Intra-fourth Ventricular Schwannoma in Pediatric Age Group: Report of Second Case in the Western Literature with Review of Literature.

Schwannoma originates from the myelin sheath of peripheral nerves. It accounts for about 8% of all intracranial tumors. Commonly, schwannoma is located in the extra-axial locations; intra-axial schwannomas are extremely uncommon. The schwannoma arising from fourth ventricle is extremely uncommon and authors in a detailed PubMed and MEDLINE search could find only seven cases reported in the literature in the form of isolated cases report, who were managed surgically, with only one being a pediatric case. Authors report second case of intra-fourth ventricular schwannoma occurring in the pediatric age group. The hypothesis of intraventricular schwannoma is postulated to be aberrantly placed multipotent cell during embryogenesis and later transforming into Schwann cell and producing schwannoma. Pertinent literature is reviewed along with diagnosis, and management of such rare case is discussed briefly.

INTRODUCTION

Schwannoma originates from the myelin sheath. It is commonly located in the extradural compartment and peripheral nerves. It accounts for approximately 8% of all intracranial tumors.[123] The intraventricular schwannomas are extremely uncommon. They account for up to 8% of all primary brain tumors. The schwannomas in the fourth ventricle are extremely rare, but only one case of pediatric schwannoma occurring in a 7-year-old boy has been described[456789] previously and was reported by Redekop et al.[9] In this case, the boy was managed surgically with excellent neurological outcome. The authors report a pediatric case of intraventricular schwannoma in a 14-year-old boy, who was managed surgically successfully with total excision. To the best knowledge of the authors, the current case represents the second case in the Western literature, which originated and located in the fourth ventricle [Table 1].

Table 1

Review of previously published cases of fourth ventricular schwannoma managed surgically

CASE ILLUSTRATION

A 16-year-old schoolboy presented with progressive worsening headache and gait ataxia for 6 months. On admission, he was conscious and alert. The general physical examination showed stable vital. Visual acuity was normal; fundi revealed bilateral papilledema. With full extraocular movement with horizontal gaze nystagmus. Rest of the neurological examination was within normal limit.

Hematological and biochemical parameters were within normal limit. Cranial magnetic resonance imaging (MRI), T1-weighted, sagittal, shows the presence of a mass lesion confined within the fourth ventricle causing brainstem compression with obstructive hydrocephalus [Figure 1a]. The figure shows a hyperintensity on axial T1-weighted. Axial section MRI image shows the expansion of the fourth ventricle [Figure 1b] due to the lesion and hydrocephalus. The boy underwent surgery under general anesthesia in prone position. A suboccipital craniectomy was performed and lesion was soft, suckable, moderately vascular with well-defined plane of cleavage, total resection was obtained. Hemostasis was achieved. The histopathological report was suggestive of schwannomas.

Figure 1

(a) Magnetic resonance imaging of the brain of a 14-year-old boy; sagittal section, contrast-enhanced image shows the presence of mass in fourth ventricle, showing uniform enhancement and producing obstructive hydrocephalus. (b) Magnetic resonance imaging of the brain, axial section, contrast-enhanced image, showing the presence of uniformly enhancing mass lesion in the fourth ventricle

DISCUSSION

Schwannomas are benign tumors. They account for about 8% of brain tumors and 25% of spinal tumors. About 95% of schwannomas remain localized extra-axially, but they rarely can also occur within the brain and spinal cord parenchyma or ventricular system.[10] They originate from the myelin-forming Schwann cells of peripheral nerves or at the Obersteiner–Redlich zone of the vestibular division of the eighth cranial nerve.[311]

Intraventricular schwannomas are rare, particularly among children. The intracerebral schwannoma is a rare, benign neoplasm. It is usually located superficially or adjacent to a ventricle. As Schwann cells do not lie within the central nervous system, the exact mechanism of occurrence of intraventricular schwannomas still remains uncertain, and many hypotheses are postulated to explain the occurrence of intra-axial schwannomas as well. To our knowledge, there are no Schwann cells covering central nervous system fibers. Schwann cells are present in peripheral fibers and in autonomic tissue surrounding vessels. We hypothesized the origin of intraventricular schwannomas is related to aberrantly placed multipotent cell during embryogenesis, which acts as ectopic foci, and later on with the passage of time, it transforms into Schwann cell producing schwannoma.

In 1977, Russel and Rubinstein[11] proposed that proliferation of primary mesenchymal cells could form foci of differentiated Schwann cells and used the term schwannosis for these cells. Redekop et al.[9] reported the case of a 7-year-old boy with a fourth ventricle schwannoma and put hypothesis for occurrence as a result of a failed migration of neural crest cells during embryogenesis and consequent neoplastic proliferation of an ectopic population of cells similar to the theory provided by Ramamurthy et al.[712]

Characteristic imaging features may include calcification, cyst formation, and evidence of peritumoral edema or gliosis. Common differential, of intra-fourth ventricle schwannoma includes ependymoma, choroid plexus papilloma, and juvenile pilocytic astrocytoma is common-enhancing tumors of the fourth ventricle and may encompass the differential diagnosis.

The differential diagnosis of an intracerebral schwannoma includes several other neoplasms that may occur in children and young adults. These include pilocytic astrocytoma, pleomorphic xanthoastrocytoma, and ganglioglioma.[513] Other localization can be intraparenchymal schwannomas, which are rare and have been reported more frequently in the spinal cord than within the brain. Schwannomas exhibit a number of characteristics, albeit nondiagnostic, neuroradiological features.[14]

Surgery remains standard management. It can provide a good outcome. Santos et al.[4] reported the case of a 53-year-old man, who presented with complaints of gait unsteadiness for one and half years, followed by headache vomiting few weeks prior to current admission. The MRI revealed the presence of a large mass located within the fourth ventricle, showing heterogeneously contrast enhancement and causing brainstem compression and producing obstructive hydrocephalus. He underwent suboccipital craniotomy with telovelar approach for the tumor resection. He was doing well at 6 years of follow-up with no recurrence.

Authors noted fourth ventricle schwannomas are infrequent but should always be kept in the differential diagnosis of mass lesions in the intraventricular location as they are associated with good prognosis and are easily amenable for gross total resection with microneurosurgical technique.[4]

CONCLUSION

The intraventricular schwannomas are extremely uncommon. Further those located in the fourth ventricle in the pediatric age group are extremely rare, and our case represents the second case. Although the treating neurosurgeon, pediatrician should be aware of existence of such pathology as it carries good prognosis and amenable to microneurosurgery provide excellent outcome.

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Conflicts of interest

There are no conflicts of interest.