Intratemporal facial nerve schwannoma: clinical presentation and management

A novel perspective on geniculate ganglion fossa: Cone beam computed tomography analysis of pneumatization and dehiscence

OBJECTIVE

This study aimed to analyze the prevalence and patterns of geniculate ganglion fossa (GGF) pneumatization, as well as the dehiscence and thickness of its tegmen, while evaluating their anatomical correlations. The assessment was conducted using two coronal planes aligned with the histological division of the GGF.

METHODS

Seventy cone-beam computed tomography (CBCT) scans (140 sides) were analyzed. Two coronal planes through the GGF were used, based on its histology: an anterior plane through the ganglion and a posterior plane through the facial nerve fibers. Pneumatization was assessed by identifying air cells within a 2 mm range of the GGF, examining its superior, lateral, medial, and inferior walls, and classifying the pneumatization patterns. The GGF tegmen dehiscence was evaluated in both planes and categorized as intact, partial, or total. Based on combined findings, five dehiscence types were defined, ranging from type 1 (no dehiscence) to type 5 (complete dehiscence in both coronal planes). The classification reflects the progressive extent of tegmen dehiscence across these planes.

RESULTS

Type 1 (intact GGF tegmen) was the most common, observed in 47.1 % of cases, while partial dehiscence (types 2-4) and complete dehiscence (type 5) were found in 39.3 % and 13.6 % of cases, respectively. Pneumatization was predominantly lateral (95 %), corresponding to the epitympanum, while superior pneumatization within the GGF tegmen occurred in 33.6 % of cases. Circumferential pneumatization, involving all GGF walls, was very rare (1 case, left side). Superior pneumatization correlated with a significantly greater mean GGF tegmen thickness compared to non-pneumatized cases (2.6 ± 1.3 mm vs. 1.2 ± 0.7 mm). GGF tegmen dehiscence did not significantly influence tegmen tympani dehiscence (prevalence of 72.9 %), indicating no clear association.

CONCLUSION

Assessing GGF morphology in anterior and posterior planes, thus correlated with the histological division of its neural content, can enhance preoperative planning and help predict and minimize surgical risks in this complex and delicate region.

Long-term follow-up results of facial nerve schwannoma with good facial nerve function: a multicenter study

PURPOSE

Facial nerve schwannomas (FNSs) are rare intracranial tumors, and the optimal management of these tumors remains unclear. We investigated the long-term follow-up results of FNS with good facial nerve function.

METHODS

At nine medical centers in the Korean Facial Nerve Study Group, 43 patients undergoing observation periods longer than 12 months for FNS with good facial nerve function (House-Brackmann grade ≤ II) were enrolled, and clinical and radiographic data were obtained for these cases.

RESULTS

The mean follow-up period was 63 months. In the majority of cases, tumors involved multiple segments (81.4%) and only eight cases were confined to a single site. There were no cases where the tumor was confined to the extratemporal region. Tumor size increased slightly, with an average estimated change of 0.48 mm/year. Twenty (46.5%) of 43 patients showed no change in tumor size. Seven patients (16.3%) showed worsening House-Brackmann (H-B) grade, of which two patients deteriorated from H-B grade I to II, four worsened to grade III, and one deteriorated to grade IV. The remaining 36 patients (83.7%) showed no change in facial nerve function. There was no difference in H-B grade according to tumor size at the time of diagnosis or change in tumor size.

CONCLUSION

We conducted a large-scale observational study of FNS with good facial nerve function. Our study showed that many patients maintained facial nerve function during long-term follow-up. Conservative management with regular examination and imaging can be an appropriate option for managing FNS with good facial nerve function.

Detailed Radiomorphometric Analysis of the Surgical Corridor for the Suprageniculate Approach

BACKGROUND

The suprageniculate fossa (SGF) is located between the geniculate ganglion, the middle cranial fossa (MCF) and the anterior semicircular canal (ASCC). An endoscopic transcanal approach has been recently proposed to treat the different lesions in this area. The aim of the study is to describe the anatomical pathway of this approach by measuring the dimensions of its boundaries while checking their correlation with the pneumatization of the SGF area.

METHODS

This is a retrospective anatomical analysis of Cone Beam CT scans of 80 patients, for a total of 160 temporal bones analyzed. Two checkpoints were measured for the SGF route, as an internal and an external window. These are triangles between the MCF dura, the geniculate ganglion and the ASCC on parasagittal and axial planes. The pneumatization of the SGF was also assessed, classified and correlated with the measured dimensions.

RESULTS

The depth of the SGF was 7.5 ± 1.8 mm. The width of the external window was 7.5 ± 1.9, 5.6 ± 2.4 and 1.6 ± 1.6 mm for the posterior, middle and anterior points of measurement, respectively. The height of the internal window was 7.6 ± 1.2, 4.5 ± 1.5 and 1.7 ± 1.7 mm for the posterior, middle and anterior points of measurement, respectively. Type A pneumatization was found in 87 cases, type B in 34 and type C in 39. The degree of pneumatization directly correlated to the depth and height of the fossa.

CONCLUSIONS

The suprageniculate approach route is defined by the internal and external windows which should be evaluated during a pre-surgery imaging assessment. The detailed anatomy of the approach and the novel classification of the pneumatization of the SGF are here described which may be useful to plan a safer procedure with minimal complications.

Facial Reanimation After Intratemporal Facial Nerve Schwannoma Resection: A Systematic Review

Objective: To systematically analyze the outcomes of reanimation techniques that have been described for patients undergoing non-fascicle sparing resection of intratemporal facial schwannomas. Methods: A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines of the PubMed, MEDLINE, and Cochrane Central Register of Controlled Trials databases. Results: Eight hundred forty studies were screened with 22 meeting inclusion criteria comprising 266 patients. Most facial nerve reanimations (81.2%) were performed using an interposition nerve graft. The remaining patients underwent hypoglossal-facial nerve transposition (13.9%), primary anastomosis (3.4%), and free muscle transfer (0.1%). Of the reported interposition grafts, the two most utilized were the great auricular (113/199) and sural (86/199) nerves. Interposition nerve grafts resulted in significantly better outcomes in facial nerve function postoperatively than hypoglossal-facial transposition (3.48 vs. 3.92; p < 0.01). There was no difference between interposition grafts. Conclusion: This study systematically reports that interposition nerve grafts, after resection of intratemporal facial schwannoma, result in superior outcomes than hypoglossal-facial nerve transposition in these patients.

Characteristics and Management of Facial Nerve Schwannomas and Hemangiomas

OBJECTIVES

To characterize facial nerve (FN) schwannomas (FNSs) and FN hemangiomas (FNHs) and their clinical features and management strategies, and to describe the results of cable nerve grafting after FN sectioning during tumor removal.

METHODS

This retrospective study included 84 FNS cases and 42 FNH cases managed between July 1989 and July 2020 at a quaternary referral center for skull base pathology. Clinical details, locations, management, and results of cable nerve grafting at 1 year and during an average period of 3.12 years were evaluated. Sural nerve interpositioning was performed for patients who experienced FN paralysis for less than 1 year and underwent nerve sectioning during tumor removal.

RESULTS

FNSs more often involved multiple segments compared with FNHs. The cerebellopontine angle and the mastoid segments were involved in 16 (19.1%) and 34 (40.5%) FNS cases, respectively; however, the cerebellopontine angle and the mastoid segments were involved in 0 and 7 (16.7%) FNH cases, respectively. Sectioned nerves of 99 patients (78.6%) were restored using interposition cable grafting. At the last follow-up evaluation, 56.3% of FNSs and 60.7% of FNHs attained House-Brackmann (HB) grade III. Lower preoperative HB grades were associated with poorer postoperative outcomes. For FNSs, the mean HB grades were 4.13 at 1 year postoperatively and 3.75 at the last follow-up evaluation ( p = 0.001); however, for FNHs, the mean HB grades were 4.04 postoperatively and 3.75 at the last follow-up evaluation. Therefore, extradural coaptation yielded better outcomes.

CONCLUSION

FNSs can occur along any part of the FN along its course, and FNHs are concentrated around the area of geniculate ganglion. The results of cable inter positioning grafts are better in patients with preoperative FN-HB-III or less when compared with higher grades. The outcome of the interpositioning continues to improve even after 1 year in extradural coaptation.

Facial Nerve Neurolymphomatosis That Extends to Both the Brainstem and Extracranial Regions

A 73-year-old female developed right facial paralysis of House-Brackmann (H-B) grade III and was diagnosed with Bell's palsy. After three months of steroid therapy, she developed progressive hearing loss, and an MRI revealed a tumor in the right internal auditory canal. Within a few months, the right facial nerve palsy recurred, and the patient was treated with Gamma Knife radiosurgery. The tumor in the irradiated region disappeared, but new dysphagia was observed, and a right parotid gland tumor was detected for the first time. Tumors of the right parotid gland and the digastric muscle of the jaw were surgically resected, and a diagnosis of diffuse large B-cell lymphoma was made. The tumor had invaded the cranial nerves and brainstem region, and the patient did not wish to undergo further medical therapy. This was a case of malignant lymphoma that started as facial paralysis and invaded the brainstem, and testing for possible lymphoma at an early stage prior to radiotherapy was desirable.

Giant Facial Nerve Schwannoma with Extra-Temporal Involvement: A Series Of Two Cases

Facial nerve schwannoma is a rare benign tumor of temporal bone arising from the schwann cells with incidence of 0.8%. They can arise from any segment of facial nerve with geniculate ganglion being the most common and labyrinthine segment the second commonest site. Intra-temporal location is common while only 9% of the cases have extra-temporal or parotid gland involvement. Bony remodeling or scalloping of the facial canal and the surrounding bone is the classic radiological feature of schwannoma. However schwannomas of temporal bone location can show bony erosions. The management option depends on site, extent, facial nerve function and hearing status. Surgery is reserved for large tumors with poor facial functions, hearing loss and giddiness. Giant facial nerve schwannoma with extra-temporal involvement is a rare entity with only handful number of cases reported in the literature. We present a series of two cases of giant facial nerve schwannoma with parotid gland involvement.

[Clinical analysis of 32 cases of facial nerve schwannomas]

Objective:To elucidate the clinical characteristics, surgical strategy, facial nerve repair methods and outcomes of facial nerve schwannomas（FNS）. Methods:The clinical data of patients with FNS treated between January 2010 and December 2018 at Sun Yat-sen Memorial Hospital of Sun Yat-sen University were retrospectively collected, including the sidedness of FNS, clinical manifestations, imaging data, the extent of tumor, clinical management, preoperative and postoperative facial nerve function. Results:The major clinical manifestations of the 32 patients with FNS were facial palsy（27, 84.4%）, hearing loss（27, 84.4%）, tinnitus（22, 68.8%）, ear mass（15, 46.9%）, and stuffy feeling in the ear（13, 40.6%） respectively. Thirty patients were preoperatively diagnosed with FNS and 2 patients were misdiagnosed. 31 patients underwent resection of FNS, except one patient who was selected for long-term follow-up observation. The choice of surgical approach was based on the location, extent and auditory function of the FNS involved as well as the patient's wishes. The surgical approach was decided based on the location and extent of the tumor: 9 patients were operated via the inferior temporal fossa type A（Fisch A） approach; 8 patients were operated via the mastoid approach; 7 patients were operated via the enlarged mastoid approach; 3 patients were operated via the combined mastoid-cranial middle fossa approach; 1 patient was operated via the cranial middle fossa approach; 3 patients were operated via the combined Fisch A-cranial middle fossa approach. 28 patients（87.5%） had FNS with multiple segments of facial nerve involved. The most involved segment was the vertical segment of the facial nerve（26, 81.3%）. 15 patients underwent facial nerve repair simultaneously, including 7 cases of auricular nerve-facial nerve graft and 8 cases of facial nerve-sublingual nerve anastomosis. 4 cases had improved facial nerve function after auricular nerve-facial nerve graft and 2 cases had improved function after facial nerve-sublingual nerve anastomosis. Among patients who underwent facial nerve repair,the best outcome was H-B Ⅲ. Conclusion:The patients with FNS mainly presented with facial palsy and hearing loss. Temporal bone CT and cranial MR plain & enhanced scan served well to confirm the diagnosis. The improvement rate of postoperative facial nerve function was significantly higher in patients who underwent nerve repair than in those who did not. Hence, facial nerve repair should be considered. Compared with facial nerve-sublingual nerve anastomosis, auricular major nerve-facial nerve graft might be a better choice for improving postoperative facial nerve function.

Surgery versus radiosurgery for facial nerve schwannoma: a systematic review and meta-analysis of facial nerve function, postoperative complications, and progression

OBJECTIVE

Intracranial facial nerve schwannomas (FNS) requiring treatment are frequently recommended for surgery or stereotactic radiosurgery (SRS). The objective of this study was to compare facial nerve function outcomes between these two interventions for FNS via a systematic review and meta-analysis.

METHODS

A search of the Ovid EMBASE, PubMed, SCOPUS, and Cochrane databases from inception to July 2019 was conducted following PRISMA guidelines. Articles were screened against prespecified criteria. Facial nerve outcomes were classified as improved, stabilized, or worsened by last follow-up. Incidence was pooled by random-effects meta-analysis of proportions.

RESULTS

Thirty-three articles with a pooled cohort of 519 patients with FNS satisfied all criteria. Twenty-five articles described operative outcomes in 407 (78%) patients; 10 articles reported SRS outcomes in 112 (22%). In the surgical cohort, facial nerve function improved in 23% (95% CI 15%-32%), stabilized in 41% (95% CI 32%-50%), and worsened in 30% (95% CI 21%-40%). In the SRS cohort, facial nerve function was improved in 20% (95% CI 9%-34%), stable in 66% (95% CI 54%-78%), and worsened in 9% (95% CI 3%-16%). Compared with SRS, microsurgery was associated with a significantly lower incidence of stable facial nerve function (p < 0.01) and a significantly higher incidence of worsened facial nerve function (p < 0.01). Tumor progression and complication rates were comparable. Outcome certainty assessments were very low to moderate for all parameters.

CONCLUSIONS

Unfavorable facial nerve function outcomes are associated with surgical treatment of intracranial FNS, whereas stable facial nerve function outcomes are associated with SRS. Therefore, SRS should be recommended to patients with FNS who require treatment, and surgery should be reserved for patients with another indication, such as decompression of the brainstem. Further study is required to definitively optimize and validate management strategies for these rare skull base tumors.

Management of facial nerve schwannoma: when is the timing for surgery

PURPOSE

Although the estimated prevalence is extremely low, facial nerve schwannoma (FNS) is the most common primary tumor of the facial nerve (FN). In the present study, the outcome of surgical management in 18 patients with FNS was analyzed and an appropriate time for surgery was proposed.

MATERIALS AND METHODS

A total of 18 patients with FNS who underwent surgical management by a single surgeon from 1999 to 2018 were retrospectively analyzed.

RESULTS

Among the 18 patients, five had no facial paralysis before surgery. Near-total removal was performed in three cases, and two cases were managed with decompression. In 13 cases with various degree of preoperative facial palsy, nerve continuity was lost during surgery. FN was reconstructed using cable graft in ten cases, direct anastomosis in one case, and facial-hypoglossal nerve transfer in one case. Facial reanimation surgery without FN reconstruction was performed in one case due to a long-standing facial paralysis before surgery. Preoperative House-Brackmann (H-B) grade in all patients was significantly worse as tumor size increased. The correlation was not observed between the duration and severity of preoperative facial palsy. Analysis of 12 patients who underwent FN reconstruction revealed that all patients with good preoperative facial function (H-B grade II-III) recovered to H-B grade III after surgery (7/7, 100%). However, patients with poor preoperative facial function (H-B grade IV or worse) had only a 40% (2/5) chance of improving to grade III after surgery. Preoperative tumor size and duration of facial palsy did not affect postoperative final facial function.

CONCLUSION

We suggest that H-B grade III facial palsy is the best time for surgical intervention, regardless of the tumor size or duration of facial palsy.

Trends in the Management of Non-Vestibular Skull Base and Intracranial Schwannomas

The aim of this review is to analyze the latest trends in the management of non-vestibular skull base and intracranial schwannomas in order to optimize tumor control and quality of life. Non-vestibular cranial nerve schwannomas are rare lesions, representing 5–10% of cranial nerve schwannomas. Management decisions should be individualized depending on tumor size, location and associated functional deficits. Generally, large sized schwannomas exerting significant mass effect with increased intracranial pressure are treated surgically. In some cases, even after optimal skull base resection, it is not possible to achieve a gross total resection because tumor location and extent and/or to reduce morbidity. Thus, subtotal resection followed by stereotactic radiosurgery or fractioned radiotherapy offers an alternative approach. In certain cases, stereotactic radiosurgery or radiotherapy alone achieves good tumor control rates and less morbidity to gross total resection. Finally, given the slow growth rate of most of these tumors, observation with periodic radiographic follow-up approach is also a reasonable alternative for small tumors with few, if any, symptoms.

Intratemporal facial nerve schwannomas: multicenter experience of 80 cases

PURPOSE

To provide more data on the clinical presentation and natural evolution of facial nerve schwannomas and to provide guidance for therapeutic decision making.

METHODS

A retrospective case review of eighty patients diagnosed with a facial nerve schwannoma between 1990 and 2018 in ten tertiary referral centers in Europe was performed. Patients' demographics, symptomatology, audiometry, anatomical site (segments involved), size and whenever possible volume measurement were registered.

RESULTS

At presentation, transient or persistent facial palsy was the most common symptom, followed by hearing loss. The schwannoma involved more than one segment in the majority of the patients with the geniculate ganglion being most commonly involved. Initial treatment consisted of a wait and scan approach in 67.5%, surgery in 30% and radiation therapy in 2.5% of the patients. Tympanic segment schwannomas caused mainly conductive hearing loss and were more prone to develop facial palsy at follow-up. Internal auditory canal or cerebellopontine angle schwannomas presented with significantly more sensorineural hearing loss.

CONCLUSIONS

Although modern imaging has improved diagnosis of this tumor, choosing the best treatment modality remains a real challenge. Based on the literature review and current findings, more insights into the clinical course and the management of facial nerve schwannomas are provided.

Facial nerve schwannoma mimicking chronic suppurative otitis media: A case report

RATIONALE

Facial nerve schwannoma (FNS) is a rare slow-growing nerve sheath tumor derived from Schwann cells. FNS with normal facial nerve function may sometimes be misdiagnosed as otitis media because of similar ontological symptoms such as purulence, tympanic membrane damage, and hearing loss.

PATIENT CONCERNS

A 68-year-old woman was referred to our department because of otorrhea and hearing loss in the right ear for 20 years. Otoscopy revealed abundant purulent secretions deep in the right external auditory canal, and granulation proliferation in the posterior part of membranae tensa. Audiogram showed a right mixed hearing loss with an 85-dB pure-tone average and 35-dB air-bone gap.

DIAGNOSIS

This patient was misdiagnosed as chronic suppurative otitis media before surgery. During surgery, a mass was found, and intraoperative frozen section histopathology confirmed an FNS.

INTERVENTIONS

This patient was subjected to mastoidectomy for curing chronic suppurative otitis media initially. During surgery, a mass was found attached and widely extended into the tympanic and mastoid segments. We removed most part of the mass, however found the mass deriving from the vertical part of the facial nerve. Intraoperative frozen section histopathology confirmed an FNS. So we removed the incurs and malleus, and searched for the edge of the mass. The mass involved multisegments of facial nerve including the tympanic, vertical and pyramidal segments. The tumor was removed completely, and nerves were repaired using greater auricular nerves.

OUTCOMES

After surgery, the patient had facial nerve paralysis of House-Brackmann (HB) Grade VI. Facial function recovered to HB Grade III at 30 months after surgery. The patient was followed up for 5 years. She had a facial function of HB grade III at the most recent follow-up.

LESSONS

FNS is rare and tend to be misdiagnosed. It is important to combine the imaging modalities of computed tomography and magnetic resonance imaging to evaluate FNS before surgery. The primary goal of managing FNS is to maintain normal facial function as long as possible; therefore, tailored strategy should be taken for managing FNS.

Management of Facial Nerve Schwannoma: A Multicenter Study of 50 Cases

Objective  In the management of facial nerve schwannoma (FNS), surgical tumor resection is now often being replaced with more conservative approaches, such as observation with serial imaging or stereotactic radiosurgery (SRS). Given the scarcity of these lesions, determining the optimal management of FNS remains challenging and subject of debate with multiple treatment approaches supported in the literature. Methods  A retrospective chart review was performed in two academic centers for patients diagnosed with FNS between 1996 and 2017. The clinical presentation, treatment modalities employed, tumor control rates, and facial nerve function (FNF) outcomes (House-Brackmann system) were assessed and analyzed. Results  The study comprised 50 adult patients. Initial treatment modalities included observation with serial clinicoradiologic review in 27 patients (54%), surgery in 17 patients (34%), and SRS in 6 patients (12%). The FNF were decreased in more than half of the patients who had surgery. Nonetheless, more than 80% of the patients who were initially managed with observation or SRS had stable or improved FNF. Conclusion  A prevailing trend toward more conservative treatment modalities for FNS has evolved over time, providing relatively long-term preservation of FNF. As there are multiple management options available, it is of paramount importance that the treating physician be familiar with all treatment modalities and outcomes and counsel patients appropriately. The surgery should be reserved for large tumors and poor FNF at initial presentation or follow-up while watchful observation with imaging is the treatment of choice for rest of the patients.

A retrospective study on facial nerve schwannomas: a disease with a high risk of misdiagnosis and hearing loss

The objective is to increase awareness of facial nerve schwannomas (FNSs). Clinical data from 32 cases with FNSs who received surgical treatment from 2005 to 2015 were reviewed retrospectively. The clinical data included age, sex, presentations, duration, facial nerve function, temporal-bone high-resolution computed tomography (CT) and magnetic resonance imaging (MRI) findings, surgical approaches, and postoperative histopathological examination. 16 men and 16 women were included, aged 7-69 years. The average age at diagnosis was approximately 44 years. The mean duration of disease was 65 months, and the mean tumor diameter was 22.4 mm. A tendency of multisegment involvement was observed in 29 FNS cases. Geniculate ganglion and tympanic segments were the most commonly involved segments. Meanwhile, the incidence of misdiagnosis of this disease was 50%. We observed that when FNSs involved the proximal portion of genicular ganglion, the hearing function tended to be worse than when the FNSs only involved the genicular ganglion and/or its distal portion (p < 0.05); in such cases, the hearing loss tended to become more severe with a longer duration of the disorder (p < 0.05). Multiple segment involvement is common in patients with FNS. We need to be more aware of the hearing function when FNSs involve the proximal portion of genicular ganglion. Misdiagnoses of FNS are common, and patients can be misdiagnosed with Bell's palsy, otitis media, or other diseases. Image studies should be conducted for differential diagnosis. Once the decision to perform surgical resection was made, reconstruction of the facial nerve should be considered.