Vestibular schwannoma surgery via the retrosigmoid transmeatal approach

Removal of grade IV vestibular schwannomas by retrosigmoid approach: results of a cumulative series of two European centers

INTRODUCTION

The aim of our study was to study the association between end-of-surgery facial nerve stimulation threshold and extent of tumor resection in case of grade IV vestibular schwannomas.

MATERIALS AND METHODS

Grade IV VSs represent a surgical challenge as a risk/benefit ratio must be considered in balancing a satisfactory extent of resection against a good postoperative functional outcome. We reviewed a cumulative series of 57 patients with large/giant VSs who were operated on by retrosigmoid approach in the period from 2008 to 2018 in two European centers, namely San Filippo Neri Hospital, Rome, Italy and Masaryk Hospital, Usti nad Labem, Czech Republic. Extent of resection, intraoperative direct electrical stimulation threshold of facial nerve and postoperative facial outcome were examined.

RESULTS

Total or near-total resection was accomplished in 40 (75.5%) cases. Two groups were compared: total or near-total resection (T + NT) and subtotal resection (ST); the end-of-surgery facial nerve stimulation threshold significantly differed (T + NT: 0.24 mA, ST: 0.44 mA, p = 0.036). A critical cutoff was found at 0.2mA; values similar or inferior to this correctly predicted total or near-total resection in 86.7% of cases. Thirty (56.6%) patients had a normal postoperative facial outcome (HB1). Among the 40 patients in T + NT group, 32 (80%) retained an acceptable facial function (HB1-2).

CONCLUSIONS

Lower facial nerve stimulation thresholds positively predict a broader extent of resection and total or -near total resection should be accomplished in such cases. Judicious (subtotal) resection is preferred if threshold values increase while dissecting firmly adherent tumors.

Sheep Head Cadaveric Model for the Transmeatal Extensions of the Retrosigmoid Approach

The transmeatal extension of the retrosigmoid approach is an important procedure used in the treatment of various pathologies affecting the posterior fossa, petroclival region, and jugular foramen. Mastering this technique requires a high level of manual skill, particularly in temporal bone drilling. The objective of this study was to describe an easily accessible and cost-effective model of the transmeatal extension of the retrosigmoid approach using cadaveric sheep heads. Five cadaveric sheep heads, fixed in alcohol and formalin with intravascular-colored silicone injection, were prepared for this study. Two heads (four sides) were designated for illustrative anatomical specimens, while three heads (six sides) were used for surgical simulation. Additionally, one head was used to prepare and dissect a dry skull. All critical steps of the transmeatal approach, including both supra- and inframeatal extensions, were successfully replicated on the model. A comparative anatomical analysis was conducted, focusing on the technical nuances of the model. The cadaveric sheep head serves as an effective model for the retrosigmoid approach with transmeatal extensions, primarily for training manual haptic skills. While the sheep model cannot precisely replicate human anatomy, it still offers valuable training opportunities for neurosurgeons, particularly when human cadaveric specimens are unavailable.

Predictive value of facial motor-evoked potential and electromyography for facial motor function in vestibular schwannoma surgery

PURPOSE

Intraoperative neuromonitoring (IONM) aims to preserve facial nerve (FN) function during vestibular schwannoma (VS) surgery. However, current techniques such as facial nerve motor evoked potentials (FNMEP) or electromyography (fEMG) alone are limited in predicting postoperative facial palsy (FP). The objective of this study was to analyze a compound fEMG/FNMEP approach.

METHODS

Intraoperative FNMEP amplitude and the occurrence of fEMG-based A-trains were prospectively determined for the orbicularis oris (ORI) and oculi (OCU) muscle in 322 VS patients. Sensitivity and specificity of techniques to predict postoperative FN function were calculated. Confounding factors as tumor size, volume of intracranial air, or IONM duration were analyzed.

RESULTS

A relevant immediate postoperative FP was captured in 105/322 patients with a significant higher risk in large VS. While fEMG demonstrated a high sensitivity (77% and 86% immediately and 15 month postoperative, respectively) for identifying relevant FP, specificity was low. In contrast, FNMEP have a significantly higher specificity of 80.8% for predicting postoperative FP, whereas the sensitivity is low. A retrospective combination of techniques demonstrated still an incorrect prediction of FP in ~ 1/3 of patients.

CONCLUSIONS

FNMEP and fEMG differ in sensitivity and specificity to predict postoperative FP. Although a combination of IONM techniques during VS surgery may improve prediction of FN function, current techniques are still inaccurate. Further development is necessary to improve IONM approaches for FP prediction.

Semisitting position for cerebello-pontine angle surgery: Analysis of complications and how to avoid it

OBJECTIVE

To analyze the primary complications related to semisitting position in patients undergoing cerebelo-pontine angle surgery.

METHODS

Retrospective data analysis from patients undergoing elective tumoral cerebelo-pontine angle surgery in a semisitting position. The incidence, severity, occurrence moment, treatment, duration, and outcomes of venous air embolism (VAE), pneumocephalus, postural hypotension, and other complications were recorded. Neurointensive care unit (NICU), length of stay (LOS), hospital LOS, and modified Rankin scale scores were calculated six months after surgery.

RESULTS

Fifty patients were operated on. Eleven (22%) presented VAE (mean duration 8±4.5min): five (10%) during tumor resection, and four (8%) during dural opening. Ten (20%) were resolved by covering the surgical bed, air bubbles aspiration, jugular compression, and one (2%) tilted to a steep Trendelenburg position. One (2%) had intraoperative hemodynamic instability. The only variable associated with VAE was meningioma at histopathology OR=4.58, p=0.001. NICU was higher in patients with VAE (5.5±1.06 vs. 1.9±0.20 days, p=0.01). There were no differences in the Rankin scale. All patients presented postoperative pneumocephalus with a good level of consciousness, except one (2%) who required evacuation. Seven patients (14%) showed postural hypotension, three (6%) after positioning, and one (2%) after developing a VAE; all were reversed with usual vasoactive drugs. No other position-related complications or mortality were registered in this series.

CONCLUSIONS

The semisitting position is a safe option with the knowledge, prevention, detection, and early solution of all the possible complications. The development of VAE rarely implies hemodynamic instability or greater disability after surgery. Postoperative pneumocephalus is very common and rarely requires evacuation. Excellent cooperation between anesthesia, nursing, neurophysiology, and neurosurgery teams is essential to manage complications.

Thermal Analysis of an Ultrasonic Aspirator Micro Claw Tool Compared With Standard High-Speed Drilling During Internal Auditory Canal Opening in a Cadaveric Model

BACKGROUND

The ultrasonic aspirator micro claw tool (UAmCT) can be used to remove the bone of the internal auditory canal (IAC) during vestibular schwannoma resection via the retrosigmoid approach (RSA) without the risk of a spinning drill shaft. However, the thermal profile of the UAmCT during IAC removal has not been reported.

OBJECTIVE

To compare the thermal profile of the UAmCT during access of the IAC to that of a conventional high-speed drill (HSD) and to present an illustrative case of this application.

METHODS

IAC opening via RSA was performed in 5 embalmed cadaveric specimens using the UAmCT with 3, 8, and 15 mL/min irrigation on the left and the HSD at 75 000 revolutions per minute and 0%, 14%, and 22% irrigation on the right. Peak bone surface temperatures were measured 4 times in 20-second intervals, and statistical analyses were performed using SPSS software. An illustrative case of a vestibular schwannoma resected via an RSA using the UAmCT to access the IAC is presented.

RESULTS

The IAC was opened in all 5 specimens using both the UAmCT and HSD without complication. The mean peak bone surface temperatures were significantly lower with the UAmCT compared with the HSD ( P < .001). The UAmCT did not meaningfully prolong the operating time in the illustrative case, and the IAC was accessed without complication.

CONCLUSION

The UAmCT may be a safe and effective alternative to HSD for IAC opening during vestibular schwannoma resection via the RSA. Larger studies under clinical conditions are required to further validate these findings.

After the Knife: A Detailed Roadmap for Vestibular Schwannoma Resection in the Semi-Sitting Position - How I do it

BACKGROUND

Vestibular schwannoma surgery remains a neurosurgical challenge, with known risks, dependent on a number of factors, from patient selection to surgical experience of the team. The semi-sitting position has gained popularity as an alternative to the traditional supine position for vestibular schwannoma resection due to potential advantages such as improved surgical exposure due to clearer surgical field and anatomical orientation. However, there is a lack of standardized protocols for performing the procedure in the semi-sitting position, leading to variations in surgical techniques and outcomes.

METHODS

In this study, we aimed to establish a standardized approach for vestibular schwannoma resection using the semi-sitting position. Initiating after final position for semi-sitting, the authors have divided the surgical steps into five major parts for improved understanding and replication. Surgical techniques were analyzed through one hundred steps to identify commonalities, determining the optimal procedural steps for the semi-sitting position using surgical video for visual conceptualization.

RESULTS

The analysis described one hundred steps for vestibular schwannoma resection in the semi-sitting position, with visual demonstration of the various parts of the procedure through surgical videos. Specific recommendations for each step were outlined, including appropriate approach, monitoring strategies, and tumor and posterior fossa structures manipulation. Five major parts of the procedure were identified, leading to a reproducible standardization of the surgical procedure of vestibular schwannoma resection in the semi-sitting position.

CONCLUSIONS

This study provides a comprehensive standardized protocol for the semi-sitting procedure in vestibular schwannoma resection. By establishing a consistent approach, surgeons can minimize variations in surgical techniques and improve patient outcomes. The identified steps and recommendations can serve as a valuable resource for surgical teams involved in vestibular schwannoma resection and facilitate the dissemination and reproducibility of best practices.

Supratentorial cerebrospinal fluid diversion using image-guided trigonal ventriculostomy during retrosigmoid craniotomy for cerebellopontine angle tumors

Background

Cerebellar contusion, swelling and herniation is frequently encoutered upon durotomy in patients undergoing retrosigmoid craniotomy for cerebellopontine angle (CPA) tumors, despite using standard methods to obtain adequate cerebellar relaxation.

Objective

The aim of this study is to report an alternative cerebrospinal fluid (CSF)-diversion method using image-guided ipsilateral trigonal ventriculostomy.

Methods

Single-center retro- and prospective cohort study of n = 62 patients undergoing above-mentioned technique. Prior durotomy, CSF-diversion was performed to the point where the posterior fossa dura was visibly pulsatile. Outcome assessment consisted of the surgeon's intra- and postoperative clinical observations, and postoperative radiological imaging.

Results

Fifty-two out of n = 62 (84%) cases were eligible for analysis. The surgeons consistently reported successful ventricular puncture and a pulsatile dura prior durotomy without cerebellar contusion, swelling or herniation through the dural incision in n = 51/52 (98%) cases. Forty-nine out of n = 52 (94%) catheters were placed correctly within the first attempt, with the majority of catheter tips (n = 50, 96%) located intraventricularly (grade 1 or 2). In n = 4/52 (8%) patients, postoperative imaging revealed evidence of a ventriculostomy-related hemorrhage (VRH) associated with an intracerebral hemorrhage [n = 2/52 (4%)] or an isolated intraventricular hemorrhage [n = 2/52 (4%)]. However, these hemorrhagic complications were not associated with neurological symptoms, surgical interventions or postoperative hydrocephalus. None of the evaluated patients demonstrated radiological signs of upward transtentorial herniation.

Conclusion

The method described above efficiently allows CSF-diversion prior durotomy to reduce cerebellar pressure during retrosigmoid approach for CPA tumors. However, there is an inherent risk of subclinical supratentorial hemorrhagic complications.

Factors Associated with Acute Obstructive Hydrocephalus After Retrosigmoid Approach for Extra-Axial Cerebellopontine Angle Tumors

BACKGROUND

This study aimed to identify the risk factors for acute obstructive hydrocephalus (AOHCP) after extra-axial cerebellopontine angle (CPA) tumor surgery using the retrosigmoid (RS) approach.

METHODS

This retrospective study assessed 154 patients (100 vestibular schwannomas, 34 CPA meningiomas [MNGs], 9 trigeminal schwannomas, and 11 petroclival MNGs) who underwent surgical resection using the RS approach by a single surgeon between August 2010 and September 2019. AOHCP was defined as postoperative ventricular enlargement due to cerebrospinal fluid flow obstruction caused by surgery-related cerebellar injury within 1 week. The radiological characteristics of the tumors were classified, and the surgical outcomes were reviewed. We analyzed the impact of different factors on the development of AOHCP after surgery.

RESULTS

AOHCP developed in 17 (11%) patients, all of whom were treated with external ventricular drain insertion. Multivariate analysis showed that CPA MNGs (odds ratio [OR], 37.98), grade of tumor extension beyond the petroclival junction (grade 1: OR, 16.42; grade 2: OR, 17.47), major fourth ventricle compression (OR, 17.77), and surgery-related hemorrhage (OR, 7.64) were associated with AOHCP. Surgery-related hemorrhage was observed in 17 (11%) patients. 9 (6%) patients underwent ventriculoperitoneal shunt surgery because of persistent HCP.

CONCLUSIONS

An increased risk of AOHCP after the RS approach was observed in patients with extra-axial CPA tumors with clival extension and major fourth ventricle compression. Compulsive and meticulous hemostasis must be achieved because postoperative hemorrhage is associated with AOHCP.

Presence of a fundal fluid cap on preoperative magnetic resonance imaging may predict long-term facial nerve function after resection of vestibular schwannoma via the retrosigmoid approach

OBJECTIVE

Preservation of neurological function is a priority when performing a resection of a vestibular schwannoma (VS). Few studies have examined the radiographic value of a fundal fluid cap—i.e., cerebrospinal fluid in the lateral end of a VS within the internal auditory canal—for prediction of postoperative neurological function. The aim of this study was to clarify whether the presence of a fundal fluid cap on preoperative magnetic resonance images has a clinical impact on facial nerve function after resection of VSs.

METHODS

The presence of a fundal fluid cap and its prognostic impact on long-term postoperative facial nerve function were analyzed.

RESULTS

A fundal fluid cap was present in 102 of 143 patients who underwent resection of sporadic VSs via the retrosigmoid approach. Facial nerve function was acceptable (House-Brackmann grade I–II) immediately after surgery in 82 (80.4%) patients with a fundal fluid cap and in 26 (63.4%) of those without this sign. The preservation rate of facial nerve function increased in a time-dependent manner after surgery in patients with a fundal fluid cap but plateaued by 3 months postoperatively in those without a fundal fluid cap; the difference was statistically significant at 12 months (96.1% vs 82.9%, p = 0.013) and 24 months (97.1% vs 82.9%, p = 0.006) after surgery. The presence of a fundal fluid cap had a significantly positive effect on long-term facial nerve function at 24 months after surgery when tumor size and intraoperative neuromonitoring response were taken into account (OR 5.55, 95% CI 1.12–27.5, p = 0.034).

CONCLUSIONS

Neuromonitoring-guided microsurgery for total resection of VSs is more likely to be successful in terms of preservation of facial nerve function if a fundal fluid cap is present. This preoperative radiographic sign could be helpful when counseling patients and deciding the treatment strategy.

[Cochlear nerve continuity preservation during retrosigmoid ablative osteotomy of the internal auditory canal for advanced vestibular schwannomas]

The data of 86 patients with retrosigmoid microsurgical resection of vestibular schwannoma in tumor stage Koos II-IV were evaluated. In more than two thirds of the cases it was shown that the cochlear nerve followed the facial nerve, which is easily identified by electroneurography, in recurrent similar patterns in the region of the internal auditory canal. Starting from the fundus, this facilitated early identification and thus preservation of continuity of the cochlear nerve in the course of the internal auditory canal. This was of particular importance when safe functional preservation could not be guaranteed due to tumor size or formation despite intraoperative derivation of somatosenoric potentials, but when the possibility of subsequent hearing rehabilitation with a cochlear implant should be granted. Preoperative MRI sequences gave an indication of the possible nerve courses in some cases, but intraoperative imaging in the internal auditory canal was superior to MRI.

Microsurgical Gross Total Resection of an Intracanalicular-Cisternal (Koos-4) Vestibular Schwannoma via a Retrosigmoid Approach with Intraoperative Endoscopic Assistance

We present the case of a 23-year-old female with a history of progressive hearing loss in the left ear, dizziness, and vertigo. Magnetic resonance imaging demonstrated a left mass extending from the internal auditory canal into the cerebellopontine angle (Koos-4).¹ A retrosigmoid approach assisted with a microinspection tool was chosen.^2-5 Microsurgical near total resection was achieved. The patient presented a postoperative facial deficit (House-Brackman grade 2 postoperative), with complete resolution after 2 months. Video 1 highlights the critical steps of the retrosigmoid approach and the benefit of using the microinspection tool for vestibular schwannoma resection.

Optimal Volume of the Residual Tumor to Predict Long-term Tumor Control Using Stereotactic Radiosurgery after Facial Nerve-preserving Surgery for Vestibular Schwannomas

BACKGROUND

Intended subtotal resection (STR) followed by adjuvant gamma knife radiosurgery (GKRS) has emerged as an effective treatment option for facial nerve (FN) preservation in vestibular schwannomas (VSs). This study aimed to identify the optimal cut-off volume of residual VS to predict favorable outcomes in terms of both tumor control and FN preservation.

METHODS

This retrospective study assessed the patients who underwent adjuvant GKRS for residual VS after microsurgery. A total of 68 patients who had been followed up for ≥ 24 months after GKRS were included. Tumor progression was defined as an increase in tumor volume (TV) of ≥ 20%. House-Brackmann grades I and II were considered to indicate good FN function.

RESULTS

The median residual TV was 2.5 cm³ (range: 0.3-27.4). The median follow-up period after the first adjuvant GKRS was 64 months (range: 25.7-152.4). Eight (12%) patients showed tumor progression. In multivariate analyses, residual TV was associated with tumor progression (P = 0.003; hazard ratio [HR], 1.229; 95% confidence interval [CI], 1.075-1.405). A residual TV of 6.4 cm³ was identified as the cut-off volume for showing the greatest difference in progression-free survival (PFS). The 5-year PFS rates in the group with residual TVs of < 6.4 cm³ (54 patients) and that with residual TVs of ≥ 6.4 cm³ (14 patients) were 93.3% and 69.3%, respectively (P = 0.014). A good FN outcome was achieved in 57 (84%) patients. Residual TV was not associated with good FN function during the immediate postoperative period (P = 0.695; odds ratio [OR], 1.024; 95% CI, 0.908-1.156) or at the last follow-up (P = 0.755; OR, 0.980; 95% CI, 0.866-1.110).

CONCLUSION

In this study, residual TV was associated with tumor progression in VS after adjuvant GKRS following STR. As preservation of FN function is not correlated with the extent of resection, optimal volume reduction is imperative to achieve long-term tumor control. Our findings will help surgeons predict the prognosis of residual VS after FN-preserving surgery.

Cortical and subcortical gray matter changes in patients with chronic tinnitus sustaining after vestibular schwannoma surgery

Tinnitus is attributed to partial sensory deafferentation resulting in a central maladaptive neuroplasticity. Unfortunately, the agent of deafferentation is usually unknown or irreversible. In patients with unilateral vestibular schwannoma (VS), however, the auditory nerve is affected by a benign tumor. Hence, removal of the tumor can cease the tinnitus. In turn, sustaining complaints after surgery indicate cortical neuroplasticity. The present study is a cross sectional study which aims to track cortical structural changes by surface-based morphometry in 46 VS patients with sustained (i.e. centralized) or ceased (i.e. peripheral) tinnitus after surgery. A volumetric analysis of cortical and subcortical gray matter (GM) anatomy was performed on preoperative high-resolution MRI and related to the presence of hearing impairment, pre- and/or postoperative tinnitus. Patients with sustained (i.e. chronic) tinnitus showed an increased GM volume of the bilateral caudate nucleus, the contralateral superior colliculus, the middle frontal and middle temporal gyrus, the fusiform gyrus as well as the ipsilateral pars orbitalis when compared to those patients in whom tinnitus ceased postoperatively. Chronic tinnitus in VS patients is associated with characteristic structural changes in frontal, temporal and subcortical areas. Notably, a significant GM change of the caudate nucleus was detected providing further support for the striatal gaiting model of tinnitus.

Occurrence and management of postoperative pneumocephalus using the semi-sitting position in vestibular schwannoma surgery

Background

The semi-sitting position in neurosurgical procedures is still under debate due to possible complications such as venous air embolism (VAE) or postoperative pneumocephalus (PP). Studies reporting a high frequency of the latter raise the question about the clinical relevance (i.e., the incidence of tension pneumocephalus) and the efficacy of a treatment by an air replacement procedure.

Methods

This retrospective study enrolled 540 patients harboring vestibular schwannomas who underwent posterior fossa surgery in a supine (n = 111) or semi-sitting (n = 429) position. The extent of the PP was evaluated by voxel-based volumetry (VBV) and related to clinical predictive factors (i.e., age, gender, position, duration of surgery, and tumor size).

Results

PP with a mean volume of 32 ± 33 ml (range: 0–179.1 ml) was detected in 517/540 (96%) patients. The semi-sitting position was associated with a significantly higher PP volume than the supine position (40.3 ± 33.0 ml [0–179.1] and 0.8 ± 1.4 [0–10.2], p < 0.001). Tension pneumocephalus was observed in only 14/429 (3.3%) of the semi-sitting cases, while no tension pneumocephalus occurred in the supine position. Positive predictors for PP were higher age, male gender, and longer surgery duration, while large (T4) tumor size was established as a negative predictor. Air exchange via a twist-drill was only necessary in 14 cases with an intracranial air volume > 60 ml. Air replacement procedures did not add any complications or prolong the ICU stay.

Conclusion

Although pneumocephalus is frequently observed following posterior fossa surgery in semi-sitting position, relevant clinical symptoms (i.e., a tension pneumocephalus) occur in only very few cases. These cases are well-treated by an air evacuation procedure. This study indicates that the risk of postoperative pneumocephalus is not a contraindication for semi-sitting positioning.

Electrophysiological predictors of hearing deterioration based on AEP monitoring during petroclival meningioma resection

The objective of this study was to calculate the risk of postsurgical hearing deterioration as a function of changes in the amplitude and latency of the most stable components (waves III and V) of the auditory evoked potential (AEP) during petroclival meningioma resection surgery. We retrospectively analyzed intraoperative AEP monitoring results and pre- and postsurgical hearing status in 40 consecutive patients who were surgically treated for petroclival meningiomas. Statistical analyses were conducted to identify the most sensitive and specific way to predict hearing dysfunction after surgery. Patients' mean age was 59 ± 10 years, and 31 (77.5%) were women. Twelve (30%) patients presented with clinically detectable hearing impairment preoperatively. At the first postoperative assessment, four of those 12 patients reported subjective improvement, and eight reported hearing deterioration. Of those eight, four remained stable and four recovered hearing by the last assessment. Wave III latency reached its highest specificity (100%) and sensitivity (71.43%) at x = 143%. Wave V latency, on the other hand, reached its highest sensitivity (71%) and specificity (93%) at x = 124%. Finally, wave V amplitude reached its highest sensitivity (100%) and specificity (79%) at x = 74%. Intraoperative alterations of wave III latency and wave V amplitude seem to be highly sensitive and specific at predicting the risk of auditory dysfunction in patients undergoing petroclival meningioma resection and should be used to determine maximum resection with preservation of function.

The impact of the MIB-1 index on facial nerve outcomes in vestibular schwannoma surgery

Background

Facial nerve palsy is a severe morbid condition that occurs after vestibular schwannoma (VS) surgery. The objective of this study was to evaluate facial nerve outcomes based on surgical techniques, tumour size, and immunohistochemical factors.

Methods

One hundred eighteen patients with VS were retrospectively analysed. Gross total resection (GTR) was achieved in 83 patients, and subtotal resection (STR) was achieved in 35 patients. Follow-up was 60 months (median). Facial nerve outcomes were assessed for 24 months after surgery. Analysis of the MIB-1 index was performed in 114 patients (97%) to evaluate recurrence and facial nerve outcomes.

Results

Immediately after surgery, 16 of 35 patients (45.7%) with STR and 21 of 83 patients (25.3%) with GTR had a good (House-Brackmann (HB) score ≤ 2) facial nerve outcome (p = 0.029). Semi-sitting positioning (p = 0.002) and tumour size class of 3 (> 4 cm) were also associated with worse HB outcomes after 2 years (p = 0.004) in univariate analyses. The MIB-1 index was significantly correlated with diffuse infiltration of tumour-associated CD45⁺ lymphocytes (r = 0.63, p = 0.015) and CD68⁺ macrophages (r = 0.43, p = 0.021). ROC analysis found an AUC of 0.73 (95% CI = 0.60–0.86, p = 0.003) for the MIB-1 index in predicting poor facial nerve outcomes. Binary logistic regression analysis revealed an MIB-1 index ≥ 5% (16/28 (57.1%) vs. 5/40 (12.5%); p < 0.001, OR = 14.0, 95% CI = 3.2–61.1) and a tumour size class of 3 (6/8 (75.0%) vs. 2/8 (25.0%); p = 0.01, OR = 14.56, 95% CI = 1.9–113.4) were predictors of poor HB scores (≥ 3) after 1 year.

Conclusions

An MIB-1 index ≥ 5% seems to predict worse long-term facial nerve outcomes in VS surgery.

Surgical management of collision-tumors between vestibular schwannoma and meningioma in the cerebellopontine angle in patients with neurofibromatosis type 2

INTRODUCTION

When vestibular schwannoma (VS) collides with meningioma at the cerebellopontine angle (CPA), a particular threat occurs. Sudden acceleration of tumor growth and unpredictable involvement of cranial nerves results in a special environment that aggravates management. The goal of this study was to analyze the extent of resection, postoperative facial and cochlear function, surgical strategy, and survival rates in patients with neurofibromatosis type 2 (NF2) with meningioma-vestibular schwannoma (M-VS) collision tumors.

METHODS

A total of 1284 VS, including 165 NF2 VS were operated at our department between January 2004 and May 2018. Out of these cases, a group of six NF2 patients with seven M-VS collision tumors was found following careful analysis of neuroradiological data and pathological and surgical reports. Patients were evaluated for extent of tumor resection and, furthermore, postoperative facial and hearing function.

RESULTS

Six patients with NF2 with seven M-VS collision tumors were included in this study. Mean age was 32 ± 8.2 years. A gross total resection (GTR) of both colliding tumors was achieved in only one case, a GTR of the meningioma and a subtotal resection (STR) of the VS in four cases and in two cases only, the meningioma was removed. In five of the cases, facial function was intact or good (House and Brackmann grades I-II) at long-term follow-up (mean follow-up 22 months). No mortality occurred during follow-up.

CONCLUSIONS

Collision between M and VS at the CPA is a particular phenomenon in NF2 patients that may aggravate the situation with less favorable surgical outcome than NF-2 VS without meningioma.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

Postoperative Tinnitus After Vestibular Schwannoma Surgery Depends on Preoperative Tinnitus and Both Pre- and Postoperative Hearing Function

Objective

Tinnitus is one of the most common symptoms before and/or after the surgical removal of a vestibular schwannoma (VS) affecting almost half of the patients. Although there is increasing evidence for the association of hearing impairment and VS-associated tinnitus, the effect of hearing deterioration due to surgery and its relation to the postoperative tinnitus (postTN) is poorly investigated. This knowledge, however, might (i) enlighten the pathophysiology of VS-associated tinnitus (i.e., peripheral or central origin) and (ii) improve preoperative patient counseling. The aim of this study was to understand the predisposition factors for a postTN in relation to hearing outcome after surgery.

Methods

This retrospective study analyzed the presence of tinnitus in 208 patients with unilateral VS before and after surgical removal. A binomial logistic regression was performed to ascertain the effect of pre- and postoperative hearing as well as age, gender, tumor side, and size, and intraoperative cochlear nerve resection (CNR) on the likelihood of postoperative VS-associated tinnitus.

Results

Preoperative tinnitus was the strongest predictor of postTN. In addition, deterioration of functional hearing was increasing, while functional deafferentation (i.e., postoperative hearing loss) of non-functional hearing was reducing the risk of postTN. At the same time, patients with no preoperative tinnitus but complete hearing loss had the lowest risk to suffer from postTN. Patient age, gender, tumor side, and size as well as CNR played a subordinate role.

Conclusion

While the presence of preoperative tinnitus was the strongest predictor of postTN, there is a distinct relationship between hearing outcome and postTN depending on the preoperative situation. Functional or anatomical deafferentation due to surgical tumor removal does not prevent postTN per se.

Endoscopic assistance in retrosigmoid transmeatal approach to intracanalicular vestibular schwannomas - An alternative for middle fossa approach. Technical note

BACKGROUND

Complete surgical removal of intracanalicular vestibular schwannomas with nerve VII and VIII sparing and without worsening patient's status is challenging. Also the choice of an optimal surgical technique, which is usually limited to selection between retrosigmoid transmeatal (RT) and middle fossa (MF) approach, can be a challenge. Although many previous studies documented superiority of RT to MF approach and vice versa, still no consensus has been reached regarding an optimal approach to intracanalicular vestibular schwannomas. In this technical note, we present RT approach with an endoscopic assistance and highlight its advantages over MF approach in surgical management of pure intracanalicular vestibular schwannomas.

METHOD

RT approach with an endoscopic assistance is presented as an optimal surgical treatment for intracanalicular vestibular schwannomas, and its advantages are compared to those offered by MF approach.

RESULTS

Under an endoscopic guidance, we found a residual tumor in the fundus of the inner acoustic canal and performed its gross total resection.

CONCLUSIONS

RT approach is an excellent technique suitable for safe radical surgical treatment of T1 vestibular schwannomas; this technique is associated with lower morbidity risk than MF approach.

Does attempt at hearing preservation microsurgery of vestibular schwannoma affect postoperative tinnitus?

Background. The aim of this study was to analyze the effect of vestibular schwannoma microsurgery via the retrosigmoid-transmeatal approach with special reference to the postoperative tinnitus outcome. Material and Methods. A prospective study was performed in 89 consecutive patients with unilateral vestibular schwannoma indicated for microsurgery. Patient and tumor related parameters, pre- and postoperative hearing level, intraoperative findings, and hearing and tinnitus handicap inventory scores were analyzed. Results. Cochlear nerve integrity was achieved in 44% corresponding to preservation of preoperatively serviceable hearing in 47% and useful hearing in 21%. Main prognostic factors of hearing preservation were grade/size of tumor, preoperative hearing level, intraoperative neuromonitoring, tumor consistency, and adhesion to neurovascular structures. Microsurgery led to elimination of tinnitus in 66% but also new-onset of the symptom in 14% of cases. Preservation of useful hearing and neurectomy of the eighth cranial nerve were main prognostic factors of tinnitus elimination. Preservation of cochlear nerve but loss of preoperative hearing emerged as the main factor for tinnitus persistence and new onset tinnitus. Decrease of THI scores was observed postoperatively. Conclusions. Our results underscore the importance of proper pre- and intraoperative decision making about attempt at hearing preservation versus potential for tinnitus elimination/risk of new onset of tinnitus.