Multinodular and Vacuolating Neuronal Tumor (MVNT): A Distinctive Brain MRI Pattern in a Young Woman with Auditory Hallucinations
MRI characteristics, differential diagnosis, clinical correlation, management, and the emerging role of AI in Multinodular and Vacuolating Neuronal Tumor
Introduction
A young woman with recurrent auditory hallucinations, disorganized
thinking, and disorganized behavior may initially be evaluated primarily from a
psychiatric perspective. However, when structural brain imaging is performed,
an apparently normal CT examination does not completely exclude a subtle
cerebral lesion.
This case illustrates an important neuroradiologic entity: Multinodular
and Vacuolating Neuronal Tumor (MVNT).
MVNT is an uncommon neuronal tumor characterized by multiple small nodules
clustered within the superficial subcortical white matter. On MRI, these
nodules may create a distinctive bubbly or bubble-like appearance,
particularly on T2-weighted and FLAIR images. The lesions are typically
nonaggressive in appearance, with little or no mass effect, surrounding edema,
diffusion restriction, or contrast enhancement.
The diagnosis is particularly important because recognition of a typical
MVNT imaging pattern may prevent unnecessary invasive procedures.
In the present case, the patient was a woman in her twenties with a
history of schizoaffective disorder, manic type, who developed recurrent
auditory hallucinations together with disorganized thought and behavior. Brain
CT showed no specific abnormality. MRI, however, demonstrated a characteristic
clustered nodular lesion in the subcortical white matter adjacent to the right
orbital gyrus.
The final diagnosis was Multinodular and Vacuolating Neuronal Tumor.
1. Clinical Presentation: When Psychiatric Symptoms
Lead to Brain MRI
The patient had been diagnosed with schizoaffective disorder, manic type,
and had been receiving medication and follow-up. She was subsequently
hospitalized because of recurrence of auditory hallucinations and disorganized
thought and behavior.
From a clinical perspective, recurrence of psychiatric symptoms can
naturally lead clinicians to consider psychiatric disease activity first.
The imaging finding, however, introduces another question:
Is the structural abnormality responsible for the patient's symptoms?
This question requires particular caution.
The detection of MVNT does not by itself establish that the lesion is the
cause of auditory hallucinations or behavioral abnormalities. MVNT may be
discovered incidentally, and reported clinical manifestations are
heterogeneous.
Therefore, the radiologist should distinguish between two separate
statements:
A lesion is present.
and
The lesion explains the patient's symptoms.
The first may be established by MRI. The second requires clinical
correlation.
This distinction is especially important when the presenting symptoms are
psychiatric rather than clearly focal neurological.
2. CT May Be Normal While MRI Reveals the Lesion
The brain CT examination in this case did not demonstrate a specific
abnormality.
This is an important practical point.
A normal CT examination does not mean that the brain is completely normal
at the microscopic or subtle structural level.
CT is highly valuable for acute hemorrhage, major mass effect,
hydrocephalus, trauma, and other urgent conditions. However, small superficial
subcortical lesions can be difficult to appreciate on CT.
MRI provides substantially greater soft-tissue contrast and is
particularly useful for subtle lesions involving the cerebral cortex and
subcortical white matter.
For MVNT, the diagnostic information comes primarily from the combination
of:
- T1-weighted imaging
- T2-weighted imaging
- FLAIR
- Diffusion-weighted
imaging
- ADC correlation
- Contrast-enhanced imaging
- Anatomical localization
Thus:
Normal CT does not exclude a subtle MRI-detectable lesion.
3. What Is Multinodular and Vacuolating Neuronal
Tumor?
Multinodular and Vacuolating Neuronal Tumor is a rare cerebral neuronal
tumor characterized by multiple small nodules and vacuolated neuronal elements.
The entity was initially described in a series of seizure-associated
lesions and subsequently became recognized as a distinctive neuronal tumor
entity.
MVNT is included among neuronal tumors in the modern classification of
central nervous system tumors.
Its biological nature has historically generated discussion because many
lesions show a remarkably indolent clinical and radiological course. Some
earlier interpretations emphasized malformative or hamartomatous
characteristics, whereas current classification recognizes MVNT as a distinct
neuronal tumor entity.
For practical neuroradiology, however, the most important issue is not
terminology alone.
The essential question is:
Does the MRI demonstrate the characteristic MVNT pattern?
That pattern can be summarized as:
Multiple clustered subcortical nodules + T2/FLAIR hyperintensity + bubbly
appearance + little or no enhancement + minimal mass effect.
4. Why Does MVNT Have a Bubbly Appearance?
The characteristic imaging appearance reflects the multinodular
architecture of the lesion.
Histologically, MVNT contains multiple small nodules with vacuolated cells
and neuronal and glial characteristics. Individual nodules may be separated by
relatively preserved brain tissue or mild gliosis.
On MRI, this architecture can appear as a cluster of small signal
abnormalities rather than as a single solid mass.
This produces the characteristic:
“Bubbly” or “bubble-clustered” appearance.
The terminology itself provides a useful memory aid:
Multinodular → multiple small nodules
Vacuolating → vacuolated tissue
Neuronal tumor → neuronal differentiation
When these elements are expressed together on MRI, the pattern becomes
highly recognizable.
5. MRI Findings in This Case
The key finding in this case is a group of relatively well-defined small
nodules in the subcortical white matter adjacent to the right orbital gyrus.
The lesion demonstrates:
- T2 hyperintensity
- Persistent FLAIR
hyperintensity
- Clustered multinodular
architecture
- Bubbly appearance
- No definite diffusion
restriction
- No definite contrast
enhancement
- No significant
surrounding mass effect
This combination is highly characteristic of MVNT.
The anatomical location is also important.
Although some nodules may contact the inferior cortex, the overall center
of the abnormality is within the superficial subcortical region.
This cortical-subcortical relationship is useful when distinguishing MVNT
from other epilepsy-associated neuronal or glioneuronal tumors.
6. Figure-by-Figure MRI Interpretation
Figure 1. Sagittal T1-Weighted MRI
The first MRI image is a sagittal T1-weighted image.
A subtle signal abnormality may be appreciated in the region adjacent to
the right orbital gyrus.
T1-weighted imaging is useful for establishing anatomical localization and
evaluating the overall morphology of the lesion.
However, T1-weighted imaging alone is not the sequence that best
demonstrates the characteristic MVNT pattern.
Radiologic Interpretation
A subtle abnormality is present in the superficial subcortical region
adjacent to the right orbital gyrus, without a conspicuous solid mass.
Key Point
The diagnosis of MVNT depends more heavily on the combination of
T2-weighted and FLAIR findings than on T1 signal intensity alone.
Figure 2. Axial T2-Weighted MRI
Figure 2 demonstrates the characteristic T2-weighted appearance.
Multiple small hyperintense nodules are clustered in the subcortical white
matter adjacent to the right orbital gyrus.
The nodules collectively produce a bubbly appearance.
Radiologic Interpretation
Multiple small T2-hyperintense nodules form a clustered lesion in the
superficial subcortical white matter.
Key Diagnostic Combination
The important observation is not simply:
“T2 hyperintensity.”
It is:
“T2 hyperintensity + multiple small nodules + subcortical location +
minimal mass effect.”
This combination should raise strong consideration of MVNT.
Figure 3. Axial MRI: Anatomical Localization
Figure 3 further demonstrates the anatomical relationship of the lesion.
The lesion is located within the subcortical white matter adjacent to the
right orbital gyrus.
Some nodules approach the inferior cortical surface, but the overall
distribution remains predominantly subcortical.
Radiologic Interpretation
The clustered nodules are centered in the superficial subcortical region
with a relatively well-defined margin.
Why Location Matters
The relationship between the lesion and the cortical ribbon is an
important component of the differential diagnosis.
A cortical-centered lesion suggests a different diagnostic framework from
a predominantly superficial subcortical clustered lesion.
Figure 4. Axial FLAIR MRI
FLAIR is one of the most informative sequences in this case.
The abnormal signal remains hyperintense rather than being suppressed.
This is particularly useful for distinguishing MVNT from lesions that
contain fluid with CSF-like signal characteristics.
Radiologic Interpretation
The clustered subcortical nodules remain hyperintense on FLAIR.
Clinical Significance
Persistent FLAIR hyperintensity supports the diagnosis of MVNT and helps
distinguish it from dilated perivascular spaces, which generally follow CSF
signal and suppress on FLAIR.
FLAIR is therefore not simply an additional sequence. It is an important
component of the differential diagnosis.
Figure 5. Axial DWI
Figure 5 is the Axial DWI image.
This figure should be interpreted carefully.
The case description indicates that there is no definite diffusion
restriction.
However, the broader imaging literature has described a relatively bright
diffusion appearance in some MVNT lesions. This is an important distinction
because DWI signal intensity and true diffusion restriction are not synonymous.
Radiologic Interpretation
The lesion does not demonstrate definite restricted diffusion in this
case.
DWI should be interpreted together with the corresponding ADC map when
available.
Important Practical Point
DWI bright signal ≠ automatically true restricted diffusion.
A genuine diffusion restriction generally requires correlation with
reduced ADC.
Therefore, the radiologist should avoid diagnosing restricted diffusion
solely because a lesion appears relatively bright on DWI.
Figure 6. Sagittal MRI
The sagittal image provides additional information about the longitudinal
distribution of the lesion.
The clustered nodules extend along the superficial subcortical region
adjacent to the cortex.
There is no convincing infiltrative mass or extensive surrounding edema.
Radiologic Interpretation
The lesion maintains a multinodular subcortical configuration without
aggressive mass-like behavior.
Clinical Significance
Multiplanar assessment is useful for determining the full extent of the
lesion and its relationship to the cortical surface.
Figure 7. Axial MRI: Final Lesion Assessment
Figure 7 demonstrates the final imaging appearance of the lesion.
Multiple clustered nodules are identified in the subcortical white matter
adjacent to the right orbital gyrus.
The lesion demonstrates:
- T2/FLAIR hyperintensity
- Multinodular architecture
- No definite diffusion
restriction
- No contrast enhancement
- No significant mass
effect
Radiologic Impression
The imaging pattern is highly characteristic of:
Multinodular and Vacuolating Neuronal Tumor (MVNT).
This is the final diagnosis described in the case.
7. The Four Most Important MRI Features
When MVNT is suspected, four features deserve particular attention.
1. Clustered nodules
The lesion is composed of multiple small nodules rather than a single
dominant mass.
2. Subcortical location
The lesion is centered in the superficial subcortical white matter.
3. T2/FLAIR hyperintensity
The nodules remain hyperintense on T2-weighted and FLAIR imaging.
4. Lack of aggressive features
There is no significant enhancement, edema, or mass effect.
The combination is much more informative than any single imaging
characteristic.
8. Differential Diagnosis: MVNT Versus DNET
One of the most important differential diagnoses is Dysembryoplastic
Neuroepithelial Tumor (DNET).
The two lesions may overlap considerably.
Both can occur in younger patients, both may be associated with seizures,
and both may demonstrate a multinodular or bubbly appearance on MRI.
The anatomical relationship to the cortex is therefore particularly
important.
|
Imaging Feature |
MVNT |
DNET |
|
Typical location |
Superficial subcortical
white matter |
More characteristically
cortical |
|
T2 signal |
Hyperintense |
Hyperintense |
|
FLAIR |
Usually remains hyperintense |
Variable |
|
Cortical involvement |
Relatively limited |
Common |
|
Enhancement |
Usually absent |
Usually absent, but variable |
|
Mass effect |
Minimal or absent |
Usually limited |
|
DWI |
Bright diffusion signal may
occur |
Different diffusion pattern
may occur |
|
Seizures |
May occur |
Strongly associated |
|
Overall morphology |
Clustered subcortical
nodules |
Often cortical multinodular
architecture |
No single feature should be interpreted in isolation.
The most useful approach is to evaluate:
FLAIR pattern + DWI/ADC + cortical involvement + anatomical distribution.
9. MVNT Versus Dilated Perivascular Spaces
Dilated perivascular spaces can also appear as multiple small lesions.
However, their signal characteristics are usually similar to cerebrospinal
fluid.
Consequently, they typically suppress on FLAIR.
MVNT nodules generally remain hyperintense on FLAIR.
This creates a practical distinction:
CSF-like signal with FLAIR suppression → consider perivascular spaces.
Persistent FLAIR hyperintensity with clustered subcortical nodules →
consider MVNT.
The distinction is particularly useful when the lesions are small.
10. MVNT Versus Gangliocytoma
Gangliocytoma is another neuronal tumor that may enter the differential
diagnosis.
However, typical MVNT tends to demonstrate multiple small clustered
nodules, whereas gangliocytoma is more likely to appear as a mass-like lesion.
The characteristic bubbly subcortical architecture therefore favors MVNT.
Again, the complete imaging pattern is more important than any single
signal characteristic.
11. Why the Absence of Mass Effect Matters
The lack of significant mass effect is a subtle but important clue.
Many aggressive neoplasms alter the architecture of the surrounding brain.
They may produce:
- edema
- tissue expansion
- ventricular compression
- sulcal effacement
- midline shift
- infiltrative distortion
A typical MVNT generally does not behave this way.
The clustered nodules can appear striking on T2 and FLAIR images while
producing surprisingly little distortion of adjacent brain structures.
This apparent discrepancy is one of the useful pattern-recognition clues
in neuroradiology.
12. Contrast Enhancement
Typical MVNT generally demonstrates little or no contrast enhancement.
The absence of enhancement in this case therefore supports the diagnosis.
However, the lack of enhancement should not be used as an isolated
diagnostic criterion.
A nonenhancing lesion can represent many different pathological entities.
The diagnostic value comes from the combination:
Clustered morphology + superficial subcortical location + T2/FLAIR
hyperintensity + minimal mass effect + no definite enhancement.
13. Clinical Symptoms and Imaging Correlation
The clinical presentation in this case is unusual because the primary
symptoms are auditory hallucinations and disorganized thought and behavior
rather than seizures.
MVNT has been associated with seizures and other neurological symptoms,
but not every symptom occurring in a patient with MVNT should be attributed to
the lesion.
The right orbital gyrus location does not, by itself, establish that the
lesion is responsible for the psychiatric presentation.
Therefore, the appropriate radiologic approach is to describe the lesion
accurately and allow the clinical team to determine its relevance in the
broader clinical context.
This is a general principle that extends beyond MVNT:
Imaging correlation is not the same as causal attribution.
14. Management: Does MVNT Require Surgery?
A typical MVNT may not require immediate biopsy or surgical treatment,
particularly when it is discovered incidentally, and the patient has no symptoms
clearly attributable to the lesion.
This is why MVNT has been described in the literature as a “leave-me-alone”
lesion.
The practical objective is to avoid unnecessary invasive intervention when
the imaging phenotype is characteristic, and the clinical course is indolent.
However, observation is not synonymous with ignoring the lesion.
Further evaluation may be appropriate when there are:
- Drug-resistant seizures
- A convincing clinical
relationship between the lesion and seizures
- Atypical imaging findings
- Diagnostic uncertainty
- Progressive enlargement
- New enhancement
- Significant edema
- Increasing mass effect
- Other features suggesting
an alternative diagnosis
Thus, management should be individualized according to the imaging
phenotype and clinical context.
15. Long-Term Follow-Up and Prognosis
Typical MVNT lesions often demonstrate a stable clinical and radiological
course.
The case material describes studies in which lesions remained stable
during follow-up, supporting an indolent behavior.
A multicenter study involving 64 patients reported T2/FLAIR hyperintensity
without enhancement and no observed size change during a median follow-up
period of two years.
A 2025 systematic review also reported generally stable lesions during
follow-up.
These observations support imaging surveillance as an important management
strategy for appropriately selected patients.
Nevertheless, stability should be demonstrated rather than assumed.
Serial MRI provides an objective method for assessing:
- Lesion size
- Number of nodules
- Signal characteristics
- Enhancement
- Surrounding edema
- Mass effect
16. When Should the Diagnosis Be Reconsidered?
A typical MVNT pattern should not prevent the radiologist from
reconsidering the diagnosis when the lesion behaves atypically.
Features that should prompt renewed evaluation include:
Progressive growth
A clearly enlarging lesion should trigger reconsideration.
New contrast enhancement
Development of substantial enhancement may suggest an alternative
pathological process.
Increasing edema
Prominent surrounding edema is not characteristic of a typical MVNT.
Increasing mass effect
Progressive distortion of adjacent structures is atypical.
Hemorrhage
Hemorrhagic change should prompt evaluation for alternative diagnoses.
Clinical-radiological discordance
A dramatic change in neurological status without corresponding imaging
stability may require broader clinical assessment.
The diagnosis should therefore always remain linked to the actual imaging
phenotype.
17. A Practical MRI Checklist for MVNT
When confronted with a possible MVNT, the following checklist can be
applied systematically.
Step 1 — Location
Is the lesion located in the superficial subcortical white matter?
Step 2 — Morphology
Are multiple small nodules clustered together?
Step 3 — T2
Are the nodules hyperintense on T2-weighted imaging?
Step 4 — FLAIR
Does the abnormal signal remain hyperintense rather than suppressing like
CSF?
Step 5 — DWI/ADC
Is there a bright diffusion appearance?
If DWI is bright, is there actual ADC reduction?
Step 6 — Contrast
Is there definite enhancement?
Step 7 — Mass effect
Is there edema, sulcal effacement, or significant mass effect?
Step 8 — Cortex
Is the lesion predominantly cortical or subcortical?
Step 9 — Prior MRI
Has the lesion changed over time?
Step 10 — Clinical correlation
Is there a plausible relationship between the lesion and the patient's
symptoms?
This structured approach helps prevent overcalling and undercalling
unusual neuronal lesions.
18. Advanced MRI
Conventional MRI is often sufficient to recognize a typical MVNT pattern.
When the diagnosis remains uncertain, additional sequences or advanced MRI
techniques may be considered, including:
- DWI/ADC
- SWI or T2*
- Perfusion MRI
- MR spectroscopy
- Contrast-enhanced
T1-weighted imaging
The purpose of additional imaging should be clear.
The goal is not simply to obtain more sequences.
The goal is to determine whether the lesion behaves like a typical
indolent MVNT or whether there are features suggesting another tumor or
pathological process.
Multiparametric MRI can therefore increase diagnostic confidence when the
conventional appearance is not completely characteristic.
19. The Role of Artificial Intelligence
MVNT also illustrates an important challenge for medical AI.
Artificial intelligence systems are increasingly used for lesion
detection, segmentation, classification, and longitudinal monitoring.
In principle, an AI-assisted system could identify:
- clustered subcortical
nodules
- T2/FLAIR signal
abnormalities
- lesion volume
- spatial distribution
- cortical relationship
- diffusion characteristics
- enhancement
- interval changes
AI could potentially be particularly useful for longitudinal comparison.
For example, an automated system could compare serial MRI examinations and
calculate whether the lesion has changed in volume or morphology.
However, rare diseases create a major challenge for machine learning.
MVNT is far less common than glioma, metastasis, stroke, or other
frequently represented conditions. Consequently, training datasets may contain
relatively few examples.
A system trained primarily on common brain lesions may classify an MVNT as
another low-grade tumor or nonspecific T2/FLAIR abnormality.
Therefore:
Rare-lesion recognition remains an area in which expert radiologic pattern
recognition is particularly important.
AI should support interpretation rather than replace clinical and
radiological judgment.
20. The Central Lesson of This Case
This case demonstrates several important principles of neuroradiology.
First
A normal CT examination does not exclude a subtle cerebral lesion.
Second
MRI pattern recognition can be extremely powerful in rare neuronal tumors.
Third
The characteristic combination of clustered subcortical nodules, T2/FLAIR
hyperintensity, lack of significant enhancement, and minimal mass effect should
raise consideration of MVNT.
Fourth
DNET is an important differential diagnosis, and cortical involvement,
FLAIR characteristics, and diffusion behavior can help distinguish the two.
Fifth
DWI signal should not be equated automatically with true restricted
diffusion. ADC correlation remains essential.
Sixth
The presence of a structural lesion does not automatically establish a
causal relationship with psychiatric symptoms.
Seventh
Recognition of a typical MVNT pattern can prevent unnecessary biopsy or
surgery.
21. Final Diagnosis
The imaging findings in this case can be summarized as:
Young woman with recurrent auditory hallucinations and disorganized
thought and behavior
- Normal brain CT
- Clustered small nodules in the subcortical white matter adjacent to the right orbital gyrus
- Bubbly T2/FLAIR hyperintensity
- No definite diffusion restriction
- No contrast enhancement
- No significant mass effect
Multinodular and Vacuolating Neuronal Tumor (MVNT)
The diagnosis is supported by the characteristic radiological phenotype
described in the case.
22. Radiology Take-Home Message
MVNT may initially appear complicated because of its unusual name and
rarity.
From a radiologic perspective, however, its characteristic appearance can
be remembered with a single phrase:
“Bubbly clustered nodules in the subcortical white
matter.”
When this pattern is accompanied by persistent FLAIR hyperintensity,
absence of significant enhancement, minimal mass effect, and no definite
diffusion restriction, MVNT should be considered.
The next step is not automatically surgery.
The next step is accurate imaging characterization and appropriate
clinical correlation.
In selected patients with a typical imaging appearance and indolent
clinical course, recognition of MVNT can prevent unnecessary invasive
procedures.
That is one of the most valuable roles of modern neuroradiology: not
simply identifying disease, but also recognizing when a striking imaging
abnormality does not necessarily require aggressive intervention.
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Medical Disclaimer
This article is intended for medical education and discussion of
neuroimaging findings. It does not replace individualized clinical assessment,
neurological or psychiatric evaluation, multidisciplinary consultation, or
formal radiological interpretation. Diagnosis and management should be
determined by qualified specialists based on the complete clinical history and
imaging findings.
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