Differentiation of Spinal Schwannomas and Myxopapillary Ependymomas: MR Imaging and Pathologic Features

Development of a novel prediction model for differential diagnosis between spinal myxopapillary ependymoma and schwannoma

Spinal myxopapillary ependymoma (MPE) and schwannoma represent clinically distinct intradural extramedullary tumors, albeit with shared and overlapping magnetic resonance imaging (MRI) characteristics. We aimed to identify significant MRI features that can differentiate between MPE and schwannoma and develop a novel prediction model using these features. In this study, 77 patients with MPE (n = 24) or schwannoma (n = 53) who underwent preoperative MRI and surgical removal between January 2012 and December 2022 were included. MRI features, including intratumoral T2 dark signals, subarachnoid hemorrhage (SAH), leptomeningeal seeding, and enhancement patterns, were analyzed. Logistic regression analysis was conducted to distinguish between MPE and schwannomas based on MRI parameters, and a prediction model was developed using significant MRI parameters. The model was validated internally using a stratified tenfold cross-validation. The area under the curve (AUC) was calculated based on the receiver operating characteristic curve analysis. MPEs had a significantly larger mean size (p = 0.0035), higher frequency of intratumoral T2 dark signals (p = 0.0021), associated SAH (p = 0.0377), and leptomeningeal seeding (p = 0.0377). Focal and diffuse heterogeneous enhancement patterns were significantly more common in MPEs (p = 0.0049 and 0.0038, respectively). Multivariable analyses showed that intratumoral T2 dark signal (p = 0.0439) and focal (p = 0.0029) and diffuse enhancement patterns (p = 0.0398) were independent factors. The prediction model showed an AUC of 0.9204 (95% CI 0.8532-0.9876) and the average AUC for internal validation was 0.9210 (95% CI 0.9160-0.9270). MRI provides useful data for differentiating spinal MPEs from schwannomas. The prediction model developed based on the MRI features demonstrated excellent discriminatory performance.

Clinicoradiologic Characteristics of Intradural Extramedullary Conventional Spinal Ependymoma

Purpose

Distinguishing intradural extramedullary (IDEM) spinal ependymoma from myxopapillary ependymoma is challenging due to the location of IDEM spinal ependymoma. This study aimed to investigate the utility of clinical and MR imaging features for differentiating between IDEM spinal and myxopapillary ependymomas.

Materials and Methods

We compared tumor size, longitudinal/axial location, enhancement degree/pattern, tumor margin, signal intensity (SI) of the tumor on T2-weighted images and T1-weighted image (T1WI), increased cerebrospinal fluid (CSF) SI caudal to the tumor on T1WI, and CSF dissemination of pathologically confirmed 12 IDEM spinal and 10 myxopapillary ependymomas. Furthermore, classification and regression tree (CART) was performed to identify the clinical and MR features for differentiating between IDEM spinal and myxopapillary ependymomas.

Results

Patients with IDEM spinal ependymomas were older than those with myxopapillary ependymomas (48 years vs. 29.5 years, p < 0.05). A high SI of the tumor on T1W1 was more frequently observed in IDEM spinal ependymomas than in myxopapillary ependymomas (p = 0.02). Conversely, myxopapillary ependymomas show CSF dissemination. Increased CSF SI caudal to the tumor on T1WI was observed more frequently in myxopapillary ependymomas than in IDEM spinal ependymomas (p < 0.05). Dissemination to the CSF space and increased CSF SI caudal to the tumor on T1WI were the most important variables in CART analysis.

Conclusion

Clinical and radiological variables may help differentiate between IDEM spinal and myxopapillary ependymomas.

Differentiation of spinal myxopapillary ependymomas from schwannomas by contrast-enhanced MRI

BACKGROUND

Spinal myxopapillary ependymomas (MPEs) and schwannomas (SCHs) are both frequently located at the conus and caudal regions. The differentiation between MPEs and SCHs before surgery is crucial. Signal patterns of MPEs and SCHs on T2-weighted (T2W) magnetic resonance imaging (MRI) are diverse. Gadolinium (Gd+)-enhanced areas in MRI scans areas are areas where tumor cells are abundant. Therefore, investigating these enhanced areas should facilitate the differentiation. This study aimed to evaluate Gd+ areas in MRI scans in spinal MPEs and SCHs. Furthermore, the relation between MRI pattern and pathological features was investigated.

METHODS

In total, 41 patients with spinal MPEs (n = 7) or SCHs (n = 34) around the conus medullaris were included. SCHs were classified per the Gd+ area of the tumor on T1-weighted (T1W) contrast images, into Gd+ areas with T2W hyperintensity (Gd+/T2high) (n = 4, 11.8%) or Gd+ areas with T2W isointensity (Gd+/T2iso) (n = 30, 88.2%). Four patients with Gd+/T2iso were selected randomly for comparison. In three patient groups, T2 values at the Gd+ area and tumor cell density as measured by HE stains (cell density) were compared.

RESULTS

T2 values at the Gd+ area was higher in patients with MPE than in those with SCH with Gd+/T2high, and significantly higher than that in patients with SCH with Gd+/T2iso. Cell density was significantly lower in patients with MPEs than for those with SCHs with Gd+/T2high, and those with SCHs with Gd+/T2iso.

CONCLUSION

The evaluation of the Gd+ area proved useful because it excludes cysts or necrotic portions. If the Gd+ area is hyperintense on T2WI, MPEs can be suspected. If the Gd+ area is isointense on T2WI, SCHs can be suspected. There were several exceptional cases of SCH with a Gd+ area that was hyperintense on T2WI. This could be explained by pathological findings showing low cell density, as is typical for MPEs.

Surgical outcomes of spinal cord and cauda equina ependymoma: Postoperative motor status and recurrence for each WHO grade in a multicenter study

BACKGROUND

The goals of the study are to analyze postoperative outcomes and recurrence in cases of spinal cord and cauda equina ependymoma in each World Health Organization (WHO) Grade, and to examine the influence of extent of surgical removal on prognosis. Spinal ependymoma has a relatively high frequency among intramedullary spinal cord tumors. The tumor is classified in WHO guidelines as grades I, II, and III, but few studies have examined postoperative prognosis based on these grades.

METHODS

The records of 80 patients undergoing surgery for spinal cord and cauda equina ependymoma were examined in a multicenter study using a retrospective database. Neurological motor status, pathological type, extent of resection, and tumor recurrence were evaluated.

RESULTS

The histopathological types were grade I in 23 cases (myxopapillary: 21, subependymoma: 2), grade II in 52 cases, and grade III in 5 cases (including all anaplastic cases). Total resection was performed in 60 cases (83%), and eight cases had recurrence, including 2 in WHO grade I, 2 in grade II, and 4 in grade III. The 5-year recurrence-free survival rates were 90%, 91%, and 20% in grades I, II and III, respectively. Adjuvant radiotherapy for the local site was performed in 8 cases, including 3 in grade I and 5 in grade III; however, 4 of the 5 grade III cases (80%) had recurrence after radiotherapy. Among 59 patients with normal ambulation or independence without external assistance (McCormick Grade I or II), 53 (90%) maintained the same mobility after surgery. In cases that underwent total resection, the recurrence rate was significantly lower (p < 0.01). A good preoperative motor status also resulted in significantly better postoperative recovery of motor status (p < 0.05).

CONCLUSIONS

Total resection of spinal cord and cauda equina ependymoma leads to postoperative motor recovery and may reduce tumor recurrence. Therefore, early surgery for this tumor is recommended before aggravation of paralysis.

Surgical management of solitary nerve sheath tumors originating around the epiconus or conus medullaris: a retrospective case analysis based on neurological function

The objective of this retrospective case analysis was to evaluate the surgical impact on neurological functional recovery in cases of solitary spinal nerve sheath tumors (NSTs) originating around the epiconus, conus medullaris, or cauda equina and not associated with neurofibromatosis. This 10-year surgical study included 30 cases of spinal NSTs originating around the spine level of T12-L1 (epiconus-to-conus medullaris: Epi-CM group), and 15 cases of spinal NSTs originating below the spine level of L2 (cauda equina: CE group). A minimally invasive posterior unilateral approach was applied in 22 of 30 subjects in the Epi-CM group and in 14 of 15 subjects in the CE group. Total removal of the tumor was achieved in all cases except in two cases of subpial growth and foraminal extension in the Epi-CM group at the initial surgery. Functional assessment revealed satisfactory or acceptable neurological recovery in both groups. Twelve of 30 patients (40%) in the Epi-CM group demonstrated significant motor weakness of the ipsilateral leg, predominantly manifested as drop foot before surgery, and only 4 of 12 patients demonstrated complete recovery. Ten of 30 patients (33%) in the Epi-CM group demonstrated a significant disturbance of urination before surgery, and only 6 of 10 demonstrated complete recovery. No patients in the CE group demonstrated unsatisfactory recovery of leg motor weakness or urinary disturbance. The present study suggests that surgeons should be aware that spinal NSTs originating around the epiconus or conus medullaris may result in delayed or inadequate functional recovery, even after successful surgical resection of tumors.

Contrast MRI Findings for Spinal Schwannoma as Predictors of Tumor Proliferation and Motor Status

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

The goal of this study was to examine the relationship of the proliferation potency based on the MIB-1 index and motor status with features of T2-weighted images (T2WI) and contrast T1-weighted images (T1WI) of spinal schwannoma.

SUMMARY OF BACKGROUND DATA

Spinal schwannomas account for 55% of spinal tumors, but the relationship of cellular proliferation with MRI findings for spinal schwannoma is unknown.

METHODS

The subjects were 48 patients (22 males and 26 females) with spinal schwannoma who were classified into three subgroups: iso/homo, high/rim, and hetero/hetero, based on T2WI/contrast T1WI. A retrospective analysis of tumor size and MIB-1 index was performed in the context of these MRI findings. Intraoperative findings and pre- and postoperative motor performance were also examined.

RESULTS

The average tumor size was 32.4 mm (range 10-130 mm) and the average MIB-1 index was 3.8% (range 1-12). In the three subgroups, there were no significant differences in sex, age, duration of disease, tumor lesion, and dumbbell type. In the hetero/hetero group, the tumor size was significantly greater and the MIB-1 index was significantly higher (both P < 0.05), than the other two groups. The tumor adherence rate was significantly higher for hetero tumors (P < 0.05) and preoperative paralysis was more common in cases with tumor adhesion. The rate of paralysis improvement at 1 month was significantly lower for hetero tumors, but all cases had improved at 6 months.

CONCLUSION

Contrast T1WI MRI was useful for prediction of the proliferative activity and growth of spinal schwannomas, which are associated with increased tumor size and adhesion. A heterogeneous pattern on contrast T1WI indicated an increase in size and adhesion of the tumor. This pattern reflected the preoperative motor status and postoperative motor recovery.

LEVEL OF EVIDENCE

4.

Clinical Features and Prognostic Factors of Patients With Nerve Sheath Tumors in the Cervical Spine

STUDY DESIGN

A retrospective study was performed.

OBJECTIVE

The aim of the study was to illustrate the long-term follow-up results and discuss the possible factors that may affect outcomes of patients with cervical spinal nerve sheath tumors (CSNSTs).

SUMMARY OF BACKGROUND DATA

Nerve sheath tumors are the most common neoplasms in the spine, but minimal information was published in the literature, especially when regarding to prognostic factors due to the benign nature. The objective of our study was to present long-term follow-up results and discuss the possible factors that may affect outcomes of patients with CSNSTs.

METHODS

A retrospective analysis of patients with CSNSTs was performed by survival analysis. The local relapse-free survival (LRFS) and overall survival (OS) rates were estimated using the Kaplan-Meier method to identify potential prognostic factors. Factors with P values ≤0.1 were subjected to multivariate analysis by Cox regression analysis. P values ≤0.05 were considered statistically significant.

RESULTS

A total of 169 patients with CSNSTs were included in the study. All patients received surgical treatment. The mean follow-up period was 72.1 months (median 62.0, range 1-158). Local recurrence was detected in 14 patients after surgery in our center, whereas death occurred in 9 patients with a mean follow-up of 27.2 months (median 24, range 1-84). The statistical analyses suggested that resection mode and pathology type were independent prognostic factors for LRFS and OS. In addition, postoperative recurrence was an adverse independent factor to OS.

CONCLUSION

Total resection could significantly improve the LRFS and OS for patients with CSNSTs, whereas malignant CSNST was associated with worse prognosis. Moreover, postoperative recurrence was an adverse independent factor to OS.

LEVEL OF EVIDENCE

4.

Spinal perimedullary vein enlargement sign: an added value for the differentiation between intradural-extramedullary and intramedullary tumors on magnetic resonance imaging

INTRODUCTION

The purpose of this study was to determine the added value of the perimedullary spinal vein enlargement sign on magnetic resonance imaging (MRI) in distinguishing intradural-extramedullary tumors (IDEMTs) from intramedullary spinal tumors (IMTs).

METHODS

Two hundred and eight consecutive spinal intradural tumors with histopathologic confirmation (21 IMTs, 187 IDEMTs) were enrolled. Two readers blinded to the final pathological diagnosis and clinical data independently assessed the venous enlargement sign to determine the 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 for the common MRI findings, vein enlargement sign, and a combination of both.

RESULTS

Intraobserver agreement and interobserver agreement for both readers was excellent. The sensitivity, specificity, and accuracy of common MRI findings for differentiating IDEMTs from IMTs were 83.4, 95.2, and 89.3 %, respectively. Thirty-one IDEMTs were mistakenly diagnosed as IMTs, in which seven were cases with vein enlargement signs. By applying the vein enlargement sign to the common MRI findings, the specificity remained at 95.2 %, while the sensitivity improved to 89.3 % and the accuracy increased to 92.3 %.

CONCLUSION

The spinal perimedullary vein enlargement sign is useful in assessing intradural tumors and to differentiate IDEMTs from IMTs.

Minimally invasive removal of lumbar intradural extramedullary lesions using the interlaminar approach

OBJECT Posterior midline laminectomy or hemilaminectomy has been successfully applied as the standard microsurgical technique for the treatment of spinal intradural pathologies. However, the associated risks of postoperative spinal instability increase the need for subsequent fusion surgery to prevent potential long-term spinal deformity. Continuous efforts have been made to minimize injuries to the surrounding tissue resulting from surgical manipulations. The authors report here their experiences with a novel minimally invasive surgical approach, namely the interlaminar approach, for the treatment of lumbar intraspinal tumors. METHODS A retrospective review was conducted of patients at the Second Affiliated Hospital of Zhejiang University School of Medicine who underwent minimally invasive resection of lumbar intradural-extramedullary tumors. By using an operative microscope, in addition to an endoscope when necessary, the authors were able to treat all patients with a unilateral, paramedian, bone-sparing interlaminar technique. Data including preoperative neurological status, tumor location, size, pathological diagnosis, extension of resections, intraoperative blood loss, length of hospital stay, and clinical outcomes were obtained through clinical and radiological examinations. RESULTS Eighteen patients diagnosed with lumbar intradural-extramedullary tumors were treated from October 2013 to March 2015 by this interlaminar technique. A microscope was used in 15 cases, and the remaining 3 cases were treated using a microscope as well as an endoscope. There were 14 schwannomas, 2 ependymomas, 1 epidermoid cyst, and 1 enterogenous cyst. Postoperative radiological follow-up revealed complete removal of all the lesions and no signs of bone defects in the lamina. At clinical follow-up, 14 of the 18 patients had less pain, and patients' motor/sensory functions improved or remained normal in all cases except 1. CONClUSIONS When meeting certain selection criteria, intradural-extramedullary lumbar tumors, especially schwannomas, can be completely and safely resected through a less-invasive interlaminar approach using a microscope, or a microscope in addition to an endoscope when necessary. This approach was advantageous because it caused even less bone destruction, resulting in better postoperative spinal stability, no need for facetectomy and fusion, and quicker functional recovery for the patients. Individualized surgical planning according to preoperative radiological findings is key to a successful microsurgical resection of these lesions through the interlaminar space.

How do spinal schwannomas progress? The natural progression of spinal schwannomas on MRI

OBJECT

Little is known about the progression of spinal schwannomas. The aim of this study was to determine the natural progression of spinal schwannomas and establish the risk of tumor growth.

METHODS

This study retrospectively analyzed data from 23 patients (12 men and 11 women, 40–89 years old) with schwannomas detected by MRI. The mean follow-up period was 5 years (range 2–10 years). The absolute and relative growth rates of the tumors were calculated.

RESULTS

The average tumor size was 1495 mm3 at the initial visit and 2224 mm3 at the final follow-up. The average absolute growth rate was 139 mm3 per year, and the average relative growth rate was 5.3% per year. Tumors were classified into 3 groups based on enhancement patterns: isointense/hyperintense (iso/high; 11 cases), rim enhancement when enhancement was peripheral (high/rim; 5 cases), and heterogeneous/heterogeneous (hetero/hetero; 7 cases) based on Gd-enhanced T2-weighted MRI. The average absolute growth rates of the 3 lesion groups were 588 mm3, 957 mm3, and 3379 mm3, respectively (p < 0.01).

CONCLUSIONS

Although the tumors classified as iso/high and high/rim on T2-weighted Gd-enhanced MR images were small and grew very little, most tumors with hetero/hetero classification increased in size. Hetero/hetero-type tumors should be followed closely and may require surgery.

Extramedullary Conus Ependymoma Involving a Lumbar Nerve Root with Filum Terminale Attachment

PURPOSE

In the current report, we describe a case of an extramedullary ependymoma involving a lumbar nerve root near conus medullaris. Spinal ependymomas commonly present as intramedullary tumors in the cervical or thoracic cord or as tumors arising from the conus medullaris or the filum terminale. In this case, we showed an extramedullary conus ependymoma involving a lumbar nerve root with filum terminale attachment.

CASE PRESENTATION

A 69-year-old woman presented with lower back pain, but without sensory disturbance or motor weakness in her lower extremities.

CLINICAL ASSESSMENT

Magnetic resonance imaging revealed an intradural mass at T12-L1 at the conus medullaris, which was totally resected. Histopathology revealed a non-myxopapillary ependymoma (WHO grade 2). Postoperatively, the patient did well and displayed no neurological deficits. Moreover, no radiotherapy was required.

CONCLUSIONS

This report documented a rare case of intradural extramedullary ependymoma located at the conus medullaris, involving the lumbar nerve root, and attached to the filum terminale. Although extramedullary ependymomas at this region are more frequently classified as myxopapillary, histopathological examination revealed this tumor as a non-myxopapillary ependymoma.