AJR 2001; 177:1479-1481
© American Roentgen Ray Society
Diffusion-Weighted MR Imaging in a Patient with Spinal Meningioma
James D. Eastwood1,2,
Dennis A. Turner3,
Roger E. McLendon4 and
James M. Provenzale1,2
1
Department of Radiology, Box 3808, Duke University Medical Center, Durham, NC
27710-3808.
2
Department of Radiology, Durham Veterans' Affairs Medical Center, 508 Fulton
St., Durham, NC 27705.
3
Department of Neurosurgery, Duke University Medical Center, Durham, NC
27710.
4
Department of Anatomic Pathology, Duke University Medical Center, Durham, NC
27710.
Received March 12, 2001;
accepted after revision May 10, 2001.
Address correspondence to J. D. Eastwood.
Introduction
Diffusion-weighted MR imaging provides unique tissue contrast that reflects
the microscopic motions of tissue water. Diffusion-weighted imaging is well
established as a useful clinical tool for the evaluation of brain
abnormalities, most notably stroke
[1]. However, until recently
diffusion-weighted imaging of the spine has been technically limited. We
report the findings in a case of intraspinal meningioma studied with
diffusion-weighted imaging. Knowledge of the diffusion-weighted imaging
appearance of intraspinal abnormalities should be helpful to physicians who
interpret MR studies of the spine. To our knowledge, the diffusion-weighted
imaging findings of an intraspinal tumor have not previously been reported in
the literature.
Case Report
A 48-year-old man presented with 8 months of progressive bilateral hand
tingling, numbness, and weakness. Physical examination showed mild bilateral
hand weakness and decreased sensation to a pinprick. MR images of the cervical
spine, including diffusion-weighted images, showed a contrast-enhancing mass
with both intradural extramedullary and extradural components that extended
into the C4 and C5 neural foramen (Figs.
1A,1B,1C,1D,1E).
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Fig. 1A. —48-year-old man with numbness, tingling, and weakness in both
hands. T2-weighted turbo spin-echo sagittal MR image (TR/effective TE,
2665/120) shows ovoid hypointense mass in spinal canal.
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Fig. 1B. —48-year-old man with numbness, tingling, and weakness in both
hands. T1-weighted sagittal MR image (TR/TE, 615/15) after infusion of
gadolinium contrast material shows diffuse signal enhancement of mass.
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Fig. 1C. —48-year-old man with numbness, tingling, and weakness in both
hands. T1-weighted transverse MR image after infusion of contrast material
shows extent of tumor in spinal canal and C4-C5 neural foramen
(arrow).
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Fig. 1D. —48-year-old man with numbness, tingling, and weakness in both
hands. Diffusion-weighted sagittal MR image using peripheral pulse gating and
navigator correction (TR/effective TE, 1 pulse-to-pulse interval/70; b value,
554 sec/mm2) shows signal intensity of mass (open arrows)
to be intermediate, less than that of brainstem (large solid arrow)
and greater than that of vertebral bodies (small solid arrows).
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Fig. 1E. —48-year-old man with numbness, tingling, and weakness in both
hands. Apparent diffusion coefficient map (two-point technique; b values, 0,
554) shows mass (arrows) as structure of intermediate intensity.
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All scanning was performed on a 1.5-T clinical MR scanner (Intera Master;
Philips, Best, The Netherlands). Multishot spin-echo echoplanar
diffusion-weighted scanning was performed in the sagittal plane. Each
diffusion-weighted scan used peripheral pulse gating (from a pulse oximeter
placed on the patient's finger) and navigator echo motion correction. The TR
was one pulse-to-pulse interval, and the TE was 70 msec. A rectangular field
of view measured 250 x 188 mm and was displayed by a matrix of 256
x 192. The number of signal averages was 2. Total scanning time was 2
min 53 sec. One scan without diffusion-sensitizing gradients (i.e., a b = 0
image) and three scans with diffusion-sensitizing gradients were obtained. The
three scans using diffusion-sensitizing gradients were identical except for
the orientation of the gradients. Diffusion-weighted scans were obtained with
diffusion-sensitizing gradients oriented in each of three directions:
anteroposterior, left—right, and superoinferior. For each of the three
diffusion-weighted scans, the degree of diffusion sensitization (b value) was
554 sec/mm2. The three diffusion-weighted scans acquired in this
way were then averaged to create an isotropic diffusion-weighted image. Using
the first scan (b = 0) and the isotropic diffusion-weighted image (b = 554), a
map of isotropic apparent diffusion coefficient (ADC) was created using
software available on the scanner. The isotropic ADC map was then transferred
to an imaging workstation (Easy Vision; Philips) for region-of-interest
analysis. A hand-drawn region of interest (433 mm2) that included
the central portion of the tumor on the ADC map showed a mean ADC value of
1.42 ± 0.44 x 10-5 cm2/sec. The mean ADC
value measured in the spinal cord was 0.65 x 10-5
cm2/sec.
The patient subsequently underwent surgery that included resection of the
mass, which had both extradural and intradural components. Pathologic
examination revealed the mass to be consistent with a benign (World Health
Organization grade I) [2],
well-differentiated meningothelial meningioma
(Fig. 1F). Histologic
examination showed the tumor had abundant intercellular collagen and overall
low cellularity.
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Fig. 1F. —48-year-old man with numbness, tingling, and weakness in both
hands. Photomicrograph of sectioned spinal tumor shows tumor with spindle
cells (arrowhead) arranged in loose whorls of cells associated with
psammoma body centrally (arrow). Nuclei were bland in appearance,
with rare intranuclear cytoplasmic invaginations evident (not shown). Note
lack of mitotic figures and no evidence of necrosis.
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Discussion
Diffusion-weighted imaging is an established MR imaging method with a
number of clinical and research applications for brain imaging
[1,
3,
4]. Until recently, however,
reports describing in vivo diffusion-weighted imaging of the spine have been
rare. Diffusion-weighted imaging of the spine presents a technical challenge,
mainly because of the relatively small size of the spinal canal (requiring
high spatial resolution) and the pulsatile motions of the cerebrospinal fluid
and the spinal cord. Diffusion-weighted imaging is a technique that is highly
sensitive to artifacts related to motion. Before development of successful
techniques to correct the negative effects of pulsatile motion,
diffusion-weighted imaging in the spine was limited mainly to evaluation of
the osseous vertebral column, an anatomic location largely unaffected by
pulsatile motions such as those occurring in the spinal canal. Recent
improvements in diffusion-weighted imaging pulse sequence design have
addressed previous limitations and now permit diffusion-weighted imaging of
intraspinal structures such as the spinal cord
[5,
6].
Two techniques (both used in this study) appear to be of particular value
for limiting the negative effects of motion on diffusion-weighted imaging of
intraspinal structures. First, peripheral pulse gating using a pulse oximeter
signal diminishes artifacts caused by pulsatile motions in the spinal canal
that are synchronous with cardiac pulsation
[5]. By using the signal from
the pulse oximeter to trigger the initiation of the scanner pulse sequence,
gross motion between excitations can be limited. Second, the use of a
navigator echo (i.e., an additional, refocused echo obtained to determine the
presence of phase errors caused by motion) further helps to limit the adverse
effects of motion on image quality
[5,6,7].
Navigator echo technology for diffusion-weighted imaging is not presently
widely available for routine use, but it is offered as an optional feature by
some MR scanner manufacturers.
Our study used a multishot echoplanar imaging technique for the acquisition
of data for the diffusion-weighted scans. This technique was used instead of a
single-shot echoplanar imaging technique for two main reasons: improved image
signal-to-noise ratio and decreased susceptibility artifacts. An echoplanar
imaging technique was chosen over a fast spin-echo technique—a technique
that might be expected to produce fewer artifacts caused by magnetic
susceptibility—because diffusion-weighted imaging using an echoplanar
technique is expected to provide images with a greater signal-to-noise
ratio.
Published reports of diffusion-weighted imaging in the spine have shown its
value for evaluating osseous spinal abnormalities. Specifically,
diffusion-weighted images have been used to help differentiate osteoporotic
compression fractures from compression fractures due to metastatic tumor
deposits
[7,8,9].
As experience with diffusion-weighted imaging in the spine increases,
evaluation of intraspinal masses could be similarly improved by the use of
diffusion-weighted imaging.
Meningiomas are among the most common primary tumors arising in the spine.
By reporting the diffusion-weighted imaging appearance and mean ADC value
associated with a common intraspinal tumor, this article seeks to provide
information that could be helpful to physicians who use diffusion-weighted
imaging of the spine.
We are unaware of any prior descriptions of the diffusion-weighted imaging
findings of intraspinal tumors. Nonetheless, previously published studies of
intracranial tumors suggest that diffusion-weighted imaging may provide useful
information about central nervous system tumor histology. One study showed ADC
values measured in intracranial meningiomas ranging from 0.4 to 1.8 x
10-5 cm2/sec
[3]. Notably, the mean ADC
values measured in meningiomas with malignant histologic findings or cellular
atypia were significantly lower than the mean ADC values measured in
meningiomas with benign histologic findings. Also, a study of cerebral gliomas
by Sugahara et al. [4]
documented that tumor cellularity correlates negatively with mean tumor ADC
values. In that study, tumors with high cellularity had low mean ADC values,
and tumors with low cellularity had high mean ADC values.
The relationship of the ADC values to histologic findings in the tumor in
our patient corresponds well to the findings of the previously mentioned
studies. The ADC value of 1.42 x 10-5 cm2/sec in
our case is within the range of values for benign meningiomas previously
published (0.62-1.8 x 10-5 cm2/sec) and well above
values found in malignant and atypical meningiomas
[3]. In addition, the
relatively high ADC value seen in our patient corresponded to a low degree of
cellularity, such as has been reported in cerebral gliomas
[4]. The mean isotropic ADC
value measured in the spinal cord in our patient (0.65 x 10-5
cm2/sec) was similar to previously published ADC values measured in
the anteroposterior direction in normal spinal cords
[6].
In conclusion, we have reported the diffusion-weighted imaging findings of
a benign intraspinal meningioma. Recent improvements in scanning technique
(such as the use of navigator echo correction of motion) have made
diffusion-weighted imaging a promising modality for the study of intraspinal
abnormalities.
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Introduction
Case Report
