Colloid cyst

Colloid cyst

Description, Causes and Risk Factors:

Alternative Name: Neuroepithelial cyst.

Colloid cyst is the he most common tumor located within the third ventricle of brain. This benign tumor can cause a blockage of cerebrospinal fluid (CSF), leading to increase intracranial pressure and sometimes lead to death.

Colloid cysts of the third ventricle, which represent the best known form of neuroepithelial cyst, are rare tumors (0.25-0.5% of all intracranial tumors). The origin of this benign pathologic structure has been controversial, but the most widely accepted theory suggests an origin in the primitive neuroepithelium of the tela choroidea (the portion of the pia mater that covers the ependymal roof or, in the case of the lateral ventricle, medial wall of a cerebral ventricle). Neuroepithelial cysts are also found in the lateral ventricles; this has been documented in many cases at autopsy, but the cysts have been visualized rarely on CT and MR.

Colloid cyst

It can be assumed that the very strategic position of a colloid cyst in the anterior part of the third ventricle, allowing it to obstruct one or both foramina of Monro, thus creating acute hydrocephalus, probably accounts for the more common recognition of cysts in this location and descriptions in the clinical and radiologic literature.

Before CT, ventriculography and encephalography could establish the correct diagnosis, but did not provide any information about the content of the cysts. With the introduction of CT, the interest of radiologists was aroused by the very polymorphous appearance of these lesions, which were reported as very hyperdense relative to brain parenchyma. The explanation for the increased density has only rarely been found to be hemorrhage or gross calcification. Therefore, several hypotheses have been proposed concerning the content of iron or other radiodense ions in the secretion products of the cyst. Reports on the contrast enhancement of these lesions, particularly in the periphery or capsule, have been contradictory. The signal pattern of colloid cysts on MR has also been described as heterogeneous.

A few cases have been reported, showing different components in the so-called colloid matrix of the cyst; it has been suggested that the unusual signal pattern is caused by the inclusion of paramagnetic material.


The signs and symptoms produced by these lesions are primarily related to increased intracranial pressure due to obstructive hydrocephalus.

The most frequent findings are: headache, change in mental status, nausea and vomiting, ataxia (balance difficulty), visual disturbance, emotional lability/affect change (changes in mood/emotional context), depersonalization, and increased sleepiness.

Colloid Cysts may also cause symptoms by pressure on adjacent structures, which results in symptoms such as disturbances in memory, emotion, and personality.

As the Cyst enlarges, it intermittently obstructs the flow of CSF (cerebrospinal fluid) at the level of the foramen of Monro (a vital interconnecting pathway within the Brain's ventricular cavities). With continued growth, the obstruction becomes complete.


Your doctor will usually make the diagnosis from the symptoms that you have. There can be similar symptoms with the other disease so there will need to be some tests done to confirm the diagnosis. The first test is usually a CAT (computerized axial tomography) scan. This will usually show the presence of lesions. The ventricles may be enlarged. The next step is usually CT and MRI scans, which form the basis for diagnosing colloid cysts. They also provide information regarding the presence or absence of hydrocephalus (an abnormal condition in which cerebrospinal fluid collects in the ventricles of the brain). These lesions appear as round or oval masses in the anterior and superior portion of the third ventricle of the brain, at the level of the foramen of Monro.


Treatment options may be generally surgery. There are 2 types of operations that may be performed to remove the colloid cyst. Your surgeon will discuss the surgical approach with you prior to surgery.

ENDOSCOPIC REMOVAL OF COLLOID CYST: This approach utilizes the fact that there is often hydrocephalus associated with the colloid cyst. Two small incisions are made 2 cms off the midline on the left and right. Small burr holes are created and an endoscope (small telescopic camera) is inserted through the brain tissue into the ventricle. This is connected up to a video monitor allowing direct visualization of the colloid cyst. A second port is inserted through the second burr hole allowing the passage of instruments into the ventricle. The colloid cyst is then removed in its entirety and the instruments and endoscope carefully removed. The small incisions are then closed with staples or stitches.

CRANIOTOMY & EXCISION OF COLLOID CYST: An incision will be made in the midline at the top of the head after a general anaesthetic has been administered. The neurosurgeon will then raise a small piece of bone (craniotomy) and, using the microscope, carefully separate the two hemispheres of the brain. The hemispheres are connected lower down by a structure called the corpus callosum, and the front few centimeters of this structure immediately overlies the third ventricle. As such, a small incision is made in the corpus callosum allowing identification of the colloid cyst. The cyst is then removed in its entirety. The bone is then replaced and secured with some titanium plates and the incision closed with staples or stitches.

Risks of the procedures:

    Infection - superficial wound infection or deeper infections including meningitis, osteomyelitis.

  • Bleeding - which may be superficial or deep causing intracerebral hematoma and stroke-like symptoms.

  • Weakness, numbness, speech disturbance or paralysis (stroke like symptoms).

  • Memory dysfunction.

  • Hydrocephalus - which may be temporary or permanent and may require a second operation.

  • Epilepsy which may require medication.

  • Coma.

  • Death (rare).

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

Reference and Source are from:

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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