Advanced multiparametric magnetic resonance imaging of multinodular and vacuolating neuronal tumor

The Mickey Mouse's hand sign in brain MRI points out multinodular and vacuolating neuronal tumors in mesial temporal lobe structures

PURPOSE

Multinodular and vacuolating neuronal tumor (MVNT) is a rarely diagnosed neoplastic lesion often associated with adult-onset focal seizures. In some situations, atypical MRI features of MVNT may mimic other long-term epilepsy associated tumors (LEATs) or diffuse low-grade gliomas. In such a context, the identification of distinct clinical markers is recommended.

METHODS

We retrospectively analyzed the neuroimaging features of histologically confirmed MVNT lesions of our epilepsy surgery cohort. All the identified MVNT patients had a mesial temporal lobe location. The MRI features from the MVNT population were compared to those from non-MVNT lesions randomly selected in our cohort. Non-MVNT lesions consisted of (i) other tumoral lesions belonging to LEATs group, (ii) infiltrative tumoral lesions such as grade 2, IDH-mutant Gliomas, and (iii) non-tumoral, highly epileptogenic lesions, such as hippocampal sclerosis.

RESULTS

MRI analysis of patients with MVNT noticed an unusual FLAIR hyperintense signal extending from the uncus to the anterior white commissure through the sublenticular region. This neuroimaging abnormality visually mimicked "Mickey Mouse's hand" on coronal plane. The "Mickey Mouse's hand" sign was identified in 6 patients out of 9 (66.7%) MVNT patients. We did not identify the Mickey Mouse's hand sign in other control lesions (0/11 ganglioglioma, 0/11 glioma, 0/150 hippocampal sclerosis), except in one patient with dysembryoplastic neuroepithelial tumors (DNET) (1/15; 6.7%). All patients showing the "Mickey Mouse's hand" sign were seizure-free after surgery.

CONCLUSIONS

The Mickey Mouse's hand sign represents a straightforward and easy-to-remember neuroimaging feature, that does not require advanced MRI sequences and that could help clinicians facing mesial temporal lesions to rapidly raise the suspicion of MVNT diagnosis.

Multinodular and Vacuolating Neuronal Tumors: Imaging Features, Diagnosis, and Management Challenges

Background/Objectives: Multinodular and vacuolating neuronal tumors (MNVTs) are a type of recently identified benign neuroepithelial tumor with debated malformative or neoplastic origins. This review summarizes their neuroanatomical localization, imaging, histopathology, immunohistochemistry, and diagnostic challenges. Methods: A systematic review of PUBMED/MEDLINE was performed in December 2024. Results: Of 118 screened articles, 39 were eligible, covering 299 patients. MNVTs are often asymptomatic "leave me alone" lesions, discovered incidentally, though nonspecific symptoms (59.9%) and seizures (19.7%) are reported. Immunohistochemistry reveals variable profiles, reflecting complex cellular differentiation. The characteristic "bubble-like" MRI pattern along the subcortical ribbon and superficial white matter is a reliable diagnostic feature. Rare cortical involvement and atypical band-like lesions occur. MRI signal intensity varies. Over a mean follow-up of 36 months, lesions were stable or non-recurrent, with only one case of progression. Conclusion: MVNT imaging mimics other glioneuronal lesions, but reliable diagnostic MRI features include a "bubble-clustered" appearance, lack of cortical involvement, absence of enhancement, and temporal lobe predominance. Hemodynamic and metabolic properties support the diagnosis. Most lesions remain stable, requiring no treatment. Surgical resection is reserved for cases with uncontrolled seizures or atypical locations where the diagnosis is unclear.

Multinodular and Vacuolating Neuronal Tumors of the Cerebrum: A Systematic Review of the Literature

Multinodular and vacuolating neuronal tumors (MVNTs) of the cerebrum are rare, seizure-related, low-grade tumors of the central nervous system that usually affect young adults. First described by Huse et al. in 2013, these neoplasms are usually located within the deep cortical ribbon and the superficial white matter and have a characteristic cytoarchitecture of cells with neuronal and glial differentiation that form multiple nodules with conspicuous vacuolation. Because of their benign nature and indolent clinical course, radiologically based differentiation from other entities is of paramount importance to avoid unnecessary surgical intervention. To the best of our knowledge, our study represents the first systematic review in the literature aiming to delineate the characteristics of MVNTs regarding epidemiology, clinical manifestation, histopathology, imaging, and management. PubMed/MEDLINE and SCOPUS databases were systematically investigated for MVNT cases until November 2023. The search yielded 29 case reports comprising 41 patients with a mean age of 32.6 years and 7 case series with 164 patients. MVNTs were most commonly located in the supratentorial compartment, affecting the temporal, frontal, or parietal lobes. Their most frequent initial clinical manifestation was either seizures or headaches. On conventional magnetic resonance imaging techniques, they usually appear hypointense in T1-weighted images and hyperintense in T2-weighted and fluid-attenuated inversion recovery images and lack perilesional edema or postcontrast enhancement. MVNTs do not seem to change size or recur, even after partial resection of the tumor, indicating their indolent course, and, thus, surveillance with serial magnetic resonance imaging is the most appropriate management technique for these lesions.

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.

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.

Bright diffusion sign: A sensitive and specific radiologic biomarker for multinodular and vacuolating neuronal tumor

BACKGROUND AND PURPOSE

Accurate differentiation between multinodular and vacuolating neuronal tumor (MVNT) and dysembryoplastic neuroepithelial tumor (DNET) is important for treatment decision-making. We aimed to develop an accurate radiologic diagnostic model for differentiating MVNT from DNET using T2WI and diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

A total of 56 patients (mean age, 47.48±17.78 years; 31 women) diagnosed with MVNT (n = 37) or DNET (n = 19) who underwent brain MRI, including T2WI and DWI, were included. Two board-certified neuroradiologists performed qualitative (bubble appearance, cortical involvement, bright diffusion sign, and bright apparent diffusion coefficient [ADC] sign) and quantitative (nDWI and nADC) assessments. A diagnostic tree model was developed with significant and reliable imaging findings using an exhaustive chi-squared Automatic Interaction Detector (CHAID) algorithm.

RESULTS

In visual assessment, the imaging features that showed high diagnostic accuracy and interobserver reliability were the bright diffusion sign and absence of cortical involvement (bright diffusion sign: accuracy, 94.64 %; sensitivity, 91.89 %; specificity, 100.00 %; interobserver agreement, 1.00; absence of cortical involvement: accuracy, 92.86 %; sensitivity, 89.19 %; specificity, 100.00 %; interobserver agreement, 1.00). In quantitative analysis, nDWI was significantly higher in MVNT than in DENT (1.52 ± 0.34 vs. 0.91 ± 0.27, p < 0.001), but the interobserver agreement was fair (intraclass correlation coefficient = 0.321). The overall diagnostic accuracy of the tree model with visual assessment parameters was 98.21 % (55/56).

CONCLUSION

The bright diffusion sign and absence of cortical involvement are accurate and reliable imaging findings for differentiating MVNT from DNET. By using simple, intuitive, and reliable imaging findings, such as the bright diffusion sign, MVNT can be accurately differentiated from DNET.

Advanced multiparametric MRI and FDG-PET/CT in multinodular and vacuolating neuronal tumor: A pathologically confirmed case

Multinodular and vacuolating neuronal tumor (MVNT) is a relatively new disease concept proposed in 2013 and was classified as a separate tumor type in 2021 by the World Health Organization (WHO) classification. MVNT can cause seizures but is a benign disease, with no cases of enlargement or postoperative recurrence reported. Recent reports described advanced MRI features in MVNT cases, but the diagnosis of MVNT is usually based on characteristic MRI findings of clusters of nodules. Here, we report advanced multiparametric MRI and FDG-PET/CT findings in a case of MVNT with epileptiform symptoms that was pathologically confirmed by surgery.

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.

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.

The 2021 World Health Organization Classification of Tumors of the Central Nervous System: What Neuroradiologists Need to Know

Neuroradiologists play a key role in brain tumor diagnosis and management. Staying current with the latest classification systems and diagnostic markers is important to provide optimal patient care. Publication of the 2016 World Health Organization Classification of Tumors of the Central Nervous System introduced a paradigm shift in the diagnosis of CNS neoplasms. For the first time, both histologic features and genetic alterations were incorporated into the diagnostic framework, classifying and grading brain tumors. The newly published 2021 World Health Organization Classification of Tumors of the Central Nervous System, May 2021, 5th edition, has added even more molecular features and updated pathologic diagnoses. We present, summarize, and illustrate the most salient aspects of the new 5th edition. We have selected the key "must know" topics for practicing neuroradiologists.