Overview
An arachnoid cyst is a fluid-filled sac that develops between the brain or spinal cord and the arachnoid membrane, which is one of the three layers of tissue that cover and protect the brain and spinal cord. These cysts are filled with cerebrospinal fluid (CSF), the same clear liquid that normally surrounds and cushions the brain. Arachnoid cysts are sometimes called leptomeningeal cysts. Many arachnoid cysts are present from birth (congenital) and form during early development when the arachnoid membrane splits or duplicates abnormally. They can also develop later in life after head injury, infection, or surgery, though this is less common. The majority of arachnoid cysts are found in the middle cranial fossa (near the temples), but they can occur anywhere along the brain or spinal cord. Many people with arachnoid cysts have no symptoms at all, and the cyst is discovered by accident during brain imaging for another reason. When symptoms do occur, they depend on the cyst's size and location and may include headaches, nausea, dizziness, seizures, hearing or vision problems, and balance difficulties. In infants, a growing cyst may cause an abnormally large head. Treatment ranges from watchful waiting for cysts that cause no problems to surgical options such as fenestration (creating an opening in the cyst wall) or placement of a shunt to drain excess fluid. Most people with arachnoid cysts have an excellent outlook, especially when the cyst is small and not causing symptoms.
Key symptoms:
HeadachesNausea and vomitingDizziness or balance problemsSeizuresHearing changes or hearing lossVision problemsAbnormally large head in infantsDevelopmental delays in childrenWeakness or numbness in arms or legsDifficulty with coordinationFeeling of pressure in the headBehavioral changesFatigueBack pain (for spinal cysts)
Clinical phenotype terms (50)— hover any for plain English
Sporadic
Usually appears on its own, not inherited from a parent
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for Arachnoid cyst.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Arachnoid cyst.
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Caregiver Resources
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Social Security Disability
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Questions for your doctor
Bring these to your next appointment
- Q1.What is the size and exact location of the cyst, and is it likely to grow?,Does this cyst need treatment now, or can we safely monitor it over time?,How often should follow-up imaging be done?,What symptoms should prompt me to seek emergency care?,If surgery is recommended, which approach do you suggest and what are the risks?,Are there any activity restrictions, such as contact sports?,Could this cyst be related to any underlying genetic condition?
Common questions about Arachnoid cyst
What is Arachnoid cyst?
An arachnoid cyst is a fluid-filled sac that develops between the brain or spinal cord and the arachnoid membrane, which is one of the three layers of tissue that cover and protect the brain and spinal cord. These cysts are filled with cerebrospinal fluid (CSF), the same clear liquid that normally surrounds and cushions the brain. Arachnoid cysts are sometimes called leptomeningeal cysts. Many arachnoid cysts are present from birth (congenital) and form during early development when the arachnoid membrane splits or duplicates abnormally. They can also develop later in life after head injury,
How is Arachnoid cyst inherited?
Arachnoid cyst follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.