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					Pictorial Essay
The MRI Appearance of Tumefactive Demyelinating Lesions
Curtis A. Given II1,2, B. Scott Stevens2, Charles Lee2
emyelinating diseases of the central nervous system are frequently encountered pathologic entities; multiple sclerosis is the most common. The typical appearance of these lesions on MRI, with preferential involvement of the

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major white matter tracts in a periventricular distribution, provides little diagnostic dilemma. When the disease manifests as a single large or tumefactive demyelinating lesion within a cerebral hemisphere, the correct diagnosis is often not made until after surgical

biopsy or resection. In this pictorial essay, the MRI appearance of tumefactive demyelinating lesions will be reviewed and findings on newer MRI techniques will be discussed. Tumefactive demyelinating lesions are generally thought of as solitary lesions,

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Fig. 1.—21-year-old woman presenting with new-onset seizure and biopsy-proven tumefactive demyelinating lesion. A, Enhanced axial T1-weighted spin-echo image reveals large left frontal lesion with incomplete ring of enhancement (arrow), open on gray matter side of lesion. There is faint enhancement within dilated, centrally located venous structures (arrowhead), suggestive of demyelinating lesion. B, Enhanced coronal T1-weighted spin-echo image reveals large left frontal lesion with incomplete ring of enhancement (arrow). C, Unenhanced axial T2-weighted spin-echo image reveals relatively little mass effect or surrounding vasogenic edema given size of lesion.

Received January 23, 2003; accepted after revision May 23, 2003.
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Department of Surgery, University of Kentucky Chandler Medical Center, Rm. HX-311C, 800 Rose St., Lexington, KY 40536. Address correspondence to C. A. Given II. Department of Diagnostic Radiology, University of Kentucky Chandler Medical Center, Lexington, KY 40536.

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Given et al. greater than 2 cm, with imaging characteristics mimicking neoplasms. These lesions more commonly occur in women with an average age of 37 years [1, 2]. With rare exception, the tumefactive demyelinating lesions do not originate as a postinfectious or postvaccination response. Although the exact pathogenesis is not clearly understood, most patients respond favorably to corticosteroid therapy and do not progress to multiple sclerosis [1]. Symptoms are generally atypical for multiple sclerosis and usually relate to the presence of a focal mass lesion: focal neurologic deficit, seizure, or aphasia [3]. Without a history of multiple sclerosis, the clinical presentation and radiographic appearance of these lesions often lead to biopsy. In a review of 31 cases, Kepes [1] proposed that tumefactive demyelinating lesions represent an intermediate lesion between those typically seen with multiple sclerosis and acute disseminated encephalomyelitis. Pathologically, these lesions are indistinguishable from typical multiple sclerosis plaques and are characterized by infiltrating foamy macrophages intermingled between reactive astrocytes [3]. Significant quantities of lipid may accumulate within the plaques as a result of myelin breakdown. The axons are relatively preserved within the lesions, but more recent investigation has shown axonal jury within multiple sclerosis plaques. The pathologic diagnosis may be challenging based on the initial frozen-section specimen when the primary suspicion is malignancy. Tumefactive demyelinating lesions have been misinterpreted as gliomas, with the correct diagnosis being revealed only after histologic evaluation [2, 3]. Thus, the preoperative diagnosis, or at least consideration, of a demyelinating process is imperative to avoid unnecessary resection or adjunctive therapy [2].
Imaging Features Suggestive of Tumefactive Demyelinating Lesions
Large Lesion with Little Mass Effect and Edema

Tumefactive demyelinating lesions tend to be circumscribed lesions with little mass effect or vasogenic edema [2] (Fig. 1). They typically involve the supratentorial compartment and are centered within the white matter, although they may extend to involve the cortical gray matter.
Ringlike or Open-Ring Enhancement

Approximately half of tumefactive demyelinating lesions have pathologic contrast enhancement, usually in the form of ring enhancement [2, 4] (Figs. 1 and 2). Commonly the enhancement patterns will be in the form of an open ring, with the incomplete portion of the ring on the gray matter side of the lesion [4]. More typical active multiple sclerosis plaques exhibit this open-ring or arclike

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Fig. 2.—50-year-old man presenting with slurred speech and biopsy-proven tumefactive demyelinating lesion. A, Unenhanced axial T2-weighted spin-echo image reveals large lesion centered within left temporal lobe with surrounding vasogenic edema. B, Enhanced axial T1-weighted spin-echo image reveals open ring of enhancement (arrow) along gray matter side of lesion. C, Unenhanced axial T2-weighted spin-echo image obtained 2 months after corticosteroid therapy reveals striking reduction in size of lesion and associated edema. D, Enhanced axial T1-weighted spin-echo image obtained at same setting as C reveals resolution of abnormal enhancement.

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MRI of Tumefactive Demyelinating Lesions pattern of enhancement only 9% of the time [5]. The enhancing portion of the ring is believed to represent the leading edge of demyelination and thus favors the white matter side of the lesion [5]. The central nonenhancing core represents a more chronic phase of the inflammatory process.
Central Dilated Veins Within the Lesion

within tumefactive demyelinating lesions [6, 7] (Fig. 4). Cha et al. [6] reported the mean relative cerebral blood volume (rCBV) within tumefactive demyelinating lesions was lower than that within the contralateral normal-appearing white matter and substantially less than that found in high-grade gliomas and lymphomas.
Rapid Resolution After Steroid Therapy

(Figs. 3 and 5). As such, they should be listed in the differential diagnosis of “butterfly” lesions, with glioblastoma multiforme and lymphoma.
Increased Diffusion

Cha et al. [6] noted a dilated vascular structure running centrally within several of the studied tumefactive demyelinating lesions on T2 echoplanar images from MRI perfusion studies. These vascular structures were believed to represent dilated veins draining toward distended subependymal veins (Figs. 1 and 3).
Decreased Perfusion

Most tumefactive demyelinating lesions will show an excellent response to corticosteroid therapy with a substantial decrease in size or disappearance of the lesions on follow-up imaging [1] (Fig. 2).
Imaging Features Not Specific for Tumefactive Demyelinating Lesions
Corpus Callosum Involvement

Diffusion imaging reveals mildly increased apparent diffusion coefficients within tumefactive demyelinating lesions (Fig. 3). This proves to be a useful tool in differentiating ring-enhancing tumefactive demyelinating lesions from cerebral abscesses, the latter being associated with restricted diffusion centrally within the lesion. Necrotic neoplasms may display a similar increase in diffusion coefficients centrally within the lesion, making diffusion less helpful in differentiating from neoplasms.
Tumorlike Spectrum on Proton MR Spectroscopy

There have been several case reports and series showing decreased perfusion with MRI

Tumefactive demyelinating lesions can spread through or originate within the corpus callosum

Proton MR spectroscopy provides insight into the chemical composition of lesions. Pri-

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Fig. 3.—39-year-old woman presenting with severe headache, bilateral lower extremity pain, and biopsy-proven tumefactive lesion. A, Unenhanced axial T2-weighted spin-echo image reveals large left parietal lesion with extension into splenium of corpus callosum (arrowhead). B, Enhanced axial T1-weighted gradient-echo image reveals contrast enhancement of dilated veins (arrow) located centrally within lesion. C, Unenhanced axial apparent diffusion coefficient (ADC) map shows predominately increased diffusion (arrow) within lesion. D, Single-voxel proton spectroscopy image obtained using point-resolved sequence (PRESS, TR/TE, 1,500/135) placed along medial border of lesion at area of enhancement reveals elevated choline (Cho) and suppressed N-acetylaspartate (NAA) relative to creatine (Cr) and prominent lactate (Lac) doublet.

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Given et al.

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Fig. 4.—22-year-old woman with tumefactive demyelinating lesion. A, Unenhanced axial FLAIR spin-echo MRI shows well-circumscribed mass in right frontal lobe with little surrounding edema. B, Enhanced axial T1-weighted spin-echo image reveals homogeneous enhancement of mass. C, Color overlay image of mean relative cerebral blood volume map plotted onto T2 echoplanar image shows no increase in blood volume within lesion relative to contralateral healthy white matter. (Reprinted with permission from [6])

mary glial cell tumors produce a characteristic spectrum consisting of elevated choline with suppressed levels of N-acetylaspartate. Additionally, there may be detectable levels of lipids and lactate corresponding to necrosis and anaerobic metabolism associated with the glial tumors (primarily glioblastoma multiforme). Several nonneoplastic brain lesions (including tumefactive demyelinating le-

sions) may produce an identical MR spectrum, mimicking a neoplastic process [7, 8] (Fig. 3).
Magnetization Transfer

Decreased magnetization transfer values have been shown in plaques and healthy-appearing white matter of patients with multiple sclerosis. The magnetization transfer effect

within tumefactive demyelinating lesions has not been extensively published, but a similar decline in magnetization transfer values was observed in a single case report [7]. The utility of magnetization transfer in the diagnosis of these tumefactive demyelinating lesions will have to be explored because neoplastic processes can show a similar decline in magnetization transfer values.

Fig. 5.—62-year-old man presenting with a severalmonth history of blurring vision and biopsy-proven tumefactive demyelinating lesion. A, Unenhanced axial T2-weighted spin-echo image reveals large lesion (arrow) centered within right temporal–occipital region with extension into splenium of corpus callosum. B, Enhanced axial T1-weighted spin-echo image reveals patchy enhancement (arrowhead) along anterior margin of lesion.

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MRI of Tumefactive Demyelinating Lesions
Conclusion

Tumefactive demyelinating lesions prove to be a diagnostic dilemma to neurosurgeons, radiologists, and pathologists. The MRI appearance of these lesions can aid in preoperative diagnosis and assist with the final pathologic interpretation, potentially sparing the patient unnecessary and possibly debilitating procedures and therapies. Perhaps the most useful diagnostic tool is the open ring of enhancement and relatively sparse mass effect and edema associated with these oftensizeable lesions. The presence of centrally dilated veins within the lesion and decreased

perfusion appear to be additional characteristic features.
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References
1. Kepes JJ. Large focal tumor-like demyelinating lesions of the brain: intermediate entity between multiple sclerosis and acute disseminated encephalomyelitis? a study of 31 patients. Ann Neurol 1993;33:18–27 2. Dagher AP, Smirniotopoulos J. Tumefactive demyelinating lesions. Neuroradiology 1996;38:560–565 3. Paley RJ, Persing JA, Doctor A, et al. Multiple sclerosis and brain tumor: a diagnostic challenge. J Emerg Med 1989;7:241–244 4. Masdeu JC, Moreira J, Trasi S, Visintainer P, Cava6.

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liere R, Grundman M. The open ring: a new imaging sign in demyelinating disease. J Neuroimaging 1996;6:104–107 He J, Grossman RI, Ge Y, Mannon LJ. Enhancing patterns in multiple sclerosis: evolution and persistence. AJNR 2001;22:664–669 Cha S, Pierce S, Knopp EA. Dynamic contrast-enhanced T2-weighted MR imaging of tumefactive demyelinating lesions. AJNR 2001;22:1109–1116 Ernst T, Chang L, Walot I, Huff K. Physiologic MRI of a tumefactive multiple sclerosis lesion. Neurology 1998;51:1486–1488 Saindane AM, Soonmee C, Meng L, Xiaonan X, Knopp EA, Zagzag D. Proton MR spectroscopy of tumefactive demyelinating lesions. AJNR 2002;23:1378–1386

The full text and images from the American Journal of Roentgenology may also be viewed online at www.arrs.org or www.ajronline.org.

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