Synopsis
Magnetic resonance
imaging (MRI) is widely used to narrow the differential diagnosis in the preoperative
study of spinal cord tumors. The use of a medium in MRI is preferred to improve
visualization of tumor’s intrinsic characteristics and boundaries, and to
identify reactive changes (such as cysts and dilated veins) in adjacent
tissues. Most times, it is easy to determine whether a lesion arises from the
spinal cord itself or from the IDEM space according to common MRI findings,
however, at other times, this might be difficult. There have been reported
cases of schwannoma located at IDEM space misdiagnosed with IMT.
Thus, radiologists
must discern the characteristic imaging features of IDEMs to distinguish them from IMTs. The presence of vein enlargement is
often a sign in some cases of intradural spinal tumors , most of
which are extramedullary. A perimedullary vein enlargement sign around an
intradural spinal tumor (without dilated veins in the tumor)has not
been reported, which might be an imaging mark to differentiate IDEMTs from IMTs.The
purpose of this study was to determine the added value of the perimedullary
spinal vein enlargement sign on MRI in helping to distinguish IDEMTs from IMTs.Purpose
To determine the added value of perimedullary spinal vein
enlargement sign on magnetic resonance imaging (MRI) in distinguishing intradural-extramedullar spinal tumors (IDEMTs) from
intramedullary spinal
tumors (IMTs).
Materials and Methods
This
study was approved by the ethics committee, for the retrospective nature,
informed consent was waived, included 208 consecutive spinal intradural tumors
(age range, 2-77 years; mean age, 47±9 years) with histopathologic confirmation: 21 IMTs (mean age, 46±7 years); 187 IDEMTs (mean age, 48±15
years). Two readers blinded to the final pathological diagnosis and clinical
data, independently assessed the venous enlargement sign to determine agreement
between them, and jointly distinguished IDEMTs from IMTs according to the
common MRI findings. Sensitivity, specificity and accuracy for the
diagnosis of IDEMTs were calculated of common MRI findings, vein enlargement
sign and a combination of both.
All images were acquired using
three different MR scanners at 3.0T (Philips Achieva 3.0T TX, Best, The
Netherlands; MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany; General Electric
Medical Systems, Milwaukee, WI, USA). The common MRI findings for the diagnosis of IDEMTs
were the following: (1) eccentric (transverse diameter of the tumor
was smaller than Sagittal diameter of vertebral canal); (2) spinal cord near the
tumor is compressed by tumor, at an acute angle, and without edema and
syrinx; (3)
extended cavitas subarachnoidealis around the tumor; (4) the appearance, T1/T2
signal, enhancement of the common IDEMTs as
follows: (a) schwannoma and neurofibroma— equal/low signals in T1weighted
imaging and high signals in T2 weighted imaging,
homogeneous or inhomogeneous enhancement; (b) meningioma—homogeneous, equal/low signals in T1weighted imaging, low/slightly
high signal in T2 weighted imaging, heterogeneous enhancement,
tail of spinal dura sign; (c) teratoma—longitudinally
growing along the canal; T1/T2 weighted images
show mixed inhomogeneous intensity signals with no enhancement.
Results
Spinal perimedullary venous enlargement was clearer on the contrast
enhanced MR images than on T2 weighted images. Intraobserver agreement (κ = 1)
and interobserver agreement (κ = 0.956) for both reader were excellent. The
sensitivity, specificity and accuracy of the common MRI findings for differentiating IDEMTs from
IMTs were 83.4%, 95.2% and
89.3%, respectively, causing 31 IDEMTs to be
mistakenly diagnosed as IMTs, in which 7 were cases with vein enlargement signs.
By applying the vein enlargement sign to the
common MRI findings, sensitivity improved to 89.3%, and accuracy
increased to 92.3%.
Conclusion
The spinal perimedullary vein enlargement
sign is useful in assessing intradural tumors and to differentiate IDEMTs from IMTs.
Discussion
Spinal
tumors arising from the nerve roots or close to it would easily press on the
radiculomedullary vein, causing the vein enlargement sign. Most of the schwannoma,
a part of meningioma, and hemangioblastomas of spinal nerve roots comply
with such standards, and all are IDEMTs. The results of this study, showed that
96% of intradural spinal tumors with the venous dilation sign was located in
IDEM spaces, and most of those were located eccentrically of spinal cord on the
axial T2 weighted images (82.3%), while others filled up the entire sagittal
diameter of the spinal canal.
Spinal hemangioblastomas
are rare, benign, capillary-rich tumors, composing
about 2% to 8% of all intramedullary spinal cord tumors About one-third of the tumors are associated with von
Hippel-Lindau disease[25], most of which are multiple small tumors(10 mm or less) without
dilated perimedullary veins[26]. When
a hemangioblastoma larger than 10 mm, it is often associated with syrinx
and vascular flow voids in or around the tumor and perimedullary. Vascular malformation was the main cause of the
sign in hemangioblastomas,
in which feeding arteries were deviated by
the malformation from the normal to intraspinal circulation, called “steal”
phenomenon, reducing arteriovenous pressure, and extending the draining vein;
therefore, edema or syrinx were always present around the spinal cord surrounding
the tumor because of ischaemia in the area under the feeding arteries . When using the sign alone, it is
difficult to differentiate IDEMTs from IM hemangioblastomas, but the spinal hemangioblastomas
wih perimedullary vein enlargement sign can also be seen dilated veins in
tumors, making itself easy to differentiate correctly. So the sign in our paper
refers to the mean that the perimedullary vein enlargement and without dilated
veins in the tumor.
Acknowledgements
No acknowledgement found.References
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