Evolution in the assessment and management of trigeminal schwannoma

Management of large Trigeminal Schwannoma: long-term oncologic and functional outcome from a multicentric retrospective cohort

OBJECTIVE

Trigeminal schwannoma (TS), though a rare and benign tumor, becomes a significant surgical challenge due to its intricate location. This study aims to detail the long-term functional outcomes and tumor control post-surgical resection.

METHOD

We analyzed a multicentric retrospective cohort of 39 patients operated on for a TS in five tertiary centers between January 1993 and July 2022.

RESULTS

Six TS (15%) were in the middle fossa (type M), two (5%) in the posterior fossa (type P), and two (5%) were extracranial (type E). Twenty-nine (75%) were Dumbbell shape: Eighteen (47%) were MP type, seven (18%) were MPE type, and four (10%) were ME type. Fifth nerve symptoms were the foremost preoperative complaint: hypesthesia (51%), trigeminal neuralgia (36%), and paresthesia (30%). We report a favorable evolution course for 61% of preexisting deficits (half of patients with preoperative paresthesia and neuralgia improved while only 5% of preoperative hypesthesia improved). Postoperative hypesthesia was the most frequent de novo deficit 14 (74%) and resolved in solely half the cases. Various approaches were used according to tumor type. Gross total resection (GTR), Subtotal resection (STR), and partial resection (PR) were achieved in respectively 33% (N = 13), 10% (N = 4), and 56% (N = 22) of patients. The mean clinical and radiological FU was 63 months (12 - 283 months). GTR led to no sign of recurrence (mean FU: 60 months - range: 12-283 months). For STR or PR (67%): 23 (88%) were assigned to a Wait-&-rescan policy (WS group) which offered stability in 70% (N = 16). Three cases (8%) underwent a complementary GKS (GammaKnife) on the residual lesion (GK group) without tumor change.

CONCLUSION

For large TS, the completeness of resection must consider the potential functional burden of surgery. With giant infiltrating lesions, a strategy of planned subtotal resection, complemented by radiosurgery, either complementary or uppon regrowth, may provide similar oncological outcomes.

Trigeminal Schwannoma: A Retrospective Analysis of Endoscopic Endonasal Management, Treatment Outcomes, and Neuropathic Sequelae

Introduction  Trigeminal schwannomas (TS) are rare skull base tumors that have been associated with significant neuropathic sequalae for patients. The authors aim to evaluate the clinical features, treatment outcomes, and neuropathic sequelae following endoscopic endonasal approach (EEA) for TS. Methods  The study involves a retrospective review of patients who underwent EEA for resection of TS at a single academic institution between 2004 and 2020. Radiographic and clinical data were recorded and analyzed. Results  A total of 16 patients were abstracted, with a mean age at the time of surgery of 44 years with a slight female (1.83:1) predominance. Primary preoperative symptomatology included facial pain/neuralgia ( n  = 5, 31.3%), facial hypoesthesia ( n  = 4, 25.0%), and headache ( n  = 4, 25.0%). Following TS resection, patients were found to have facial hypoesthesia ( n  = 11, 68.8%), neuropathic keratopathy ( n  = 4, 25.0%), and mastication musculature atrophy ( n  = 3, 18.8%). Patients with preoperative facial pain/neuralgia ( n  = 5, 31.3%) were significantly more likely to try adjunctive pain therapies ( p  = 0.018) as well as seek pain consultation ( p  = 0.018). Patients with preoperative migraines ( n  = 2, 12.5%) were significantly more likely to trial adjunctive pain therapies ( p  = 0.025) and undergo evaluation with pain specialists ( p  = 0.025). Finally, patients with preoperative pharmacologic agent utilization were significantly more likely to trial adjunctive pain therapies ( p  = 0.036) and pursue pain consultation ( p  = 0.036). Conclusion  Some degree of trigeminal dysfunction may be more common than previously reported following EEA for TS resection. Factors that appear to play a role in the development of trigeminal dysfunction include pre-existing pain syndromes such as facial pain/neuralgia or headache and preoperative medication utilization.

Outcomes following surgical resection of trigeminal schwannomas: a systematic review and meta-analysis

Although typically benign, trigeminal schwannomas (TS) may require surgical resection when large or symptomatic and can cause significant morbidity. This study aims to summarize the literature and synthesize outcomes following surgical resection of TS. A systematic review was performed according to PRISMA guidelines. Data extracted included patient and tumor characteristics, surgical approaches, and postoperative outcomes. Odds ratios (OR) with corresponding 95% confidence intervals (CI) were used for outcome analysis. The initial search yielded 1838 results, of which 26 studies with 974 patients undergoing surgical resection of TS were included. The mean age was 42.9 years and 58.0% were female. The mean tumor diameter was 4.7 cm, with Samii type A, B, C, and D tumors corresponding to 33.4%, 15.8%, 37.2%, and 13.6%, respectively. Over a mean symptom duration of 29 months, patients presented with trigeminal hypesthesia (58.7%), headache (32.8%), trigeminal motor weakness (22.8%), facial pain (21.3%), ataxia (19.4%), diplopia (18.7%), and visual impairment (12.0%). Surgical approaches included supratentorial (61.4%), infratentorial (15.0%), endoscopic (8.6%), combined/staged (5.3%), and anterior (5.7%) or posterior (4.0%) petrosectomy. Postoperative improvement of facial pain (83.9%) was significantly greater than trigeminal motor weakness (33.0%) or hypesthesia (29.4%). The extent of resection (EOR) was reported as gross total (GTR), near total, and subtotal in 77.7%, 7.7%, and 14.6% of cases, respectively. Over a mean follow-up time of 62.6 months, recurrence/progression was noted in 7.4% of patients at a mean time to recurrence of 44.9 months. Patients with GTR had statistically significantly lower odds of recurrence/progression (OR: 0.07; 95% CI: 0.04-0.15) compared to patients with non-GTR. This systematic review and meta-analysis report patient outcomes following surgical resection of TS. EOR was found to be an important predictor of the risk of recurrence. Facial pain was more likely to improve postoperatively than facial hypesthesia. This work reports baseline rates of post-operative complications across studies, establishing benchmarks for neurosurgeons innovating and working to improve surgical outcomes for TS patients.

Hybrid endoscopic-microscopic surgery for dumbbell-shaped trigeminal schwannoma: case report and literature review

Background

The surgery of dumbbell-shaped trigeminal neurinomas (TN) remains one of the most formidable challenges for neurosurgeons because of its location at great depth in the cranium and proximity to vital neurovascular structures.

Objective

To describe the feasibility of a novel technique, synchronous endoscopy and microsurgery via combined far-lateral supracerebellar-infratentorial and subtemporal approach, for resection of this rare entity.

Methods

A 53-year-old women presented with progressive left facial numbness for 2 months. Imaging examinations revealed a left-sided dumbbell-shaped TN afflicting the middle and posterior cranial fossa, and a single-stage combined multiportal endoscopic microscopic approach was attempted for tumor resection. Initially, a purely endoscopic far-lateral supracerebellar-infratentorial approach was used to remove the posterior fossa component with the aid of tentorium incision. Subsequently, a microsurgical subtemporal interdural approach was performed for the exposure and separation of tumor within the Meckel cave. Finally, the tumor was pushed into the porus trigeminus under microscopy, thus enabling tumor extraction for the supracerebellar space under endoscopy without anterior petrosectomy.

Results

The patient evolved favorably without additional neurological deficit after surgery, and postoperative imaging showed a complete resection of the tumor.

Conclusion

We describe the first account of multi-corridor hybrid surgery for removal of TN in a dumbbell configuration, which enables one-stage total tumor removal with minimal added morbidity. This hybrid technique may be an effective piece of the surgeon's armamentarium to improve outcomes of patient with complex skull-base lesions. Further studies with larger case numbers are warranted to confirm the prognostic significance of this technique.

Gamma knife radiosurgery for trigeminal schwannomas: A systematic review and meta-analysis

BACKGROUND

Gamma knife radiosurgery (GKRS) has been deemed as the gold standard stereotactic radiosurgery (SRS) mode for the treatment of intracranial tumors, cerebrovascular diseases and brain functional diseases. Our study was aimed to systematically evaluate the efficacy, safety, and complications of gamma knife radiosurgery for trigeminal schwannomas.

METHOD

We performed a systematic review and meta-analysis to analyze the clinical outcomes of patients with trigeminal schwannomas treated primarily or adjunctly with GKRS. We searched two databases, Pubmed and Embase, for studies published before January 1, 2021, using GKRS for trigeminal schwannomas. Studies reporting treatment of other schwannomas, or other forms of SRS such as linear accelerator and Cyberknife were excluded to reduce its heterogeneity.

RESULTS

Our search achieved 351 studies, of which 35 were assessed for full-text eligibility. 19 studies were included in the meta-analysis. 456 of 504 patients (0.94, 95% CI 0.91-0.96, I² = 3.02%, p < 0.01) from 18 studies had local control, and 278 of 489 patients (0.63, 95%CI 0.48-0.78, I² = 88.75%, p < 0.01) from 16 studies experienced tumor regression or disappearance. 231 of 499 patients (0.50, 95% CI 0.37-0.62; I² = 83.89%, P < 0.01) from 17 studies had clinical symptoms improved. There was no significant difference in tumor control between those treated with GKRS as either primary treatment or adjuvant to surgery(p = 0.390).

CONCLUSION

GKRS is an efficacious primary and adjuvant method of treating trigeminal schwannomas, with reliable tumor control rates. Randomized controlled trials are needed to further and comprehensively evaluate the benefit-to-risk ratio of gamma knife radiosurgery.

Genetic Events and Signaling Mechanisms Underlying Schwann Cell Fate in Development and Cancer

In this review, we describe Schwann cell development from embryonic neural crest cells to terminally differentiated myelinated and nonmyelinated mature Schwann cells. We focus on the genetic drivers and signaling mechanisms mediating decisions to proliferate versus differentiate during Schwann cell development, highlighting pathways that overlap with Schwann cell development and are dysregulated in tumorigenesis. We conclude by considering how our knowledge of the events underlying Schwann cell development and mouse models of schwannoma, neurofibroma, and malignant peripheral nerve sheath tumor can inform novel therapeutic strategies for patients with cancers derived from Schwann cell lineages.

Surgical Outcome of Trigeminal Schwannomas

Simple Summary

Trigeminal schwannomas are the most common among non-vestibular schwannomas. Treatment of trigeminal schwannomas may be challenging due to critical anatomical relations and involvement of different aspects of the skull base. Advances in microsurgery have led to improved outcomes over the last decades, whereas in contrast, some advocate stereotactic radiotherapy as an effective therapy, controlling the tumor volume with few complications. In this manuscript, we present outcome and adverse events in a contemporary cohort of trigeminal schwannomas and discuss surgical advantages and disadvantages of different performed classic skull-base approaches.

Abstract

(1) Background: As resection of trigeminal schwannomas is challenging, due to anatomical involvement of the anterior, middle and posterior fossa, the appropriate approach is important. We report our experience with surgical resection of trigeminal schwannomas by simple and classic skull-base approaches. (2) Methods: We performed a retrospective single-center study including patients who underwent surgery for trigeminal schwannoma tumors between June 2007 and May 2020, concentrating on surgical technique, extent of resection, postoperative outcome and complications. (3) Results: We included 13 patients (median age 57.5 with range of 36-83 years, 53.8% (7/13) female. The most common preoperative clinical presentations were facial pain in six (46.2%), hypoacusis in four (30.8%), trigeminal nerve hypesthesia in 11 (V1 46.2% (6/13), V2 (61.5% (8/13), V3 46.2% (6/13)) and headache in three (23.1%) patients. In three cases, the tumor was resected in a two-stage technique. The intradural subtemporal approach was performed in six cases, the extradural technique in two cases, the retrosigmoid approach in five cases, a Kawase approach in two cases and the transnasal endoscopic approach in one case. The gross total resection rate was 76.9% (10/13) and the median follow-up time 24.0 (0–136) months. Three (23.1%) patients developed postoperative anesthesia in at least one branch of the trigeminal nerve. Trigeminal motor function was preserved in 11 (84.6%) patients. Ten of the 11 patients (76.9%) who reported decreased gustation, cerebellar ataxia, visual impairment, or headache improved postoperatively. Two (15.4%) patients exhibited minimal facial palsy (House and Brackmann II–III), which resolved during the follow-up. The total adverse event rate requiring surgical intervention during follow-up was 7.7%. Surgery-related mortality was 0%. (4) Conclusions: Trigeminal schwannomas are rare benign lesions with intra- and extracranial extension. Considering the low operative morbidity and satisfying functional outcome, gross total resection of trigeminal schwannomas is achievable by classic, but also individually tailored approaches. More invasive or combined techniques were not needed with meticulous surgical planning.

Schwannoma on the nasal dorsum and tip with sensory changes

Schwannomas, which originate from Schwann cells in the peripheral nervous system, are slowgrowing and uncommon benign tumors. Most schwannomas (90%) occur in isolation, and multiple occurrences are a characteristic feature of neurofibromas. Schwannomas of the nose and nasal tip are particularly unusual. Although a few cases of schwannomas of the sinusoidal tract and nasal septum have been reported, schwannomas arising from the nasal dorsum area and tip are extremely rare. Sensory abnormalities are also a very rare symptom. We excised a schwannoma on the nasal dorsum through direct incision and a schwannoma on the nasal tip through open rhinoplasty. No postoperative complications involving recurrence, hematoma, or infection occurred. The possibility of neurological changes should be considered in cases of an abnormality in the peripheral nervous system. Schwannoma must be kept in mind as a possible cause of neurological changes localized to a specific dermatome, and should always be considered in the differential diagnosis of a mass on the nose.

Endoscopic transorbital and endonasal approach for trigeminal schwannomas: a retrospective multicenter analysis (KOSEN-005)

OBJECTIVE

Trigeminal schwannomas are rare neoplasms with an incidence of less than 1% that require a comprehensive surgical strategy. These tumors can occur anywhere along the path of the trigeminal nerve, capable of extending intradurally into the middle and posterior fossae, and extracranially into the orbital, pterygopalatine, and infratemporal fossa. Recent advancements in endoscopic surgery have suggested a more minimally invasive and direct route for tumors in and around Meckel's cave, including the endoscopic endonasal approach (EEA) and endoscopic transorbital superior eyelid approach (ETOA). The authors assess the feasibility and outcomes of EEA and ETOA for trigeminal schwannomas.

METHODS

A retrospective multicenter analysis was performed on 25 patients who underwent endoscopic surgical treatment for trigeminal schwannomas between September 2011 and February 2019. Thirteen patients (52%) underwent EEA and 12 (48%) had ETOA, one of whom underwent a combined approach with retrosigmoid craniotomy. The extent of resection, clinical outcome, and surgical morbidity were analyzed to evaluate the feasibility and selection of surgical approach between EEA and ETOA based on predominant location of trigeminal schwannomas.

RESULTS

According to predominant tumor location, 9 patients (36%) had middle fossa tumors (Samii type A), 8 patients (32%) had dumbbell-shaped tumors located in the middle and posterior cranial fossae (Samii type C), and another 8 patients (32%) had extracranial tumors (Samii type D). Gross-total resection (GTR, n = 12) and near-total resection (NTR, n = 7) were achieved in 19 patients (76%). The GTR/NTR rates were 81.8% for ETOA and 69.2% for EEA. The GTR/NTR rates of ETOA and EEA according to the classifications were 100% and 50% for tumors confined to the middle cranial fossa, 75% and 33% for dumbbell-shaped tumors located in the middle and posterior cranial fossae, and 50% and 100% for extracranial tumors. There were no postoperative CSF leaks. The most common preoperative symptom was trigeminal sensory dysfunction, which improved in 15 of 21 patients (71.4%). Three patients experienced new postoperative complications such as vasospasm (n = 1), wound infection (n = 1), and medial gaze palsy (n = 1).

CONCLUSIONS

ETOA provides adequate access and resectability for trigeminal schwannomas limited in the middle fossa or dumbbell-shaped tumors located in the middle and posterior fossae, as does EEA for extracranial tumors. Tumors predominantly involving the posterior fossa still remain a challenge in endoscopic surgery.

Cystic trigeminal schwannomas

Trigeminal Schwannomas are less than 1% of intracranial tumors, of which only 7% have a cystic component. We documented 2 cases of males with cystic trigeminal Schwannomas, their symptoms, the diagnosis process and the imaging characteristics. In addition, a review of the literature is performed, with emphasis on the radiological classification of this rare entity, that constitutes a diagnostic challenge for the radiologist, who has an essential role in the approach to the disease and therefore in its management.

Denervation of the Eustachian Tube and Hearing Loss Following Trigeminal Schwannoma Resection

Objectives To discuss eustachian tube dysfunction (ETD) as a cause of hearing loss and to discuss its pathogenesis following resection of trigeminal schwannomas.

Methods Presented herein are two cases of trigeminal schwannoma that were resected surgically with sacrifice of the motor branch of the trigeminal nerve. Neither of the cases had evidence of extracranial extension nor preoperative ETD. Both patients developed ETD and have been followed without evidence of schwannoma recurrence.

Conclusions Trigeminal schwannomas are rare tumors that typically require surgical resection. Hearing loss is a potential postsurgical deficit and warrants evaluation by an otolaryngologist with consideration given to a preoperative audiogram. ETD as a result of trigeminal motor branch sacrifice should be included in the differential diagnosis of postoperative hearing loss in this patient subset as it may be reversed with placement of a tympanostomy tube.

Surgical management of trigeminal schwannomas: defining the role for endoscopic endonasal approaches

OBJECT

Because multiple anatomical compartments are involved, the surgical management of trigeminal schwannomas requires a spectrum of cranial base approaches. The endoscopic endonasal approach to Meckel's cave provides a minimal access corridor for surgery, but few reports have assessed outcomes of the procedure or provided guidelines for case selection.

METHODS

A prospectively acquired database of 680 endoscopic endonasal cases was queried for trigeminal schwannoma cases. Clinical charts, radiographic images, and long-term outcomes were reviewed to determine outcome and success in removing tumor from each compartment traversed by the trigeminal nerve.

RESULTS

Four patients had undergone endoscopic resection of trigeminal schwannomas via the transpterygoid approach (mean follow-up 37 months). All patients had disease within Meckel's cave, and 1 patient had extension into the posterior fossa. Gross-total resection was achieved in 3 patients whose tumors were purely extracranial. One patient with combined Meckel's cave and posterior fossa tumor had complete resection of the extracranial disease and 52% resection of the posterior fossa disease. One patient with posterior fossa disease experienced a sixth cranial nerve palsy in addition to a corneal keratopathy from worsened trigeminal neuropathy. There were no CSF leaks. Over the course of the study, 1 patient with subtotal resection required subsequent stereotactic radiosurgery for disease progression within the posterior fossa.

CONCLUSIONS

Endoscopic endonasal approaches appear to be well suited for trigeminal schwannomas restricted to Meckel's cave and/or extracranial segments of the nerve. Lateral transcranial skull base approaches should be considered for patients with posterior fossa disease. Further multiinstitutional studies will be necessary for adequate power to help determine relative indications between endoscopic and transcranial skull base approaches.

Endoscopic Endonasal Resection of Trigeminal Schwannomas

The surgical management of trigeminal schwannomas (TNs) entails the use of a variety of cranial base approaches for their effective surgical management. Although an extended middle fossa or posterior petrosal approach may be more appropriate for disease with primarily posterior fossa involvement, the expanded endoscopic approaches are suited for tumors with predominately middle fossa and/or extracranial involvement along the V2 and V3 divisions and limited posterior fossa extension. The endoscopic endonasal resection of TNs within the middle fossa, pterygopalatine fossa, and infratemporal fossa is reviewed in this article with a brief discussion of reported outcomes.

A suggestion of modified classification of trigeminal schwannomas according to location, shape, and extension

Background

Comprehensive knowledge of the anatomical features of trigeminal schwannomas (TSs) is essential in planning surgery to achieve complete tumor resection. In the current report, we propose a modified classification of TSs according to their location of origin, shape, and extension into the adjacent compartment, and discuss appropriate surgical strategies with this classification.

Methods

We retrospectively analyzed 49 patients with TS who were treated surgically by a single neurosurgeon at the Asan Medical Center between 1993 and 2013.

Results

There were 22 males and 27 females, with the median age of 40 years (range, 21-75 years). Median tumor size was 4.0 cm in diameter (2.0-7.0 cm). Tumors were classified as follows: Type M (confined to the middle fossa; 8 cases, 19.0%), P (confined to the posterior fossa; 2 cases, 4.8%), MP (involving equally both middle and posterior fossae; 5 cases, 11.9%), Mp (predominantly middle fossa with posterior fossa extension; 6 cases, 14.3%), Pm (predominantly posterior fossa with middle fossa extension; 16 cases, 38.1%), Me (predominantly middle fossa with extracranial extension; 4 cases, 9.5%). Surgical approach was chosen depending on the tumor classification. More specifically, a frontotemporal craniotomy and extradural approach with or without zygomatic or orbitozygomatic osteotomy was applied to M- or Mp-type tumors; a lateral suboccipital craniotomy with or without suprameatal approach was applied to the majority of P- or Pm-type tumors; and a posterior transpetrosal approach was used in four tumors (three Pm and one MP). Gross total resection was achieved in 95.9% of patients, and the overall recurrence rate was 4.1% (2 patients). Postoperatively, trigeminal symptoms were improved or unchanged in 51.0% of cases (25 patients). Surgical complications included meningitis (5 patients) and cerebrospinal fluid leakage (3 patients). There was no mortality.

Conclusion

TSs are well to be classified with our modified classification and able to be removed effectively and safely by selecting appropriate surgical approaches.

Endoscope-Assisted Retrosigmoid Intradural Suprameatal Approach for Surgical Treatment of Trigeminal Schwannomas

BACKGROUND:

Trigeminal schwannomas are the most common intracranial nonvestibular schwannomas, and the dumbbell-shaped subtype is the most challenging.

OBJECTIVE:

To evaluate the efficiency and safety of the endoscope-assisted retrosigmoid intradural suprameatal approach (EA-RISA) for dumbbell trigeminal schwannomas and to compare EA-RISA with classic RISA.

METHODS:

A retrospective study of all patients with trigeminal schwannomas was performed with a focus on dumbbell tumors. Tumors were classified according to a modified Samii classification. Extent of tumor removal, outcome, and morbidity rates in the 2 subgroups were compared.

RESULTS:

Twenty patients were enrolled: 8 had dumbbell-shaped tumors (type C1), 8 had middle fossa tumors (A1-3), 3 had extracranial extension (D2), and 1 had posterior fossa tumor. Gross total resection was achieved in 15 and near-total resection in 5 patients. In 4 patients with dumbbell tumors, the classic RISA (Samii approach) was used; EA-RISA was used in the other 4 patients. The extent of petrous apex drilling was determined individually on the basis of the anatomic variability of suprameatal tubercle and degree of tumor-induced petrous apex erosion; in 2 patients, only minimal drilling was needed. The endoscope was applied after microsurgical tumor removal and in 3 of 4 patients revealed a significant unrecognized tumor remnant in the anterolateral and superolateral aspects of the Meckel cave. Thus, the EA-RISA technique allowed gross total resection of the tumor.

CONCLUSION:

The EA-RISA enlarges the exposure obtained with the classic RISA. Its judicious use can help achieve safe and radical removal of dumbbell-shaped trigeminal schwannomas (C1 type).

Endoscopic approach to the trigeminal nerve: an anatomic study

OBJECTIVE

To describe an endoscopic perspective of the surgical anatomy of the trigeminal nerve.

METHODS

Nine adult cadaveric heads were dissected endoscopically.

RESULTS

Opening the pterygopalatine fossa is important because many key anatomical structures (V2, pterygopalatine ganglion, vidian nerve) can be identified and traced to other areas of the trigeminal nerve. From the pterygopalatine ganglion, the maxillary nerve and vidian nerve can be identified, and they can be traced to the gasserian ganglion and internal carotid artery. An anteromedial maxillectomy increases the angle of approach from the contralateral nares due to an increase in diameter of the piriform aperture, and provides excellent access to the mandibular nerve, the petrous carotid, and the cochlea.

CONCLUSIONS

Identification of key anatomical structures in the pterygopalatine fossa can be used to identify other areas of the trigeminal nerve, and an anteromedial maxillectomy is necessary to expose the ipsilateral mandibular nerve and contralateral cranial level of the trigeminal nerve.

Radiographic association of schwannomas with sensory ganglia

OBJECTIVE

Clinical experience suggests that the majority of schwannomas arise within sensory ganglia, suggesting that intraganglionic glial cells represent a potential cell of origin for schwannomas. To support this clinical impression, we reviewed magnetic resonance imaging (MRI) studies performed over a 5-year period at our institution to determine the relationship of cranial and spinal nerve schwannomas with the ganglia of the associated nerves.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

Patients undergoing imaging study at our institution over a 5-year period.

INTERVENTION(S)

Radiographic images at our institution were reviewed as well as published studies to determine the anatomic location of schwannomas.

MAIN OUTCOME MEASURE(S)

Anatomic location of schwannomas.

RESULTS

A total of 372 patients were found over the 5-year study period, 31 of those were diagnosed with neurofibromatosis Type 2 (NF2). Vestibular schwannomas comprised the greatest number of schwannomas, followed by spinal schwannomas. In NF2 patients, spinal schwannomas were the most common tumor, followed by vestibular schwannomas. In NF2 patients and those with sporadic schwannomas, the overwhelming majority of tumors arose in nerves with a sensory component and were associated with the sensory ganglia of the nerves (562/607, 92.6%). Very few tumors arose from pure motor nerves. This is supported by review of published articles on anatomic location of schwannomas.

CONCLUSION

Schwannomas are strongly associated anatomically with the ganglia of sensory nerves. These findings raise the possibility that intraganglionic glial cells give rise to the majority of schwannomas.

Endoscopic endonasal management of trigeminal schwannomas extending into the infratemporal fossa

Extracranial trigeminal schwannomas extending into the infratemporal fossa are rare. The traditional surgical approaches to the infratemporal fossa are associated with complications, such as facial nerve dysfunction, hearing loss, dental malocclusion and cosmetic problems. We report eight patients (four males, four females, age range=31-62 years) who were treated between 2004 and 2009 for extracranial trigeminal schwannomas extending into the infratemporal fossa. Schwannomas were surgically removed using a purely endoscopic endonasal approach. The maximum diameters of the tumours ranged from 30 mm to 70 mm and all tumours were completely removed. There were no intraoperative or postoperative complications in this series. There were no recurrences during the follow-up period which ranged from 10 to 74 months (mean=30 months). The purely endoscopic endonasal approach may provide a minimally invasive and safe approach to remove extracranial trigeminal schwannomas extending into the infratemporal fossa. Radical resection was associated with an excellent long-term outcome in this series.

Trigeminal Schwannomas: Skull Base Approaches and Operative Results in 105 Patients

BACKGROUND:

Trigeminal schwannomas make up 0.8% to 8% of all intracranial schwannomas.

OBJECTIVE:

To analyze our surgical experience with trigeminal schwannomas.

METHODS:

We performed 107 operations on 105 patients harboring trigeminal schwannomas over the past 30 years. We classified the tumors as peripheral, ganglion cavernous, posterior fossa root, and dumbbell types according to the portion of the nerve that gave rise to the tumor.

RESULTS:

Fourteen were peripheral-type tumors (13.1%), 39 (36.4%) were ganglion cavernous type, 22 (20.6%) were posterior fossa root type, and 32 (30.0%) were dumbbell type. Sixty-five tumors were solid, 35 were mixed, and only 7 were cystic. Among solid tumors, 14 were vascular, fibrous, and adherent to adjacent structures. Total or near-total removal was performed in 86 cases (81.9%), and subtotal removal was achieved in 18 (17.1%). The most common symptom was facial hypesthesia, occurring in 69 patients. This symptom improved in 11 patients, persisted in 50 patients, and worsened in 8 patients after surgery. New postoperative hypesthesia was observed in 8 patients. The second most common symptom was facial pain, observed in 24 patients. Facial pain subsided in 22 and persisted in 2 patients after surgery. Diplopia was observed in 21 patients. This symptom improved postoperatively in 14 patients, persisted in 6 patients, and worsened in 1 patient.

CONCLUSION:

The present series demonstrates acceptable results using microsurgical treatment to remove trigeminal schwannomas. Pain and diplopia may be relieved after surgery; however, hypesthesia frequently remains or may be worsened by surgery.

Linear Accelerator Radiosurgery for Nonvestibular Schwannomas

BACKGROUND:

Nonvestibular schwannomas are uncommon tumors of the brain often treated by surgical resection. Surgery may be associated with high morbidity.

OBJECTIVE:

We present a series of nonvestibular schwannomas treated with linear accelerator radiosurgery during a 19-year period.

METHODS:

This is a retrospective analysis of patients who underwent treatment of nonvestibular schwannomas at the University of Florida with linear accelerator radiosurgery between August 1989 and February 2008. Forty-nine patients underwent treatment during the study period, and 6 were lost to follow up. The mean age was 51 years (range, 17-82 years), 39% had previous surgical resection, and 67% presented with preradiosurgery cranial nerve deficits. There were 25 trigeminal, 18 jugular foramen, 2 facial, 2 oculomotor, 1 hypoglossal, and 1 high cervical schwannomas. The median tumor volume was 5.3 mL (range, 0.3-24.5 mL), treated with a median dose of 1250 cGy (range, 1000-1500 cGy). Study endpoints were actuarial local tumor control and neurological outcome.

RESULTS:

Forty-three patients were available for a median follow-up of 37 months (range, 6-210 months). Actuarial local tumor control was 97% at 1 year, 91% at 4.5 years, and 83% at 5 years. There were 4 new cranial nerve deficits (9%) including facial numbness (2 patients), anesthesia dolorosa (1 patient), and facial weakness (1 patient). Thirty-nine percent had documented clinical and/or symptomatic improvement. There were no other morbidity and no mortality with treatment.

CONCLUSION:

Radiosurgery for nonvestibular schwannomas offers good actuarial local tumor control and has superior morbidity compared with surgical resection. This is the largest linear accelerator radiosurgical series, and the second largest radiosurgical series reported to date.

Surgery for a case of three-compartment trigeminal schwannoma : technical aspects

Complete removal of three-compartment trigeminal schwannomas is a challenge to neurosurgeons. To expand exposure of each compartment, the combination and modification of skull base approaches are necessary. The 61-year-old woman was admitted with chronic headache. Preoperative magnetic resonance imaging showed 47×50×40 mm-sized tumor originating primarily in the middle cranial fossa extended to the posterior and the infratemporal fossa. We performed operation in five stage; 1. Zygomatic osteotomy, 2. Inferior temporal fossa plate removal and foramen ovale opening, 3. Cavernous sinus opening, 4. Tailored anterior petrosectomy, 5. Meckel's cave opening. Combination of skull base surgery should be concerned according to the patient. In this study, extradural basal extension with zygomatic osteotomy, interdural posterior extension with tailored anterior petrosectomy, and intracavernous exploration are reasonable options for remodeling three-compartment lesion into a single compartment. Tailoring of bone resection and exploring through natural pathway between meningeal layers accomplish single-stage operation for complete removal of tumors.

Nonvestibulocochlear cranial nerve schwannomas

OPINION STATEMENT

Nonvestibulocochlear cranial nerve schwannomas traditionally have been managed by surgical excision. Although debulking surgery is still considered the first treatment option for larger tumors, stereotactic radiosurgery is now preferred for smaller tumors because of its high tumor control rate and low treatment-related morbidity. Furthermore, an initial period of radiologic and clinical observation following the diagnosis should be strongly considered for smaller tumors because some may not grow or may grow at a slow rate. Medical management of tumor-associated symptoms (when present) should not be ignored. Most importantly, the time has come to embark on the first randomized controlled trials comparing clinical and radiologic observation, surgery, and radiosurgery in the management of cranial nerve schwannomas.

Idiopathic trigeminal neuropathy with trigeminal mass lesion on MRI: Neoplasm or not?

The objective of the present study was to investigate clinical and magnetic resonance imaging (MRI) features of idiopathic trigeminal neuropathy with transient MR abnormalities mimicking a neoplasm (ITNmn). We retrospectively evaluated clinical and MRI features in two cases of ITNmn seen in our institution in comparison with those of previously reported five cases. The most common symptom was altered facial sensation and numbness limited to one or more trigeminal nerve divisions (100%). ITNmn commonly affected not only the second and third divisions (86% and 57%, respectively) but also the first division (71%). The most common findings on MRI were enlargement and gadolinium enhancement of the trigeminal nerve, which were similar to those seen in neoplasms (100%). The abnormalities spontaneously regressed in all five evaluable cases. ITNmn should be added in the differential diagnosis of non-specific mass-like lesions in trigeminal neuropathy and be observed carefully without surgical treatment.

Giant cranionasal schwannoma

Giant schwannomas concomitantly involving the intracranial and nasal cavities are rare. We report a 22-year-old male patient with a giant schwannoma involving the frontal skull base and extending into the nasal cavity. The patient had a 2-year history of nasal obstruction that was originally misdiagnosed as nasal polyps. A CT scan and an MRI revealed a large cranionasal tumor. Surgery was performed using a coronal incision with a bilateral frontal skull base extradural approach. The tumor originated from the anterior skull base and the dura and nasal mucosa were intact. Histopathology was consistent with a schwannoma. Schwannoma should be listed as part of the differential diagnosis of a cranionasal tumor and the surgical approach should be carefully selected to achieve total resection.

Surgical management of trigeminal schwannomas

OBJECT

The authors provide a detailed review of the surgical management of trigeminal schwannomas (TSs) and also discuss the best surgical approach based on the surgical anatomy and tumor extension.

METHODS

A series of 17 patients with TSs who were surgically treated between 1987 and 2008 at the authors' institution is reported. The lesions were small (< 3 cm) in 2, medium (between 3 and 4 cm) in 5, large (> 4 cm) in 6, and giant (> 5 cm) in 4 cases. Preoperative symptoms included trigeminal hypesthesia (53%), facial pain (53%), headaches (35.3%), hearing impairment (17.6%), seizures (17.6%), diplopia (11.8%), ataxia (11.8%), and hemiparesis and increased intracranial pressure with papilledema (5.9%). The mean follow-up duration was 10.5 years (121.6 months), with an average of 0.8 patients per year.

RESULTS

Total tumor excision was possible in 16 patients, with no surgery-related deaths. Postoperative trigeminal anesthesia was observed in 7; trigeminal motor function was preserved in 7. Two developed cerebrospinal fluid leakage, 2 presented with mild facial palsy, and 1 patient with neurofibromatosis Type 2 had recurrence of the tumor, which was uneventfully removed. Of the 9 who reported facial pain, only 1 remained symptomatic postoperatively.

CONCLUSIONS

The best treatment for TSs is complete microsurgical removal. Postoperative preservation of trigeminal nerve function is possible when resection of the lesion is performed at well-established skull base neurosurgical centers. Although good results have been reported with radiosurgery, no cure can be obtained with this therapeutic modality. Instead, this treatment should be reserved only for nonresectable and residual tumors within the cavernous sinus.