|Year : 2014 | Volume
| Issue : 4 | Page : 927-931
MRI diagnosis of intradural extramedullary tumors
Rui Gu, Jia-Bei Liu, Qiao Zhang, Guang-Yao Liu, Qing-San Zhu
Department of Orthopedics, China-Japan Union Hospital, Jilin University, Changchun, China
|Date of Web Publication||9-Jan-2015|
Department of Orthopedics, China-Japan Union Hospital, Jilin University, No. 126 Xiantaida Street, Changchun 130033
Source of Support: None, Conflict of Interest: None
Objective: This study evaluates the magnetic resonance imaging (MRI) manifestation of intradural extramedullary (IDEM) tumors to improve the imaging diagnostic level.
Materials and Methods: From January 2005 to December 2012, a retrospective analysis of the MRI examination was performed on 108 patients with IDEM tumors confirmed by surgical pathology postoperatively in our hospital. According to the pathological classification; the gender, age, location, size, foraminal state extension, signal intensity (compared with the spinal cord), and enhancement were recorded and statistically analyzed.
Results: A total of 108 cases (111 lesions) were reported; 69 (70 lesions), 31 (31 lesions), three (five lesions), four (four lesions), and one (one lesion) of which were schwannoma, meningioma, neurofibroma, teratoma, and metastatic tumor, respectively. MRI manifestations of different IDEM tumors have certain specificities.
Conclusion: MRI is the preferred examination method for to diagnose IDEM tumors and provide a reliable imaging basis for clinical treatment and prognosis judgment.
Keywords: Diagnosis, intradural extramedullary tumors, magnetic resonance imaging
|How to cite this article:|
Gu R, Liu JB, Zhang Q, Liu GY, Zhu QS. MRI diagnosis of intradural extramedullary tumors. J Can Res Ther 2014;10:927-31
| > Introduction|| |
Intradural extramedullary (IDEM) tumors account for about 60% of the intraspinal tumors,  and include schwannomas , (30%; incidence rate, 0.3-0.4 cases annually per 100,000 people), meningiomas , (25%; incidence rate, 0.32 cases annually per 100,000 people), neurofibromas, teratomas, lipomas, and metastatic tumors. Early diagnosis and timely treatment are important to improve the life quality of patients. Imaging diagnosis provides a reliable and decisive basis for the treatment of IDEM tumors. In this paper, a retrospective analysis of magnetic resonance imaging (MRI) manifestation was performed on 108 patients with this disease diagnosed by pathological surgery, which aims to improve the diagnostic level of this disease.
| > Materials and methods|| |
From January 2005 to December 2012, a retrospective analysis of the MRI examination was performed on 108 patients that were confirmed of IDEM by pathology after operation in our hospital. The patients include 61 males and 47 females, with ages ranging from 17 to 73 years (mean age, 47.3 years). In the reported cases, 69 of which were neurilemmoma; 31 of which were meningioma, three of which were neurofibroma, four of which were teratoma, and one of which was a metastatic tumor.
Achieva 3.0T TX multiple magnetic resonance instrument (Holland Philips) was applied for scanning. All patients underwent sagittal T1-weighted imaging T1WIs and T2-weighted imaging (T2WI), as well as transverse and coronal T1WI with enhanced scans. Observation of the MRI indices was interpreted by two senior professional MRI physicians using double-blind interpretation. According to the pathological classification; the gender, age, location, size, foraminal extension state, signal intensity (compared with the spinal cord), and enhancement were recorded.
χ2 and Fisher's exact tests were performed on the processed data using the statistical software Statistical Package for Social Sciences (SPSS) 13.0 with the test level α = 0.05.
| > Results|| |
In 108 cases (111 lesions), 69 of which were schwannoma (70 lesions), 31 of which meningioma (31 lesions), three of which were neurofibroma (five lesions), four of which were teratoma (four lesions), and one of which was a metastatic tumor (one lesion). [Table 1] shows the basic IDEM tumor characteristics. Most neurilemmomas and neurofibromas have long longitudinal diameters (49/75), and a portion has long transverse diameters (28/75). Tumors extending toward the foramen (43/75) are more common.
MRI manifestations of tumors
MRI signals of neurilemmoma and neurofibroma are similar, and mostly showed equal or low signals in T1WI imaging and high signals in T2WI imaging. Enhanced scans reveal homogeneous or inhomogeneous enhancement. Most meningiomas have a longitudinal diameter of ≤2.5 cm (69/75), a transverse diameter of ≤1.5 cm (67/75), and no foraminal extension. Meningioma signals were relatively homogeneous, the T1WI imaging has equal or low signal, and T2WI imaging has low or slightly high signal. Enhancement scanning of the meningioma reveals a heterogeneous enhancement, and the strengthening degree was lower than neurogenic tumors. Teratoma was longitudinally growing along the canal, and the patients of this group have no foraminal extension. T1WI and T2WI show mixed inhomogeneous intensity signals with no enhancement.
Parts of the data showed that schwannoma (68/70), meningioma (31/31), and neurofibromatosis (5/5) are markedly enhanced, with an insignificant difference between these diseases (P > 0.05). Teratoma is not enhanced or markedly strengthened, with a significant difference with other tumors (P < 0.05). Meningioma showed homogeneous enhancement (31/31) and has a significant difference (P < 0.01) compared with other tumors. Schwannomas (57/70) are mostly strengthened circularly, with significant difference (P < 0.05) compared with other tumors.
| > Discussion|| |
The MRI has a high soft tissue resolution, in which the tumor, spinal cord, and cerebrospinal fluid (CSF) are clearly observed. And multifaceted, multiangle display the relationship between tumor and spinal cord, subarachnoid, being accurate positioning. Common features of IDEM tumors include spinal cord compression deformation, opposite side shift, tumor ipsilateral subarachnoid broadening, and contralateral subarachnoid narrowing. Combined with the features, MRI is positioned accurately on this tumor. The positioning accuracy of the patients of this group was 93.7%, which was consistent with the previous literature.  The IDEM tumor simultaneously shows different signals and enhanced features, and can obtain a more reliable qualitative diagnosis. Schwann cell neurilemmoma and neurofibroma originate from the nerve sheath, and are often called neurogenic tumors. Schwannomas are the most common IDEM tumors that are mostly solitary nodular and are prone to cystic degeneration. A few schwannomas are multiple nodular and form a complete capsule. The incidence rate of solitary neurofibroma is lower than that of schwannoma, mainly for neurofibromatosis. Schwannomas and neurofibromas are located in any spinal canal segment, mainly at the neck and the thoracic segment, and some at the lumbar. About 5-10% of the nerve fiber tumor cases undergo malignant transformation.  T1WI imaging shows multiple or low signal, and T2WI imaging shows high signal. Enhanced scanning reveals obvious homogeneous or inhomogeneous enhancement [Figure 1] and [Figure 2]. Schwannomas and neurofibromas respectively have annular enhancements and irregular configurations. Asano  found that the Antonio B area in schwannoma had more liquid, and often had cyst formation. Most schwannomas (63/70) and all neurofibromas in this group have cystic degeneration, which is consistent with the related reports. , Only one case have recurrent and multiple schwannomas. The incidence of solitary neurofibroma was relatively high,  and two out of three cases of neurofibroma in this group were multiple. A single case of neurofibroma was reported to have a visible, central star-shaped tumor with low signal intensity in T2WI. This intensity was not enhanced after enhancement, which corresponds to the nerve fiber in the tumor. Schwannomas in all groups had no such syndrome. In addition, one case of neurofibroma in the group showed a dural tail sign that was previously reported, , and implies that this sign was not the peculiar MRI feature of meningioma.
|Figure 1: Magnetic resonance imaging (MRI) showed intradural oval space-occupying lesion with smooth margin at T12-L2 level. (a) Lesion presented with hypointensity on T1-weighted imaging (T1WI); (b) lesion with fluid levels presented with hyperintensity on T2WI, and (c) lesion showed marked annular enhancement on enhancement scanning|
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|Figure 2: MRI showed intradural irregularly shaped space-occupying lesion with heterogeneous signal at L2-4 level. (a) Lesion presented with isointensity on T1WI, (b) lesion with curved impression on vertebral bodies of L2-4 presented with heterogeneous hyperintensity on T2WI, and (c) lesion showed marked heterogeneous enhancement on enhancement scanning|
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Incidence of meningioma is only second to schwannoma, which mostly originates from the arachnoid granular cell. The majority of this disease affect elderly women, because of the relation to the estrogen effect. , Meningioma is mainly located in the cervical and upper thoracic segments, and rarely occurs in the lumbosacral. Most cases of this group are located in the lumbar (19/31), but are inconsistent with those previously reported, because most meningiomas are small and have no marked symptoms in the neck or the upper extremity. This tumor often has a wide substrate without pedicle and a rare cystic degeneration. All meningiomas of this group show cystic degeneration. T1WI imaging has an equal and low signal, and T2WI imaging has a slightly low or high signal. Meningioma is heterogeneously enhanced and has a strengthening degree lower than the neurogenic tumor because of the relation to tumor calcification [Figure 3]. Among 31 meningioma patients in this group, 17 are calcified, and all pathological findings of schwannoma show no calcification.  The dural tail sign aids in the diagnosis of meningioma. Twelve cases have thickened and enhanced local tumor adjacent meninges that form a line similar to a dural tail sign, which is indicative of the reactive hyperplasia or direct invasion that has an important diagnostic value. However, several meningiomas lack this sign and result in misdiagnosis. One patient in this group had a larger tumor located in the lumbar. The MRI manifestation was atypical and was misdiagnosed as a neurogenic tumor. Two MRI cases of this group show equal T1 and T2 signals, and have homogeneous enhancements preoperatively diagnosed as meningioma. Tumors run along the nerve root and nerve roots in the operation - Tumors packaged the nerve root as seen in the operation, and were diagnosed via postoperative pathological diagnosis as schwannoma. Although the sand body is the most common meningioma pathological type, large areas of calcification are sparse, and the MRI inexactly displays the calcification. Combination with computed tomography (CT) may help observe the minute calcification in meningioma.
|Figure 3: MRI showed intradural irregularly shaped space-occupying lesion with broader base at T4-5 level. (a) Lesion presented with isointensity on T1WI, (b) Lesion presented with hypointensity on T2WI, and (c) lesion showed marked heterogeneous enhancement on enhancement scanning with 'dural tail sign'|
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Embryonal tumors originate from embryonic remnants, including teratoma, lipoma, epidermoid cysts, and dermoid cyst. Teratomas mostly occur below the cone at a younger age - and mostly affect women. T1WI and T2WI show mixed signals with inhomogeneous intensities, in which the pathological basis is an organ-like structure derived from three germ layers. Visible observations include short and wide T1 and T2 signals within the tumor, mixed signals to calcified components of long T1 and T2 cystic structures, and the short T2 signals confirmed by CT scanning. [Figure 4] reveals that no enhancement is observed. Sagittal scans clearly show the combined spinal cord abnormalities, subcutaneous lipoma, and sacral sinus. ,, All patients in this group show no enhancement after the enhanced scanning. One and two cases of diastematomyelia and tethered cord syndrome are reported. All cases are diagnosed preoperatively. This group has no lipoma, epidermoid cyst, and dermoid cysts.
|Figure 4: MRI showed intradural oval space-occupying lesion with smooth margin at L3-4 level. (a) Lesion presented with heterogeneous hyperintensity on T1WI, (b) lesion presented with heterogeneous hypointensity on T2WI, (c) lesion showed no enhancement on enhancement scanning|
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Spinal metastases mostly occur in epidurals; IDEM spinal metastases are rare  and can occur in any segment of the spinal canal , mostly thoracic segments - followed by lumbar, and in the cervical and sacral segments.  The case was a rare metastatic intraspinal subdural extramedullary tumor, with primary lesions originating from the esophagus and are located in the three lumbar levels of cauda equina. The MRI displays the tumor signal and the relation with the surrounding tissue, which is important for the diagnosis of subdural extramedullary metastases. However, the shape and the location have overlaps because of the effect of tumor signal enhancement, which causes difficulties in qualitative diagnosis. Homogeneous long T1 and long T2 signals of IDEM metastases have no marked specificities, and the imaging features of meningioma are similar with that of schwannoma, which is often clinically misdiagnosed [Figure 5]. Schuknecht  reported that the tumor enhancement is markedly strengthened, and the detected lesions are more valuable than myelography. Enhanced scans of the patients of this group reveal homogeneous and adjacent dural enhancements, as well as the corresponding level spinal cord compression and forward shift. The postoperative pathological diagnosis reports a small-cell malignant tumor, and is considered a metastatic small-cell carcinoma upon combination with the immune marker results.
|Figure 5: MRI showed intradural oval space-occupying lesion at L4 level. (a) Lesion presented with isointensity on T1WI, (b) lesion presented with hypointensity on T2WI, and (c) lesion showed marked enhancement on enhancement scanning|
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In summary, MRI has a high spinal soft tissue resolution that can avoid bone artefacts. This method can obtain a more accurate reliable localization and qualitative diagnosis based on the specific features of different tumors. Noninvasive MRI examination is the preferred method in the diagnosis of spinal IDEM tumor and can provide a reliable imaging basis for clinical treatment and prognosis judgment.
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