A brain cyst is an abnormal fluid-filled sac in the brain. A cyst may contain blood, pus, or other material. In the brain, a cyst may contain cerebrospinal fluid (CSF). CSF normally bathes and cushions the brain and spinal cord. Often, a brain cyst starts before birth.
A brain cyst is usually benign (not cancer). Benign also means that the growth doesn't spread to other parts of the body. But 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.
Types of brain cysts
Arachnoid cyst. This is also known as a leptomeningeal cyst. It's a cyst between the brain and the arachnoid membrane. This membrane is one of the protective layers around the brain. An arachnoid cyst contains CSF. These appear most often in children, but they may also occur in adults. This type of cyst happens more often in men than in women. It often causes no symptoms.
Colloid cyst. This is a gel-filled cyst. It often forms in 1 of the 4 ventricles of the brain. The ventricles are places in the brain where CSF is stored. A cyst can block the flow of CSF from time to time. It can also cause positional headaches. These are headaches that happen when you are in a certain position.
Dermoid cyst. This is a rare type of cyst. It forms when a few skin cells get trapped when the brain and spinal cord form before birth. This type of cyst may even contain sweat gland cells or hair follicle cells. These often appear in children.
Epidermoid cyst. This 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. An epidermoid cyst does not contain sweat glands or hair follicle cells. They grow very slowly. This type of cyst usually first appears when a person is an adult.
Pineal cyst. This occurs on the pineal gland in the middle of the brain. This type of cyst usually only shows up on an imaging scan done for another reason. A pineal cyst does not often cause problems. If it does grow large, it can sometimes affect vision. This type of cyst can appear in people of any age.
What causes a brain cyst?
In many cases, a brain cyst forms during the first few weeks when a baby is growing in the womb. In rare cases, an arachnoid cyst may form after a head injury or other trauma to the brain. Or there may be a link between a brain cyst and a benign or cancerous tumor. In many cases, the cause of a brain cyst is not known.
Symptoms of a brain cyst
A cyst may cause no symptoms unless it grows large. The symptoms depend on which part of the brain the cyst is growing in. Symptoms may be caused by blockage of the normal flow of CSF. This can lead to more pressure on the brain (intracranial pressure).
Symptoms can occur a bit differently in each person, but can include:
Diagnosing a brain cyst
A brain cyst may be found when it shows up on an imaging scan done for another reason. In other cases, you may have symptoms from the cyst. Your primary healthcare provider may refer you to a neurologist. This is a doctor who diagnoses and treats diseases of the central nervous system. Or you may be referred to a neurosurgeon. This is a surgeon who does brain or spinal cord surgery.
Your healthcare provider will ask about your medical history and symptoms. He or she will give you a physical exam. This may include a nervous system 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:
CT scan. This is a test that uses a series of X-rays and a computer to create images of the inside of the body. Scans may be done of your brain and spinal cord.
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 done again over time to see if the cyst is growing.
Treatment for a brain cyst
If the cyst is small, not growing, and not likely to cause symptoms, your healthcare provider may advise watching it. This is done with imaging tests over time. If you have symptoms, you may need surgery to remove the cyst. Treatment can vary by the type of cyst.
Call 911 if either of these occurs:
Severe sudden headache
When to call your healthcare provider
Call your healthcare provider right away if you have any of these:
Back and leg pain
Hearing or vision problems
Nausea and vomiting
Trouble with balance and walking
Numbness and tingling in arms or legs
Vertigo or dizziness
Confusion or trouble staying awake