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Neuronal and mixed neuronal-glial tumor — Clinical Guidelines

Overview

Multinodular and vacuolating neuronal tumors (MVNTs) are rare, benign neoplasms primarily affecting young to middle-aged adults, often presenting with seizures and nonspecific neurological symptoms. These tumors are characterized by multiple nodules with prominent neuronal differentiation and vacuolation, typically located in the cerebral hemispheres, particularly within the temporal lobes. Accurate diagnosis and management are crucial to avoid unnecessary aggressive interventions and to ensure appropriate surveillance. Understanding the imaging characteristics and clinical behavior of MVNTs is essential for effective patient care in day-to-day practice 1 3 5.

Pathophysiology

The exact molecular and cellular mechanisms underlying the development of MVNTs remain incompletely understood. These tumors are thought to arise from progenitor cells with dual neuronal and glial potential, leading to a mixed cellular composition characterized by neuronal nodules interspersed with glial elements. The vacuolation observed in MVNTs likely reflects a combination of cellular differentiation stages and potential metabolic or storage abnormalities. Immunohistochemical studies highlight the expression of early neuronal markers such as OLIG2 and MAP2 alongside late markers like NeuN, suggesting a spectrum of neuronal maturation within the tumor 2 10. The presence of these diverse cellular features underscores the complexity of their histogenesis and may influence their clinical behavior and imaging characteristics.

Epidemiology

MVNTs are exceedingly rare, with limited data available on their incidence and prevalence. Reported cases predominantly affect adults, with a median age at diagnosis ranging from the third to fifth decade 3 5. There is no clear sex predilection noted in the literature, and geographic distribution appears to be sporadic without identifiable risk factors. Given the rarity and recent recognition of MVNTs by the World Health Organization in 2016, long-term epidemiological trends are yet to be established comprehensively 5.

Clinical Presentation

Patients with MVNTs typically present with focal neurological symptoms, most commonly seizures, often refractory to initial antiepileptic therapy. Headaches and cognitive disturbances may also occur but are less specific. Radiological discovery often precedes clinical symptoms, highlighting the incidental nature of diagnosis in many cases. Atypical presentations can include focal motor deficits or language impairments, particularly when tumors are located in eloquent brain regions 3 4.

Diagnosis

The diagnosis of MVNTs relies heavily on neuroimaging and histopathological examination. Key diagnostic criteria include:

Imaging Characteristics:

- Multiple nodular lesions, often subcortical, appearing hypointense on T1-weighted images and hyperintense on T2-weighted images. - FLAIR hyperintensity extending in characteristic patterns, such as the "Mickey Mouse's hand" sign in mesial temporal lobe involvement 4. - Bright diffusion sign on diffusion-weighted imaging (DWI) can be particularly useful in differentiating MVNTs from dysembryoplastic neuroepithelial tumors (DNETs) 6.

Histopathological Features:

- Presence of multiple nodules composed of vacuolated neuronal cells. - Immunolabeling for early neuronal markers (e.g., OLIG2, MAP2) and late markers (e.g., NeuN, synaptophysin) 2 10.

Required Tests:

- MRI with T1-weighted, T2-weighted, and FLAIR sequences. - DWI for assessing the bright diffusion sign. - Surgical biopsy for definitive histopathological diagnosis.

Differential Diagnosis:

- Dysembryoplastic neuroepithelial tumor (DNET) - Low-grade gliomas (e.g., diffuse low-grade gliomas) - Focal cortical dysplasia (FCD) - Other epileptogenic lesions such as hippocampal sclerosis 3 6 7.

Management

Initial Management

Surgical Intervention: Gross total resection is often curative and recommended for symptomatic lesions or those causing significant mass effect.

- Specifics: Microsurgical resection targeting complete removal of visible tumor nodules. - Monitoring: Postoperative MRI to confirm resection extent and identify residual lesions.

Medical Management:

- Antiepileptic Therapy: Initiate or adjust antiepileptic drugs based on seizure control post-surgery. - Examples: Levetiracetam, Lamotrigine, or other second-generation antiepileptic drugs as needed. - Monitoring: Regular follow-up to assess seizure control and side effects.

Refractory Cases

Second-Line Therapies: Consider in cases of persistent seizures or tumor recurrence.

- Options: Vagus nerve stimulation (VNS), stereoelectroencephalography (SEEG) for deep-seated lesions. - Monitoring: Regular neurological assessments and imaging to evaluate treatment efficacy.

Contraindications

Surgical Contraindications: Significant comorbidities that increase surgical risk, such as severe cardiopulmonary disease.

Medical Contraindications: Known severe allergies or intolerances to specific antiepileptic drugs.

Complications

Acute Complications: Postoperative seizures, infection, and neurological deficits related to surgical manipulation.

- Management Triggers: Immediate postoperative monitoring, prophylactic antibiotics, and close neurological assessment.

Long-Term Complications: Recurrence of seizures or tumor growth, necessitating further intervention.

- Management Triggers: Regular follow-up MRIs and clinical evaluations to detect early signs of recurrence or progression.

Prognosis & Follow-Up

The prognosis for patients with MVNTs is generally favorable, with most tumors being benign and indolent. Prognostic indicators include complete surgical resection and absence of residual disease on follow-up imaging. Recommended follow-up intervals typically include:

Initial Follow-Up: MRI within 3-6 months post-surgery to assess resection completeness.

Subsequent Follow-Up: Annual MRI scans for at least 5 years to monitor for any recurrence or changes in tumor characteristics 1 3.

Special Populations

Pediatrics: MVNTs are exceedingly rare in pediatric populations, but when encountered, management parallels adult cases with emphasis on minimizing surgical risks.

Elderly Patients: Increased surgical risk considerations due to comorbidities; tailored multidisciplinary approaches are essential.

Pregnancy: Management is conservative, focusing on symptomatic relief with antiepileptic drugs, avoiding surgery unless absolutely necessary due to risks associated with anesthesia and delivery 7.

Key Recommendations

Surgical Resection: Gross total resection is recommended for symptomatic MVNTs to achieve potential cure and symptom relief (Evidence: Strong 3).

MRI Surveillance: Implement regular MRI follow-up (annually for at least 5 years post-diagnosis) to monitor for recurrence or changes (Evidence: Moderate 1).

DWI for Differentiation: Utilize diffusion-weighted imaging to differentiate MVNTs from DNETs, leveraging the bright diffusion sign (Evidence: Moderate 6).

Antiepileptic Therapy: Initiate or adjust antiepileptic drugs based on seizure control post-surgery, with regular follow-up for efficacy and side effects (Evidence: Moderate 3).

Multidisciplinary Approach: Consider a multidisciplinary team including neurosurgeons, epileptologists, and radiologists for comprehensive management (Evidence: Expert opinion 7).

Tailored Management for Special Populations: Adjust management strategies based on patient-specific factors such as age and comorbidities (Evidence: Expert opinion 7).

Histopathological Confirmation: Ensure definitive diagnosis through surgical biopsy and histopathological examination (Evidence: Strong 2).

Monitor for Recurrence: Closely monitor patients for signs of recurrence or new neurological symptoms post-surgery (Evidence: Moderate 1).

Avoid Unnecessary Aggressive Interventions: Given the benign nature of MVNTs, avoid aggressive treatments unless clinically indicated (Evidence: Expert opinion 5).

Educate Patients: Provide detailed patient education regarding the benign nature of MVNTs and the importance of follow-up care (Evidence: Expert opinion 7).

References

1 Dogra S, Zagzag D, Young M, Golfinos J, Orringer D, Jain R. Long-Term Follow-up of Multinodular and Vacuolating Neuronal Tumors and Implications for Surveillance Imaging. AJNR. American journal of neuroradiology 2023. link 2 Rima S, Rao S, Mahadevan A, Yasha TC, Arimappamagan A, Sadashiva N et al.. Multinodular and vacuolating neuronal tumour: emphasis on expression of early and late neuronal immunomarkers. Journal of clinical pathology 2026. link 3 Carmichael A, Arshad U, Heinemann DM, Reddy SC, Kalluri A, Serrano-Farias A et al.. Radiologic characterization and clinical management of multinodular and vacuolating neuronal tumor (MVNT): a retrospective institutional cohort study. Journal of neuro-oncology 2025. link 4 Frazzini V, Mathon B, Shor N, Nichelli L, Bielle F, Navarro V. The Mickey Mouse's hand sign in brain MRI points out multinodular and vacuolating neuronal tumors in mesial temporal lobe structures. Journal of neuro-oncology 2025. link 5 Vlachos N, Lampros M, Alexiou GA, Styliara E, Xydis V, Voulgaris S et al.. Multinodular and Vacuolating Neuronal Tumors of the Cerebrum: A Systematic Review of the Literature. World neurosurgery 2025. link 6 Pak A, Choi HJ, You SH, Yang KS, Kim B, Choi SH et al.. Bright diffusion sign: A sensitive and specific radiologic biomarker for multinodular and vacuolating neuronal tumor. Journal of neuroradiology = Journal de neuroradiologie 2024. link 7 Alizada O, Ayman T, Akgun MY, Sar M, Urganci N, Kemerdere R. Multinodular and vacuolating neuronal tumor of the cerebrum: Two cases and review of the literature. Clinical neurology and neurosurgery 2020. link 8 Abdel Razek AAK, Elsebaie NA, Zamora C, Castillo M. Imaging of Neuronal and Mixed Glioneuronal Tumors. Journal of computer assisted tomography 2020. link 9 Demir MK, Yapıcıer O, Yılmaz B, Kılıç T. Magnetic resonance imaging findings of mixed neuronal-glial tumors with pathologic correlation: a review. Acta neurologica Belgica 2018. link 10 Nagaishi M, Yokoo H, Nobusawa S, Fujii Y, Sugiura Y, Suzuki R et al.. Localized overexpression of alpha-internexin within nodules in multinodular and vacuolating neuronal tumors. Neuropathology : official journal of the Japanese Society of Neuropathology 2015. link

Neuronal and mixed neuronal-glial tumor