AJR 2004; 183:1176-1177
© American Roentgen Ray Society
Hyperintensity of Spinal Cryptococcus Infection on Diffusion-Weighted MR Images
Lejla Aganovic,
Rana S. Hoda and
Zoran Rumboldt
Medical University of South Carolina Charleston, SC 29425
A 20-year-old man presented with a 2-month history of progressive lower
back and flank pain. No neurologic deficits were detected at clinical
examination. Medical history was significant for pulmonary sarcoidosis for
which he was self-medicated with prednisone. A radiograph of the lumbar spine
showed irregularities involving the endplates of the L1 and L2 vertebral
bodies without significant loss of intervertebral disk height.
MRI showed destructive lesions involving T12–L2 vertebrae,
T12–L1 disk, paraspinal muscles, and posterior epidural space from T12
to L3 levels (Fig. 1A). The
mass was spreading along the L1–L2 neural foramen into the right psoas
muscle. Contrast-enhanced images showed rim enhancement of the lesions
(Fig. 1B). Diffusion-weighted
imaging was also performed and showed prominent hyperintensity
(Fig. 1C), with the apparent
diffusion coefficient values of the lesions ranging from 0.90 to 1.20 x
10–3 mm2/sec
(Fig. 1D). This multifocal,
multilevel distribution involving vertebrae, epidural space, and surrounding
muscles and the relative sparing of disk space was considered consistent with
a granulomatous spinal process. Evidence of hyperintensity on
diffusion-weighted imaging was helpful because this finding was thought to be
indicative of an infectious process rather than sarcoid lesions.
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Fig. 1A. —20-year-old man with sarcoidosis and epidural
Cryptococcus infection. STIR MR image obtained in sagittal plane
shows increased signal intensity in L1 vertebral body (arrow) and
minimal extension into intervertebral disk space. Mass with abnormal signal
(arrowheads) extending from T12 through L2 vertebrae is also present
in epidural space and posterior elements.
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Fig. 1B. —20-year-old man with sarcoidosis and epidural
Cryptococcus infection. Contrast-enhanced fat-suppressed T1-weighted
MR image corresponding to B shows diffuse enhancement of abnormal
areas. Portion of L1 vertebral body (arrow) and small areas in
epidural space (arrowheads) reveal no enhancement, consistent with
areas of bony destruction and possible abscesses.
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Fig. 1C. —20-year-old man with sarcoidosis and epidural
Cryptococcus infection. Diffusion-weighted midsagittal MR image shows
hyperintensity of involved vertebral body, epidural space, and posterior
elements. Lesions are more conspicuous than on conventional images.
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Fig. 1D. —20-year-old man with sarcoidosis and epidural
Cryptococcus infection. Apparent diffusion coefficient midsagittal
image shows intermediate signal of lesions, slightly lower compared with
normal intervertebral disks. Apparent diffusion coefficient values ranged from
0.90 to 1.20 x 10-3 mm2/sec for lesions and from
1.65 to 1.72 x 10-3 mm2/sec for normal disks.
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Cytologic smears obtained after CT-guided biopsy of one of the lesions
showed noncaseating granulomas, which enabled us to render a preliminary
diagnosis of sarcoidosis. Formal evaluation of the cytologic smears revealed
numerous intracellular (in histiocytes within granulomas) and extracellular
round to oval, variably sized (range, 5–10 µm) encapsulated
fungal organisms with characteristic teardropshaped narrow budding
(Fig. 1E). The final diagnosis
was cryptococcal infection with a granulomatous response. Special stains for
Cryptococcus organisms, including Gomori methenamine-silver and
mucicarmine, confirmed the diagnosis. The patient was placed in a brace and
was subsequently treated with antimycotic medications, followed by complete
recovery without any neurologic sequelae.
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Fig. 1E. —20-year-old man with sarcoidosis and epidural
Cryptococcus infection. Photomicrograph of cytologic smear shows
noncaseating granuloma with intracellular and extra-cellular fungal organisms.
Organisms are round to oval, variably sized, and encapsulated; some show
characteristic teardrop-shaped narrow budding (arrows).
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The cytopathologic differential diagnoses of granulomatous inflammation
involving bone include tuberculosis, fungal organisms, sarcoidosis,
foreign-body reaction, and metastatic tumors. There is an association between
sarcoidosis and skeletal cryptococcal infection with 20% of patients with this
infection having coincidental sarcoidosis. The cellular response in
cryptococcal infection varies with the stage of the disease: the early lesions
appear to be gelatinous, whereas the older lesions may incite a granulomatous
response [1].
Cryptococcus infection should be included in the differential
diagnosis of granulomatous inflammation.
Diffusion-weighted imaging has been widely used in the evaluation of brain
disorders including acute ischemia and brain abscesses
[2]. MRI with a
diffusion-weighted sequence has also been successfully applied to help
differentiate benign from malignant vertebral body collapse
[3]. To the best of our
knowledge, there has been only one recent report of hyperintensity on
diffusion-weighted imaging of a vertebral body abscess in which the
quantitative apparent diffusion coefficient value was not obtained
[4]. The apparent diffusion
coefficient values in our patient are slightly higher compared with the ones
reported in patients with brain abscesses and metastatic vertebral fractures
and similar to those in patients with degenerated intervertebral disks. Recent
advances in acquisition techniques designed to reduce motion-related artifacts
have made spinal diffusion-weighted imaging more practical, and this sequence
is becoming included in our routine imaging protocol. This case supports the
use of diffusion-weighted imaging in the evaluation of patients with spinal
infection, including granulomatous and fungal infections, to find
characteristic hyperintensity, similar to intracranial abscesses.
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- Eastwood JD, Vollmer RT, Provenzale JM. Diffusion-weighted imaging
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AJNR 2002;23:496
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