Tumefactive Demyelination: A Deceptive Lesion That Mimics Brain Tumor
Desmielinización tumefactiva: una lesión engañosa que imita un tumor cerebral
종양성 탈수초화: 뇌종양을 모방하는 기만적인 병변
Introduction: Tumor or Demyelinating Disease?
When a mass-like lesion is identified in the central nervous system, radiologists often consider glioma, metastasis, or abscess high on the differential diagnosis list. However, some of these lesions represent tumefactive demyelination, a form of demyelinating disease that mimics neoplastic processes.
In this article, we review a real clinical case and explore the pathophysiology, epidemiology, clinical features, imaging findings, treatment, and prognosis of tumefactive demyelination.
Case Presentation: A 46-Year-Old Man with Slurred Speech and Facial Weakness
A previously healthy 46-year-old man presented to the emergency department with progressively worsening slurred speech for 10 days, followed by right facial droop and numbness, which he noticed while brushing his teeth. A non-contrast CT scan from an outside hospital had initially suggested a “stroke.”
However, his clinical presentation and progression were not entirely consistent with a typical ischemic event. Further investigation with brain MRI revealed unexpected findings.
Imaging Findings
Figure 1. MRI T2/FLAIR showing a round hyperintense lesion in the posterior left frontal lobe with a distinct T2-FLAIR mismatch sign and minimal surrounding edema.
A well-circumscribed, round lesion was seen in the posterior left frontal lobe. On FLAIR images, the T2-FLAIR mismatch sign was evident. Mild perilesional edema and gyral expansion were also noted.
Figure 2. Post-contrast MRI demonstrating an open ring enhancement pattern. This imaging feature is more commonly seen in demyelinating lesions than in neoplastic processes.
Following gadolinium administration, the lesion showed incomplete rim enhancement, with the open side of the ring facing the cortex and the denser enhancement toward the ventricle.
Differential Diagnosis and Final Diagnosis
| Differential Diagnosis | Imaging Clues |
|---|---|
| High-grade glioma | Irregular enhancement and mild mass effect are possible, but the age and presentation are atypical. |
| Metastasis | Solitary lesion without multiple foci makes this less likely. |
| Abscess | Rim enhancement present, but ring morphology is not typical of an abscess. |
| Tumefactive Demyelination | Presence of T2-FLAIR mismatch, incomplete ring enhancement, and additional white matter lesions. |
Final diagnosis: Tumefactive demyelination, confirmed via lumbar puncture and cerebrospinal fluid (CSF) analysis indicating demyelinating pathology.
Treatment and Clinical Course
The patient received intravenous methylprednisolone (1g/day) for 5 days, with gradual symptomatic improvement. He was then transitioned to an oral steroid taper.
A follow-up MRI at 4 months showed complete resolution of the previously seen mass-like lesion with only residual patchy T2 hyperintensity.
 |
| Figure 3. Follow-up MRI at 4 months showed resolution of the lesion and residual non-enhancing T2 signal abnormalities. |
Discussion: Understanding Tumefactive Demyelination
Etiology and Pathophysiology
Tumefactive demyelination represents an atypical variant of CNS demyelinating disease, most often associated with multiple sclerosis (MS). The hallmark is a mass-like lesion ≥2 cm, characterized by central myelin destruction resulting from T-cell–mediated immune responses and associated inflammation.
Epidemiology
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Typically occurs in patients aged 30–50 years
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Affects both genders
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10–20% of cases may evolve into definite MS over time
Clinical Manifestations
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Hemiparesis
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Paresthesia
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Aphasia or dysarthria
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Visual field defects
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Headache or seizures
Key Imaging Features
| Imaging Sign | Interpretation |
|---|---|
| T2-FLAIR mismatch | Strongly associated with IDH-mutant gliomas, but also seen in tumefactive demyelination |
| Incomplete ring enhancement | The open ring typically faces the cortex; the solid portion points toward the ventricle |
| Mild mass effect | Less pronounced than neoplastic lesions |
| Additional white matter lesions | May indicate prior demyelinating activity |
Management
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IV methylprednisolone (e.g., Solu-Medrol 1 g/day for 5 days)
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Oral steroid taper
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Immunomodulatory therapy may be considered for relapse prevention
Prognosis
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Most patients experience clinical and radiologic improvement
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A subset may later develop relapsing-remitting MS
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Early and accurate diagnosis is crucial to avoid unnecessary surgery or biopsy
Quiz
1. Which of the following best describes the lesion in this case?
(1) Acute infarction
(2) Chronic infarction
(3) Giant Virchow-Robin space
(4) T2-FLAIR mismatch sign suggests a specific subtype of glioma
(5) None of the above
Answer: (4)
Explanation: T2-FLAIR mismatch is highly specific for IDH-mutant, 1p/19q non-codeleted gliomas, but can also be seen in demyelinating lesions.
2. What is the next best diagnostic step?
(1) Retrieve previous non-contrast CT
(2) Perform contrast-enhanced MRI
(3) Administer tPA
(4) Conservative observation
(5) Neurosurgical consultation for biopsy
(6) Whole-body CT to search for primary malignancy
Answer: (2)
Explanation: Contrast-enhanced MRI is critical to distinguish between neoplasm and demyelination.
3. What does the enhancement pattern most likely indicate?
(1) Abscess with complete ring enhancement
(2) Brain metastasis
(3) Incomplete ring enhancement suggests demyelination
(4) Subacute infarct
(5) Heterogeneous enhancement of tumor components
Answer: (3)
4. Which MRI feature is typical of tumefactive demyelination?
(1) Cortical-centered enhancement
(2) Central necrosis
(3) Intense, uniform enhancement
(4) Incomplete ring enhancement open toward the cortex
(5) Hemorrhagic transformation
Answer: (4)
5. What is the expected follow-up imaging finding?
(1) Lesion enlargement
(2) Increased enhancement
(3) Resolution of mass with residual T2 signal
(4) New lesion development
(5) Infarction
Answer: (3)
Conclusion
Tumefactive demyelination is a critical diagnostic entity that can mimic primary or secondary brain tumors on imaging. Key features such as the T2-FLAIR mismatch sign, incomplete ring enhancement, and presence of additional white matter lesions aid in differentiation.
Accurate diagnosis prevents unnecessary surgical intervention and allows for effective treatment with corticosteroids, often resulting in full clinical and radiological recovery.
References
[1] Y. Jain et al., “T2-FLAIR mismatch sign in gliomas and mimics,” AJNR Am J Neuroradiol, vol. 41, no. 6, pp. 888–894, 2020.
[2] J. Kim et al., “Imaging of Tumefactive Demyelination,” Radiographics, vol. 34, no. 7, pp. 1931–1946, 2014.
[3] J. Lucchinetti et al., “A new clinicopathologic subtype of multiple sclerosis,” N Engl J Med, vol. 343, no. 13, pp. 938–949, 2000.
[4] D. Lee et al., “Differentiation between glioblastoma and tumefactive demyelination using imaging,” Neuroradiology, vol. 63, pp. 1879–1888, 2021.
[5] J. Z. Mamlouk, “Diagnostic criteria and imaging of tumefactive MS,” Neuroimaging Clin N Am, vol. 23, no. 2, pp. 229–243, 2013.
[6] T. H. Na et al., “Enhancement patterns in tumefactive demyelinating lesions,” Clin Imaging, vol. 54, pp. 98–105, 2019.
[7] M. C. Barnett et al., “Multiple sclerosis: lesion evolution,” J Neurol Neurosurg Psychiatry, vol. 75, pp. 946–948, 2004.
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