What is Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)?
A colloid cyst is a harmless lump usually found in the third ventricle of the brain, near the foramen of Monro, which is towards the front of the brain’s third ventricle. The cyst is lined with specialized skin cells and filled with a jelly-like substance. This substance often contains mucin (a type of protein), old blood, cholesterol, and ions.
Colloid cysts can cause a range of symptoms such as headaches, double vision, memory problems, and dizziness. In rare cases, they can even cause sudden death. When these cysts cause symptoms, the most common ones are headaches, nausea, and vomiting. These symptoms are due to obstructive hydrocephalus, a condition where the cyst blocks the flow of cerebrospinal fluid from the lateral ventricles at the foramen of Monro, which is a connection point between the lateral and third ventricles of the brain.
What Causes Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)?
The exact cause of colloid cysts is still unknown and the subject of much debate. During the early 20th century, scientists believed that these cysts may originate from a leftover part of a very early stage of brain development called the paraphysis element. This structure is found at the front part of a region in the brain called the diencephalon, located between the two hemispheres of the top part of the brain, known as the telencephalon.
However, since colloid cysts have been discovered in other areas of the brain like the cerebellum, frontal lobe, and pontomesencephalon, there are other theories about their origin. Some possible causes include leftover respiratory epithelium, a specific type of cyst called an ependymal cyst from the diencephalon, or the inward folding of the lining of the lateral ventricle of the brain which may result in a cyst formation.
Risk Factors and Frequency for Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
Colloid cysts form a very small percentage of all primary brain tumors, actually less than 2%. Over 99% of these cysts are found near the foramen of Monro, which is located at the front end of the third ventricle in the brain.
This type of tumor accounts for roughly 1 out of 5 tumors that develop within the brain’s ventricles. Although most people diagnosed with a colloid cyst are between their 30s and 70s, there have been rare reports of cases as early as the first year of a person’s life.
Signs and Symptoms of Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
Colloid cysts are often discovered unintentionally during brain scans for unrelated issues. When these cysts cause symptoms, they primarily lead to a condition called noncommunicating hydrocephalus. This condition triggers various symptoms such as:
- Headaches
- Nausea
- Vomiting
- Tiredness
- Coma
- Potentially death
If the hydrocephalus develops gradually, the person might experience more subtle issues like urinary incontinence, difficulty with walking, frequent falling, changes in mental function, and memory problems.
For people with asymptomatic colloid cysts, their physical examination results should be normal. However, if a colloid cyst leads to hydrocephalus, physical signs could include tiredness, trouble moving the eyes upwards, imbalance while walking, increased reflex responses, and potential indications of long-term hydrocephalus like an abnormal appearance of the optic disc (papilledema) or involuntary response to certain frontal stimuli (frontal release signs).
Testing for Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
If a colloid cyst is suspected, the patient needs to be evaluated immediately in case there’s a risk for sudden brain fluid buildup and neurological deterioration. This includes checking the patient’s airways, breathing, and circulation. A thorough neurological exam should be conducted to identify any neurological deficits. However, imaging such as X-rays, CT scans, and MRIs are the primary tools used to evaluate patients with a suspected colloid cyst.
X-ray images of the head may not highlight a colloid cyst clearly. Therefore, CT scans and MRI scans are more valuable. A CT scan of the head can be done swiftly to identify any sudden buildup of brain fluid. In these scans, the colloid cyst usually appears as a dense, round mass near the channel that allows cerebrospinal fluid to exit the brain’s ventricles. Rarely, these cysts may appear with equal, lower, or calcified density.
An MRI scan is the preferred method to image colloid cysts. On the T1 sequence of the MRI, the appearance of a colloid cyst can vary. It can look either brighter, the same, or darker compared to the surrounding brain tissue. If a contrast dye is given, the colloid cysts usually do not brighten up. However, sometimes, a slight brightening might appear around the cyst, probably due to a stretched blood vessel.
On the T2 sequence of the MRI, most colloid cysts appear darker. They may also give a mixed signal. If the T2 image shows low signal intensity, this could suggest that the contents of the colloid cyst are thick and hence harder to aspirate. Most colloid cysts have similar intensity to the surrounding cerebrospinal fluid on an advanced type of MRI sequence called FLAIR. Typically, the signal intensity in diffusion-weighted imaging is decreased for most colloid cysts.
Treatment Options for Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
If a colloid cyst, a noncancerous growth in the brain, is causing symptoms such as blockages in the brain’s fluid-filled chambers (hydrocephalus), it needs to be treated. In urgent situations where the hydrocephalus is life-threatening, the first step is to ensure the patient has a secure airway to breathe and a good blood circulation. To relieve this dangerous build-up of fluid, a drain can be inserted into the brain, which can save the patient’s life.
Once the immediate danger has passed, the healthcare provider can determine the best way to handle the colloid cyst. There are three main treatment options available: removal through surgery (craniotomy), taking it out with an endoscope, or reducing its size by suction (stereotactic aspiration).
A craniotomy is a type of brain surgery in which a section of the skull is temporarily removed to allow access to the brain. The colloid cyst can be reached in two ways. One way, a transcallosal approach, separates the two frontal halves of the brain and creates a pathway to the cyst through the front of the corpus callosum, a major nerve fiber bundle. The alternate method, a transcortical route, involves creating a passageway directly through the brain tissue itself. This brain surgery carries some risk but could potentially prevent further procedures, as removing a colloid cyst with a craniotomy often lowers the chance of the cyst returning.
Removing a colloid cyst through endoscopic surgery typically carries less upfront risk. With endoscopic removal, a small tube equipped with a light and camera, and tools required for the surgery, are guided through a small opening in the scalp and skull to get to and remove the cyst. However, this method isn’t suitable for all colloid cysts and might result in both a slightly elevated risk of other surgeries being needed later.
For stereotactic aspiration, a needle is introduced through a small opening in the skull then guided through the brain to reach the cyst, allowing the fluid inside to be drained off and thereby reducing its size. However, thicker cysts or those in challenging locations may not be suitable for this technique. While it carries the least immediate surgery risk, this technique is associated with a higher reoperation rate than craniotomy or endoscopic removal, as the cyst might refill and cause symptoms again over time.
If the cyst isn’t causing any symptoms and is smaller or located more towards the third brain ventricle’s center, surgery might not be needed. Healthcare professionals will usually monitor these cysts with regular imaging check-ups. If these cysts cause hydrocephalus, most surgeons would agree on the need for surgery. Infrequent but serious instances have been reported where untreated cysts caused a sudden, serious obstruction leading to hydrocephalus and fatality.
What else can Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle) be?
When assessing an MRI or CT scan of the brain, a formation that looks like a colloid cyst could actually be several different things. These might include:
- Craniopharyngioma (a rare type of brain tumor)
- Ependymoma (another rare type of brain tumor)
- Germinoma (a type of germ cell tumor)
- Giant cell astrocytoma (a type of brain tumor)]
- Hemorrhage (bleeding within the brain)
- Lymphoma (a form of cancer that begins in infection-fighting cells of the immune system, called lymphocytes)
- Meningioma (a type of non-cancerous brain tumor)
- Metastasis (cancer cells that have spread to the brain from another part of the body)
- Pilocytic astrocytoma (a brain tumor that occurs more often in children and young adults)
- Pituitary tumor (a growth in the pituitary gland, located at the base of the brain)
Each of these conditions can look somewhat similar to a colloid cyst on a scan, making careful examination essential for accurate diagnosis.
What to expect with Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
Some colloid cysts can remain harmless for many years, even decades. However, some can gradually increase in size or cause a slow or sudden build-up of fluid in the brain, known as subacute or acute hydrocephalus. If these cysts are fully removed through surgery, the outlook is generally good and it’s uncommon for them to come back. Although it’s rare, there have been cases of sudden death linked to colloid cysts, typically due to an abrupt blockage causing hydrocephalus.
Possible Complications When Diagnosed with Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
Colloid cysts can lead to several complications, such as:
- Excessive accumulation of cerebrospinal fluid in the brain, known as hydrocephalus
- Shifting of brain tissues, referred to as brain herniation
- Internal bleeding in the lesion, known as intralesional hemorrhage
- Unfortunately, in severe cases, these cysts can also result in death
Preventing Colloid Brain Cyst (Benign Brain Cyst Typically in the Third Ventricle)
Patients who are being monitored should be advised to immediately go to the closest emergency department if they start experiencing severe headaches or vomiting.
