Dermoid, Epidermoid and Arachnoid Cysts


A cyst is a fluid-filled sac (not a tumor) that can be found inside the brain. It is characterized as a congenital abnormality because it forms before birth. Cysts can occur anywhere in the brain.

Dermoid cysts form from trapped skin cells during the development of the brain and spinal cord. They form in a baby before he/she is born. They often contain cells from sweat glands or hair follicles. These cysts typically appear in children.

Epidermoid cysts form from trapped skin cells during the development of the brain and spinal cord. They also form in a baby before he/she is born. They do not contain cells from sweat glands or hair follicles. These cysts typically appear in adults, as they are slow growing.

Arachnoid cysts form in the space between the arachnoid membrane and brain. They are filled with cerebrospinal fluid (CSF). They typically appear in children but can occur in adults also.

Signs and Symptoms

Most brain cysts are benign (not dangerous) and do not change or grow over time. In fact, most cysts in the brain do not cause any symptoms and most of the time are found incidentally on imaging studies of the brain or spine (for example, a head CT or brain MRI done to look for something else. In some cases, a cyst can grow and put pressure on the brain that is next to it. When this happens, signs and symptoms can develop based on the location of the cyst such as:

  • Headaches – often in the area of the cyst
  • Nausea and vomiting
  • Seizures
  • Loss of balance or trouble walking
  • Weakness in the legs or arms
  • Changes in bowel function
  • Trouble urinating

Although rare, a brain cyst can rupture or hemorrhage and require immediate attention and possible surgery. If you have a brain cyst and develop a sudden headache with vomiting or seizures, you should seek immediate medical attention.

Potential Causes

There are several potential causes of brain cysts, including abnormal development, infection, infarction and trauma.


Diagnosis of a cyst starts with a physical exam and medical history. Other procedures and tests may be needed to diagnose a cyst, including a detailed neurological exam , head CT or magnetic resonance imaging (MRI) scan.

If a cyst is found and is not causing any problems, it will be imaged again in about a year with either a head CT or quick MRI of the brain to make sure the cyst has not changed.

Treatment Options

A customized treatment plan is put together for you based on:

  • The type of cyst
  • The cyst’s size
  • Your age and general health
  • Your tolerance for treatment
  • Your preferences

Arachnoid cysts are usually treated by draining the cyst of CSF and placing a shunt, a permanent tube that drains the CSF and directs it elsewhere to be absorbed. 

There are many ways to put in a shunt. A VP shunt goes from your head to your belly. A small area of hair will be shaved from your head. This is where the surgeon will create a hole and put a small tube or catheter into the brain, sometimes using a special type of X-ray to do this. The tubing is then connected to a longer piece, which is placed in the belly through a small incision or incisions. A valve sits between these two tubes to direct and control flow; some valves can be sped up or slowed down in the office with a special magnet.

An LP shunt puts the first catheter into an area in your spine (back) and the rest into your belly.

A VA shunt is like a VP shunt, but the final catheter is placed in the heart instead of the belly. There are other places the end of the shunt can be placed as well. All of these allow fluid to drain and be absorbed properly.

Dermoid and epidermoid cysts are commonly removed surgically through a procedure such as neurosurgery or open microsurgery. This type of surgery requires a highly specialized and meticulous approach. This approach is done through the nose and sphenoid sinus to locate the tumor, using a microscope or special high-powered loupes (glasses) to visualize the tumor and remove it. You will need to stay in the hospital for a few days after surgery, with the length of stay determined by the extent of surgery. You will undergo a brain MRI with and without contrast after surgery to make sure that complete removal of the tumor has occurred.


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