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Genetic and Rare Diseases Information Center (GARD)

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Arachnoid cysts

Other Names for this Disease
  • Arachnoid cysts, intracranial
  • Intracranial arachnoid cysts
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Your Question

This was found in an ultrasound of my grandson. If it is removed is there a normal life or are there more problems down the road? The doctors talked with her about aborting the baby. That really makes me think bad things are to come.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is the long-term outlook for individuals with a primary arachnoid cyst?

Even though most arachnoid cysts are congenital (present at birth), they usually do not cause any symptoms throughout an individual's life. Whether symptoms develop depends upon the size and the specific location of the cyst within the brain. Small cysts usually do not cause symptoms, and most remain constant in size. However, some do increase in size and eventually cause symptoms to appear, especially if they press against a cranial nerve, the brain, or the spinal cord. If the cyst puts increased pressure on structures of the brain, neurological symptoms may develop. These symptoms can include developmental delays, behavioral changes, an inability to control voluntary movements (ataxia), difficulties with balance and walking and cognitive impairment. Weakness or paralysis on one side of the body (hemiparesis) has also been reported.[1] Symptoms often resolve or improve with treatment but if left untreated, progressive growth of an arachnoid cyst can eventually cause permanent, severe neurological damage.[2]
Last updated: 7/11/2013

What is known about the long-term outlook associated with arachnoid cysts diagnosed prenatally?

Factors that reportedly seem to influence the prognosis for a fetus with an arachnoid cyst include the size (and whether it is growing), gestational age at the diagnosis, and the location of the cyst. Small cysts are usually asymptomatic. Interhemispheric cysts (those that extend between the 2 hemispheres) are often associated with complete or partial agenesis of the corpus callosum and carry a risk of causing intellectual disability. Brain compression by a large cyst may lead to hydrocephalus and may cause seizures, headache, and neurological signs after birth. The neurological prognosis often depends on the possibility of surgical treatment.[3]

In a study of 54 fetuses with arachnoid cysts diagnosed in the second and third trimesters of pregnancy, a good prognosis was reported in 88% of the cases in terms of behavior, neurological development, and intelligence at 4 years of age. Several pregnancies were terminated because they were associated with other brain abnormalities. Some reports describe complete resolution of the cysts and that cysts rarely progress after birth.[3]

A fetal MRI can help physicians to see and monitor compression of the aqueduct, communication between the cyst and the ventricles, and corpus callosum abnormalities.[4] Because arachnoid cysts have a somewhat uncertain prognosis, knowing what to do when learning about an arachnoid cyst during pregnancy can be difficult. Some individuals may consider termination of pregnancy due to the uncertainty of the prognosis.[3]

Individuals who have learned that an arachnoid cyst has been diagnosed during the pregnancy should consider meeting with a genetic counselor. A genetic counselor can interpret information about the condition, review available options, and provide supportive counseling to individuals and their family members.
Last updated: 7/11/2013

How can I find a genetics professional in my area?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:
Last updated: 10/18/2013