Sequential MRI and MR spectroscopy in embolized meningiomas: correlation with surgical and histopathological findings

Embolization of Skull Base Meningiomas with Embosphere® Microspheres: Factors Predicting Treatment Response and Evaluation of Complications

OBJECTIVE

Preoperative embolization for intracranial meningiomas can cause tumor necrosis, reduce intraoperative blood loss, and facilitate surgery. This study aimed to evaluate the efficacy of tumor embolization using Embosphere® microspheres for skull base meningiomas and analyze post-embolization plain computed tomography (CT) and magnetic resonance imaging (MRI) scans to identify findings that could potentially predict treatment response.

METHODS

Between April 2014 and April 2020, 80 patients with skull base meningiomas presenting at our medical center underwent embolization with Embosphere® microspheres. The effects of tumor embolization were evaluated through a comparison of post-embolization plain CT and contrast-enhanced MRI.

RESULTS

A total of 143 vessels (102/108 external carotid artery branches; 41/65 internal carotid artery branches) from 80 skull base meningiomas were embolized with Embosphere® microspheres. Microspheres 100-300 μm in size were used in two cases, microspheres 300-500 μm in size were used in 12 cases, and microspheres 500-700 μm in size were used in 66 cases. Post-embolization contrast-enhanced MRI showed reductions in enhancing lesions within the tumor in 55/80 cases. Post-embolization plain CT scans showed high-density lesions within the tumor in 41/55 cases. Thus, reductions in enhancing lesions on post-embolization contrast-enhanced MRI were statistically significantly associated with the presence of high-density lesions on post-embolization plain CT (P<0.001). Embolization-related neurological complications occurred in three cases.

CONCLUSIONS

Embosphere® microspheres are user friendly and effective embolic materials for the embolization of skull base meningiomas. Post-embolization contrast-enhanced MRI and plain CT findings may be useful for evaluating the effects of tumor embolization.

Hypervascular vestibular schwannoma: A case report and review of the literature

Vestibular schwannomas, also known as acoustic neuromas, are benign tumors that arise from Schwann cells near the transition from glial cells to Schwann cells. While most vestibular schwannomas are hypovascular tumors, a small percentage constitute the hemorrhagic and/or hypervascular vestibular schwannomas (HVS) subtype. We describe a case of a 36-year-old female who presented with nausea, vomiting, and an acute decrease in vision in her right eye. Computed tomography of the head demonstrated a hemorrhagic lesion in the right hemisphere with evidence of ventricular effacement. Follow-up magnetic resonance imaging revealed a mass in the right cerebellopontine angle that was hypointense on T1-weighted imaging and mild hyperintense heterogeneous signal on T2-weighted imaging, suggestive of a hemorrhagic vestibular schwannoma. It is important for radiologists to recognize the unique clinical and radiological features of HVS in the initial diagnostic assessment of cerebellopontine angle tumors and to distinguish it from common (hypovascular) vestibular schwannomas and other related pathologies. A preoperative diagnosis of HVS allows clinicians to become familiar with the unique characteristics of the tumor and to devise a feasible operative strategy prior to surgical resection.

Arterial spin labeling imaging correlates with the angiographic and clinical vascularity of vestibular schwannomas

PURPOSE

Hypervascular vestibular schwannomas (HVSs) are a type of the vestibular schwannomas (VSs) that are extremely difficult to remove. We examined whether HVSs can be predicted by using arterial spin labeling (ASL) imaging.

METHODS

A total of 103 patients with VSs underwent ASL imaging and digital subtraction angiography (DSA) before surgery. Regional cerebral blood flow (CBF) of gray matter and regional tumor blood flow (TBF) were calculated from ASL imaging, and we defined the ratio of TBF to CBF as the relative TBF (rTBF = TBF/CBF). Angiographic vascularity was evaluated by DSA, and clinical vascularity was evaluated by the degree of intraoperative tumor bleeding. Based on the angiographic and clinical vascularity, the VSs were divided into two categories: HVS and non-HVS. We compared rTBF with angiographic and clinical vascularities, retrospectively.

RESULTS

The mean rTBFs of angiographic non-HVSs and HVSs were 1.29 and 2.58, respectively (p < 0.0001). At a cutoff value of 1.55, the sensitivity and specificity were 93.9% and 72.9%, respectively. The mean rTBFs of clinical non-HVS and HVSs were 1.45 and 2.22, respectively (p = 0.0002). At a cutoff value of 1.55, the sensitivity and specificity were 79.4% and 66.7%, respectively.

CONCLUSION

The rTBF calculated from ASL imaging correlates well with tumor vascularity and may be useful for predicting HVSs before surgery.

Extent of T1+C Intensity Is a Predictor of Blood Loss in Resection of Meningioma

INTRODUCTION

Surgery for meningioma is associated with significant blood loss. Preoperative embolization has been associated with reduction of blood loss and has been noted to decrease intensity on T1 + contrast sequences. We investigate potential relationships between blood loss and the extent of T1 + contrast intensity.

METHODS

Forty-two patients who underwent surgical resection of intracranial meningioma were retrospectively reviewed from August 2009 to May 2016. Clinical data were extracted (age, gender, location of meningioma, grade of meningioma, need for blood transfusion during surgery, preoperative and postoperative hematocrit level, estimated blood loss [EBL], and duration of surgery). Using OsiriX MD, the tumor volume, sinus involvement, peritumoral edema, extent of resection, and T1 index (average T1+C intensity across the tumor normalized to value at basilar artery) were assessed.

RESULTS

With EBL, univariate analysis for gender, tumor volume, and T1 index showed correlations with P value <0.1. A logistic regression to predict EBL <300 mL and ≥300 mL using the 3 variables yielded T1 index (odds ratio [OR], 31.22; 95% confidence interval [CI], 1.14-855.65), gender (OR, 0.17; 95% CI, 0.03-0.96), and tumor volume (OR, 1.05; 95% CI, 1.00-1.10) as significant predictors (all P < 0.05). With duration for surgery, gender, tumor volume, need for blood transfusion, and preoperative hematocrit exhibited P value <0.05; multivariate analysis did not show a significant model.

CONCLUSIONS

Along with gender and tumor volume, extent of T1+C intensity is also an independent predictor of EBL. This finding may be helpful for surgical management of meningioma.

Safety and efficacy of medium-sized particle embolisation for skull-base meningioma

AIM

To determine the effectiveness and safety of preoperative tumour embolisation for skull-base meningiomas via external carotid artery (ECA) feeders using medium-sized (150-250 μm) polyvinyl alcohol (PVA) particles.

MATERIALS AND METHODS

This study included 114 consecutive patients with skull-base meningiomas who underwent preoperative tumour embolisation using medium-sized PVA particles from January 2004 to December 2013. Tumours were categorised according to feeding artery as follows: type 1, tumour staining at ECA angiography only; type 2, tumour staining at both the ECA and internal carotid artery (ICA) angiography; or type 3, little or no tumour staining at ECA angiography. The effectiveness was based on the percent reduction in the enhanced area: >75% was considered effective, 25-75% was considered partially effective, and <25% was considered ineffective.

RESULTS

Tumour embolisation was performed in patients with dominant feeding vessels originating from the ECA. Procedural-related complications occurred in two (1.8%) patients. Post-procedural MRI images were available for 51 patients, which revealed effective embolisation in only 13 (25.5%) patients. Identification of an ICA feeding vessel was associated with ineffective embolisation (p=0.011). Effective embolisation was associated with low estimated blood loss during surgery.

CONCLUSION

ECA embolisation using medium-sized PVA is ineffective in patients in whom a definitive ICA feeding vessel was identified, even if preprocedural angiography showed that the dominant feeder originated from the ECA. When the risks of surgical morbidity and mortality are expected to be high, ICA feeder embolisation should also be considered.

Intracranial Meningiomas: A 30-Year Experience and Literature Review

Intracranial meningiomas are tumors arising from the covering cells of the arachnoid layer of the dura mater or from the intraventricular choroid plexus. While mostly benign tumors, they still represent a major challenge to neurosurgeons and other medical disciplines involved in their diagnostic and therapeutic management. Although this review intends to give some state-of-the-art information from the literature, it is mainly based on personal experiences since more than 30 years caring for more than 1500 meningioma patients and point to a few new strategies to further improve on patient outcome.Diagnostics are based on magnetic resonance imaging which shows the relationship between tumor and surrounding intracranial structures, particularly the brain but also the vasculature and to some extent the cranial nerves. Furthermore, it may suggest the grading of the tumor and is very helpful in the postoperative diagnosis of complications and later follow-up course.Surgery still is the main treatment with the aim to completely remove the tumor; also in cases of recurrence, other additional options include radiotherapy and radiosurgery for incompletely removed or recurrent meningiomas. Postoperative chemotherapy has not been shown to provide substantial benefit to the patient especially in highly malignant meningiomas.All therapy options should be intended to provide the patient with the best possible functional outcome. Patients' perspective is not always equivalent to surgeons' perspectives. Neuropsychological evaluation and additional guidance of patients harboring meningiomas have proven to be important in modern neurosurgical intracranial tumor treatment. Their help beyond neurosurgical care facilitates the patients to lead an independent postoperative life.

Pre-operative intracranial meningioma embolization

Pre-operative embolization is a routinely utilized therapeutic adjunct to the resection of hypervascular lesions of the head and neck. In particular, pre-operative cerebral angiography and tumor embolization has become standard practice at many centers in the management of select intracranial meningiomas. However, controversy remains regarding its specific indications and clinical utility. In this article, we examine the principles of meningioma embolization, emphasizing the indications, risks and benefits associated with its use in the pre-operative setting.

New pathology classification, imagery techniques and prospective trials for meningiomas: the future looks bright

PURPOSE OF REVIEW

Advances in functional and metabolic imaging have been added to the diagnostic armamentarium for meningioma. New prospective trials have been initiated, and it is foreseen that American Society of Clinical Oncology evidence-level II will be soon available for this brain tumor. This review will focus on recent advances in radiology and their significance for clinical care. The new WHO classification will be detailed.

RECENT FINDINGS

Brain invasion is an important criterion in the 2007 WHO classification for atypical meningioma. Apparent diffusion coefficient values on MRI observed with grade II and grade III meningiomas are significantly decreased when compared to benign tumors. [F]fluorodeoxyglucose PET may also predict tumor grade and tumor recurrence. Radio-labeled amino acid PET may be used to delineate target volume for radiotherapy planning. Stereotactic biopsy guidance and functional therapy monitoring could be foreseen using PET-MRI. One phase II study is assessing the benefit of dose escalation for nonbenign meningioma and another evaluates the therapeutic strategy of observation, standard- and high-dose radiotherapy for low-risk, intermediate-risk and high-risk patients.

SUMMARY

The use of functional MRI, with or without PET imaging, may be useful in assessing the potential clinical outcome of meningioma. Various therapeutic strategies, including observation and high-dose radiotherapy, are evaluated in two ongoing phase II studies.

MR spectroscopy in patients with intracranial meningiomas

With magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), we tried to get more pre-operative information in patients with suspicious meningioma concerning the histologic diagnosis especially regarding WHO Grades I and II meningiomas. Apart from the known spectra and metabolites such as choline, creatine and N-acetyl-aspartate (NAA), recent publications have shown that lactate is often found in necrotic tumor tissue. Within a 2 year period, 39 patients with an intracranial meningioma were studied with MRS. In 62.5% of histologic atypical meningiomas (WHO Grade II), a lactate peak could be demonstrated in the pre-operative MRS. Interestingly, also patients with multiple meningiomas show different spectra of their tumors.