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What are arachnoid cysts?
What are the symptoms of arachnoid cysts?
How are arachnoid cysts diagnosed?
How are arachnoid cysts treated?
What is the prognosis?
Arachnoid cysts are cerebrospinal fluid-filled sacs that are located between the brain or spinal cord and the arachnoid membrane, one of the three membranes that cover the brain and spinal cord. Primary arachnoid cysts are present at birth and are the result of developmental abnormalities in the brain and spinal cord that arise during the early weeks of gestation. Secondary arachnoid cysts are not as common as primary cysts and develop as a result of head injury, meningitis, or tumors, or as a complication of brain surgery. The majority of arachnoid cysts form outside the temporal lobe of the brain in an area of the skull known as the middle crania fossa. Arachnoid cysts involving the spinal cord are more rare.
What are the symptoms of arachnoid cysts?
The location and size of the cyst determine the symptoms and when those symptoms begin. Most individuals with arachnoid cysts develop symptoms before the age of 20, and especially during the first year of life, but some people never have symptoms. Males are four times more likely to have arachnoid cysts than females.
Typical symptoms of an arachnoid cyst around the brain include headache, nausea and vomiting, seizures, hearing and visual disturbances, vertigo, and difficulties with balance and walking. Arachnoid cysts around the spinal cord compress the spinal cord or nerve roots and cause symptoms such as progressive back and leg pain and tingling or numbness in the legs or arms.
How are arachnoid cysts diagnosed?
Diagnosis usually involves a brain scan using computerized tomography (CT) or magnetic resonance imaging (MRI) scans, which help to distinguish fluid-filled arachnoid cysts from other types of cysts. There are no blood tests or other types of non-imaging modalities that can reliably diagnose arachnoid cysts.
How are arachnoid cysts treated?
There has been active debate about how to treat arachnoid cysts. The need for treatment depends mostly upon the location and size of the cyst. If the cyst is small, not disturbing the surrounding tissue, and not causing any symptoms, some doctors will refrain from treatment. For symptomatic patients who are good candidates for surgery (craniotomy), microneurosurgical techniques are used to remove the membranes of the cyst or open the cyst so its fluid can drain into the cerebrospinal fluid and be absorbed. On occasion a shunt may be placed in the cyst to drain its fluid into the abdominal cavity where it is absorbed.
Untreated arachnoid cysts may cause permanent and severe neurological damage if the cyst progressive expands and puts pressure on the brain/spinal cord or causes hemorrhage due to stretching of vessels. When treated, symptoms usually resolve or improve within a relatively short period of time.
