Accessory Nerve Schwannoma with Medulla Oblongata Compression: Microsurgical Resection by Far Lateral Suboccipital Transcondylar Approach: 2-Dimensional Operative Video.

Schwannomas overall account for approximately 8% of primary brain tumors, with the majority of them arising from the vestibular nerves.1,2 Non-vestibular schwannomas are considered rare, particularly ones arising from the accessory nerve, comprising only around 4% of craniovertebral junction schwannomas.3,4 The far lateral approach and its variations is an important tool in the armamentarium of skull base neurosurgeons. It allows adequate exposure for accessing ventral and ventrolateral lesions of the craniocervical junction.5-13 A 60-year-old female presented with a 3-month history of difficulty walking and progressive right-sided weakness. MR imaging demonstrated an extraaxial solid lesion at the craniocervical junction with significant enhancement on post-contrast imaging. The lesion was ventrolateral to the medulla, causing compression, displacement, and peritumoral edema. The patient consented to the procedure and underwent a far lateral suboccipital craniotomy with C1 hemilaminectomy in a lateral position. Tumor origins were identified at the left accessory nerve rootlet. The patient's postoperative course was uneventful. Follow-up MR imaging revealed gross total resection and complete resolution of hemiparesis 3 months after the surgery. Microsurgical resection of tumors at the craniocervical junction is challenging. Preoperative planning and tailoring the approach are essential in the decision-making process to safely perform surgery. This video demonstrates, in detail, the steps, relevant anatomy, and technical nuances for accessory nerve schwannoma removal. To the best of our knowledge, this is the first operative video showing the resection of a pure accessory nerve schwannoma with compression of the medulla. Under our institutional ethical review board regulations, approval was not necessary.

Evaluation of multiparametric MRI differentiating pleomorphic adenoma from schwannoma in parapharyngeal space.

PURPOSE: This study aimed to investigate whether multiparametric magnetic resonance imaging (MRI) including dynamic contrast-enhanced (DCE) and diffusion weighted (DW) MRI can differentiate pleomorphic adenoma (PA) from schwannoma in the parapharyngeal space. METHODS: Forty-six patients with pathologically proven PAs and 47 schwannomas in the parapharyngeal space were enrolled. All patients underwent conventional MRI, and DW-MRI and DCE-MRI were performed in 30 and 33 patients, respectively. Fisher's exact, Mann-Whitney-U tests and Independent samples t-test were used to compare variables between PAs and schwannomas. Multivariate logistic regression analysis was used to examine the diagnostic performance of MRI parameters. RESULTS: The PAs usually show lobulation sign, posterior displacement of ICA and attached to the parotid gland deep leaf, while bird beak configuration, anterior displacement of ICA and involvement of foramen jugular were more commonly seen in the schwannomas(all p < 0.001). The washout rate of PAs was found to be higher than that of schwannomas (p = 0.035), whereas no significance was found in the other DCE-MRI parameters and in ADCs(p > 0.05). Using a combination of conventional MRI features including lobulation sign, bird beak configuration, direction of internal carotid artery(ICA) displacement and attached to the parotid gland in multivariate logistic regression analysis, sensitivity, specificity, and accuracy in differential diagnosis of PAs and schwannomas were 97.8%, 91.5% and 94.6%, respectively. CONCLUSION: Conventional MRI can effectively differentiate PAs from schwannomas in the parapharyngeal space with a high diagnostic accuracy. The DCE-MRI and DWI have limited added diagnostic value to conventional MRI in the differential diagnosis.

Ancient Schwannoma Along the Patellar Tendon: Unveiling a Rare Clinical Phenomenon With Literature Review.

Ancient schwannoma, a rare subtype of schwannoma, a benign tumor originating from nerve sheaths, can arise from various nerves, except for the optic, olfactory, spinal, and autonomic nervous systems. Schwannomas are typically characterized by the presence of neoplastic Schwann cells and tend to develop eccentrically. Malignant transformations of schwannomas are exceptionally uncommon. In this case report, a 42-year-old male presented with a painful lump on the front of his left knee. The lump was described as an extra-articular swelling below the kneecap, situated over the patellar tendon. Initially, ultrasonography (USG) indicated the presence of a slow-flow vascular malformation in the infrapatellar region of the left knee. However, subsequent magnetic resonance imaging (MRI) revealed a well-defined mass in the subcutaneous plane below the knee, with minimal septations, leading to an initial suspicion of a large sebaceous cyst. Further investigation through histopathological analysis confirmed the diagnosis of an extra-articular schwannoma. This finding highlights the importance of thorough examination and diagnostic techniques in differentiating between various types of soft tissue masses. Schwannomas, although uncommon in certain locations, should be considered in the differential diagnosis of painful lumps, even in atypical anatomical sites such as the knee.

Intraventricular schwannomas: A case report and a literature review.

Intraventricular schwannomas are extremely rare, typically benign tumors originating from Schwann cells, which are not normally found within the ventricular system. Their presence challenges conventional understanding of tumor origins and complicates diagnosis and management. We report the case of a 19-year-old female presenting with a drop attack and headache, with no significant medical history. MRI revealed a heterogeneously enhancing lesion in the right lateral ventricle. Differential diagnoses included malignant tumors; however, histopathological examination post-surgical resection confirmed an intraventricular schwannoma. Postoperative outcomes were favorable, with successful CSF diversion via a right occipital ventriculoperitoneal shunt for isolated right temporal hydrocephalus. This case is notable for its atypical presentation in a young patient, challenging the conventional understanding that intraventricular schwannomas primarily affect older individuals. In addition, the correct diagnosis and successful management of a rare intraventricular schwannoma underscores the importance of considering this rare diagnosis in patients with nonspecific neurological symptoms and intraventricular lesions. This case, alongside the literature review, enriches the body of evidence on intraventricular schwannomas, highlighting the critical role of surgical intervention and the need for a comprehensive diagnostic approach.

The outcome of the retrosigmoid approach in the decompression of vestibular schwannomas - a retrospective cohort study of 60 consecutive cases.

This multicenter retrospective cohort study aimed to evaluate the effectiveness of the retrosigmoid surgical approach in decompressing vestibular schwannomas, focusing on tumor decompression, neurological function preservation, and postoperative complications. A cohort of 60 patients, operated between 2016 and 2019, was analyzed for age, sex, symptoms, tumor size, surgery duration, complications, mortality, and facial/auditory functions using established criteria. Hearing loss was observed in 80% of patients, mainly progressive, with tumor size emerging as a critical prognostic factor. Facial weakness affected 10% of patients preoperatively; postoperatively, 35% of patients had affected facial nerve function, with 10% exhibiting poor or no facial nerve function, linked to resection extent rather than tumor size. Tinnitus was more prevalent with larger tumors, whereas headaches were common irrespective of size. Balance disorders improved after surgery, especially in case of larger tumors. Functional recovery varied, with 41.67% of patients returning to their previous activity within 4 months, 25% within 4-12 months, and 33.33% remaining inactive. The mortality rate was low at 3.3 %, with two deaths out of 60 patients after surgery. This analysis highlights surgery risks for vestibular schwannomas (e.g., facial nerve decline, tinnitus, headaches), but also emphasizes benefits like improved balance and low mortality. Many patients regain professional activity, stressing the importance of informed treatment decisions for this condition.

Repeat stereotactic radiosurgery for progressive vestibular schwannomas after primary gamma knife radiosurgery.

PURPOSE: Limited data provides guidance on the management of vestibular schwannomas (VSs) that have progressed despite primary Gamma Knife radiosurgery (GKRS). The present article reports our long-term experience after repeat GKRS for VS with sustained progression after solely primary GKRS management. METHODS: A retrospective review of 1997 patients managed between 1987 and 2023 was conducted. Eighteen patients had sustained tumor progression after primary GKRS and underwent repeat GKRS. The median repeat GKRS margin dose was 11 Gy (IQR: 11-12), the median tumor volume was 2.0 cc (IQR: 1.3-6.3), and the median cochlear dose in patients with preserved hearing was 3.9 Gy (IQR: 3-4.1). The median time between initial and repeat GKRS was 65 months (IQR: 38-118). RESULTS: The median follow-up was 70 months (IQR: 23-101). After repeat GKRS, two patients had further tumor progression at 4 and 21 months and required partial resection of their tumors. The 10-year actuarial tumor control rate after repeat GKRS was 88%. Facial nerve function was preserved in 13 patients who had House-Brackmann grade 1 or 2 function at the time of repeat GKRS. Two patients with serviceable hearing preservation (Gardner-Robertson grade 1 or 2) at repeat GKRS retained that function afterwards. In patients with tinnitus, vestibular dysfunction, and trigeminal neuropathy, symptoms remained stable or improved for 16/16 patients, 12/15 patients, and 10/12 patients, respectively. One patient developed facial twitching in the absence of tumor growth 21 months after repeat GKRS. CONCLUSIONS: Repeat GKRS effectively controlled tumor growth and preserved cranial nerve outcomes in most patients whose VS had sustained progression after initial primary radiosurgery.

Planned Subtotal Resection following Stereotactic Radiosurgery of Koos 3 and 4 Vestibular Schwannomas.

Background/Objectives: Surgical resection of medium to large vestibular schwannomas (VSs, Koos grade 3 and 4) is a widely used approach, although stereotactic radiosurgery (SRS) is increasingly proposed as initial treatment. The quality of life-centered approach is challenged in cases where tumor growth control cannot be achieved with SRS, thus necessitating salvage surgery. We present a series of eight consecutive patients who required surgery due to continued tumor growth after SRS. Methods: Of the 146 patients with VS grades 3 and 4 initially treated with SRS, only eight patients (mean age, 54 ± 7.2 years; range, 42-63 years) required subsequent surgery. Their mean tumor volume was 9.9 ± 3.2 cm3. The mean time from SRS to first tumor progression and planned subtotal resection was 23 ± 5.9 months and 45 ± 17.5 months, respectively. SRS was not performed after the surgery in favor of a "wait and rescan" approach. Tumor residue was monitored on follow-up magnetic resonance imaging. In all patients, tumor growth control after planned subtotal resection was maintained at 63 ± 19.8 months. Results: None of the 146 patients had serious complications after SRS. In the eight patients who required surgery, tumor growth between 22% and 212% (mean, 4 cm3) was reported within 26 to 84 months after SRS. Before salvage surgery, they scored 1 point on the House-Brackmann scale. Subtotal excision was performed, and VIIth nerve function was preserved in all patients. At 63 ± 19.8 months, 3 patients had a House-Brackmann score of 1, four patients had a score of 2, and one patient had a score of 3. Conclusions: Surgical excision of medium to large VS after SRS can be relatively safe, provided that a quality of life-centered approach of subtotal resection is used.

Customized Vestibular Rehabilitation for Vestibular Schwannoma Excision via Translabyrinthine Approach: A Single-Center Experience.

Objectives: To evaluate the effectiveness of intensive customized vestibular rehabilitation after vestibular schwannoma (VS) excision. Methods: 52 patients who underwent VS removal via a translabyrinthine approach from 2020 to 2022 were involved in this study. Bedside examination, video head impulse test (vHIT), functional head impulse test (fHIT), and the dizziness handicap inventory (DHI) were performed before and after the rehabilitation, which consisted of 10 sessions of specifically designed vestibular, visual, and physical integrated training. Results: After rehabilitation, the vHIT showed overall unchanged values on the affected and healthy side. In contrast, the scores of fHIT, which explores the higher connection of the vestibular system with visual and cerebellar pathways, improved on both the pathological and healthy sides after training (p-value 0.004 and 0.000, respectively). The effectiveness of the rehabilitation was reinforced by the DHI scores, which were considerably lower after training. Conclusions: To our knowledge, this is the first study to explore fHIT outcomes after removal of VS, estimating the impact of rehabilitation on the overall compensation process. The outcomes support the role of extensive postsurgical rehabilitation in the compensatory process, even just a few days after surgery.

Intraoperative Hearing Monitoring Using ABR and TT-ECochG and Hearing Preservation during Vestibular Schwannoma Resection.

Background: Quick and appropriate diagnostics and the use of intraoperative monitoring (IM) of hearing during vestibular schwannoma (VS) resection increase the likelihood of hearing preservation. During surgery, various methods of IM can be used, i.e., auditory brainstem responses (ABRs), transtympanic electrocochleography (TT-ECochG), and direct cochlear nerve action potentials. The aim of the study was to evaluate the prognostic values of IM of hearing using ABR and TT-ECochG in predicting postoperative hearing preservation and to evaluate relationships between them during various stages of surgery. Methods: This retrospective study presents the pre- and postoperative audiological test results and IM of hearing records (TT-ECochG and ABR) in 75 (43 women, 32 men, aged 18-69) patients with diagnosed VS. Results: The preoperative pure tone average hearing threshold was 25.02 dB HL, while after VS resection, it worsened on average by 30.03 dB HL. According to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Hearing Classification, before and after (pre/post) surgery, there were 47/24 patients in hearing class A, 9/8 in B, 2/1 in C, and 17/42 in D. In speech audiometry, the average preoperative speech discrimination score at an intensity of 60 dB SPL was 70.93%, and after VS resection, it worsened to 38.93%. The analysis of electrophysiological tests showed that before the tumor removal the I-V ABR interlatencies was 5.06 ms, and after VS resection, it was 6.43 ms. Conclusions: The study revealed correlations between worse postoperative hearing and changes in intraoperatively measured ABR and TT-ECochG. IM of hearing is very useful in predicting postoperative hearing in VS patients and increases the chance of postoperative hearing preservation in these patients.

Intracapsular Enucleation of Cervical Sympathetic Chain Schwannoma: Improved Strategy of Intraoperative Hemostasis and Better Outcome.

Objective: Intracapsular enucleation (ICE) of cervical sympathetic chain schwannoma (CSCS) is associated with technical difficulties, with diffuse hemorrhage being the main challenge in our previous attempts. This article presents our new strategy for achieving better hemostasis during ICE procedures in CSCS cases. Methods: A retrospective review of CSCS cases treated at our tertiary medical institution was undertaken between April 2018 and February 2024. Only cases with successful ICE were included. Results: A total of 8 cases were included, with 4 male and 4 female patients and an age range of 23 to 77 (average and median ages were 48.5 and 49.5 years, respectively). The presenting symptom was a neck mass for all the patients, with 4 masses on the left and 4 on the right sides. Enucleation was first undertaken for the first 3 cases (before March 2022), followed by hemostasis; this strategy was quite difficult and time-consuming. For the remaining 5 cases, a new strategy was developed to preemptively manage any potential nourishing vessel between the capsule and tumor parenchyma, which significantly decreased operation time (P = .0155) and facilitated hemorrhage control. First bite syndrome (FBS) was avoided in all cases. Postoperative Horner's syndrome (HS) was avoided in 1 patient (Case 6, new strategy) but occurred in 7 patients, taking 8 days to 1 month to recover with the new strategy (4 patients), significantly shorter (P = .0364) than before (3 patients, 1-3 months). The median duration of follow-up was 20 months. No recurrence was documented. Conclusions: ICE was achieved for CSCS cases, especially with our newly developed strategy, by preemptively and securely managing potential nourishing vessels. Operation time and duration of recovery of postoperative HS could both be shortened. Moreover, FBS could be avoided.

A grand mimicker of pulmonary malignancy: The massive mediastinal intercostal nerve tumour.

Mediastinal mass-like manifestations often cause alarm and instigate a myriad of investigative testing to rule out insidious malignant processes. However, a unique and benign finding, the schwannoma can present either incidentally or while in pursuit of a symptomatic presentation. Given its rarity, limited literature exists on these neurogenic tumours with less than three dozen reported cases. No specific guidelines exist regarding the extent of required advanced imaging or degree of invasive evaluation. Therefore, practitioners confronted with these intrathoracic tumours may find management challenging or delayed. We present a case discussing a large benign tumour causing symptomatic burden, the investigative methods implored and treatment modality. We add to the literature another unique presentation of an intercostal nerve sheath tumour with schwannoma pathology.

Intradural cystic schwannomas of the spine: A case-based systematic review of an unusual tumor.

Introduction: Cystic schwannomas have only been reported in a few case reports/series. As a result, they may be misdiagnosed and a standardized management approach remains challenging to establish. Research question: The aim of this study was to compile all reported cases of cystic schwannomas and analyze the perioperative course based on a systematic review of the literature with an additional two cases from the authors' experience. Material and methods: We conducted a search of MEDLINE and CENTRAL databases for spinal intradural extramedullary cystic schwannomas, in accordance to the PRISMA statement. All title/abstracts were screened, and a full-text review of the remaining articles was conducted. The results were compiled in tables and summarized using means and standard deviation (SD), median and interquartile range, and percentage and 95% confidence intervals. Results: We identified 263 articles, of which 35, which reported 54 cases, were included. Including our case-reports (n = 56), patients had a mean age of 47.7 years (SD ± 13.0 years) at presentation, 57% were males, and most lesions were lumbar (43%). The most common symptoms were pain (82%) and muscle weakness (68%) with 84% of patients showing neurological findings. 70% of patients showed a complete relief of symptoms after surgery and 96% reported improvement. Only four complications were reported. Discussion and conclusion: Schwannomas should be considered in the differential diagnosis of intradural extramedullary cystic lesions. Patients typically present with subacute to chronic pain and/or neurologic changes. Surgical resection is the primary therapeutic modality and usually has a good to excellent outcome.

Likelihood-of-harm/help of microsurgery compared to radiosurgery in large vestibular schwannoma.

PURPOSE: It has been shown that in large vestibular schwannomas (VS), radiosurgery (SRS) is inferior with respect to tumor control compared to microsurgical resection (SURGERY). However, SURGERY poses a significantly higher risk of facial-function deterioration (FFD). The aim of this study was to illustrate the effectiveness in terms of number-needed-to-treat/operate (NNO), number-needed-to-harm (NNH), and likelihood-of-harm/help (LHH) by comparing both treatment modalities in large VS. METHODS: This was a retrospective, dual-center cohort study. Tumor size was classified by Hannover Classification. Absolute risk reduction and risk increase were used to derive additional estimates of treatment effectiveness, namely NNO and NNH. LHH was then calculated by a quotient of NNH/NNO to illustrate the risk-benefit-ratio of SURGERY. RESULTS: Four hundred and forty-nine patients treated met the inclusion criteria. The incidence of tumor recurrence was significantly higher in SRS (14%), compared to SURGERY (3%) resulting in ARR of 11% and NNO of 10. At the same time, SURGERY was related to a significant risk of FFD resulting in an NNH of 12. Overall, the LHH calculated at 1.20 was favored SURGERY, especially in patients under the age of 40 years (LHH = 2.40), cystic VS (LHH = 4.33), and Hannover T3a (LHH = 1.83) and T3b (LHH = 1.80). CONCLUSIONS: Due to a poorer response of large VS to SRS, SURGERY is superior with respect to tumor control. One tumor recurrence can be prevented, when 10 patients are treated by SURGERY instead of SRS. Thus, LHH portrays the benefit of SURGERY in large VS even when taking raised FFD into account.

Spinal extradural meningioma: Report of two cases.

Purely extradural spinal meningiomas are rare and often confused with metastases and schwannomas. Only a few cases have been described in the literature, and they are located mainly in the cervical and dorsal regions. We present two cases of extradural meningiomas, one well-defined nodular growth present at a cervicodorsal junction that was confused with schwannoma preoperatively and the other typical meningioma extending both intra and extradurally in the upper dorsal spine.

Delayed Facial Nerve Dysfunction Following CyberKnife® Radiosurgery for Vestibular Schwannoma.

OBJECTIVE: The incidence and risk factors for facial nerve dysfunction (FND) following CyberKnife® therapy for vestibular schwannoma (VS) remain poorly understood. This study investigates whether differential radiation doses to vulnerable segments of the facial nerve may be associated with FND outcomes. METHODS: Patients were identified who underwent CyberKnife® radiosurgery for VS at a single institution. Basic demographics, tumor characteristics, and facial nerve function were collected. Total radiation doses to tumor, internal auditory canal (IAC), and labyrinthine segment of facial nerve (LSFN) were evaluated. RESULTS: Six out of 64 patients experienced FND following CyberKnife® treatment for VS (9.38%, 6/64). Patients with FND were compared to those without FND (control). Of the 64 patients, complete radiation records were obtained for 30 patients (6 FND vs. 24 control). There were no significant differences in demographic or tumor characteristics between control and FND cohorts. More severe FND (HB ≥ 4) had significantly larger tumors (3.74 vs. 1.27 cm3, p = 0.037) with directionally decreased time to FND (3.50 vs. 33.5 months, p = 0.106) than patients with HB < 4, respectively. There were directionally, nonsignificant differences between maximum radiation doses to the LSFN (2492.4 vs. 2557.0 cGy, p = 0.121) and IAC (2877.3 vs. 2895.5 cGy, p = 0.824) between the control and FND cohorts, respectively. CONCLUSIONS: FND may represent an underrecognized sequelae of CyberKnife® radiosurgery for VS that can occur many months following treatment. Further studies are needed to elucidate the effect of differential radiation exposure to the facial nerve with FND following treatment. LEVEL OF EVIDENCE: III (Retrospective Cohort Study) Laryngoscope, 2024.

Schwannoma in the Rectum: A Case Report.

A woman in her 60s with a past medical history of recurrent Helicobacter pylori (H. pylori) presented for surgical consultation after a colonoscopy revealed a mass in the rectum. Preoperative biopsy revealed mucosal excrescence with no dysplasia or malignant changes. The final pathology showed a solid, submucosal rectal mass that was positive for SOX10 and S100 on immunohistochemistry, supporting our diagnosis of Schwannoma. This case emphasizes the importance of considering schwannomas in the differential diagnosis of patients presenting with a rectal mass no matter how rare it may be.

Evidence for inflammation in normal-appearing brain regions in patients with growing sporadic vestibular schwannoma: A PET study.

Background: Nonauditory symptoms can be a prominent feature in patients with sporadic vestibular schwannoma (VS), but the cause of these symptoms is unknown. Inflammation is hypothesized to play a key role in the growth and symptomatic presentation of sporadic VS, and in this study, we investigated through translocator protein (TSPO) positron emission tomography (PET) whether inflammation occurred within the "normal appearing" brain of such patients and its association with tumor growth. Methods: Dynamic PET datasets from 15 patients with sporadic VS (8 static and 7 growing) who had been previously imaged using the TSPO tracer [11C](R)-PK11195 were included. Parametric images of [11C](R)-PK11195 binding potential (BPND) and the distribution volume ratio (DVR) were derived and compared across VS growth groups within both contralateral and ipsilateral gray (GM) and white matter (WM) regions. Voxel-wise cluster analysis was additionally performed to identify anatomical regions of increased [11C](R)-PK11195 binding. Results: Compared with static tumors, growing VS demonstrated significantly higher cortical (GM, 1.070 vs. 1.031, P = .03) and whole brain (GM & WM, 1.045 vs. 1.006, P = .03) [11C](R)-PK11195 DVR values. The voxel-wise analysis supported the region-based analysis and revealed clusters of high TSPO binding within the precentral, postcentral, and prefrontal cortex in patients with growing VS. Conclusions: We present the first in vivo evidence of increased TSPO expression and inflammation within the brains of patients with growing sporadic VS. These results provide a potential mechanistic insight into the development of nonauditory symptoms in these patients and highlight the need for further studies interrogating the role of neuroinflammation in driving VS symptomatology.

Image features and clinical analysis of retroperitoneal pelvic schwannoma: a case report.

BACKGROUND: Schwannomas are benign usually encapsulated nerve sheath tumors derived from the Schwann cells, and affecting single or multiple nerves. The tumors commonly arise from the cranial nerves as acoustic neurinomas but they are extremely rare in the pelvis and the retroperitoneal area. Retroperitoneal pelvic schwannomas often present with non-specific symptoms leading to misdiagnosis and prolonged morbidity. CASE PRESENTATION: We report the case of a 59-year-old woman presenting with a feeling of heaviness in the lower abdomen who was found to have a retroperitoneal pelvic schwannoma originating from the right femoral nerve. She had a history of two resections of peripheral schwannomas at four different sites of limbs. After conducting magnetic resonance imaging, this pelvic schwannoma was misdiagnosed as a gynecological malignancy. The tumor was successfully removed by laparoscopic surgery. Pathological analysis of the mass revealed a benign schwannoma of the femoral nerve sheath with demonstrating strong, diffuse positivity for S-100 protein. CONCLUSIONS: Although retroperitoneal pelvic schwannoma is rare, it should be considered in the differential diagnosis of pelvic masses, especially in patients with a history of neurogenic mass or the presence of neurogenic mass elsewhere.

Electromagnetic field-induced adaptive response in Schwann cells through DNA methylation, histone deacetylation, and oxidative stress.

Schwannomas are benign tumors of the peripheral nervous system arising from the transformation of Schwann cells (SCs). On the whole, these tumors are related to alterations of the neurofibromin type 2 gene, coding for the oncosuppressor merlin, a cytoskeleton-associated protein belonging to the ezrin-radixin-moesin family. However, the underlying mechanisms of schwannoma onset and progression are not fully elucidated, whereas one of the challenges might be the environment. In this light, the exposure to electromagnetic field (EMF), generated by the use of common electrical devices, has been defiantly suggested as the cause of SCs transformation even if the evidence was mostly epidemiologic. Indeed, insubstantial mechanisms have been so far identified to explain SCs oncotransformation. Recently, some in vitro evidence pointed out alterations in proliferation and migration abilities in SCs exposed to EMF (0.1 T, 50 Hz, 10 min). Here, we used the same experimental paradigma to discuss the involvement of putative epigenetic mechanisms in SCs adaptation to EMF and to explain the occurrence of hypoxic alterations after the exposure. Our findings indicate a set of environmental-induced changes in SCs, toward a less-physiological state, which may be pathologically relevant for the SCs differentiation and the schwannoma development.

Ultrasound-guided lesser occipital nerve combined with great auricular nerve block for vestibular schwannoma craniotomy via a suboccipital retrosigmoid approach: a prospective, double-blind randomized controlled trial.

PURPOSE: This aim of this study was to investigate the analgesic efficacy and safety of lesser occipital nerve combined with great auricular nerve block (LOGAB) for craniotomy via a suboccipital retrosigmoid approach. METHODS: Patients underwent vestibular schwannoma resection via a suboccipital retrosigmoid approach were randomly assigned to receive ultrasound-guided unilateral LOGAB with 5 ml of 0.5% ropivacaine (LOGAB group) or normal saline (NSB group). Numeric rating scale (NRS) scores at rest and motion were recorded within 48 h after surgery. Mean arterial pressure (MAP), heart rate (HR), opioid consumption and other variables were measured secondly. RESULTS: Among 59 patients who were randomized, 30 patients received ropivacaine, and 29 patients received saline. NRS scores at rest (1.8 ± 0.5 vs. 3.2 ± 0.8, P = 0.002) and at motion (2.2 ± 0.7 vs. 3.2 ± 0.6, P = 0.013) of LOGAB group were lower than those of NSB group within 48 h after surgery. NRS scores of motion were comparable except for 6th and 12th hour (P < 0.05) in the LOGAB group. In LOGAB group, MAP decreased significantly during incision of skin and dura (P < 0.05) and intraoperative opoid consumption was remarkably reduced (P < 0.01). Postoperative remedial analgesia was earlier in the NSB group (P < 0.001). No patients reported any adverse events. CONCLUSION: Among patients undergoing craniotomy for vestibular schwannoma via a suboccipital retrosigmoid approach, LOGAB may be a promising treatment for perioperative analgesia and has the potential to maintain intraoperative hemodynamic stability. CLINICAL TRIAL REGISTRATION NUMBER: Chictr.org.cn ChiCTR2000038798.