AJR 2004; 182:195-199
© American Roentgen Ray Society
The MRI Appearance of Tumefactive Demyelinating Lesions
Curtis A. Given, II1,2,
B. Scott Stevens2 and
Charles Lee2
1 Department of Surgery, University of Kentucky Chandler Medical Center, Rm.
HX-311C, 800 Rose St., Lexington, KY 40536.
2 Department of Diagnostic Radiology, University of Kentucky Chandler Medical
Center, Lexington, KY 40536.
Received January 23, 2003;
accepted after revision May 23, 2003.
Address correspondence to C. A. Given II.
Introduction
Demyelinating 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 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, 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
post-vaccination 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.
1A,
1B,
1C). They typically involve the
supratentorial compartment and are centered within the white matter, although
they may extend to involve the cortical gray matter.
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Fig. 1A. —21-year-old woman presenting with new-onset seizure and
biopsy-proven tumefactive demyelinating lesion. 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.
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Fig. 1B. —21-year-old woman presenting with new-onset seizure and
biopsy-proven tumefactive demyelinating lesion. Enhanced coronal T1-weighted
spin-echo image reveals large left frontal lesion with incomplete ring of
enhancement (arrow).
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Fig. 1C. —21-year-old woman presenting with new-onset seizure and
biopsy-proven tumefactive demyelinating lesion. Unenhanced axial T2-weighted
spin-echo image reveals relatively little mass effect or surrounding vasogenic
edema given size of lesion.
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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.
1A,
1B,
1C and
2A,
2B,
2C,
2D). 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 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.
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Fig. 2A. —50-year-old man presenting with slurred speech and
biopsy-proven tumefactive demyelinating lesion. Unenhanced axial T2-weighted
spin-echo image reveals large lesion centered within left temporal lobe with
surrounding vasogenic edema.
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Fig. 2B. —50-year-old man presenting with slurred speech and
biopsy-proven tumefactive demyelinating lesion. Enhanced axial T1-weighted
spin-echo image reveals open ring of enhancement (arrow) along gray
matter side of lesion.
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Fig. 2C. —50-year-old man presenting with slurred speech and
biopsy-proven tumefactive demyelinating lesion. Unenhanced axial T2-weighted
spin-echo image obtained 2 months after corticosteroid therapy reveals
striking reduction in size of lesion and associated edema.
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Fig. 2D. —50-year-old man presenting with slurred speech and
biopsy-proven tumefactive demyelinating lesion. Enhanced axial T1-weighted
spin-echo image obtained at same setting as C reveals resolution of
abnormal enhancement.
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Central Dilated Veins Within the Lesion
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.
1A,
1B,
1C and
3A,
3B,
3C,
3D).
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Fig. 3A. —39-year-old woman presenting with severe headache, bilateral
lower extremity pain, and biopsy-proven tumefactive lesion. Unenhanced axial
T2-weighted spin-echo image reveals large left parietal lesion with extension
into splenium of corpus callosum (arrowhead).
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Fig. 3B. —39-year-old woman presenting with severe headache, bilateral
lower extremity pain, and biopsy-proven tumefactive lesion. Enhanced axial
T1-weighted gradient-echo image reveals contrast enhancement of dilated veins
(arrow) located centrally within lesion.
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Fig. 3C. —39-year-old woman presenting with severe headache, bilateral
lower extremity pain, and biopsy-proven tumefactive lesion. Unenhanced axial
apparent diffusion coefficient (ADC) map shows predominately increased
diffusion (arrow) within lesion.
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Fig. 3D. —39-year-old woman presenting with severe headache, bilateral
lower extremity pain, and biopsy-proven tumefactive lesion. 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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Decreased Perfusion
There have been several case reports and series showing decreased perfusion
with MRI within tumefactive demyelinating lesions
[6,
7] (Fig.
4A,
4B,
4C). 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.
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Fig. 4C. —22-year-old woman with tumefactive demyelinating lesion.
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])
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Rapid Resolution After Steroid Therapy
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.
2A,
2B,
2C,
2D).
Imaging Features Not Specific for Tumefactive Demyelinating Lesions
Corpus Callosum Involvement
Tumefactive demyelinating lesions can spread through or originate within
the corpus callosum (Figs. 3A,
3B,
3C,
3D and
5A,
5B). As such, they should be
listed in the differential diagnosis of "butterfly" lesions, with
glioblastoma multiforme and lymphoma.
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Fig. 5A. —62-year-old man presenting with a several-month history of
blurring vision and biopsy-proven tumefactive demyelinating lesion. Unenhanced
axial T2-weighted spin-echo image reveals large lesion (arrow)
centered within right temporal–occipital region with extension into
splenium of corpus callosum.
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Fig. 5B. —62-year-old man presenting with a several-month history of
blurring vision and biopsy-proven tumefactive demyelinating lesion. Enhanced
axial T1-weighted spin-echo image reveals patchy enhancement
(arrowhead) along anterior margin of lesion.
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Increased Diffusion
Diffusion imaging reveals mildly increased apparent diffusion coefficients
within tumefactive demyelinating lesions (Fig.
3A,
3B,
3C,
3D). 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
Proton MR spectroscopy provides insight into the chemical composition of
lesions. Primary 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 lesions) may
produce an identical MR spectrum, mimicking a neoplastic process
[7,
8] (Fig.
3A,
3B,
3C,
3D).
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.
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 often-sizeable lesions. The presence of centrally
dilated veins within the lesion and decreased perfusion appear to be
additional characteristic features.
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Introduction
Imaging Features Suggestive of...
