Colloid Cyst

A colloid cyst is a benign, fluid-filled sac that arises in the area of the brain known as the third ventricle. The common surgical treatments for colloid cyst are shunt placement, craniotomy, and endoscopic craniotomy; in some cases only observation is necessary.

Filled with a proteinaceous fluid, these growths are considered cysts, not “true” brain tumors. However, they are still categorized as intraventricular tumors, and they may cause symptoms that require intervention.

Generally, when no cyst is present, cerebrospinal fluid circulates through the brain’s ventricular system, nourishing and cushioning the brain and spinal cord. Colloid cysts may interfere with the body’s ability to maintain the proper balance and circulation of this fluid.

The third ventricle resides deep in the brain, close to the middle of the head. Colloid cysts are attached most commonly either to the roof of the third ventricle or to the choroid plexus—a structure at the center of the third ventricle. Both these locations are in proximity to crucial routes for fluid and blood circulation.

Nearby, the foramina of Monro connect the roof of the third ventricle to the lateral ventricles. If a cyst obstructs the path of cerebrospinal fluid through the foramina of Monro, hydrocephalus and increased intracranial pressure may result, with potentially serious and, in rare instances, life-threatening consequences.

Colloid cysts account for 15 to 20 percent of all masses that arise in the ventricles.


Colloid cysts are often asymptomatic and found incidentally during imaging tests.

If symptoms do occur, they typically include hydrocephalus and signs related to increased intracranial pressure, namely headaches that are most severe in the morning upon waking, nausea, vomiting, and blurry vision. Also, gait abnormality, changes in personality, memory loss, diplopia, papilledema, and drop attacks may occur.

If the increased intracranial pressure is not treated, sudden death is also possible.


A neurological examination is often conducted to identify symptoms. This exam consists of assessing swallowing, sense of smell, sensation, hearing, eye movements, motor function, balance, and coordination. Also, an ophthalmologic examination may be performed to evaluate eye health and detect any problems.

The key component to diagnosing colloid cysts is imaging studies. Either magnetic resonance imaging (MRI) scan or computed tomography (CT) scan can be used to show the fluid-filled tumor, and either can be conducted with or without contrast enhancement.

To confirm a diagnosis, biopsy of the tumor must be performed. This is typically done at the time of surgical resection.

Risk Factors

The cause of colloid cysts is unclear at this time, but it is believed that these tumors begin during embryonic development.

Colloid cysts are rare, making up only about 2 percent of primary brain tumors. Nearly all occur in adults, most often those in their 40s or 50s.


At Columbia, our neurosurgeons use the most sophisticated surgical techniques to treat colloid cysts, providing the best possible results for patients.

If the tumor is small and asymptomatic, it may be observed closely with periodic imaging tests and treated later if necessary.

The standard first step in treatment is typically brain tumor surgery; however, if the patient is experiencing severe neurological deterioration as a result of hydrocephalus, immediate intracranial pressure relief is needed, and can be achieved by inserting a shunt before surgery.

Colloid cysts can be surgically resected a few different ways. Our neurosurgeons select the approach that is most likely to be effective for each patient’s unique tumor.

  • The traditional method of tumor removal is a craniotomy—an open surgical technique. Where the opening is made on the skull depends on a number of factors, including tumor size.
  • Advances in microsurgical technique allow some small cysts to be extracted by means of a minimally invasive procedure called endoscopic craniotomy. The long, flexible surgical tool known as an endoscope makes it possible for surgeons to perform a resection through a burr hole made behind the hairline.

In both traditional craniotomy and endoscopic craniotomy, the colloid filling is gently drained from the cyst, and then the cyst wall and any remnants are resected. Either of these approaches can yield complete resection, usually resulting in a cure. Hydrocephalus typically resolves after total removal of the colloid cyst; however, if it does not, a shunt may need to be inserted temporarily.