A solid mass with a cystic component arising in the occipital horn of the lateral ventricle in an elderly woman

Abstract

AnswerB. Intraventricular meningioma. DiscussionIntraventricular lesions are unusual and represent less than 10% of all intracranial neoplasms. Tumours that primarily or exclusively involve the ventricular system constitute a heterogeneous group. Certain histologic tumour types predominantly occur in children, whereas others are more common in adults. It is important to differentiate between a true intraventricular lesion and an intraparenchymal tumour invaginating into the ventricle. The presence of a liquoral cap around the lesion can be suggestive of an intraventricular neoplasm. In addition, the surrounding brain parenchyma may be less affected by an intraventicular neoplasm, and any areas of altered MRI signal at imaging may be more suggestive of a local irritative effect than local infiltration. Nevertheless, on MRI, low-grade parenchymal tumours often look indistinguishable from intraventricular meningiomas. 1 The epidemiology of ependymoma shows a clear preference for younger age groups, although the occurrence of supratentorial ependymomas in adults has been described. Ependymomas appear as a well-circumscribed mass that arises from the ventricle walls and occupies ventricular space. MRI appearances of ependymoma are comparable to those of intraventricular meningiomas. In addition, cystic areas are common in these lesions. 2 Therefore the reported lesion could be an ependymoma based on the neuroimaging. However, ependymomas often tend to be inhomogeneous on T1-weighted MRI, and show variable enhancement with contrast administration. Ependymoma would be rare in a patient of this age.Choroid plexus tumours are intraventricular papillary lesions that are observed usually in childhood. However, there are reports of patients with choroid plexus papillomas with specific chromosomal aberrations that occur equally in adult and paediatric patients. On non-enhanced CT the tumour appears as a smooth or lobulated mass, hyperdense in relation to surrounding brain parenchyma. With intravenous contrast, there is marked, homogeneous enhancement. With MRI these tumours show an isointensity on T1-weighted MRI and iso-hypointensity on T2-weighted MRI, with marked enhancement after gadolinium. On CT scans and MRI, the mass may appear similar to an intraventricular meningioma except for a variable hyperintense signal on T2-weighted MRI and flow voids. 1 Thus, the reported lesion could be a choroid plexus papilloma, however the well demarcated round border of the neoplasm, plus the patient age, made this unlikely.In adults, atrial intraventricular meningiomas are among the most common tumours in the lateral ventricle. Although rare, accounting for only 0.7% of all meningiomas, they occur in the left lateral ventricle of middle-aged or older women. The cells of origin are believed to be arachnoid cap cells confined to the choroid plexus. 3 CT scans reveal a sharply demarcated lobular mass with hyperattenuation and periventricular oedema. On MRI, the lesion can appear as isointense to hypointense compared to gray matter on T1-w...