Tumours of the ventricular system

EPENDYMOMA

Intracranial ependymomas originate from cells lining the ventricular cavities. Most arise in the 4th ventricle and in this site occur predominantly in children. Both low grade and malignant forms are found and tumour cells may seed throughout CSF pathways.

In the 4th ventricle, ependymomas present with cerebellar signs or, more commonly, with signs and symptoms of raised intracranial pressure from CSF obstruction. Vomiting is often an early feature from direct brain stem involvement.

CT scanning shows an isodense mass, with or without calcification, lying within the 4th ventricle and usually enhancing with contrast. MRI more clearly delineates the anatomical relationships.

Management

The aim is complete operative removal, although infiltration of the floor of the 4th ventricle may prevent 4th ventricle this. Most clinicians advise ependymoma radiotherapy postoperatively, but its value is limited in the low grade tumours. CSF metastases are treated by total neuraxis irradiation

Prognosis

Despite relatively slow growth, results are often disappointing with 5-year survival ranging from 20-50%.

CHOROID PLEXUS PAPILLOMA

Rare, benign tumour with a granular surface and a gritty texture. They develop from the choroid plexus - in the 4th ventricle - adults,

- in the lateral ventricle - children. Malignant forms occasionally occur in children.

Most patients presenĀ» with hydrocephalus, either due to obstruction or to excessive CSF secretion from the tumour. CT scanning shows a hyperdense mass within the ventricular system. Operative removal gives good results.

COLLOID CYST OF THE THIRD VENTRICLE

A benign cyst, containing a mucoid fluid may arise from embryological remnants in the roof of the third ventricle. When of sufficient size (about 2 cm) it occludes CSF drainage from both lateral ventricles through the foramen of Munro.

Clinical features: Symptoms may be intermittent, possibly due to a ball-valve effect, with episodes of loss of consciousness, sudden weakness of legs, or even sudden death.

CT scan shows a small round mass of increased density, lying level with the foramen of Munro, causing lateral ventricular dilatation. The cyst wall will enhance following contrast on MRI.

These cysts can be drained through a stereotactically placed needle or an endoscope, but with this treatment, recurrence is almost inevitable. Operative removal through a transcallosal or transventricular approach carries little additional risk.

MENINGIOMA: rarely arises in the lateral ventricles. Often symptoms are mild and long standing. Operative removal only becomes necessary when symptoms and signs appear.

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