Natural history of lesions with the MR imaging appearance of multinodular and vacuolating neuronal tumor

Imaging of pediatric glioneuronal and neuronal tumors

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

Two medicolegal autopsy cases of multinodular and vacuolating neuronal tumor revealed by postmortem MRI

The multinodular and vacuolating neuronal tumor (MVNT) is a recently recognized brain lesion. MVNT has a characteristic appearance in MRI images and is potentially epileptogenic. To the best of our knowledge, no report has yet described this pathological entity in the forensic medicine literature. We present two medicolegal autopsy cases where postmortem MRI (PMMR) was useful to detect this lesion. Case 1: a man in his 30s, with about a 7-year history of intractable epilepsy and known MVNT died suddenly. Although MVNT was not detected in the initial morphological evaluation during autopsy, PMMR of the formalin-fixed brain revealed the lesion in the left frontal lobe. Histopathology confirmed it as a MVNT. Case 2: a man in his 20s hanged himself to death. PMMR prior to autopsy revealed MVNT in his brain, and the diagnosis was confirmed by a detailed histopathological evaluation. In both cases, postmortem CT was not useful for evaluation. The cases suggested that MVNT can cause sudden, unexpected epileptic death, and pre- or post-autopsy PMMR may be useful to detect it.

Collision tumor: Multinodular and vacuolating neuronal tumor with isocitrate dehydrogenase-mutant diffuse astrocytoma

Herein, we report a case of a collision tumor involving a multinodular and vacuolating neuronal tumor (MVNT) and a diffuse astrocytoma. A collision tumor between these two entities has not previously been reported. The patient is a 35-year-old woman who presented with new-onset hearing loss and ringing in her right ear. Magnetic resonance imaging identified a non-enhancing mass involving the gray matter and subcortical white matter of the left middle frontal gyrus. Additionally, tiny clustered nodules were noted along the underlying subcortical ribbon and superficial subcortical white matter of the left superior frontal gyrus. The patient underwent a left frontal craniotomy and complete resection of the mass. Histologic examination of the resected specimen demonstrated a collision tumor consisting of a diffuse astrocytoma (isocitrate dehydrogenase [IDH] mutant, central nervous system [CNS] World Health Organization [WHO] grade 2) and an MVNT, with the latter demonstrating characteristic morphologic and immunohistochemical features.

The 2021 WHO Classification for Gliomas and Implications on Imaging Diagnosis: Part 3-Summary of Imaging Findings on Glioneuronal and Neuronal Tumors

The fifth edition of the World Health Organization classification of central nervous system tumors published in 2021 reflects the current transitional state between traditional classification system based on histopathology and the state-of-the-art molecular diagnostics. This Part 3 Review focuses on the molecular diagnostics and imaging findings of glioneuronal and neuronal tumors. Histological and molecular features in glioneuronal and neuronal tumors often overlap with pediatric-type diffuse low-grade gliomas and circumscribed astrocytic gliomas (discussed in the Part 2 Review). Due to this overlap, in several tumor types of glioneuronal and neuronal tumors the diagnosis may be inconclusive with histopathology and genetic alterations, and imaging features may be helpful to distinguish difficult cases. Thus, it is crucial for radiologists to understand the underlying molecular diagnostics as well as imaging findings for application on clinical practice. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Long-Term Follow-up of Multinodular and Vacuolating Neuronal Tumors and Implications for Surveillance Imaging

BACKGROUND AND PURPOSE

Most multinodular and vacuolating neuronal tumors (MVNTs) are diagnosed and followed radiologically without any change across time. There are no surveillance guidelines or quantitative volumetric assessments of these tumors. We evaluated MVNT volumes during long follow-up periods using segmentation tools with the aim of quantitative assessment.

MATERIALS AND METHODS

All patients with MVNTs in a brain MR imaging report in our system were reviewed. Patients with only 1 brain MR imaging or in whom MVNT was not clearly the most likely diagnosis were excluded. All MVNTs were manually segmented. For all follow-up examinations, absolute and percentage volume change from immediately prior and initial examinations were calculated.

RESULTS

Forty-eight patients (32 women; median age, 50.5 years at first scanning) underwent 158 brain MRIs. The median duration between the first and last scan was 15.6 months (interquartile range, 5.7-29.6 months; maximum, 6.4 years) and between consecutive scans, it was 6.7 months (interquartile range, 3.3-12.4 months; maximum, 4.9 years). Pearson correlation coefficients between days since immediately prior scan versus absolute and percentage volume change from immediately prior scan were r = 0.05 (P = .60) and r = 0.07 (P = .45), respectively. For the relationship between days since the first scan versus absolute and percentage volume change from the first scan, values were r = -0.06 (P = .53) and r = -0.04 (P = .67), respectively.

CONCLUSIONS

MVNT segmentation across follow-up brain MR imaging examinations did not demonstrate significant volume differences, suggesting that these tumors do not enlarge with time. Hence, frequent surveillance imaging of newly diagnosed MVNTs may not be necessary.

Incidental findings on brain magnetic resonance imaging (MRI) in adults: a review of imaging spectrum, clinical significance, and management

Utilization of brain MRI has dramatically increased in recent decades due to rapid advancement in imaging technology and improving accessibility. As a result, radiologists increasingly encounter findings incidentally discovered on brain MRIs which are performed for unrelated indications. Some of these findings are clinically significant, necessitating further investigation or treatment and resulting in increased costs to healthcare systems as well as increased patient anxiety. Moreover, management of these incidental findings poses a significant challenge for referring physicians. Therefore, it is important for interpreting radiologists to know the prevalence, clinical consequences, and appropriate management of these findings. There is a wide spectrum of incidental findings on brain MRI such as asymptomatic brain infarct, age-related white matter changes, microhemorrhages, intracranial tumors, intracranial cystic lesions, and anatomic variants. This article provides a narrative review of important incidental findings encountered on brain MRI in adults with a focus on prevalence, clinical implications, and recommendations on management of these findings based on current available data.

Radiological and clinical features of multinodular and vacuolating neuronal tumor (MVNT)

Background

To investigate the imaging findings and clinical features of multinodular and vacuolating neuronal tumor (MVNT).

Methods

We retrospectively sought for cases that have suspicious imaging findings for MVNT through the hospital information system. The patients’ demographics and clinical symptoms were extracted. All available images were re-examined.

Results

Headache was the most common complaint (n = 7). Other complaints included seizure, stroke-like symptoms and numbness. Conventional MRI revealed that all lesions consisted of tiny, sharply marginated, round or ovoid nodules following the gyral contour. These nodules were hyperintense on T2 and FLAIR WI, hypointense on T1 WI. All lesions were characterized by a lack of enhancement and diffusion restriction. Mass effect and peripheral edema were not observed. MVNT presented as an incidental finding in one case who complained gynecomastia and had pituitary adenoma on pituitary MRI. All lesions were supratentorial—mostly on the right side (10/11)—and located in subcortical white matter. Follow-up MRI was available for 11 patients with a mean of 14.8 months (3–40 months). No change in lesion size and morphology was observed in these follow-up images.

Conclusions

Radiological and clinical follow-up data suggest MVNT may exhibit indolent behavior. If asymptomatic, patients can be followed by imaging alone. Surgery should be considered for symptomatic patients.

New Imaging Features of Multinodular and Vacuolating Neuronal Tumor Revealed by Alcohol and Illicit Drugs Consumption

It has been almost a decade since the multinodular and vacuolating neuronal tumor (MVNT) was first described. In 2021, WHO classified it as a defined entity, and it is considered one of the glioneuronal and neuronal tumors. Due to its similarities with dysembryoplastic neuroepithelial tumors (DNET), some authors consider it a variant of these, ranking in the category of malformations, but genetic alterations favor a neoplastic origin. We present a 29-year-old male with a generalized onset tonic-clonic seizure after a nightclub party. Imaging studies revealed a right temporal multinodular and vacuolating neuronal tumor confirmed by biopsy. It is considered a nonaggressive, "leave me alone" brain lesion, which does not require biopsy because of well-defined MRI characteristics. Surgery is indicated only in symptomatic cases. We consider that this lesion was revealed by his seizure, most probably provoked (with normal video EEG recording) by the consumption of a lot of alcohol, illicit drugs, and sleep loss after a club party. We recommended close monitoring, but our patient preferred the surgery. Our case added more imaging details corroborated with the histopathology features of MVNT. FLAIR images revealed hypointense nodules surrounded by hyperintense peripheral rings and areas of high signal intensity between the nodules, which correspond to the histopathological architecture. To our knowledge, this is the first case of MVNT with diffusion tensor imaging and fiber tractography imaging studies.

Multinodular and vacuolating neuronal tumor associated with focal cortical dysplasia in a child with refractory epilepsy: a case report and brief review of literature

Multinodular and vacuolating neuronal tumor (MVNT) is a rare newly identified benign lesion, firstly included in the World Health Organization classification of tumors of the central nervous system in 2016, whose neoplastic or dysplastic nature remains unclear but with a distinctive cytoarchitectural pattern and radiological features. It is usually discovered as late-onset refractory epilepsy, headache related, or an incidental lesion of adulthood. As it is typically a stable disease, many opt for follow-up, as long as it keeps remaining asymptomatic, leaving surgery for refractory epilepsy, neurological deficits, or intracranial hypertension symptoms. A subtotal or complete resection seems to control seizures and neurological manifestations. We herein present the case of a child with refractory epilepsy related to MVNT and focal cortical dysplasia, a dual pathology case in a less frequent age group and without the typical radiological imaging. We report its radiologic features, histologic description, and management, and we present a brief literature review on MVNT focusing on the pediatric cases reported. MVNT should now be another probable low-grade epilepsy-associated lesion (LEAT) in patients of all ages, with a benign and stable course as it constitutes a curable cause of focal epilepsy. As all the refractory cases, surgery should be indicated after a comprehensive evaluation of a multidisciplinary epilepsy surgery team.

Imaging of Neuronal and Mixed Glioneuronal Tumors

Neuronal and mixed glioneuronal tumors represent a group of neoplasms with varying degrees of neural and glial elements. Their age of presentation varies, but they are most commonly seen in children and young adults. With the exception of anaplastic ganglioglioma and other atypical variants, most lesions are low grade; however, they can have significant morbidity because of seizures, mass effect, or difficult to treat hydrocephalus. Although many tumors show overlapping clinical and imaging features, some have relatively distinctive imaging characteristics that may aid in narrowing the differential diagnosis. In this review, we discuss relevant clinical and pathologic characteristics of these tumors and provide an overview of conventional and advanced imaging features that provide clues as to the diagnosis.

Advanced multiparametric magnetic resonance imaging of multinodular and vacuolating neuronal tumor

BACKGROUND AND PURPOSE

Multinodular and vacuolating neuronal tumor (MVNT) of the cerebrum is a rare brain lesion with suggestive imaging features. The aim of our study was to report the largest series of MVNTs so far and to evaluate the utility of advanced multiparametric magnetic resonance (MR) techniques.

METHODS

This multicenter retrospective study was approved by our institutional research ethics board. From July 2014 to May 2019, two radiologists read in consensus the MR examinations of patients presenting with a lesion suggestive of an MVNT. They analyzed the lesions' MR characteristics on structural images and advanced multiparametric MR imaging.

RESULTS

A total of 64 patients (29 women and 35 men, mean age 44.2 ± 15.1 years) from 25 centers were included. Lesions were all hyperintense on fluid-attenuated inversion recovery and T2-weighted imaging without post-contrast enhancement. The median relative apparent diffusion coefficient on diffusion-weighted imaging was 1.13 [interquartile range (IQR), 0.2]. Perfusion-weighted imaging showed no increase in perfusion, with a relative cerebral blood volume of 1.02 (IQR, 0.05) and a relative cerebral blood flow of 1.01 (IQR, 0.08). MR spectroscopy showed no abnormal peaks. Median follow-up was 2 (IQR, 1.2) years, without any changes in size.

CONCLUSIONS

A comprehensive characterization protocol including advanced multiparametric magnetic resonance imaging sequences showed no imaging patterns suggestive of malignancy in MVNTs. It might be useful to better characterize MVNTs.

Magnetic resonance imaging findings of two cases with multinodular and vacuolating neuronal tumor

Multinodular and vacuolating neuronal tumors (MVNT) are low grade neuronal tumors classified in cerebral tumors based on 2016 WHO central nerve system classification. Previously, MVNTs were probably tumors incidentally determined by imaging methods, but they could not be diagnosed or they were misdiagnosed. Two cases are reported in the present study, for which radiological imaging was carried out for epilepsy in one and for headache in the other. The first case was a twenty seven years old female patient with headache complaint. Brain MRI examination revealed a clustering lesion of multinodular character located in an about 4.0 × 3.5 × 1.5 cm area which had a left precuneal subcortical-juxtacortical location. The other case was a male patient with epilepsy. A clustering lesion of multinodular nature was determined in an area of about 2.0 × 2.0 × 1.5 cm in cortical-subcortical area in corona radiata-convexity plane of right middle frontal girus. No changes in size or nature were determined in follow-up examinations. MVNTs are recently defined tumors, and the characteristic feature for diagnosis of these rare tumor entities could be a subcortical white matter lesion with satellite nodules that manifest itself as T2/FLAIRhyperintensity. Increasing number of case reports and studies in the literature could make the radiological and pathological signs of the condition clearer.

Infratentorial Multinodular and Vacuolating Neuronal Tumor or Multinodular and Vacuolating Posterior Fossa Lesions of Unknown Significance? Clinico-Radiologic Findings from 2 Cases

BACKGROUND

Infratentorial multinodular lesions resembling multinodular and vacuolating neuronal tumor of the cerebrum (MVNT) have been indicated in literature with 2 different names reflecting alternative perspectives: multinodular and vacuolating posterior fossa lesions of unknown significance (MV-PLUS), suggesting that these lesions may belong to a new entity, and MVNT of the brain, assuming that they actually correspond to infratentorial MVNT. Because of the limited number of cases reported and the absence of histopathologic data, it is unclear which denomination should be used.

CASES DESCRIPTION

Two patients, a 41-year-old man (case 1) suffering headache and a 44-year-old man (case 2) with vertigo, underwent magnetic resonance imaging (MRI) examination. MRI showed, in both cases, multinodular lesions involving the vermis, broadly extending to the superior part of the right cerebellar hemisphere in case 1, and involving the superior paravermian part of the left cerebellar hemisphere in case 2. The follow-up period was 3 years in case 1 and 14 years in case 2.

CONCLUSIONS

Infratentorial lesions show nodules with cystic or cyst-like signal intensity on MRI, a feature infrequently reported in supratentorial MVNT, and may involve the cortex. No variations were noted during a prolonged follow-up supporting the benign behavior of these lesions.

Multinodular and vacuolating neuronal tumor (MVNT): A presumably incidental and asymptomatic case in an intractable epilepsy patient

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Multinodular vacuolating neuronal tumor (MVNT) was initially reported as epilepsy-related brain tumor.

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MVNT can exist as incidental and asymptomatic lesions in some cases.

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It is not always necessary to perform surgical resection of MVNT even in patients with epilepsy.

Introduction

Multinodular and vacuolating neuronal tumor (MVNT) had been initially described as an epilepsy-related brain tumor, but recent studies demonstrated it could be found incidentally in non-epilepsy patients.

Case report

A 33-year-old woman with intractable post-encephalitis epilepsy presented a cluster of multinodular T2 hyperintensity in the left temporal lobe, which was very similar to the characteristics of MVNT. Long-term video electroencephalogram demonstrated that the habitual seizures were originated from bilateral temporal area and the interictal epileptic discharges were seen multifocally, although the lesions with MVNT appearance were localized in the left temporal lobe. It was presumed that the epilepsy in this patient was due to encephalitis in the past, and the link between the lesions and the epilepsy in this patient seemed weak.

Conclusion

Although MVNT had been considered as an epilepsy-related brain tumor, we suggest it is not necessarily preferable to perform surgical resection of MVNT even on patients with epilepsy, unless epileptic foci are highly related to MVNT.

Multinodular and Vacuolating Posterior Fossa Lesions of Unknown Significance

Multinodular and vacuolating neuronal tumor of the cerebrum is a rare supratentorial brain tumor described for the first time in 2013. Here, we report 11 cases of infratentorial lesions showing similar striking imaging features consisting of a cluster of low T1-weighted imaging and high T2-FLAIR signal intensity nodules, which we referred to as multinodular and vacuolating posterior fossa lesions of unknown significance. No relationship was found between the location of the lesion and clinical symptoms. A T2-FLAIR hypointense central dot sign was present in images of 9/11 (82%) patients. Cortical involvement was present in 2/11 (18%) of patients. Only 1 nodule of 1 multinodular and vacuolating posterior fossa lesion of unknown significance showed enhancement on postcontrast T1WI. DWI, SWI, MRS, and PWI showed no malignant pattern. Lesions did not change in size or signal during a median follow-up of 3 years, suggesting that multinodular and vacuolating posterior fossa lesions of unknown significance are benign malformative lesions that do not require surgical intervention or removal.

Multinodular and Vacuolating Neuronal Tumor of the Cerebrum (MVNT): A case series and review of the literature

BACKGROUND AND PURPOSE

Multinodular and Vacuolating Neuronal Tumor of the cerebrum (MVNT) is a benign -seizure associated- lesion affecting mostly adults. This new entity has been included in the 2016 World Health Organization classification of tumors of the central nervous system. Its pathologic hallmark consist of a subcortical cluster of nodular lesions located on the subcortical white matter. We aim to report a series of cases of presumed MVNT observed in our institution and review the literature.

MATERIALS AND METHODS

In this retrospective study, a search was performed on our hospital information system. Sixteen cases were included. Demographic, clinical and radiological features were detailed in a table. All patients had an MRI acquired either on a 1.5 or a 3 Tesla scanner. Sequences performed included T1, T2, GRE/SWI, T2 FLAIR and DWI. Gadolinium enhanced T1-WI wer available in 11 patients and follow-up MRI were available in 7 patients.

RESULTS

Patient ages ranged from 16 to 77 years (mean 42 years). Seizure and non-focal headache were by far the most common neurological complaints for which MRI was requested. All lesions consisted of clusters of multiple, discrete, round or ovoid, intra-axial, FLAIR and T2-WI hyperintense nodules. Follow-up MRI scans showed no changes between studies.

CONCLUSIONS

MVNT is a benign, stable lesion that exhibits a typical radiological pattern that most of the times sufficed to arrive to a diagnosis, without the need of pathological confirmation. We confirm that our demographic, clinical and radiological findings are in accordance with those published in international literature.

Clinicopathological and molecular analysis of multinodular and vacuolating neuronal tumors of the cerebrum

Multinodular and vacuolating neuronal tumor (MVNT) of the cerebrum is a recently recognized rare neuronal tumor, and its pathogenesis is unclear. We analyzed 7 cases of histologically typical MVNT: 6 were adults (mean age, 43.0 years [range, 23-56 years]) and 1 was a child (age, 10 years). The most common symptoms were seizures (n = 4) and headache (n = 2). The tumors were supratentorial (temporal, 5; frontal lobes, 2) in origin as reported. Vacuolated tumor cells were robustly positive for α-INA and Olig2 and at least partly positive for synaptophysin and MAP2, but negative for Neu-N, nestin and CD34. GFAP and vimentin were expressed in reactive astrocytes but not in tumor cells. Negative results were obtained for p53, IDH-1, BRAF^V600E, H3 K27M, EGFR, Lin28A, and L1CAM. ATRX, BRG1, INI-1, and TMHH were retained. The Ki-67 labeling index was very low (<1%), and pHH3 revealed no mitotic figure. Ultrastructural features of tumor cells were comparable with those of immature neuronal cells, with several intracytoplasmic myelin-like autophagosomes and pericellular vacuolization. No IDH1/IDH2 and BRAF^V600E mutations were found upon direct sequencing. Whole-exome sequencing revealed FGFR2-ZMYND11 gene fusion in 1 case. After gross total resection, all patients were alive without seizures. There was no tumor recurrence during an average period of 68 months (range, 23-101 months). The analysis of 7 typical cases of MVNT suggested that these lesions may be clonal tumors because FGFR2-ZMYND11 fusion was found (1 case).

Neuroimaging of Dilated Perivascular Spaces: From Benign and Pathologic Causes to Mimics

Perivascular spaces (PVSs), also known as Virchow-Robin spaces, are pial-lined, fluid-filled structures found in characteristic locations throughout the brain. They can become abnormally enlarged or dilated and in rare cases can cause hydrocephalus. Dilated PVSs can pose a diagnostic dilemma for radiologists because of their varied appearance, sometimes mimicking more serious entities such as cystic neoplasms, including dysembryoplastic neuroepithelial tumor and multinodular and vacuolating neuronal tumor, or cystic infections including toxoplasmosis and neurocysticercosis. In addition, various pathologic processes, including cryptococcosis and chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids, can spread into the brain via PVSs, resulting in characteristic magnetic resonance imaging appearances. This review aims to describe the key imaging characteristics of normal and dilated PVSs, as well as cystic mimics and pathologic processes that directly involve PVSs.

Multinodular and vacuolating neuronal tumors in epilepsy: dysplasia or neoplasia?

Multinodular and vacuolating neuronal tumor (MVNT) is a new pattern of neuronal tumour included in the recently revised WHO 2016 classification of tumors of the CNS. There are 15 reports in the literature to date. They are typically associated with late onset epilepsy and a neoplastic vs. malformative biology has been questioned. We present a series of ten cases and compare their pathological and genetic features to better characterized epilepsy‐associated malformations including focal cortical dysplasia type II (FCDII) and low‐grade epilepsy‐associated tumors (LEAT). Clinical and neuroradiology data were reviewed and a broad immunohistochemistry panel was applied to explore neuronal and glial differentiation, interneuronal populations, mTOR pathway activation and neurodegenerative changes. Next generation sequencing was performed for targeted multi‐gene analysis to identify mutations common to epilepsy lesions including FCDII and LEAT. All of the surgical cases in this series presented with seizures, and were located in the temporal lobe. There was a lack of any progressive changes on serial pre‐operative MRI and a mean age at surgery of 45 years. The vacuolated cells of the lesion expressed mature neuronal markers (neurofilament/SMI32, MAP2, synaptophysin). Prominent labelling of the lesional cells for developmentally regulated proteins (OTX1, TBR1, SOX2, MAP1b, CD34, GFAPδ) and oligodendroglial lineage markers (OLIG2, SMI94) was observed. No mutations were detected in the mTOR pathway genes, BRAF, FGFR1 or MYB. Clinical, pathological and genetic data could indicate that MVNT aligns more with a malformative lesion than a true neoplasm with origin from a progenitor neuro‐glial cell type showing aberrant maturation.