A case report on cystic meningioma in cerebellopontine angle and recommendations for management.

RATIONALE: Cystic meningioma located at the cerebellopontine angle (CPA) is an extremely rare occurrence. It is frequently misdiagnosed preoperatively. Little is known about the clinical features and outcome of this rare disease. PATIENT CONCERNS: A 70-year-old male presenting with progressive headache and gait disturbance. DIAGNOSIS: According to the symptoms, signs, and Gd-enhanced magnetic resonance images (MRI), a preoperative diagnosis of hemangioblastoma located in left CPA was made. Finally, the histological examination revealed a meningioma.
INTERVENTIONS: A complete resection, including the part of the solid mass together with cyst, was performed. OUTCOMES: The postoperative course of the patient was uneventful, and no residual or recurrent tumor was found during the 24-month follow-up period. LESSONS: Cystic meningioma should be included in the differential diagnosis of a CPA mass with atypical radiologic features, such as a large cyst and enhanced mural nodule. By summarizing the related literature, we found that the most common pathological subtype of CPA cystic meningioma is the clear cell subtype, which belongs to WHO grade II. Gross total resection including the enhanced cyst wall is extremely important. A close follow-up is necessary because of the high recurrence rate in this subset of meningioma.

Introduction

Intracranial meningioma represents the most common primary brain tumor.[ Radiologically, they frequently behave as homogeneously enhanced dural-based masses.[ Meningiomas with large cyst and enhanced mural nodule are a rare occurrence and are frequently misdiagnosed preoperatively.[ Although limited cases of cystic meningiomas have been reported in the literature, most of them were found in the cerebral hemisphere;[ cerebellopontine angle (CPA) cystic meningioma is an extremely rare occurrence and has rarely been reported. Here, we report an extremely rare case of a cystic meningioma in the left CPA and examine previously reported cases of CPA cystic meningiomas in an attempt to provide an up-to-date summary of the condition.

Case report

A 70-year-old man presented to our department with a 2-year history of a headache. Postcontrast magnetic resonance images (MRI) indicated a broad based solid enhancing tumor with a multilobulated enhancing peritumoral cyst at the left CPA (Fig. 1). Because the patient refused to undergo surgery, a wait-and-see strategy and close follow-up were applied. Two years later, he suffered from a worsened headache as well as gait disturbance. While intracranial MRI showed that the tumor had spread, enhancement of the cyst wall faded (Fig. 1). Besides, preoperative computed tomography angiography (CTA) did not find any hypervascular nodule. Subsequently, a complete resection, including the part of the solid mass together with cyst, was performed. Intraoperatively, the solid part showed a rich blood supply. Postoperative histopathological examination surprisingly revealed the diagnosis of meningothelial meningioma (WHO grade I) (Fig. 2). The postoperative course of the patient was uneventful, and no residual or recurrent tumor was found during the 24-month follow-up period.

Figure 1

Comparison of brain MRI of a 2-year interval. (A) Axial T1-, (B) T2-, (C) enhanced T1-, and (D) coronal enhanced T1-weighted MRI showed a broad based solid enhancing tumor with a multilobulated enhancing peritumoral cyst in the left CPA. (E) Axial T1-, (F) T2-, (G) enhanced T1-, and (H) coronal enhanced T1-weighted MRI of the same patient 2 years later showed a larger tumor especially an enlarged cyst and a fading enhancing rim of the cyst. MRI = magnetic resonance images, CPA = cerebellopontine angle.

Figure 2

Pathological findings. A, Meningothelial cells represented the majority of tumor stroma (HE, ×200). B, Immunoreactivity of progesterone receptor (PR, ×100). C, Epithelial membrane antigen (EMA) staining was positive (EMA, ×200). D, MIB-1 positive rate was less than 5% (MIB-1 × 200). In conclusion pathological findings indicate a meningothelial meningioma.

Discussion

Cystic meningiomas account for only 2% to 7% of all meningiomas and frequently occur in the cerebral hemisphere.[ CPA cystic meningioma is a rare occurrence; only 11 cases have been reported in the English-language literature.[ The pathogenesis, clinical features, and outcome of this rare disease remain undefined. In the present study, we report a case of CPA cystic meningioma with MRI findings and provide an up-to-date summary of CPA cystic meningiomas based on the literature reviews.

The pathogenesis of cystic formation in meningiomas remains controversial. Some authors believe that the etiology of cyst formation is different according to the location of the cyst.[ Peritumoral cysts may frequently be caused by peritumoral edema into cyst, peritumoral demyelination, intratumoral hemorrhage, or entrapment of cerebrospinal fluid.[ However, intratumoral cysts may result from ischemic necrosis, cystic degeneration, intratumoral hemorrhage, and active secretion of tumor cells.[ In our opinion, as the solid part of cyst is frequently characterized by a rich blood supply,[ we supposed that cyst formation in a meningioma might result from ultrafiltrate of tumor vessels and that increased permeability of tumor vessels may accelerate cyst formation. As stated, there is still uncertainty as to the exact pathogenesis of this phenomenon. Further studies, like the analysis of the contents of cystic fluid, as well as exploring genetic differences, are necessary to elucidate the preferred mechanisms of cystic formation in meningiomas.

We reviewed a total of 12 cases of cystic meningiomas located in CPA (Table 1),[ which exhibited several distinctions from common meningiomas. First, headache and hearing problems are the most common symptoms in CPA meningiomas, followed by gait disturbance, facial nerve involvement, and visual disorder. The duration of time is relatively short, varying from 2 to 48 months (median, 3 months). Second, different from the common meningiomas with a women predominance,[ CPA cystic meningiomas prefer to occur in young patients (median age 27.5 years), and no gender predominance was found. Third, in regards to the radiological features, the size of the cystic meningioma in CPA is relatively large, with a median largest diameter of 50 mm (range 30–60 mm). Furthermore, peritumoral cysts are relatively ordinary compared with intratumoral cysts (80% vs 20%).[ Enhancements of the cyst wall and peritumoral edema were observed in 3 of 6 (50%) and 11 of 12 (92%) patients. To our knowledge, this is the first case that reports spontaneously vanishing enhancement of the cyst wall in a central nervous system (CNS) tumor after a long-term interval. We propose that the reason might be there could be normal variability in the contrast enhancement when performed at 2 different time points. Moreover, windowing may also have an influence. Fourth, the clear cell subtype is the most common pathological subtype and accounts for 9 of 12 (75%) patients. Other subtypes include meningothelial and angiomatous subtypes; as clear cell meningiomas is classified as WHO grade II,[ with a recurrence rate of 46% to 60%,[ hence gross total resection is extremely important and should be further emphasized in CPA cystic meningiomas to avoid tumor recurrence.

Table 1

All cases of cystic meningioma located in CPA in the literature.

For cystic CPA masses with enhanced mural nodule, the most common preoperative diagnosis can be a vestibular schwannoma (VS), hemangioblastoma, and glioma.[ However, our study suggests that cystic meningiomas should also be included in the differential diagnosis. Cystic meningiomas in CPA frequently show enhancement of the adjacent dura (7/12) and peritumoral edema (11/12).[ VSs typically involve the internal auditory canal and causes widening of the porus acusticus.[ Hemangioblastomas are usually characterized by high-flow vessels, serpentine flow void on MRI, and hypervascular nodule on CTA.[ Gliomas frequently show a heterogeneous enhancing pattern, such as a “growing edge,” intratumoral necrosis, and vasogenic edma.[ Thus, when dealing with tumors manifesting as enhanced mural nodule with cysts in CPA, surgeons should at least be reminded of the possibility of cystic meningiomas, and further examinations such as thinner CT scan and CTA should be considered which would be helpful for the differential diagnosis.

For cystic meningiomas, total resection is the defined standard therapy. It is established that the enhanced mural nodule and cyst wall should be resected simultaneously as much as possible; however, issues regarding the management of the unenhanced cyst wall are still under dispute. Several authors believe that it is unnecessary to remove the unenhanced cyst wall due to it containing no, or just a little amount of tumor cells.[ Nevertheless, Boukobza et al [ found that in up to 60.4% of meningiomas, the cyst wall contains tumor tissue and should be resected simultaneously. It is reported that about 20% of the nonenhanced cyst wall contains tumor tissue.[ Furthermore, the recurrence rate is up to 9% in cases that the cyst wall was reserved.[ Based on these data, we presume that for cystic meningiomas in CPA, the nonenhanced cyst wall may contain tumor tissue. We hold that multiple biopsies of the cyst wall should be implemented to assess the presence of tumor cells. With a propensity to be an atypical meningioma (WHO grade II), adjuvant radiosurgery is vital in patients who underwent incomplete resection. In addition, close and long-term postoperative follow-up should be emphasized to detect early or late tumor recurrence.

Conclusion

For cystic tumors located in the CPA, a differential diagnosis of cystic meningioma should be considered preoperatively. The most common symptoms of cystic meningioma in CPA are headache and hearing problems. Pathologically, clear cell meningioma is the most common subtype, which has a propensity to affect young patients and a higher recurrence rate. Gross total resection is extremely important. When encountering tumors with nonenhanced cyst walls, multiple biopsies of the cyst wall intraoperatively are necessary. Furthermore, cystic meningiomas in CPA have a relatively high recurrence rate. A close follow-up for multiple years is crucial.

Author contributions

Conceptualization: Jiuhong Li.

Data curation: Jiuhong Li, Jinli Meng, Qiguang Wang, Xuhui Hui.

Formal analysis: Jiuhong Li, Qiguang Wang.

Investigation: Jiuhong Li, Yanchao Wang, Wenke Liu.

Methodology: Jiuhong Li.

Resources: Jinli Meng, Qiguang Wang, Wenke Liu, Xuhui Hui.

Supervision: Jinli Meng, Qiguang Wang, Yanchao Wang, Wenke Liu.

Validation: Jinli Meng, Yanchao Wang.

Visualization: Jinli Meng, Xuhui Hui.

Writing – original draft: Jiuhong Li.

Writing – review & editing: Jiuhong Li, Xuhui Hui.