Histology and neuro-imaging in cystic acoustic neuromas

Intratumoral Hemorrhage in Vestibular Schwannomas After Stereotactic Radiosurgery: Multi-Institutional Study

BACKGROUND AND OBJECTIVES

Intratumoral hemorrhage (ITH) in vestibular schwannoma (VS) after stereotactic radiosurgery (SRS) is exceedingly rare. The aim of this study was to define its incidence and describe its management and outcomes in this subset of patients.

METHODS

A retrospective multi-institutional study was conducted, screening 9565 patients with VS managed with SRS at 10 centers affiliated with the International Radiosurgery Research Foundation.

RESULTS

A total of 25 patients developed ITH (cumulative incidence of 0.26%) after SRS management, with a median ITH size of 1.2 cm 3 . Most of the patients had Koos grade II-IV VS, and the median age was 62 years. After ITH development, 21 patients were observed, 2 had urgent surgical intervention, and 2 were initially observed and had late resection because of delayed hemorrhagic expansion and/or clinical deterioration. The histopathology of the resected tumors showed typical, benign VS histology without sclerosis, along with chronic inflammatory cells and multiple fragments of hemorrhage. At the last follow-up, 17 patients improved and 8 remained clinically stable.

CONCLUSION

ITH after SRS for VS is extremely rare but has various clinical manifestations and severity. The management paradigm should be individualized based on patient-specific factors, rapidity of clinical and/or radiographic progression, ITH expansion, and overall patient condition.

Intratumoral hemorrhage in vestibular schwannomas after stereotactic radiosurgery

OBJECTIVE

Vestibular schwannomas (VSs) are benign tumors of the cerebellopontine angle that are typically managed with stereotactic radiosurgery (SRS). Intratumoral hemorrhage (ITH) of VSs is a rare occurrence that results in worsening vestibular and new cranial nerve deficits. Few reports have described the management and outcomes of this entity after SRS. To further delineate the incidence and impact of this event, the authors performed a retrospective review of their VS SRS patients at a single center.

METHODS

Between 1987 and 2022, 2058 patients with VSs underwent Gamma Knife radiosurgery (GKRS) at the University of Pittsburgh Medical Center. The authors performed a review of the prospectively maintained VS database at their center to identify patients with ITH. The presentation, management, and clinical and imaging outcomes of the patients are reported.

RESULTS

A total of 1902 VS patients had sufficient clinical and imaging follow-up data. Five Koos grade III (n = 1) and IV (n = 4) VS patients developed ITH after GKRS, resulting in a cumulative incidence rate of 0.26%. The age at presentation ranged from 62 to 79 years, and 3 patients were male. The time from VS diagnosis to GKRS ranged from 1 to 13 months, and the time from GKRS to ITH ranged from 2 to 130 months. Three patients had bleeding risk factors. One patient required urgent surgical intervention due to the ITH volume, while the other 4 patients were initially observed. Three patients remained stable and required no delayed intervention; 1 patient required delayed resection because of symptom progression and hemorrhagic expansion. Histopathological analysis revealed multiple fragments of S-100-positive cells, hemorrhage, and hemosiderin-laden macrophages. At last follow-up, 4 patients had clinically improved and 1 patient remained stable.

CONCLUSIONS

ITH after VS radiosurgery is a rare phenomenon with a cumulative incidence rate of 0.26% in this series. Patient-tailored management in the form of observation or resection is based on patient presentation, acuity, and ITH size.

Surgical outcome in cystic vestibular schwannomas

Background:

Cystic vestibular schwannomas (VS) form a rare subgroup that differs from the solid variant clinically, radiologically, and histopathologically. These tumors also vary in their surgical outcome and carry a different risk of post-operative complications. We analyzed our series of 64 patients with cystic VS and discuss the technical difficulties related to total excision of these tumors and focus on complication avoidance.

Materials and Methods:

A retrospective review of cystic VS surgically managed over a span of 11 years. The case records were evaluated to record the clinical symptoms and signs, imaging findings, surgical procedure, complications, and follow-up data. Post-operative facial nerve palsy was analyzed with respect to tumor size and tumor type.

Results:

Progressive hearing impairment was the most common initial symptom (76.6%). Atypical initial symptoms were present in 15 patients (23.4%). Preoperatively, 78% patients had good facial nerve function (HB grade 1, 2) and 22% had intermediate (HB grade 3, 4) to poor (HB grade 5 and 6) function. Mean tumor size was 4.1 cm. Complete tumor removal was achieved in 53 patients (83%). The facial nerve was anatomically intact but thinned out after tumor excision in 38 patients (59.4%). Ninety percent patients had either intermediate or poor facial nerve function at follow-up. Poor facial nerve outcome was associated with giant tumors and peripherally located, thin-walled cystic tumors.

Conclusion:

Resection of cystic VS is complicated by peritumoral adhesions of the capsule to the nerve. Extensive manipulation of the nerve in order to dissect the tumor–nerve barrier results in worse facial nerve outcome. The outcome is worse in peripherally located, thin-walled cystic VS as compared to centrally located, thick-walled cystic tumors. Subtotal excision may be justified, especially in tumors with dense adhesion of the cyst wall to the facial nerve in order to preserve nerve integrity.

Fluid-fluid level in cystic vestibular schwannoma: a predictor of peritumoral adhesion

OBJECT

The aim of this study was to evaluate the clinical results and surgical outcomes of cystic vestibular schwannomas (VSs) with fluid-fluid levels.

METHODS

Forty-five patients with cystic VSs and 86 with solid VSs were enrolled in the study. The patients in the cystic VSs were further divided into those with and without fluid-fluid levels. The clinical and neuroimaging features, intraoperative findings, and surgical outcomes of the 3 groups were retrospectively compared.

RESULTS

Peritumoral adhesion was significantly greater in the fluid-level group (70.8%) than in the nonfluid-level group (28.6%) and the solid group (25.6%; p < 0.0001). Complete removal of the VS occurred significantly less in the fluid-level group (45.8%, 11/24) than in the nonfluid-level group (76.2%, 16/21) and the solid group (75.6%, 65/86; p = 0.015). Postoperative facial nerve function in the fluid-level group was less favorable than in the other 2 groups; good/satisfactory facial nerve function 1 year after surgery was noted in 50.0% cases in the fluid-level group compared with 83.3% cases in the nonfluid-level group (p = 0.038).

CONCLUSIONS

Cystic VSs with fluid-fluid levels more frequently adhered to surrounding neurovascular structures and had a less favorable surgical outcome. A possible mechanism of peritumoral adhesion is intratumoral hemorrhage and consequent inflammatory reactions that lead to destruction of the tumor-nerve barrier. These findings may be useful in predicting surgical outcome and planning surgical strategy preoperatively.

A 30 year old man with an acute presentation of a cerebellopontine angle lesion

Schwannomas are slow-growing tumors with symptoms manifesting progressively. We report the case of a patient who manifested a sudden loss of consciousness as clinical presentation of an intracranial schwannoma with no acute hemorrhage or hydrocephalus. A 30-year-old male presented comatose and posturing. Cerebral CT revealed an extra-axial lesion with a heterogeneous enhancement and a cystic component located on the right cerebellopontine angle (CPA), displacing the brain stem. No acute hemorrhage or hydrocephalus was documented. Through a retrosigmoid suboccipital craniotomy, an extended subtotal tumor resection was performed. The patient experienced no functional hearing impairment and resumed his daily-life activities 3 months after surgery. Histopathological examination was compatible with a benign schwannoma. An exuberant lymphoplasmacytic infiltrate was found in many areas, signing the presence of an unusual inflammatory reaction with adjacent important intratumoral edema. We propose that the exuberant inflammatory infiltrate and the associated intratumoral edema acted as determining elements in the increase of mass effect and sudden clinical deterioration.

Cystic acoustic neuromas

Predominantly cystic acoustic neuromas are rare and they usually present with clinical and radiological features different from their more common solid counterparts. Two cases of cystic acoustic neuromas are reported here.

Vestibular schwannoma of oscillating size: A case report and review of literature

Background:

Vestibular schwannomas are benign brain tumors arising from the 8th cranial nerve with a varying natural history. Various reports have described discernable growth patterns for these tumors. However, growth predictability remains low because of slow and indeterminate changes over time with follow-up reports not usually exceeding 3 years. Our report describes the long-term follow-up of an unusual cystic schwannoma with growth patterns prior to and following treatment, adding valuable information to the variable natural history and outcome of these infrequent tumors.

Case Description:

A 68-year-old gentleman presented with a left-sided cystic vestibular schwannoma, initially managed conservatively. Imaging revealed wide variations in the size of his tumor over a period of 3 years. He was finally treated with Gamma Knife radiosurgery, and at 1 year following treatment shows tumor shrinkage with a change in tumor morphology.

Conclusion:

To our knowledge, the present case represents the first instance of a schwannoma showing wide fluctuations in tumor size and morphology over a period of time, with a good response to radiosurgery. We emphasize in this report that there is no “one size fits all” treatment paradigm for these tumors and each patient requires individualized care and intervention, taking into account their differing natural histories.

[Recurrent giant cystic vestibular schwannomas: role of cystoperitoneal shunt]

INTRODUCTION

Surgical removal of giant cystic vestibular schwannomas is difficult because of adherences between the cyst membrane, brainstem, and the VII-VIII nerve complex. The recurrence of the cyst is frequent and requires reoperation. The aim of this study was to analyze the role of the palliative cystoperitoneal shunt in giant cystic vestibular schwannomas.

MATERIALS AND METHODS

Eighty-eight patients with a diagnosis of stage III or IV vestibular schwannoma were managed surgically from January 2000 to December 2005 in our department. Six schwannomas were deemed to be cystic according to the following criteria: a voluminous cystic component with mass effect causing symptoms as well as radiological and intraoperative identification of cystic elements.

RESULTS

Complete tumor removal was achieved in two patients. After a follow-up of 5 and 7 years, these patients were asymptomatic. In four cases, we performed cyst drainage. For three patients, we implanted a permanent cystoperitoneal shunt. These patients were asymptomatic with a mean follow-up of 19.7 months.

CONCLUSIONS

The cystoperitoneal shunt with no valve is a valid palliative surgical solution to remove brain stem compression. Neuronavigation allows proper positioning of the drain and secures the procedure.

Neuropathology for the neuroradiologist: Antoni A and Antoni B tissue patterns

Histologic patterns of cellular architecture often suggest a tissue diagnosis. Distinctive histologic patterns seen within the peripheral nerve sheath tumor schwannoma include the Antoni A and Antoni B regions. The purpose of this report is to review the significance of Antoni regions in the context of schwannomas.

Microhemorrhage, a possible mechanism for cyst formation in vestibular schwannomas

OBJECT

Cystic vestibular schwannoma (VS) is a unique subgroup of VSs characterized by unpredictable expansion of the cyst component. Little is known, however, about the mechanism of cyst formation. In this study the authors compared neuroimaging and histological characteristics of cystic with solid VS to determine the pathogenesis of the cystic subgroup.

METHODS

Two cohorts, one comprising 10 patients with cystic VS and the other comprising 10 patients with solid VS, were studied. Surgery was chosen as the primary treatment in all patients, with no other modality applied. Preoperative magnetic resonance images and histological characteristics of the tumor in patients with cystic VSs were evaluated and compared with those in the group with solid VSs. Differences between the two groups were assessed using the chi-square test. Neuroimaging findings revealed that either fluid-fluid level or hemosiderin deposit was present in all cystic VSs. Histological evidence of microhemorrhage, such as hemosiderin-laden macrophages (p = 0.069), hemosiderin deposits (p = 0.019), thrombotic vessels (p = 0.008), and abnormal vessel proliferation (p = 0.006) were more prominent in cystic VSs compared with solid ones. There was no difference in Antoni type dominance and Ki-67 proliferative index between the two groups.

CONCLUSIONS

Intratumoral microhemorrhage is a possible mechanism of pathogenesis in cystic VS.

Multicystic acoustic schwannoma with intratumoral hemorrhage: a report of two cases

We encountered two multicystic acoustic schwannomas with intratumoral hemorrhage. The radiological appearance in each case was similar to that obtained with CT and MRI. From a histological perspective, in each case we observed hypervascularity with thin-walled, dilated vessels in clusters and hemosiderin depositions around the dilated vessels.

Cystic versus solid vestibular schwannomas: a series of 80 grade III-IV patients

Cystic acoustic neuromas are less frequent than solid ones and present different clinical and radiological features. Cystic schwannomas are larger, show a shorter clinical history and a different risk of postoperative complications. This study was designed to compare surgical results and complications of solid and cystic vestibular schwannomas of matching size operated upon via either a retrosygmoid or a translabyrinthine approach. The study included 80 patients presenting with grade III and IV acoustic vestibular schwannomas referred to the Neurosurgical and ENT team in the Department of Neuroscience of Torino, Italy. Twenty-six were cystic and 54 were solid tumours. Clinical history, surgical results and complications were compared between the two groups. In cystic tumors, rapid clinical worsening is common, due to sudden expansion of cystic elements. Tighter adherences are found between cystic tumours and nervous elements (particularly brainstem and possibly facial nerve), once compared to solid ones. Operative morbidity appears to be higher in cystic tumours. A wait and see policy should not to be applied to patients with cystic tumours. Careful technique, possibly sharp dissection, to divide the tumour adherences from the nervous tissue must be employed, in order to avoid lesions on brainstem veins and traction on a thin facial nerve. Severe complications may be caused by the excessive efforts to dissect brainstem adherences.

Vestibular schwannomas: correlations between magnetic resonance imaging and histopathologic appearance

BACKGROUND

The indication for surgery of vestibular schwannomas (VS) remains controversial and depends on several factors. The ability to predict their patterns of growth would allow better surgical planning. This growth may depend on tumoral proliferation but also depends on dystrophic changes.

OBJECTIVE

The aim of this study was to evaluate the role of magnetic resonance imaging (MRI) in predicting the evolution of VS. For this purpose, the authors attempted (1) to compare the MRI appearance of VS with its histopathologic features, (2) to correlate the MRI appearance of VS and its histopathologic features with its size, and (3) to evaluate the index of proliferation (IP) of each VS.

PATIENTS AND METHODS

Thirty VS were studied with MRI before surgery. The VS were measured and classified as homogeneous, heterogeneous, and cystic. After surgery, IP was evaluated with immunohistochemical study using MIB-1 monoclonal antibody, and compared with tumor size. Pathologic studies evaluated the prevalence of Antoni type A and type B tissue, the amount of fibrosis, and the presence of siderin-loaded macrophages, xanthomatous cells, and cysts.

RESULTS

The IP was low (0.2%-2.2%) and was not correlated with VS size. On MRI, 13 VS were homogeneous, 12 heterogeneous, and 5 cystic. The 13 homogeneous VS were smaller and were predominantly made of Antoni type A tissue. The 12 heterogeneous and 5 cystic VS were larger and were predominantly made of Antoni type B/mixed tissue. Heterogeneous and cystic VS showed significantly more hemosiderin deposits. There was a significant relation between the amount of hemosiderin deposits and the mean size of VS. Microscopic cysts were observed only in VS with cystic MRI appearance. Fibrosis was present in all tumors regardless of their size and MRI appearance.

CONCLUSION

A heterogeneous MRI aspect (correlated with larger mean size) not only is related to the ratio of type A to type B tissue but also is caused by other pathologic changes, mainly hemosiderin deposits and cystic formation. Increasing tumor size probably depends less on IP than on dystrophic changes (hemosiderin, cysts) and/or on the presence of type B tissue.

Cystic vestibular schwannomas: neuroimaging and growth rate

In a series of 571 vestibular schwannomas (VS) operated on in the period 1976-1992, via the translabyrinthine approach, 23 tumours (4 per cent) from 23 patients were radiologically, peroperatively and histologically identified as cystic VS. Neuroimaging examinations (CT and MRI) revealed 15 tumours (2.6 per cent) with extracystic formations and in eight cases (1.4 per cent) intratumoural cysts. In 15 cases (65 per cent), tumours were located extracanalicularly with no involvement of the internal auditory canal (IAC). The extracanalicular tumour extension including the cystic elements ranged between 10 and 60 mm with a mean of 45 mm. In eight cases out of 23 (35 per cent) other diagnostic possibilities such as trigeminal schwannoma, epidermoid cyst and meningioma were proposed at the primary evaluation. Deformation, displacement and/or impression of the fourth ventricle was demonstrated in 17 cases (74 per cent). Three patients (13 per cent) had obstructive hydrocephalus which demanded shunt insertion. Residual tumour was detected in two patients (9 per cent). Growth rate in four cases was more than 10 times higher when compared to the annual growth rate of noncystic VS. The results of this study provide data on cystic VS attenuation demonstrated by CT or MRI which may be valuable in neuroradiological diagnosis of these cystic lesions and emphasizes that the wait-and-see policy should not be applied to the cystic variant of VS.