Colloid Cyst

What is a colloid cyst?

Colloid cysts compose 0.5 - 1% of intracranial tumors. They arise from cells which are so-called "neuroepithelial" meaning that they arise from primitive cells during development. Colloid cysts are usually located in the anterior portion of the third ventricle in which location they can block the outflow pathways for the cerebrospinal fluid and cause water in the brain (hydrocephalus). Some colloid cysts are also located in the septum pelucidum.

What are the symptoms?

The signs of a colloid cyst include acute intermittent hypertension within the head due to sudden blockage of CSF flow with sudden increase in the volume of intraventricular water (remember that ventricular cerebrospinal fluid is produced at a rate of 500cc/day). There is a syndrome of sudden death associated with acute obstruction of the CSF circulation pathway due to herniation of the brain with possible compromise of the cardiovascular control center of the hypothalamus.

How is it diagnosed?

The diagnosis of colloid cyst is best made with an MR scan or CT scan. Lumbar puncture is not necessary and can in fact be dangerous for this condition.

What is the treatment?

The treatment of a colloid cyst may consist of bilateral VP shunting, but this will not take care of the affect of the cyst on the hypothalamus which it is against. Therefore it may be necessary to remove the cyst. The rationale for removing the cyst is to avoid shunt dependency, to eliminate the risk to the hypthalamic cardiovascular center as well as to eliminate the risk of tumor progression. The surgical options include an open craniotomy going through the corpus callosum of the brain. Also possible are stereotactic drainage procedures and ventriculoscopic procedures, the only problem with which is getting a total removal of the cyst.