Deep in the central part of the brain, there are four cavities (called ventricles) which are filled with water-like cerebrospinal fluid (CSF). They are connected to each other. The two larger ventricles, called lateral ventricles, are responsible for producing CSF. One is located on each side of the brain. They drain into a smaller central ventricle labelled as the third ventricle. CSF travels from the third ventricle to the fourth ventricle, which is located in the hindbrain. Here it flows out of the fourth ventricle to circulate over and cushion the spinal cord and brain.
Colloid cysts are benign growths. They are usually identified beginning in the third decade of life. The contents of the cyst have a gelatin-like consistency. Although they can rarely occur in other areas of the brain, they are mostly seen suspended from the roof in the front part of the third ventricle. Colloid cysts are typically located near the small openings where CSF drains from the lateral ventricles into the third ventricle. This opening is called the foramen of Monro.
Signs and Symptoms
Symptoms of a colloid cyst depend on the size, type and location of the cyst(s). Symptoms may be caused by a cyst pressing on a nerve or harming a part of the brain. They may also be caused by a cyst blocking the fluid that flows through and around the brain, or by brain swelling because of the buildup of fluid.
Symptoms of a colloid cyst may include:
- Intermittent severe headaches which may be relieved by lying down
- Issues with memory
- Loss of consciousness
The exact cause of colloid cyst is not fully understood. There are no certain links to any lifestyle, environmental or genetic factors.
A colloid cyst may produce symptoms, or it may be found incidentally (by chance) on a brain imaging study.
A customized treatment plan is put together for you based on:
- Your symptoms
- Size of your colloid cyst
- Your tolerance for treatments
- Observation If your colloid cyst is small and not producing any symptoms, observation is often recommended. Since the colloid cyst can grow, routine follow-up, clinically and with imaging studies, is typically performed.
- Surgery There are several ways to treat a third ventricle colloid cyst if needed. Your surgeon will discuss the various options with you.
- Stereotactic aspiration This procedure is similar to a stereotactic biopsy. The cyst contents are aspirated (suctioned out) through a needle placed into the cyst. It does not remove the cyst. Sometimes the cyst content may be very thick and difficult to aspirate. Generally, when surgery is needed, resection (removal) is the first choice if possible.
- Neuro-endoscopic removal This is a minimally invasive surgery used to remove the cyst. Through a small hole in the skull (burr hole), a tube is passed into the ventricles. A camera (endoscope) is placed down the tube, and specialized instruments are used to surgically remove the tumor.
- Open craniotomy Standard microsurgical techniques are used to remove the cyst from several different approaches.
- Ventriculoperitoneal (VP) shunt This is a common neurosurgical operation. This procedure relieves the pressure of hydrocephalus without physically removing the colloid cyst. A shunt is a thin tube that allows the CSF to drain to another area of the body (usually the abdominal cavity) to be absorbed. A shunt tube may need to be placed into both lateral ventricles.