Multi-functional Magnetic Resonance Imaging and Clinicopathological Characteristics of Ventricular Schwannoma: A Case Report and Review of the Literature
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.266295
Source of Support: None, Conflict of Interest: None
Schwannomas are generally benign tumors that emerge from the Schwann cells of the peripheral nervous system or the central nervous system. Intraventricular schwannomas are rare tumors with only 29 cases, of which 8 cases in fourth ventricle reported in the literature.,,,,,,,,,,,,,,,,,,,,,,,,,,, We report a case of fourth ventricular schwannoma with advanced magnetic resonance imaging (MRI) technology examination, and review the current literature. To our knowledge, this is the first case of intraventricular schwannoma with advanced MRI technology examination, and we focused on the imaging and clinicopathological characteristics of the ventricular schwannoma.
The institutional review board of our hospital approved this report. Written informed consent was obtained from the patient. A 25-year-old man presented a bilateral frontal headache for 1 month that was associated with vomiting and blurred vision episodes for two weeks prior to his presentation.. The neurological exam revealed bilateral papilledema. His laboratory examination was unremarkable.
The patient underwent computed tomography (CT), MRI examination (including precontrast MRI, contrast MRI, susceptibility weighted imaging [SWI], perfusion-weighted imaging [PWI], multi-b value diffusion weighted images [DWI], and diffusion kurtosis imaging [DKI]) before operation. CT images showed a heterogenous mass in fourth ventricle; the solid component was an isodensity [Figure 1]a. The MRI images [Figure 1]b, [Figure 1]c, [Figure 1]d, [Figure 1]e, [Figure 1]f, [Figure 1]g revealed a 2.9 cm × 3.0 cm × 1.8 cm heterogenous mass in fourth ventricle. The solid component presented hypointense on T1-weighted imaging, hyperintense on T2-weighted imaging and T2-fluid attenuated inversion recovery image, and with an obvious ring contrast enhancement. SWI showed hypointense in the solid component which represented micro-hemorrhage. PWI [Figure 1]h, [Figure 1]i, [Figure 1]j showed the mass was low perfusion. Multi-b value DWI [Figure 2] showed that the solid component presented hyperintense on a low b value DWI (b ≤1200), and hypointense on a high b value DWI (b: 1200–4000), and a bi-exponential model showed that the standard apparent diffusion coefficient value, D value, D* value and f value were 0.537, 0.625, 2.58, and 0.387 respectively. DKI [Figure 3] showed that the mean diffusivity was 1.40 which was lower than the value of normal tissue; the fractional anisotropy, mean kurtosis, radial kurtosis, and axial kurtosis were 0.236, 0.674, 0.720, and 0.596, respectively, which were lower than the values of normal tissue.
A suboccipital craniotomy with telovelar approach was used to access the tumor. There was a firm, gray-red appearing and rich-blood-supply tumor originating from the floor of fourth ventricle, and it was measured as 3 cm × 3 cm × 2 cm. A complete resection was performed. He recovered from his neurological deficit and was discharged on day 7 post-operatively. He was free of recurrence per MRI examination at the ten month follow-up visit.
Microscopic examination showed a spindle cell neoplasm characterized by Antoni A and Antoni B areas with verocay bodies characteristic of schwannomas. The tumor cells are immunopositive for S-100 protein, factor VIII, and vimentin. Type 4 collagen and glial fibrillary acidic protein (GFAP) stains were negative [Figure 4]. The histopathological diagnostic conclusion was intraventricular schwannoma (WHO grade I).
Intraventricular schwannomas are very rare tumors with only 29 previously reported cases in the literature. Given the rarity of its occurrence, the imaging and clinicopathological characteristics of intraventricular schwannoma are not completely understood. We report a case of fourth ventricular schwannoma with advanced MRI technology examination and review the current literature; all cases are summarized in [Table 1] and [Table 2].
The age distribution of patients with intraventricular schwannoma ranged from 7 to 78 years  (average age 34.3 years), predominate in children and young adults (≤40 years, 63.3%) and in the male gender (66.7%). The patients' age of third (38.0 years) and fourth (50.4 years) ventricle schwannoma were much older than that of lateral ventricle schwannoma (25.6 years).
There are no specific clinical presentations of intraventricular schwannomas. Their clinical presentation varies from incidental findings to symptoms of intracranial hypertension which included headache, vomiting, papilledema, and focal neurological deficits resulting from mass effect or obstructive hydrocephalus. Our patient presented with a bilateral frontal headache for 1 month that was associated with vomiting and blurred vision episodes for a two week duration.
Intraventricular schwannomas appear more frequently in the lateral ventricles (60.0%), especiallly in the right lateral ventricle (12/18), with only 9 cases (30.0%) in fourth ventricle and 3 cases (10.0%) in third ventricle [Table 2]. We have found that a schwannoma in the lateral ventricle has a feature was that the tumor was in or near the trigone area of lateral ventricles, and intimately related to the choroid plexus. Most of fourth ventricle schwannomas arise from the ventricle floor, but in one reported case, the tumor originated from the lateral recess of fourth ventricle.
The size of intraventricular schwannomas are not very large (from 1.1 cm  to 6.0 cm, mean: 3.1 cm). The tumors located in fourth ventricles (from 1.3 cm  to 5.3 cm, mean: 2.9 cm) and third ventricles (from 1.1 cm  to 1.5 cm, mean: 1.3 cm) were much smaller than those located in lateral ventricle (from 1.6 cm  to 6.0 cm, mean: 3.7 cm). On the contrary, the tumors located in fourth (44.4%) or third ventricle (50.0%) were much more likely to have hydrocephalus than the ones located in lateral ventricle (0%).
CT showed that the mass was isodense or hyperdense. MRI showed that most intraventricular schwannomas were well-defined masses (96.0%). Most had a heterogeneous signal, and 84.0% tumors showed cystic formations; the solid part of the tumor was hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging. Most (92.0%) had heterogeneous contrast enhancement. The tumors located in lateral ventricle (66.7%) were much more likely to have parenchymal edema than the ones located in fourth (33.3%) and third ventricles (0%).
The histological appearance of intraventricular schwannomas is similar to the extra-axial schwannomas, characteristically demonstrating spindle cell architecture with Antoni A and B areas. The proliferation marker MIB-1 is typically low., Immunohistochemical analysis is positive for S-100 and GFAP and negative epithelial membrane antigen and neurofilament protein., Our case showed that the tumor cells were immunopositive for S-100 protein, factor VIII and vimentin. GFAP and Type 4 collagen stains were negative.
Treatment and prognosis
Most reported cases (95.5%) appear to assume a benign course with no recurrence, and surgical resection without adjuvant therapy is considered curative except in two cases, one which was identified incidentally during autopsy  while Jung et al. published the case of a malignant intraventricular schwannoma developed cerebellar metastases at 7 months postoperative. Since these tumors are located in fourth or third ventricle, hydrocephalus as possible with subsequent need for a ventricular shunt, or endoscopic fenestration. However, this is rare and was not encountered in our patient.
Despite this similar histological appearance, intraventricular schwannomas and extra-axial schwannomas may differ in their source of origin. The etiopathologic origin of the intraventricular schwannoma is unclear until now though, there are several hypotheses.
The first hypothesis is that the neoplastic transformation of neural crest cells is displaced during embryogenesis.,,,,,, The second hypothesis is transformation of autonomic nervous tissue accompanying intrinsic arteries and choroid plexus.,,,,,,, The third hypothesis is that schwannomas arise from aberrant peripheral nerve fibers. This proliferation may arise from localized traumatic injury. The fourth hypothesis has proposed that the transformation of multipotent cells into Schwann cells and proliferation of foci of Schwann cells (“schwannosis”) as potential etiologies.,, Finally, the last hypothesis the neural stem cells may play an important role in schwannoma tumorigenesis. We have found that schwannomas in the lateral ventricles had specific feature that the tumor was in or near the trigone area of lateral ventricles, and intimately related to the choroid plexus. So we thought that the second hypothesis may potentially explain the etiopathologic origin of the intraventricular schwannoma, but this need further studying.
Intraventricular schwannomas predominate in male children and young adults, more frequently in the lateral ventricles. Most had a signal, with heterogeneous contrast enhancement; a tumor in a different ventricle may have its own imaging and clinicopathological characteristic.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
The authors thank Dandan Zheng, PhD at GE Healthcare, Beijing, China, for technical support.
Financial support and sponsorship
This study was supported by grants from the National Natural Science Foundation of China to Hui Zhang (81471652, 81771824) and Yan Tan (81701681); the Precision Medicine Key Innovation Team Project to Hui Zhang (YT1601).
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]