Monitoring Cochlear Nerve Action Potential for Hearing Preservation in Medium/Large Vestibular Schwannoma Surgery: Tips and Pitfalls.

The diagnosis of large vestibular schwannomas (VS) with retained useful hearing has become increasingly common. Preservation of facial nerve (FN) function has improved using intraoperative EMG monitoring, hearing preservation remains challenging, with the recent use of cochlear nerve action potential (CNAP) monitoring. This prospective longitudinal series of VS with useful hearing operated on using a retrosigmoid approach included 37 patients with a mean largest extrameatal VS. diameter of 25 ± 8.7 mm (81% of Koos stage 4). CNAP was detected in 51% of patients, while auditory brainstem responses (ABR) were present in 22%. Patients were divided into two groups based on the initial intraoperative CNAP status, whether it was present or absent. FN function was preserved (grade I-II) in 95% of cases at 6 months. Serviceable hearing (class A + B) was preserved in 16% of the cases, while 27% retained hearing with intelligibility (class A-C). Hearing with intelligibility (class A-C) was preserved in 42% of cases when CNAP could be monitored in the early stages of VS resection versus 11% when it was initially absent. Changes in both the approach to the cochlear nerve and VS resection are mandatory in preserving CNAP and improve the rate of hearing preservation.

Surgical management of sporadic and schwannomatosis-associated pelvic schwannomas.

Pelvic schwannomas are rare tumors that may occur either sporadically or in the context of schwannomatosis. We retrospectively reviewed the charts of patients harboring a pelvic schwannoma under conservative management or operated at our reference center between 2016 and 2023. All patients were operated by a multidisciplinary team, combining a vascular surgeon and a neurosurgeon. Twenty-four patients harboring 33 pelvic tumors were included in the cohort, including 12 patients with sporadic lesions, 2 patients with NF2-related schwannomatosis, and 10 patients with NF2-independent schwannomatosis. Multi-nodular tumors were more frequent in schwannomatosis compared to sporadic cases (p = 0.005). The mean age at diagnosis was 41 years old. Schwannomas were located on branches of the sciatic nerve (23/33, 70%), the femoral nerve (6/33, 18%), and the obturator nerve (4/33, 12%). Over the course of the study, 16 patients were operated, including 11 sporadic cases. The indication for surgery was pain (12/16, 75%) or tumor growth (4/16, 25%). Complete resection was achieved in 14 of 16 patients (87%). The mean post-operative follow-up was 37 months (range: 2-168 months). At last-follow-up, complete pain relief was achieved in all 12 patients with pre-operative pain. Post-operative morbidity included 3 long-term localized numbness and one MRC class 4 motor deficit in a multi-nodular tumor in a schwannomatosis patient. Despite its limited size, our series suggests that nerve-sparing resection of pelvic schwannomas offers satisfying rates of functional outcome both in sporadic and schwannomatosis cases, except for multi-nodular tumors.

Surgical Management of Peripheral Nerve Pathology in Patients With Neurofibromatosis Type 2.

BACKGROUND: Neurofibromatosis type 2 (NF2) is rare genetic disorder mainly characterized by the development of central nervous system lesions, but peripheral nerve pathology may also cause high morbidity including pain, motor, and sensory loss. OBJECTIVE: To describe the tumor burden of patients with peripheral nerve pathology in NF2 including peripheral neuropathies and schwannomas and the results of surgery in the latter group. METHODS: We conducted a retrospective chart review of all patients with NF2 followed up at our NF2 Reference Center to include all patients suffering from peripheral nerve pathology. Tumor detection relied on focal MRIs based on symptoms. RESULTS: Thirty-four patients harboring 105 peripheral nerve schwannomas and 1 perineurioma were included. Schwannomas were mainly located in major nerves (n = 74, 71%) compared with subcutaneous (n = 23, 22%) and intramuscular (n = 8, 7%) cases. Most schwannomas (81/90-90%) were classical discrete tumors while multinodular cases represented only 9 cases (10%). During follow-up, 63 (60%) tumors were operated in 24 patients, including 39 schwannomas of major nerves. A complete resection was achieved in most of the cases (52/63, 83%) with a complete relief of preoperative pain in most patients (57/60, 95%). Persistent motor deficits (5/39, 13%) were mostly encountered in patients operated from multinodular schwannomas (4/5, 80%). Six patients had an associated peripheral neuropathy with 5 cases of pseudo-Charcot-Marie-Tooth-associated amyotrophy. CONCLUSION: Surgery remains a safe and effective method of treating peripheral nerve schwannoma-associated pain in NF2, with the exception of rare multinodular tumors. Special attention should be drawn to patients harboring severely debilitating neuropathies and perineuriomas.

Hearing recovery after surgical resection of non-vestibular schwannoma cerebellopontine angle tumors.

PURPOSE: Post-operative outcomes for hearing after resection surgery to remove cerebellopontine angle (CPA) tumors other than vestibular schwannomas (VS) are not well understood. This study presents a series of patients with significant post-operative hearing recovery, trying to define the incidence among all patients operated on for removal of non-VS CPA tumors. METHODS: This is a retrospective observational case series of 8 patients among 69 operated on for removal of non-VS CPA tumors between 2012 and 2020. All patients had pre- and post-operative hearing measurement with pure-tone average (PTA) and speech discrimination score (SDS), according to the American Academy of Otolaryngology-Head and Neck Surgery recommendations, auditory brainstem response (ABR) measurements and imaging. RESULTS: Six meningiomas and two lower cranial nerve schwannomas operated on with a retrosigmoid approach were included for analysis. The mean pre-operative PTA and SDS were 58 ± 20.7 dB and 13 ± 17.5%, respectively. All patients had pre-operative class D hearing and asynchronous ABRs. They all showed significant hearing recovery, with an improvement of 36 ± 22.2 dB (p = 0.0025) and 85 ± 16.9% (p = 0.0001) in PTA and SDS, respectively, with mean follow-up of 21 ± 23.5 months. Seven patients recovered to a class A hearing level and one patient to class B. The ABRs became synchronous for three patients. The incidence of auditory recovery was 13% for patients operated on with a conservative approach (n = 60). CONCLUSION: A significant post-operative improvement in hearing could be a reasonable expectation in non-VS tumors extending into the CPA and a retrosigmoid approach should always be considered regardless of pre-operative hearing status.

Intraoperative facial nerve electromyography parameters to optimize postoperative facial nerve outcome in patients with large unilateral vestibular schwannoma.

BACKGROUND: Decision-making for large sporadic vestibular schwannomas (VS) resection guided by the intraoperative change in supramaximal facial nerve (FN) amplitude and latency response to optimize post-operative FN outcome. METHODS: Prospectively study of 43 patients, from January to December 2018, of large sporadic VS with preoperative normal FN function at our center. Tumors were removed through retrosigmoid (81%) or translabyrinthine (19%) approaches with FN monitoring. Intraoperative pre- and post-VS resection supramaximal (2 mA) amplitude and latency responses at the proximal FN root were recorded. RESULTS: Total, near-/subtotal VS resections (TR, NTR, STR) were achieved in 51%, 38%, and 11% of tumors, respectively, guided by no more than 40% decrease in supramaximal amplitude. Pre- and post-resection supramaximal amplitude and latency responses were lower and longer, respectively, in NTR+STR than in TR. At day 8, FN function was grade I-II in 77% of patients and grade III-V in 23%, and after 6 months, it was in grade I-II in 95% and grade III in 5%, and there was no significant difference between TR and NTR+STR. Facial palsy occurred in older patients and in the case of severe FN adhesion. At day 8, pre- and post-resection supramaximal amplitude but not latency responses were different between FN grade III-V and grade I-II. Serviceable hearing was preserved in 28% of large VS. CONCLUSIONS: Intraoperative FN monitoring guided VS resection in large VS so that 49% retained some residual tumor. Accordingly, 95% good postoperative FN function and significant hearing preservation were achieved after 6 months.

Epineural glomus tumor of the posterior interosseous nerve: Case report.

Among peripheral nerve sheath tumors, epineural glomus tumors represent a rare differential diagnosis for peripheral nerve schwannoma, displaying the same appearance on MRI. Here we present the case of a 68-year-old man complaining of pain in the left forearm, with paresthesias in the first three fingers. MRI demonstrated a round mass along the course of the posterior interosseous nerve with homogeneous contrast enhancement. Complete surgical removal successfully relieved the symptoms. Pathological analysis led to the diagnosis of glomus tumor of uncertain malignant potential. This is to our knowledge the first reported case of epineural glomus tumor of the radial nerve.

Extracapsular dissection in peripheral nerve schwannoma surgery using bright light and fluorescein sodium visualization: case series.

BACKGROUND: Schwannomas are the most frequent peripheral nerve sheath tumors and are treated by surgical resection when symptomatic. Tumor removal is performed by intraneural dissection and enucleation. In order to safely remove the tumor from the nerve, the use of sodium fluorescein has recently been proposed to distinguish the tumor from the adjacent normal nerve fibers, before incision of the tumor pseudocapsule and during intraneural tumor dissection. METHODS: We report a consecutive case series of 5 peripheral nerve schwannomas operated in 4 patients, in which we evaluate the usefulness of sodium fluorescein compared to usual visual landmarks, at each step of the surgical procedure. RESULTS: After exposition of the schwannoma, sodium fluorescein helped with the localization of intracapsular en passant nerve fascicles in only one case. Hence, the definition of a safe entry zone for capsular incision relied mainly on nerve monitoring and direct visualization of en passant nerve fascicles under microscope. During intraneural dissection, there was a sharp contrast between the fluorescent tumor and the non-fluorescent adjacent pseudocapsule in most cases but the colorimetric variation between tumor and normal tissue induced by fluorescence did not outperform the natural contrast between the yellow true capsule and the gray-red layers of the pseudocapsule. CONCLUSION: Based on these results, we consider that the limited additional value of sodium fluorescein in primary peripheral nerve schwannoma surgery does not warrant its use in daily clinical practice. Additional studies are needed to assess its usefulness during the surgery of recurrences and tumors which are intertwined with several fascicles of origin such as neurofibromas.

Limitations and pitfalls of the pedicle screw testing monitoring technique: An in vivo and in vitro study.

OBJECTIVES: Pedicle screw testing is a widely used technique in the field of neuromonitoring for spinal surgery. It was designed by Calancie et al. (1992) in order to detect pedicle breach, one of the major complications of pedicle screw fixation, which can lead to neurological impairment. However, numerous false negative and equivocal results led to its clinical relevance being questioned. We aimed to clarify these discrepancies and characterize electrical parameters underlying this technique. METHODS: In this setting, our study is divided into two parts: (1) a clinical part assessing the difference between direct pedicle hole via the pedicle perforator stimulation and indirect stimulation via the implanted screw; (2) an in vitro study testing the electrical properties (resistivity and conductivity) on a sample of different commonly used pedicle screws. RESULTS: We showed that there were discrepancies between direct perforator stimulation and pedicle screws, especially at high threshold values. These might be attributed to electrical contact discontinuity. In vitro testing revealed that the previously described resistivity variability and the instability of measures are due to the result of slight changes of position of the recording contacts. CONCLUSION: Electrical continuity is crucial in the pedicle screw test technique. This parameter cannot actually be fully ensured and can lead to discrepancies and potentially false negative results. Therefore, we recommend the use of both direct stimulation of the pedicle hole and control testing of the screw. Further studies and improvement of the technique are required to ensure its reliability.

Smile Reanimation after Unilateral Facial Palsy by Lengthening Temporalis Myoplasty: Objective and Subjective Evaluation on 25 Cases.

BACKGROUND: Comparison of functional results of lengthening temporalis myoplasty relies in current practice on subjective scales. The goal of this study was to define a simple, reproducible, objective scale validated through a comparison with a subjective scale for smile symmetrization results after temporal muscle myoplasty. METHODS: A retrospective study was conducted on 25 patients having a unilateral facial palsy and rehabilitated with lengthening temporalis myoplasty. Evaluation consisted of objective measures: smile horizontal symmetry between left and right sides, vertical symmetry, and smile width on healthy and paretic sides on preoperative and postoperative photographs. Subjective scales were also used (i.e., a numeric scale and the Terzis and Noah scale) by a jury (four professionals and four nonprofessionals) and the patient himself or herself. Each evaluation was performed in three conditions: at rest, at intermediary smile, and at maximum smile. RESULTS: Comparison of objective measures on the impaired side showed a postoperative improvement in the three conditions evaluation. Reproducibility of the numeric scale was weak for evaluation at rest and fair for maximum smile evaluation (intraclass correlation coefficient of 0.57). The Terzis and Noah scale was not reproducible from one observer to another. At maximum smile, a correlation between smile symmetry in the vertical plane, smile symmetry in the horizontal plane, and professional evaluation with the numeric scale on the one hand and global patient satisfaction on the other hand was observed. CONCLUSION: Postoperative smile horizontal symmetry between left and right sides, and smile vertical symmetry, are good indicators with which to assess postoperative results of facial palsy rehabilitation.

Effect of corticosteroids on facial function after cerebellopontine angle tumor removal: a double-blind study versus placebo.

The aim of this study was to assess the effect of corticosteroids administered intra- and postoperatively on the occurrence of facial palsy after a cerebellopontine angle (CPA) tumor resection, and to investigate pre- and intraoperative prognostic factors. A multicenter, prospective, randomized, double-blind and versus-placebo study was conducted between 2006 and 2010. Three hundred and ten patients operated on for a CPA tumor (96% vestibular schwannomas, 4% miscellaneous) were included by five participating centers. The population was stratified into patients with small (≤15 mm CPA on axial MRI views) and large tumors. In each group, patients were randomized to receive corticosteroid (1 mg/kg/day i.v. methylprednisolone intraoperatively and at postoperative days 1-5) or placebo. Steroids did not affect the facial function at postoperative days 1, 8 and 30 in patients with small or large tumors as evaluated by House and Brackmann grading.

Supramaximal stimulation during intraoperative facial nerve monitoring as a simple parameter to predict early functional outcome after parotidectomy.

CONCLUSION: A supramaximal stimulation at 2 mA during intraoperative electromyographic (EMG) facial nerve monitoring appears to be a simple and effective parameter to predict immediate postoperative injury. OBJECTIVES: To assess the role of systematic intraoperative facial nerve monitoring in predicting the early functional outcomes obtained after parotidectomy. METHODS: Data were collected from patients who underwent parotidectomy. Intraoperative EMG monitoring of the facial nerve was performed by registering two parameters, event intensity (>100 µV) and amplitude of response after a supramaximal stimulation at 2 mA, at the beginning and end of gland removal. Early postoperative clinical functional facial nerve disorder was assessed at day 2. RESULTS: Overall, 50 patients were included and an early facial dysfunction was detected in 27 cases (54%). The maximal response amplitude after supramaximal stimulation at the trunk of the facial nerve was higher in patients with normal facial function compared with those with poor outcomes at the end of surgery (p < 0.01). The postdissection to predissection ratios of maximal response amplitude, but not the stimulation thresholds, were indicative of a nerve conduction block and were significantly lower in the patient group with a poor outcome compared with the group with a normal facial outcome (p < 0.02).

[Advantage of facial rehabilitation after facial palsy]. / Béncfices de la rééducation d'une paralysie faciale périphérique.

Visible and immediate trauma, facial palsy (FP) covers functional but also psychological damage and it is essential to evaluate before a comprehensive therapeutic care tailored. Few patients, however, are emerging with a prescription for rehabilitation after a consultation. Why? This rehabilitation is it ignored? Is it absolutely necessary? It is evident in the extension of medical care to minimize the effects. Yet the foundation of rehabilitation is sadly little known and often poorly enforced. In addition to its specificity, this therapy preceded by a report called "pretreatments offers a prognosis for recovery to patient" regardless of the origin and degree of involvement of the PF.

Intraoperative electromyography and surgical observations as predictive factors of facial nerve outcome in vestibular schwannoma surgery.

OBJECTIVE: To evaluate the predictive value of electromyographic recordings for the immediate facial nerve outcome after solitary vestibular schwannoma (VS) removal. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral center. PATIENTS AND METHODS: From November 2005 to July 2007, 120 operated solitary VSs monitored by NIM Response 2.0 (Medtronic, Xomed, Jacksonville, FL, USA) were included. Intraoperative direct facial nerve stimulation at the brainstem (proximal pre site) before resection and at the brainstem (proximal post and distal sites, respectively) and internal acoustic meatus after resection were performed. Intraoperative recordings were performed on 4 muscles: Frontalis, Orbicularis oculi, Orbicularis oris, and chin muscles (CM). Postoperative facial function (House-Brackmann classification) was evaluated at postoperative Days (D) 2, 8, and 30. Grades 1 or 2 were considered as a good result. RESULTS: A good postoperative facial function was obtained in 71, 63, and 77% at postoperative D2, D8, and D30, respectively. Maximal conduction block was found at Day 8. Poor facial nerve outcomes were observed for large tumor with a facial nerve superior to the tumor with a strong adhesion to the nerve. With a stimulation threshold at proximal site after proximal site tumor resection at less than or equal to 0.04 mA, a good facial function was observed in 77% at Day 8. Using these criteria together with CM responses greater than 800 muV to supramaximal stimulation at (proximal post site) and a proximal/distal post ratio at CM response greater than 0.6, 93% of patients presented with a good facial function at Day 8. CONCLUSION: Using CM recording stimulation and supramaximal stimulation of the facial nerve in combination with thresholds seem to increase the predictive value of the monitoring for the immediate facial nerve function for VS surgery.

Do facial nerve displacement pattern and tumor adhesion influence the facial nerve outcome in vestibular schwannoma surgery?

OBJECTIVE: To assess the nerve facial displacement by a vestibular schwannoma and nerve adhesion to tumor as predictive factors of facial function outcome. STUDY DESIGN: A prospective cohort study. SETTING: Tertiary referral center. PATIENTS: Ninety-six patients undergoing a solitary vestibular schwannoma surgery during 2005 were included. Data concerning tumor size (Stage 1, intracanalicular; Stage 2, < or =15 mm in the cerebellopontine angle [CPA]; Stage 3, 15-30 mm in the CPA; and Stage 4, >30 mm in the CPA), intraoperative facial nerve displacement (Type 1, anterior to the tumor; Type 2, anterior and superior to the tumor and separated from the cochlear nerve; Type 3, superior to the tumor; and Type 4, posterior to the tumor), degree of tumor adhesion (weak, intermediate, and strong) and postoperative facial function according to the House and Brackmann classification at days 10, 30, 90 and 180 were collected. RESULTS: A good facial function (Grade 1 or 2) was reported in 73% at postoperative Day 180. Univariate analysis showed that facial outcome was better in small tumors, in displacement Types 1 and 2 (Type 1, 46%; Type 2, 34%; and Type 3, 20%), and in tumors with weak and intermediate adhesion (weak, 10%; intermediate, 38%; and strong, 52%). Facial nerve displacement and adhesion were related to tumor stage. The combination of tumor stage, adhesion, and nerve displacement in a logistic regression model was highly predictive of postoperative facial function. CONCLUSION: Facial nerve displacement and nerve adhesion to tumor are significant predictive factors of facial function outcome after vestibular schwannoma surgery in addition to tumor size.

Temporal breach management in chronic otitis media.

In a retrospective study performed at the Otolaryngology, Head and Neck Surgery Department, Pitié-Salpêtrière Hospital, Paris from 1991 to March 2007, we determined surgical procedures for the treatment of tegmen breaches in chronic otitis media. Forty-two cases were examined: 76% corresponded to chronic otitis media with cholesteatoma, and 24% to chronic otitis media without cholesteatoma. Twenty-eight cases were operated using a combined approach, eight cases using a single suprapetrous approach, and six cases using a transmastoid approach. A total of 33% of the cases showed a meningocele or a meningoencephalocele treated through either a combined or a suprapetrous approach. No recurrence or neural/meningeal infectious involvement was found after a mean time of 43 months in the 36 long-term follow-up cases operated through the combined or suprapetrous approaches. Two cases included in the study were a loss to follow-up. Three of the former cases had already been operated for supracentimetric fissure using lower approach. Two out of the six patients operated using lower approach presented post surgery cerebrospinal fluid otorrhea. Combined or suprapetrous approaches seem to be best adapted to the treatment of supracentimetric or recurrent tegmen breaches, as well as to the precise examination and repair of meningeal lesions. Treatment for tegmen breach can be achieved in a single intervention, even when there is an ongoing infection of the middle ear. The mastoid approach should be used only for infracentimetric defects when there is no neural/meningeal lesion.

Related timing for peripheral and central plasticity in hypoglossal-facial nerve anastomosis.

The aim of this work was to determine the role of peripheral facial muscle reinnervation in the central reorganization of the blink reflex (BR) after hypoglossal-facial anastomosis (HFA). An electrophysiological study was performed on seven patients who underwent HFA after facial nerve transection during surgery for acoustic neuroma. HFA was performed within 15 days after surgery in five patients (group 1) and later for the two others (group 2). We studied the motor responses (MR) and the BR evoked on the affected side, before and over 3 years after the HFA. The MR appeared by the third month for the first group, and by the sixth and twelfth for the second group. After 36 months, the amplitude of MR was significantly higher than its control value, showing hyperinnervation of the facial muscles. Study of the BR evoked only an R1-type blink response that was observed 4 and 6 months after the MR for groups 1 and 2, respectively. This central reorganization appeared closely correlated with muscle reinnervation and its related timing. The occurrence of peripheral nerve-muscle contacts seems to be a necessary condition for reorganization of the trigemino-hypoglossal-facial reflex.

An in situ hybridization and immunofluorescence study of GABA(A) and GABA(B) receptors in the vestibular nuclei of the intact and unilaterally labyrinthectomized rat.

We investigated whether the production of the sixteen subunits of the GABA(A) receptors and of the different variants of GABA Breceptors are modulated in rat medial vestibular nuclei (MVN) following unilateral labyrinthectomy. Specific alpha1-6, beta1-3, gamma1-3 and delta GABA(A) and GABA(B) B1 and B2receptor radioactive oligonucleotides were used for in situ hybridization to probe sections of rat vestibular nuclei. Specific antibodies against alpha1, beta2, beta3 and gamma2 subunits of GABA(A) receptors and against GABA( B)receptors were also used to detect a potential protein expression modulation. No asymmetry was observed by autoradiography in the intact and deafferented MVN at any time (5 h to 8 days) following the lesion and for any of the oligonucleotide probes used. Also, no difference in the alpha1, beta2, beta3 and gamma2 of the GABA(A) and in the GABA(B) receptor immunohistochemical signal could be detected between the intact and deafferented vestibular nuclei at any time following the lesion. Our data suggest that GABA(A) and GABA Breceptor density changes most probably were not involved in the early stage of the vestibular compensation process, i.e., in the restoration of a normal resting discharge of the deafferented vestibular neurons and consequently in the recovery of a normal posture and eye position.