Long-term outcomes of stereotactic radiosurgery for intracranial schwannoma in neurofibromatosis type 2: a genetic analysis perspective.

PURPOSE: Neurofibromatosis type 2 (NF2) is intractable because of multiple tumors involving the nervous system and is clinically diverse and genotype-dependent. Stereotactic radiosurgery (SRS) for NF2-associated schwannomas remains controversial. We aimed to investigate the association between radiosurgical outcomes and mutation types in NF2-associated schwannomas. METHODS: This single-institute retrospective study included consecutive NF2 patients with intracranial schwannomas treated with SRS. The patients' types of germline mutations ("Truncating," "Large deletion," "Splice site," "Missense," and "Mosaic") and Halliday's genetic severity scores were examined, and the associations with progression-free rate (PFR) and overall survival (OS) were analyzed. RESULTS: The study enrolled 14 patients with NF2 with 22 associated intracranial schwannomas (median follow-up, 102 months).　The PFRs in the entire cohort were 95% at 5 years and 90% at 10-20 years. The PFRs tended to be worse in patients with truncating mutation exons 2-13 than in those with other mutation types (91% at 5 years and 82% at 10-20 years vs. 100% at 10-20 years, P = 0.140). The OSs were 89% for patients aged 40 years and 74% for those aged 60 years in the entire cohort and significantly lower in genetic severity group 3 than in the other groups (100% vs. 50% for those aged 35 years; P = 0.016). CONCLUSION: SRS achieved excellent PFR for NF2-associated intracranial schwannomas in the mild (group 2A) and moderate (group 2B) groups. SRS necessitates careful consideration for the severe group (group 3), especially in cases with NF2 truncating mutation exons 2-13.

CT and MRI findings of intra-parenchymal and intra-ventricular schwannoma: a series of seven cases.

OBJECTIVE: To analyze the computed tomography (CT) and magnetic resonance imaging (MRI) features of patients with intra-parenchymal and intra-ventricular schwannoma. METHODS: The CT and MRI features of seven cases with intra-parenchymal and intra-ventricular schwannoma were analyzed retrospectively. RESULTS: There were four men and three women (median age, 25 years; range, 12-42 years) in this study. The median tumor size was 4.4 cm (range, 3.1-6.5 cm). The mass was, respectively, round in four cases (57.1%), lobulated in two cases (28.6%) and oval in one case (14.3%). All tumors were well-circumscribed. Septa in the mass could be observed in three cases (42.9%), and nodular calcification was observed in two cases (28.6%), which peritumoral edema (n = 3, 42.9%) and hydrocephalus (n = 3, 42.9%) could be observed. Most of these lesions (n = 6) presented iso-hypointensity on T1-weighted images and iso-hyperintensity on T2-weighted images, except one lesion showing low intensity on T2WI. In addition, a fluid-fluid level was observed in one case. After contrast agents' injection, all masses illustrated heterogeneously moderate to marked enhancement. CONCLUSIONS: A well-defined solid and cystic mass with calcification and moderate to marked delayed enhancement may be an objective account of intra-parenchymal or intra-ventricular schwannoma.

Scoring system for intraoperative diagnosis of intracranial schwannoma by squash cytology.

OBJECTIVE: To assess the utility of a newly developed squash cytology (SC)-based scoring system for accurate intraoperative diagnosis of schwannoma. METHODS: We first compared SC-based and frozen section (FS) diagnoses with final pathological diagnoses of schwannoma (16 cases), meningioma (39 cases) and low-grade astrocytoma (16 cases). Then, by logistic regression modeling, we identified features of SC preparations that were independently predictive of schwannoma. To develop a diagnostic scoring system, we assigned one point to each feature, and performed receiver operating characteristic analysis to determine the score cut-off value that was most discriminatory for differentiating schwannoma from the other tumour types. We then compared accuracy, sensitivity, and specificity of diagnosis before and after the application of the scoring system. RESULTS: Overall diagnostic concordance rates for SC and FS were almost the same, at 73.2% (52/71) and 77.5% (55/71 cases), respectively. Of the 16 SC features entered into the analysis, the following nine were found to independently predict schwannoma, and were thus incorporated into the scoring system: smooth cluster margins, few or no isolated tumour cells, fibrillary stroma, spindle-shaped nuclei, parallel arrangement of stroma, parallel arrangement of nuclei, presence of anisonucleosis, absence of nucleoli, and hemosiderin deposition. A cut-off score of four items yielded the best sensitivity, specificity and predictive values for prediction of schwannoma. Use of the scoring system improved accuracy of intraoperative diagnosis from 80.3% to 94.4%, sensitivity from 56.2% to 93.8%, and specificity from 87.3% to 94.5%. CONCLUSION: Our proposed SC-based scoring system will increase accuracy of intraoperative diagnosis of schwannoma vs non-schwannoma tumours.

Pediatric intracranial lower cranial nerve schwannoma unassociated with neurofibromatosis type 2: case report and review of the literature.

INTRODUCTION: Pediatric schwannomas are rare, and most of them are associated with neurofibromatosis type 2 (NF2) and usually located in the vestibular nerve. Herein, we present the first pediatric case of intracranial schwannoma derived from the IX/X nerve complex unrelated to NF2. CASE REPORT: The patient was a 9-year-old boy who presented with a 3-month history of headache and nausea. There was no family history of NF2. Imaging studies revealed a cystic lesion with enhanced wall in the left cerebellomedullary fissure. During the operation, the IX/X nerve complex was strongly adhered to the tumor at the jugular foramen. The tumor was totally excised, and the postoperative MRI demonstrated no residual tumor. Histopathological diagnosis was schwannoma. Genetic analysis revealed no mutation associated with NF2 and schwannomatosis. CONCLUSION: We reported the first case of pediatric lower cranial nerve schwannoma which was not associated with NF2. The schwannoma should be included as differential diagnosis of pediatric posterior fossa tumors.

Clinical and radiological features of intracranial ancient schwannomas: a single-institution, retrospective analysis.

Ancient schwannoma (AS) is a subtype of schwannoma characterized by slow progression despite degenerative changes in pathology. Although it is considered a benign tumor, most previous reports have focused on extracranial AS; therefore, the clinical characteristics of intracranial AS is not clear. We included 174 patients who underwent surgery for sporadic intracranial schwannoma, and 13 patients (7.5%) were diagnosed with AS. Cysts were significantly more common in patients with AS than conventional schwannomas (92.3% vs. 44.7%, p < 0.001), as was bleeding (38.5% vs. 6.9%, p = 0.003) and calcification (15.4% vs. 1.3%, p = 0.029). The maximum tumor diameter was also larger in patients with AS (35 mm vs. 29 mm, p = 0.017). The median duration from symptom onset to surgery (7.0 vs. 12.5 months, p = 0.740) did not significantly differ between groups, nor did the probability of postoperative recurrence (p = 0.949). Intracranial AS was strongly associated with cyst formation and exhibited a benign clinical course with a lower rate of recurrence and need for salvage treatment. Extracranial AS is reportedly characterized by a slow progression through a long-term clinical course, whereas intracranial AS did not progress slowly in our study and exhibited different clinical features to those reported for extracranial AS.

Hemorrhagic schwannoma of the trochlear nerve: Case report and a review of the literature.

Background: Schwannomas of the trochlear nerve with the absence of systemic neurofibromatosis are considerably uncommon, especially complicated by intra-tumoral hemorrhage. Due to the lack of typical clinical manifestations and imaging findings, a definite diagnosis of trochlear schwannomas before surgery is particularly difficult. Case presentation: We report the case of a 64-year-old female patient who presented with a unilaterally intermittent headache of 2-month duration and without a remarkable neurological deficit at admission. Imaging studies revealed a well-demarcated cystic-solid lesion with mixed signals beside the brainstem and suprasellar cisterna. The patient underwent a surgical operation with total resection of the tumor by a subtemporal surgical approach. The tumor was intraoperatively found to originate from the trochlear nerve and was pathologically confirmed as a hemorrhagic schwannoma with cystic degeneration. Conclusions: We describe this case in detail and conduct a concomitant survey of the literature, summarizing the clinical presentations, radiological features, surgical treatment, and the possible mechanisms of hemorrhage in relevance to trochlear nerve schwannoma.

Subfrontal Schwannoma: Case Report and Review of Literature.

BACKGROUND: Although attributing the origin of schwannomas from the olfactory nerve is nearly impossible, if they do not have Schwann cells, intracranial supratentorial schwannomas are mainly located in the anterior skull base. CASE DESCRIPTION: We present the case of a 46-year-old female who presented with right tinnitus, dizziness, and bifrontal headache, progressive, starting 2 years before. Imaging studies revealed an incidentally neoplastic, extraaxial, homogeneously appearing tumor on the right anterior skull base. The patient underwent surgical treatment with total resection of the tumor by a bicoronal approach. The histopathologic study reported schwannoma. CONCLUSION: We describe this case in detail and discuss the likely origin of this tumor, with a concomitant literature review.

Excision of hypoglossal neurinoma by condyle sparing suboccipital keyhole approach.

Hypoglossal neurinomas are rare tumors that present with gradually worsening unilateral wasting of the tongue. The tumors often attain large size prior to detection and often extend into the hypoglossal canal. Large tumors can distort the brainstem and cerebellum. Preoperative diagnosis can often be made by magnetic resonance imaging (MRI) with contrast enhancement. Traditionally, surgery for these tumors has entailed large transcondylar approaches, often necessitating occipitocervical stabilization. We managed one 23-year-old female patient with a large hypoglossal neurinoma. The tumor could be excised completely by a condyle-sparing minimally invasive suboccipital keyhole approach.

Comparison between MR imaging findings of intracranial and extracranial schwannomas.

PURPOSE: To evaluate the differences of MR imaging findings between intracranial and extracranial schwannomas. METHODS: We retrospectively reviewed the MR images of 98 schwannomas and compared the imaging findings between intracranial and extracranial schwannomas. RESULTS: The number of intratumoral cysts was greater in intracranial than in extracranial schwannomas (4.8±7.2 vs 1.8±4.1; p<0.05). CONCLUSION: The number of intratumoral cysts was different between intracranial and extracranial schwannomas.

Analysis of risk factors to predict communicating hydrocephalus following gamma knife radiosurgery for intracranial schwannoma.

Communicating hydrocephalus (HCP) in vestibular schwannomas (VS) after gamma knife radiosurgery (GKRS) has been reported in the literature. However, little information about its incidence and risk factors after GKRS for intracranial schwannomas is yet available. The objective of this study was to identify the incidence and risk factors for developing communicating HCP after GKRS for intracranial schwannomas. We retrospectively reviewed a total of 702 patients with intracranial schwannomas who were treated with GKRS between January 2002 and December 2015. We investigated patients' age, gender, tumor origin, previous surgery history, tumor volume, marginal radiation dose, and presence of tumor control to identify associations with communicating HCP following GKRS. To make predictive models of communicating HCP, we performed Cox regression analyses and constructed a decision tree for risk factors. In total, 29 of the 702 patients (4.1%) developed communicating HCP following GKRS, which required ventriculo-peritoneal (VP) shunt surgery. Multivariate analyses indicated that age (P = 0.0011), tumor origin (P = 0.0438), and tumor volume (P < 0.0001) were significant predictors of communicating HCP in patients with intracranial schwannoma after GKRS. Using machine-learning methods, we fit an optimal predictive model. We found that developing communicating HCP following GKRS was most likely if the tumor was vestibular origin and had a volume ≥13.65 cm3 . Communicating HCP is not a rare complication of GKRS for intracranial schwannomas. Under specific conditions, communicating HCP following GKRS is warranted for this patient group, and this patient group should be closely followed up.