Published online Oct 25, 2018.
https://doi.org/10.3348/jksr.2018.79.5.294
Atypical Appearance and Location of Subependymomas: A Report of Two Cases
Abstract
Subependymomas are rare benign central nervous system tumor which account of 0.7% of all intracranial tumors. Subependymomas show characteristic MR findings according to their location. However, sometimes atypical findings could be found. In addition, subependymomas can occur very rarely in the spinal cord. We report two cases of pathologically confirmed subependymoma, one of which shows atypical appearances in spite of their intraventicular location and the other of which shows rare case of spinal intramedullary subependymoma. We review the clinical symptoms and radiologic findings of two cases
INTRODUCTION
Subependymomas are rare benign central nervous system tumor corresponding histologically to WHO grade I (1). They account for 0.7% of all intracranial tumors (1). They commonly arise in the fourth (50–60%) and lateral ventricles (30–40%) (1). There are very few cases in which the subependymoma is so large that causes symptoms. Furthermore, they occur very rarely in the spinal cord and only 54 cases have been reported in the literature (1, 2) since the first case was reported by Boykin et al. (3). To the best of our knowledge, spinal intramedullary subependymoma has not been described in the Korean literature. We report two cases of subependymomas, one of which shows atypical appearances at lateral ventricle and the other of which shows rare case of intramedullary subependymoma of the spinal cord.
CASE REPORTS
Case 1
A 54-year-old man presented with dizziness for 3 weeks. Dizziness was provoked when suddenly standing up. He had no co-morbidities other than dyslipidemia. CT showed a low density tumor at right lateral ventricle with a high density foci (arrow) on non enhanced CT with minimal enhancement (arrow) on contrast enhanced CT (Fig. 1A, B). MRI revealed large intraventricular mass with internal cystic component in right lateral ventricle, abutting to septum pellucidum. The size of the mass was measured to approximately 3.5 × 2.8 × 3.2 cm. The mass had iso-intensity signal on T1-weighted image (T1WI) and hyper intensity signal on Fluid-attenuated inversion recovery (Fig. 1C, D). There was no lesion indicating extra ventricular infiltration. There were also scattered foci of hypo intensity on susceptibility weighted image (SWI) (Fig. 1E), indicating presence of calcify deposits and/or blood. The mass showed mild heterogeneous enhancement on contrast-enhanced T1WI (Fig. 1F). The patient underwent a craniotomy with resection of intraventricular mass. The pathology result was confirmed to the diagnosis of subependymoma. The patient was discharged without any post operative event.
Fig. 1
B. Contrast enhanced CT shows minimal enhancement in the mass (arrow). C. T1-weighted image reveals a large intraventricular iso-signal intensity mass (arrow) with internal cystic component in right lateral ventricle, abutting to septum pellucidum. The size of the mass is measured to approximately 3.5 × 2.8 × 3.2 cm. D. Fluid-attenuated inversion recovery shows the intraventricular mass showed high signal intensity (arrow) without evidence of extraventricular infiltration. E. There is also scatted foci of hypo-intensity (arrows) on susceptibility weighted image indicating presence of calcific deposits and/or blood. F. The axial contrast enhanced T1-weighted image shows heterogeneous enhancement (arrow).
Brain CT and MR images of intraventricular subependymoma in a 54-year-old man with dizziness for 3 weeks.
A. Non enhanced CT shows a low density tumor at right lateral ventricle with a high density foci (arrow).
Case 2
A 50-year-old man presented with a 14 months history of back pain. He also complained of pain at left thigh for 1 years. The pain did not relieved with non-steroidal anti-inflammatory drugs. There was no abnormal finding at neurological examination. Sagittal T2-weighted image (T2WI) showed a high signal intensity mass with intramedullary location at the thoracic 6 level of spinal cord (Fig. 2A). Axial T2-weighted axial image revealed a high signal intensity mass with clear cut demarcation of the interface between the spinal cord and the tumor (Fig. 2B). It was located at right side of the spinal cord with eccentric location. The mass showed subtle hypointensity on T1WI (Fig. 2C) and no demonstrable enhancement was noted at the mass on contrast-enhanced T1WI (Fig. 2D, E). There was no evidence of peritumoral edema. Imaging findings suggested the diagnosis of intramedullary tumor, and the differential diagnosis was considered as astrocytoma. T5–T6 total laminectomy was performed and a histological diagnosis was confirmed to subependymoma. Postoperatively, the patient developed paraplegia and bladder, rectal disturbance. Muscle power assessment of the lower limbs showed Grade 0 immediately after operation. However, at the time of discharge he showed slight improvement in motor examination but couldn't stand up yet. Post operative MRI revealed no tumor recurrence after 18 months.
Fig. 2
B. The axial T2WI reveals the high signal intensity mass (arrow) with clear cut demarcated interface between the spinal cord and the tumor and no definite peritumoral edema or infiltration. C. The mass shows hypo-intensity (arrow) on sagittal T1WIs. D, E. The sagittal and axial contrast enhanced T1WIs show no demonstrable enhancement (arrow). T1WI = T1-weighted images, T2WI = T2-weighted image
Spine MR images of eccentric intramedullary subependymoma in a 50-year-old man with back pain and radiating left thigh pain.
A. The sagittal T2WI shows the intramedullary high signal intensity mass (arrow) at the thoracic 6 level of spinal cord.
DISCUSSION
Subependymomas are rare benign gliomas with a prevalence of 0.4–0.7% and have been more commonly reported in elderly males with a mean age of 39–59 years (4).
Most subependymomas appear as a lobular, well-defined intraventricular mass that is hypodense to isodense to brain parenchyma with no periventricular extension on CT (4, 5). The majority of subependymomas are solid or solid with cystic components and contrast enhanced CT usually shows little or no enhancement (4, 5). Subependymomas are generally presented as a large intraventricular lesion located in the frontal horn and body of the left lateral ventricle which had iso- to hypointensity on T1WI and hyperintensity on T2WI with no enhancement or mild enhancement (4, 5).
Intracranial subependymoma can be divided into supratentorial and infratentorial according to their location. The typical MR features of supratentorial subependymoma are different compared to that of infratentorial subependymoma. First of all, calcification is rare feature of supratentorial subependymoma. Second, the enhancement pattern is also different depending on its anatomical location in most cases. As we listed in Table 1, Nishio et al. (5) reported 4 lateral ventricle subenpendymoma and none of 4 them had calcification. And only one of them showed heterogeneous enhancement , while all the other showed scarce or no enhancement. In addition to this report, according to recent study by Abdel-Aal et al. (4), combined reports of 22 lateral ventricular subependymomas show 16 (73%) cases presenting minimal or no enhancement, and 6 (27%) cases presenting heterogeneous enhancement. On the other hand, 29 (85%) cases showed heterogeneous enhancement among 34 fourth ventricular subependymomas. Our first case appeared as an atypical appearance of lateral ventricular subependymoma showing evidence of calcifications on CT and SWI, which was one of the differentiating features and exceptional heterogeneous contrast enhancement in spite of its supratentorial location. In addition to this, most of subependymomas are incidentally found and only few of them become symptomatic. The most important factors whether a subependymoma becomes symptomatic or not are location and size (9). Especially, tumors located near the septum pellucidum are more likely to cause symptoms causing obstruction of cerebrospinal fluid pathway and therefore they tends to detect at smaller size (9). However, in spite of its location abutting the septum pellucidum, our case showed relatively large size (largest diameter: 3.5 cm) when it became symptomatic.
Table 1
Review of the Previously Reported Cases of Subependymoma at Lateral Ventricle
Most supratentorial subependymomas have characteristic appearance on MR imaging such as intraventricular mass with lack of calcification and no or minimal contrast enhancement, which differentiates them from other supratentorial intraventricular tumors and also from infratentorial subependymomas. However, the large size, calcifications, high vascularity, heterogeneous enhancement and presence of symptoms, should not persuade the radiologist to exclude it from his differential diagnosis.
Spinal subependymomas are much less frequent than intracranial subepedymomas. Majority of them were intramedullary and located in the cervical (48%), thoracic (40%), or lumbar region (7%), among 54 cases which have been reported (2). One patient had holo cord subependymoma and location of rest of the 3 cases was not described (2).
Spinal intramedullary subepedymomas on MRI typically show segmental fusiform dilatation of spinal cord, which are hypointense to isointense on T1WI, hyperintense on T2WI, and occasionally display faint enhancement after contrast injection (10). The MRI findings of all reported intramedullary cervicothoracic subependymomas are shown in Table 2. Our results are consistent with those described in the literature. The intramedullary ependymoma is believed to originate in the wall of the central canal, and is classified as WHO grade II. In contrast, subependymomas may develop into huge masses and compress the cord severely, causing their characteristic eccentric localization (10). The majority of spinal subependymoma show eccentric location, in contrast to other intramedullary tumor such as ependymoma and astrocytoma showing intramedullary central location. Wu et al. (10) reported 3 cases of spinal subependymoma and all of them showed eccentric location. Due to its eccentric location, in 2016 for the first time, Toi et al. (2) reported "bamboo leaf sign" which may help distinguish this tumor from other intramedullary tumors. For example, Kremer et al. (6) reported the case of intramedullary subependymoma at T-spine, which showed steep swelling of the spinal cord displaying "bamboo leaf sign." However, in our case there was no steep swelling of the spinal cord (bamboo leaf sign) in spite of its typical eccentric location, unlike most cases reviewed at report of Toi et al. (2). Also, intraspinal subependymomas not always show bamboo leaf sign even if their eccentric location in the spinal cord. Therefore, we should not rule out a subependymoma as a differential diagnosis when there is an intramedullary mass in the spine with eccentric location.
Table 2
Review of the Previously Reported Cases of Spinal Intramedullary Subependymoma
Surgical excision is the treatment of choice for both intracranial and spinal subependymoma and post-operative radiotherapy is not recommended (1, 8).
In conclusion, we describe here two cases with atypical appearance or rare location. Therefore, we should not exclude subependymoma as a differential diagnosis though its radiologic findings are unusual.
References
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Toi H, Ogawa Y, Kinoshita K, Hirai S, Takai H, Hara K, et al. Bamboo leaf sign as a sensitive magnetic resonance imaging finding in spinal subependymoma: case report and literature review. Case Rep Neurol Med 2016;2016:9108641
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Abdel-Aal AK, Hamed MF, Al Naief NS, Vattoth S, Bag A. Unusual appearance and presentation of supratentorial subependymoma in an adult patient. J Radiol Case Rep 2012;6:8–16.
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Nishio S, Morioka T, Mihara F, Fukui M. Subependymoma of the lateral ventricles. Neurosurg Rev 2000;23:98–103.
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