What is a brain cyst?
A brain cyst is a type of abnormal fluid-filled sac in the brain. They are generally benign (not cancer). Benign also means that the growth does not spread to other parts of the body. A cyst may contain blood, pus, or other material. In the brain, cysts sometimes contain cerebrospinal fluid (CSF). CSF normally bathes and cushions the brain and spinal cord. Often, brain cysts begin before birth.
Even if a brain cyst is not cancer, it can still cause problems. The cyst may press against brain tissue and cause symptoms, such as headache, vision problems, or nausea. If this happens, you may need surgery to remove the cyst. In some cases, if the cyst is small and not growing and is not likely to cause symptoms, your healthcare provider may advise watching it instead of surgery.
There are different types of brain cysts:
- An arachnoid cyst is also known as a leptomeningeal cyst. This is a cyst between the brain and the arachnoid membrane. This membrane is one of the protective coverings around the brain. An arachnoid cyst contains CSF. These appear most often in children, but they may also happen in adults. This type of cyst happens more often among males than females.
- A colloid cyst is a gel-filled cyst. It often forms in one of the 4 ventricles of the brain. The ventricles are the CSF reservoirs in the brain. Colloid cysts usually happen in the third ventricle. This is in a central spot in the brain. The cysts can lead to blockage of CSF flow off and on, and cause positional headaches. These are headaches that happen when a person is in a certain position. These tend to appear during adulthood.
- A dermoid cyst is a rare type of cyst. It forms when a few skin cells get trapped when the brain and spinal cord form before birth. These cysts may even contain sweat gland cells or hair follicle cells. These often appear in children.
- An epidermoid cyst is also called an epidermoid tumor. Like a dermoid cyst, it forms from a bit of tissue that gets trapped when the brain and spinal cord form. Epidermoid cysts do not contain sweat glands or hair follicle cells. They grow very slowly. These cysts usually first appear when a person is an adult.
- A pineal cyst happens on the pineal gland in the middle of the brain. This type of cyst usually only shows up during an imaging scans done for another reason. Pineal cysts seldom cause problems. If they do grow large, they can sometimes affect vision. They can appear in people of any age.
What causes a brain cyst?
Many brain cysts form during the first few weeks when a baby is growing in the womb. Rarely, an arachnoid cyst might form because of a head injury or other trauma to the brain. In other cases, there may be links between a brain cyst and a benign or cancerous tumor. In many cases, the cause of a brain cyst is unknown.
What are the symptoms of a brain cyst?
The symptoms generally depend on which part of the brain the cyst is growing in. In some cases, a small cyst may not cause any symptoms. Some cysts are “silent” (cause no symptoms) until they grow large. In some cases, you may have a problem related to the area of the brain the cyst is growing in. In other cases, the symptoms may be due to blockage of the normal flow of CSF. This can cause increased pressure on the brain (intracranial pressure).
Symptoms can happen a bit differently in each person, but can include:
- Headache (common)
- Nausea and vomiting
- Vertigo or dizziness
- Hearing or vision problems
- Difficulties with balance and walking
- Facial pain
- Seizures (not common)
How is a brain cyst diagnosed?
In some cases, your healthcare provider may discover a brain cyst when it shows up on an imaging scan done for another reason. In other cases, you may be having symptoms related to the cyst. Your primary healthcare provider may refer you to a neurologist. This is a healthcare provider who specializes in diagnosing and treating diseases of the central nervous system. Or you may be referred to a neurosurgeon. This is a surgeon who performs brain or spinal cord surgery.
The process to diagnose a cyst starts with a medical history and a physical exam. Your healthcare provider will ask about your symptoms and past medical conditions. He or she may also ask about your family’s medical history. The physical exam may include a neurologic exam. Imaging tests may be done to look at the brain. Contrast dye may be used to help show more detail in the images. The tests may include:
- Computed tomography (CT) scan. This is an imaging test that uses X-rays and a computer to make detailed images of the body. Scans may be done of your brain and spinal cord.
- Magnetic resonance imaging (MRI). This test uses large magnets and a computer to create images of the body. MRI scans of your brain and spinal cord may be done to get more information about the cyst and nearby tissues.
Scans may be repeated over time to learn if the cyst is growing.
How is a brain cyst treated?
If a brain cyst is causing problems, your healthcare provider may advise removing it with surgery. If the cyst is not causing symptoms and it is not growing, your healthcare provider may choose to watch it closely with repeated brain scans. Treatment can vary by the type of cyst. For example:
- If you have an arachnoid cyst, your healthcare provider may puncture the cyst sac and drain the fluid. The fluid drains into the CSF or is pulled out with a needle. If your healthcare provider drains the cyst without removing the sac, the sac may fill with fluid again.
- If you have a dermoid or epidermoid cyst, your healthcare provider will likely remove it. The complete cyst with its sac will likely be removed. If the cyst is not fully removed, it may regrow and cause symptoms again after a few years.
- Colloid cysts often cause a buildup of excess CSF. This is known as hydrocephalus. This can create a dangerous increase in pressure within the brain. A shunt or drainage tube can relieve some of this pressure. Colloid cysts can be hard to remove because they are often located deep within the brain. To remove these, your healthcare provider may use special surgical methods with tiny endoscopic tools sent through a thin tube into the brain.
- Pineal cysts often cause no problems. It is usually possible to manage these by watching for any changes.
Key points about a brain cyst
- Brain cysts are fluid-filled sacs that may form in the brain. They are often benign (not cancer).
- Brain cysts may appear in children or adults. In some cases, brain cysts begin before birth but don’t cause any symptoms until much later.
- A brain cyst that does not cause symptoms will sometimes show up during an imaging scan done for another reason.
- There are different types of brain cysts. These include arachnoid, colloid, dermoid, epidermoid, and pineal cysts.
- Even though brain cysts are noncancerous, they may press against brain tissue and cause symptoms. Sometimes a cyst may block the normal flow of CSF. This can cause problems.
- Your neurologist or neurosurgeon may recommend surgically removing the cyst. If the cyst is small and is not likely to cause symptoms, your healthcare provider may instead recommend monitoring it to see if it remains stable. If monitoring is suggested, it is very important to keep recommended follow-up appointments.