Subependymoma of Lateral Ventricle

Case History: A 75-year-old male with complaints of occasional headache for last two years. Laboratory examination, ophthalmic examination and family history were unremarkable. Neurophysician sent patient for routine brain MRI.

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Figure 1. T2WI axial and sagittal images show a small 12x8 mm well-defined, well-circumscribed heterogenous signal intensity lesion to adjacent grey matter with tiny focal area of CSF intensity in left lateral ventricle along inter ventricular septum in the region of foramen of monro (arrow).

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Figure 2. FLAIR axial and coronal images show a small well-defined, well-circumscribed hyperintense signal intensity lesion to adjacent grey matter in left lateral ventricle along inter ventricular septum in the region of foramen of monro (arrow).

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Figure 3. T1W axial image shows isointense signal intensity lesion to adjacent grey matter with focal cystic area in left lateral ventricle along inter ventricular septum in the region of foramen of monro.

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Figure 4. Diffusion weighted axial image shows no restricted diffusion within the lesion (arrow).

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Figure 5. T1 weighted FAT SAT axial imges show minimal to mild enhancement on post contrst study within lesion.

On MRI, a small 12x8 mm well-defined, well-circumscribed lesion was noted in the left lateral ventricle along inter ventricular septum in the region of foramen of monro. It showed heterogenous signal with adjacent grey matter on T2WI (Figure 1) with a tiny focal cystic area, which followed CSF signal, hyperintense signal on FLAIR weighted images (Figure 2) and isointense to white matter on T1WI (Figure 3) and did not show restricted diffusion on diffusion weighted images (Figure 4). No susceptibility artifact was noted. On post contrast study, the lesion showed minimal to mild enhancement (Figure 5). No evidence of obstructive hydrocephalus was seen.

Diagnosis: Subependymoma of lateral ventricle

Discussion: Subependymoma are uncommon, benign (WHO grade I) tumors, which are slow growing and non-invasive. Subependymoma tend to present in middle-aged to older individuals. There is a slight male predilection (M: F 2.3:1). Typically, patients are asymptomatic and small lesions are discovered incidentally. In some cases, especially when the tumors are larger, presentation is with symptoms of raised intracranial pressure due to obstructive hydrocephalus.

Radiographic Features
CT shows isodense intraventricular mass compared to adjacent brain, which does not usually enhance. Surrounding vasogenic edema is usually absent. MRI-T1 iso shows hypointense to white matter, T2-heterogenous to adjacent white and grey matter, with susceptibility related signal drop out due to calcifications occasionally seen no adjacent parenchymal edema. On post contrast-T1 fat sat images there is usually no enhancement, although at times may demonstrate mild enhancement

Differential Diagnoses

• Ependymoma
• Intraventricular meningioma
• Central neurocytoma

References:
1. Ragel BT, Osborn AG, Whang K, et al. Subependymomas: an analysis of clinical and imaging features. Neurosurgery. 2006;58: 881–890.
2. Russell JH, Gaillard F, Drummond KJ. A mass in the fourth ventricle. J Clin Neurosci. 2009;16: 425,482.
3. Koral K, Kedzierski RM, Gimi B, et al. Subependymoma of the cerebellopontine angle and prepontine cistern in a 15-year-old adolescent boy. AJNR Am J Neuroradiol. 2008;29:190-191.
4. Tonn J, Westphal M, Rutka JT. Oncology of CNS Tumors. Springer Verlag. 2009.
5. Keating RF, Goodrich JT, Packer RJ. Tumors of the pediatric central nervous system. George Thieme Verlag. 2001.
6. Smith A, Smirniotopoulos J, Horkanyne-Szakaly I. From the Radiologic Pathology Archives: Intraventricular Neoplasms: Radiologic-Pathologic Correlation. Radiographics. 2013;33:21-43.