to venous sinuses, the mean diameter of the bone windows was 2.0-2.5 cm, the mean craniotomy time was 26.01 ± 3.46 min, and the transverse and sigmoid sinuses of 47 patients were well-exposed. We propose a "one point, two lines, and two distances" for "keyhole" localization theory, that is we use the baseline between the infraorbital margin and superior margin of the external acoustic meatus and the perpendicular line to the baseline through the top point of the digastric groove to establish a coordinate system. And the drilling point was 14.0 mm above and 6.5 mm behind the top point of the digastric groove in the coordinate system.

Endoscope-assisted microvascular decompression in hemifacial spasm with a teflon bridge.

BACKGROUND: Microvascular conflicts in hemifacial spasm typically occur at the facial nerve's root exit zone. While a pure microsurgical approach offers only limited orientation, added endoscopy enhances visibility of the relevant structures without the necessity of cerebellar retraction. METHODS: After a retrosigmoid craniotomy, a microsurgical decompression of the facial nerve is performed with a Teflon bridge. Endoscopic inspection prior and after decompression facilitates optimal Teflon bridge positioning. CONCLUSIONS: Endoscope-assisted microsurgery allows a clear visualization and safe manipulation on the facial nerve at its root exit zone.

Hearing preservation surgery for vestibular schwannoma: a systematic review and meta-analysis.

The aim of this systematic review is to analyse the role of hearing preservation surgery for vestibular schwannoma. The complications and hearing outcomes of the single surgical techniques were investigated and compared with those of less invasive strategies, such as stereotactic radiotherapy and wait and scan policy. This systematic review and meta-analysis was performed according to the PRISMA guidelines. All included studies were published in English between 2000 and 2022. Literature data show that hearing preservation is achieved in less than 25% of patients after surgery and in approximately half of cases after stereotactic radiotherapy, even if data on long-term preservation are currently not available.

Anatomical Landmarks for Transverse-Sigmoid Sinus Junction: A Cadaveric Study.

BACKGROUND AND OBJECTIVE: Accurately identifying and avoiding crucial anatomical structures within the posterior cranial fossa using superficial landmarks is essential for reducing surgical complications. Our study focuses on the top of the mastoid notch (TMN) as an external landmark of the cranium, aiming to assist in the strategic placement of the initial burr hole. In this study, we present a method for predicting the path of the transverse sinus (TS) and explore the relationship between the junction of the transverse-sigmoid sinus and the TMN. METHODS: Following anatomical dissections of the brain in cadaveric specimens, we conducted intracranial drilling from the inside surface of the cranium on 10 adult skulls (20 sides). A coordinate system was established on the posterolateral surface of the skull to assist the analysis. Using a self-leveling laser level, we set up a horizontal Frankfurt line (X-axis) and identified a vertical perpendicular line passing through the TMN to serve as the Y-axis. To identify the course of the TS, we divided the segment between the two inferomedial points into six equidistant points along the Frankfurt line. RESULTS: No significant difference was observed between the inferomedial points of the transverse-sigmoid sinus junction (TSSJ) on the left and right sides. The inferomedial point was positioned at a median of 6.6 mm (Q1: 3.7 mm, Q3: 9.4 mm) dorsally and at a median of 19.2 mm (Q1: 16.1 mm, Q3: 23.2 mm) cranially from the TMN. The upper edge of the TS was located at distances of 6.4 mm (5.7; 12.7), 10.3 mm (8.8; 12.3), and 13.8 mm (11.9; 16.3) on the right, and 4.9 mm (4.1; 7.9), 8.6 mm (7.6; 13.0), and 12.8 mm (11.7; 17.5) on the left side from the Frankfurt horizontal plane at the », ½, and ¾ line points, respectively. The bottom edge was positioned at distances of 0.6 mm (-2.7; 2.0), 2.1 mm (-0.8; 3.8), and 4.8 mm (2.4; 6.7) on the right, and 1.1 mm (-3.4; 2.4), 2.0 mm (0.2; 4.8), and 3.9 mm (3.7; 5.3) on the left from these respective points. The upper edge of the right TS was found to be statistically more distant from the Frankfurt horizontal plane at the » line point (p-value = 0.027) compared to that on the left side. The confluence of the sinus center was identified as having a median distance of 7.8 mm (4.5; 8.3) and an inferior point of 1.5 mm (0.1; 3.0) cranially to the inion. In all examined bodies (n = 10), the confluens sinuum was consistently 4.7 mm (3.3; 5.6) to the right in relation to the inion. Notably, the median of the right transverse sinus diameter (median = 9.3 mm) was found to be significantly larger than that of the left transverse sinus (median = 7.0), with a statistically significant p-value of 0.048. CONCLUSIONS: The literature regarding the external identification of the TSSJ and the course of the TS varies. In our efforts to provide a description, we have utilized the TMN as a reliable landmark for locating the TSSJ. To delineate the trajectory of the TS after its exit from the confluence of sinuses, we employed a Frankfurt horizontal plane to the inion. These findings may assist surgeons by using external skull landmarks to identify intracranial structures within the posterior fossa, particularly when image guidance devices are not available or to complement a neuronavigational system.

Multiple Intracranial Schwannomas of the Vestibular and Trigeminal Nerves: A Technical Note.

BACKGROUND: A schwannoma is a nerve sheath tumor that is formed by Schwann cells. Vestibular schwannomas are thought to account for the majority of intracranial schwannomas. Nonvestibular schwannomas account for about 10%, about half of which are trigeminal schwannomas. Multiple intracranial schwannomas originating from different cranial nerves are extremely rare. METHODS: We describe the clinical case of a 42-year-old female patient with vestibular schwannoma and multiple trigeminal schwannomas. RESULTS: That case shows how multiple trigeminal schwannomas were identified intraoperatively during elective surgery for vestibular schwannoma removal, most of which were resected. No new neurological deficits were observed in the patient. CONCLUSIONS: The presence of multiple intracranial schwannomas is extremely rare in neurosurgical practice and can change the intraoperative strategy and the course of the surgery.

The Posterior Auricularis Muscle as Superficial Landmark for the Sigmoid Sinus and Transverse-Sigmoid Sinus Junction: An Anatomical Study.

OBJECTIVE: Neuronavigation systems coupled with previously reported external anatomical landmarks assist neurosurgeons during intracranial procedures. We aimed to verify whether the posterior auricularis muscle (PAM) could be used as an external landmark for identifying the sigmoid sinus (SS) and the transverse-sigmoid sinus junction (TSSJ) during posterior cranial fossa surgery. METHODS: The PAM was dissected in 10 adult cadaveric heads and after drilling the underlying bone, the relationships with the underlying SS and TSSJ were noted. The width and length of the PAM, and the distance between the muscle and reference points (asterion, mastoid tip, and midline), were measured. RESULTS: The PAM was identified in 18 sides (9 left, 9 right). The first 20 mm of the muscle length (mean 28.28 mm) consistently overlay the mastoid process anteriorly and the proximal half of the SS slightly posteriorly on all sides. The superior border was a mean of 2.22 mm inferior to the TSSJ and, especially when the muscle length exceeded 20 mm, this border extended closer to the transverse sinus; it was usually found at a mean of 3.11 mm (range 0.0-13.80 mm) inferior to the distal third of the transverse sinus. CONCLUSIONS: Superficial landmarks give surgeons improved surgical access, avoiding overexposure of deep neurovascular structures and reducing brain retraction. On the basis of our cadaveric study, the PAM is a reliable and accurate direct landmark for identifying the SS and TSSJ. The PAM could potentially be used for guiding the retrosigmoid approach.

Retrosigmoid versus middle fossa approach for hearing and facial nerve preservation in vestibular schwannoma surgery: A systematic review and comparative meta-analysis.

BACKGROUND: Vestibular schwannomas (VS) are benign tumors arising from vestibular nerve's Schwann cells. Surgical resection via retrosigmoid (RS) or middle fossa (MF) is standard, but the optimal approach remains debated. This meta-analysis evaluated RS and MF approaches for VS management, emphasizing hearing preservation and Cranial nerve seven (CN VII) outcomes stratified by tumor size. METHODS: Systematic searches across PubMed, Cochrane, Web of Science, and Embase identified relevant studies. Hearing and CN VII outcomes were gauged using the American Academy of Otolaryngology-Head and Neck Surgery, Gardner Robertson, and House-Brackmann scores. RESULTS: Among 7228 patients, 56 % underwent RS and 44 % MF. For intracanalicular tumors, MF recorded 38 % hearing loss, compared to RS's 54 %. In small tumors (<1.5 cm), MF showed 41 % hearing loss, contrasting RS's lower 15 %. Medium-sized tumors (1.5 cm-2.9 cm) revealed 68 % hearing loss in MF and 55 % in RS. Large tumors (>3cm) were only reported in RS with a hearing loss rate of 62 %. CONCLUSION: Conclusively, while MF may be preferable for intracanalicular tumors, RS demonstrated superior hearing preservation for small to medium-sized tumors. This research underlines the significance of stratified outcomes by tumor size, guiding surgical decisions and enhancing patient outcomes.

Pathophysiology of Postoperative Hearing Disorders after Vestibular Schwannoma Resection: Insights from Auditory Brainstem Response and Otoacoustic Emissions.

Background: In order to better understand the pathophysiology of surgically induced hearing loss after vestibular schwannoma (VS) surgery, we postoperatively analyzed the hearing status in a series of patients where hearing was at least partially preserved. Methods: Hearing was assessed through tonal audiometry, speech discrimination score, maximum word recognition score (dissyllabic word lists-MaxIS), otoacoustic emissions (OAEs), and auditory brainstem response (ABR). The magnetic resonance imaging (MRI) tumor characterization was also noted. Results: In a series of 24 patients operated on for VS over 5 years, depending on the results of this triple hearing exploration, we could identify, after surgery, patients with either a myelin alteration or partial damage to the acoustic fibers, others with a likely partial cochlear ischemia, and some with partial cochlear nerve ischemia. One case with persisting OAEs and no preoperative ABR recovered hearing and ABR after surgery. Long follow-up (73 ± 57 months) revealed a mean hearing loss of 30 ± 20 dB with a drastic drop of MaxIS. MRI revealed only 25% of fundus invasion. Conclusion: a precise analysis of hearing function, not only with classic audiometry but also with ABR and OEAs, allows for a better understanding of hearing damage in VS surgery.

The auricula as a new surgical landmark for the transverse-sigmoid-sinus-transition.

Introduction: The transverse-sigmoid-sinus-transition constitutes an important landmark during a retrosigmoid craniotomy. Due to anatomical variations, the location is highly variable. Landmarks for identification of the anterior border of the sigmoid sinus have been described extensively, such as the mastoid notch, digastric point, external auditory meatus and crux of the helix curvature. There is a paucity of landmarks for the identification of the posterior border, however. Research question: We examined the relationship between the transverse-sigmoid-sinus-transition and the most-posterior-part-of-the-auricula. Material and methods: We performed a retrospective analysis of one-hundred patients (38 males and 62 females) who underwent cerebral MRI examinations at Antwerp University Hospital (Belgium). Using Brainlab®, the transverse-sigmoid-sinus-transition and most-posterior-part-of-the-auricula coordinates were calculated and compared. Left and right sides were compared in both the anteroposterior and craniocaudal axis. Results: Mean age was 56.4 ± 16.1 years. Mean MPPA-TSST-distance in the anteroposterior direction was -1.93 mm (right) and -1.96 mm (left). Mean MPPA-TSST-distance in the craniocaudal direction was -5.16 mm (right) and -5.04 mm (left). Discussion and conclusion: The transverse-sigmoid-sinus-transition seems to be located more anterior and caudal with respect to the most-posterior-part-of-the-auricula, meaning that it can be considered a save landmark. A correction of five mm needs to be applied in order to identify the inferior border of the transverse sinus. Left/right and gender had no significant influence. The most-posterior-part-of-the-auricula can be considered a fast and practical anatomical landmark for identification of the transverse-sigmoid-sinus-transition, without affecting operative fluency, especially during an emergency craniotomy.

Unusual Atrophic Nervus Intermedius in a Patient with Refractory Nervus Intermedius Neuralgia and History of Ipsilateral Sudden-Onset Central Facial Palsy and Sensorineural Hearing Loss: Cadaveric-Clinical Images with Surgical Video.

Nervus intermedius (NI) arises from the superior salivary nucleus, solitary nucleus, and trigeminal tract. It leaves the pons as 1 to 5 roots and travels between the facial and vestibulocochlear nerves before merging with the facial nerve within the internal auditory canal. The mastoid segment of the facial nerve then gives rise to a sensory branch that supplies the posteroinferior wall of the external auditory meatus and inferior pina. This complex pathway renders the nerve susceptible to various pathologies, leading to NI neuralgia. Here, the authors present an unusual intraoperative finding of an atrophic NI in a patient with refractory NI neuralgia and a history of ipsilateral sudden-onset central facial palsy and microvascular decompression for trigeminal neuralgia. The patient underwent NI sectioning via the previous retrosigmoid window and achieved partial ear pain improvement. The gross size of the NI is compared with a cadaveric specimen through stepwise dissection. This case highlights the potential significance of subtle central ischemic events and subsequent atrophy of NI in the pathogenesis of NI neuralgia, as well as the ongoing need to investigate the therapeutic efficacy of nerve sectioning.

Subclassification of Koos grade 4 vestibular schwannoma: insights into tumor morphology for predicting postoperative facial nerve function.

OBJECTIVE: Koos grade 4 vestibular schwannoma (KG4VS) is a large tumor that causes brainstem displacement and is generally considered a candidate for surgery. Few studies have examined the relationship between morphological differences in KG4VS other than tumor size and postoperative facial nerve function. The authors have developed a landmark-based subclassification of KG4VS that provides insights into the morphology of this tumor and can predict the risk of facial nerve injury during microsurgery. The aims of this study were to morphologically verify the validity of this subclassification and to clarify the relationship of the position of the center of the vestibular schwannoma within the cerebellopontine angle (CPA) cistern on preoperative MR images to postoperative facial nerve function in patients who underwent microsurgical resection of a vestibular schwannoma. METHODS: In this paper, the authors classified KG4VSs into two subtypes according to the position of the center of the KG4VS within the CPA cistern relative to the perpendicular bisector of the porus acusticus internus, which was the landmark for the subclassification. KG4VSs with ventral centers to the landmark were classified as type 4V, and those with dorsal centers as type 4D. The clinical impact of this subclassification on short- and long-term postoperative facial nerve function was analyzed. RESULTS: In this study, the authors retrospectively reviewed patients with vestibular schwannoma who were treated surgically via a retrosigmoid approach between January 2010 and March 2020. Of the 107 patients with KG4VS who met the inclusion criteria, 45 (42.1%) were classified as having type 4V (KG4VSs with centers ventral to the perpendicular bisector of the porous acusticus internus) and 62 (57.9%) as having type 4D (those with centers dorsal to the perpendicular bisector). Ventral extension to the perpendicular bisector of the porus acusticus internus was significantly greater in the type 4V group than in the type 4D group (p < 0.001), although there was no significant difference in the maximal ventrodorsal diameter. The rate of preservation of favorable facial nerve function (House-Brackmann grades I and II) was significantly lower in the type 4V group than in the type 4D group in terms of both short-term (46.7% vs 85.5%, p < 0.001) and long-term (82.9% vs 96.7%, p = 0.001) outcomes. Type 4V had a significantly negative impact on short-term (OR 7.67, 95% CI 2.90-20.3; p < 0.001) and long-term (OR 6.05, 95% CI 1.04-35.0; p = 0.045) facial nerve function after surgery when age, tumor size, and presence of a fundal fluid cap were taken into account. CONCLUSIONS: The authors have delineated two different morphological subtypes of KG4VS. This subclassification could predict short- and long-term facial nerve function after microsurgical resection of KG4VS via the retrosigmoid approach. The risk of postoperative facial palsy when attempting total resection is greater for type 4V than for type 4D. This classification into types 4V and 4D could help to predict the risk of facial nerve injury and generate more individualized surgical strategies for KG4VSs with better facial nerve outcomes.

Introducing endoscopic assistance on routinary basis for vestibular schwannomas resection: A single centre acceptance analysis.

OBJECTIVE: The use of endoscopic assistance in retrosigmoid approach for tumors of the cerebellopontine angle brought undoubted technological advantages in skull base surgery. Nonetheless, the use of the endoscope is not as widespread as it could be. The aim of the study is to analyze the impressions of neurosurgeons and otologists with different experience in vestibular schwannoma surgery, experiencing the introduction of the endoscope in surgical daily practice. METHODS: All patients undergoing vestibular schwannoma surgery were recruited in the period from January 2019 to December 2020. The endoscope-assistance and a minimum follow-up of 12 months were considered inclusion criteria. An eight items questionnaire was administered to the surgeons who used endoscope-assistance during surgery. RESULTS: A total number of 20 patients were recruited. Five surgeons experienced the use of 0° and 45° optics in the "pre-resection" and "intra-meatal" phases of the procedures. The survey gave positive feedbacks on the introduction of the endoscope in vestibular schwannoma resection. The main drawback was the difficulty to manage the use of angled optics. CONCLUSIONS: Despite the known limitations of the study, the idea of investigating surgeons' impressions on the use of the endoscope could be another motif to explain why this instrument and its diffusion is limited despite its advantages in vestibular schwannoma surgery.