Arachnoid Cyst
About -An arachnoid cyst is a fluid-filled sac that develops within the arachnoid membrane, one of the three protective layers surrounding the brain and spinal cord. The cyst usually contains cerebrospinal fluid (CSF), the clear fluid that surrounds and cushions the brain and spinal cord. Arachnoid cysts can occur in the brain (intracranial arachnoid cysts) or around the spinal cord (spinal arachnoid cysts). Many arachnoid cysts are present from birth and are called primary or congenital arachnoid cysts. Others may develop later in life following conditions such as head or spinal injury, infection, inflammation, or surgery. Most arachnoid cysts are benign (non-cancerous) and do not cause symptoms. They are sometimes discovered accidentally during a CT scan or MRI performed for another reason. Treatment may not be necessary when a cyst is small, stable, and not causing pressure or neurological problems. However, a larger cyst or one located in a sensitive area may press against the brain, spinal cord, or surrounding structures. In such cases, it can cause neurological symptoms and may require evaluation and treatment by a neurologist or neurosurgeon.
Arachnoid cysts can broadly be classified according to their location:
These cysts occur inside the skull and are the more commonly recognized type. They may develop in different areas around the brain. Symptoms depend largely on the cyst’s size and location.
These cysts develop around the spinal cord and may compress the spinal cord or nearby nerves. They can cause back pain, weakness, abnormal sensations, difficulty walking, or bladder and bowel problems.
Many people with arachnoid cysts have no symptoms at all. When symptoms occur, they usually result from pressure on the brain, spinal cord, or nearby nerves. Possible symptoms include:
- Headache
- Dizziness
- Nausea and vomiting
- Seizures
- Balance or coordination problems
- Vision problems
- Lethargy or unusual tiredness
- Developmental delay in children
- Muscle weakness
- Muscle spasms
- Tingling or abnormal sensations in the arms or legs
- Back pain, particularly with spinal arachnoid cysts
- Loss of bladder control or other bladder problems
- Difficulty walking or changes in movement
- Problems with hearing in some cases
- Changes in behavior, concentration, or cognitive function in certain patients
- Early onset of puberty in some children when a cyst affects areas involved in hormonal regulation
The symptoms vary considerably depending on the size, location, and pressure caused by the cyst. The presence of an arachnoid cyst on an imaging scan does not necessarily mean that the cyst is responsible for a person’s symptoms.
Arachnoid cysts can occur in children and may be detected during evaluation for developmental or neurological problems. Some children have no symptoms and require only observation. When a cyst affects brain development or causes pressure on surrounding structures, a child may experience:
- Developmental delay
- Headaches
- Seizures
- Nausea or vomiting
- Balance problems
- Vision changes
- Weakness or abnormal movement
- Changes in behavior or school performance
- Enlargement of the head in some infants
- Early puberty when certain brain regions are affected
Children with suspected or known arachnoid cysts should be evaluated by an appropriate pediatric specialist, particularly if neurological symptoms are present.
The exact cause of many arachnoid cysts is not known.
Most arachnoid cysts are believed to develop during fetal development. These are known as primary or congenital arachnoid cysts. They are generally not caused by anything a parent did during pregnancy. Some may be associated with developmental abnormalities of the membranes surrounding the brain or spinal cord.
Less commonly, an arachnoid cyst may develop later in life. Possible causes include:
- Head injury
- Spinal cord injury
- Meningitis or other infections involving the central nervous system
- Inflammation
- Complications associated with brain or spinal surgery
- Certain tumors or other conditions affecting the coverings of the brain or spinal cord
The cause cannot always be identified in an individual patient.
There are no well-established lifestyle-related risk factors for most arachnoid cysts because many are congenital. Certain conditions may be associated with secondary arachnoid cyst formation, including:
- Previous head or spinal injury
- Previous surgery involving the brain or spinal cord
- Meningitis or other central nervous system infections
- Certain developmental or genetic conditions
Having an arachnoid cyst does not mean that a person has cancer.
Most arachnoid cysts remain stable and cause no complications. In some cases, however, a cyst can become large enough to exert pressure on nearby structures. Possible complications include:
- Increased pressure inside the skull
- Hydrocephalus (abnormal accumulation of cerebrospinal fluid)
- Seizures
- Neurological weakness or sensory changes
- Problems with balance or walking
- Vision or hearing problems
- Developmental problems in children
- Spinal cord or nerve compression
- Bladder or bowel dysfunction in some spinal cysts
Rarely, an arachnoid cyst can rupture or bleed, particularly after significant head trauma. Sudden or severe neurological symptoms after an injury require urgent medical assessment.
Arachnoid cysts are usually diagnosed using brain or spinal imaging.
Magnetic resonance imaging (MRI) provides detailed images of the brain, spinal cord, and surrounding structures. It can help doctors determine the cyst’s size, location, and relationship to nearby tissues.
A computed tomography (CT) scan may also detect an arachnoid cyst. CT is particularly useful in emergency situations or when MRI is not immediately available.
A doctor may perform a neurological examination to evaluate:
- Muscle strength
- Reflexes
- Coordination
- Balance
- Sensation
- Vision
- Hearing
- Mental and cognitive function
In children, doctors may also assess growth and developmental milestones.
Treatment depends on several factors, including:
- The size of the cyst
- Its location
- Whether it is growing
- Whether it is causing pressure on surrounding structures
- The patient’s symptoms
- The patient’s age and overall health
Many arachnoid cysts do not require treatment. If a cyst is small, stable, and not producing symptoms, a doctor may recommend observation and periodic imaging. Follow-up MRI or CT scans may be used to determine whether the cyst changes over time.
Surgery may be considered when an arachnoid cyst causes significant symptoms, produces pressure on the brain or spinal cord, obstructs normal CSF circulation, or is associated with complications. Common surgical approaches include:
- Endoscopic fenestration: A surgeon creates an opening in the cyst so that its fluid can drain into a normal CSF pathway.
- Microsurgical fenestration: The surgeon creates one or more openings in the cyst using a surgical approach that allows the cyst contents to communicate with surrounding CSF spaces.
- Cyst shunting: In selected cases, a shunt may be placed to drain fluid from the cyst to another part of the body where it can be absorbed.
The most appropriate procedure depends on the location and characteristics of the cyst and the individual patient’s condition.
Most congenital arachnoid cysts do not simply disappear. However, many remain stable for years and never cause symptoms. Some cysts may change in size, particularly during childhood, while others remain unchanged. Regular medical follow-up may therefore be recommended when a cyst has been identified.
A person should consult a doctor if they develop persistent or unexplained neurological symptoms such as:
- Recurrent or severe headaches
- Seizures
- Persistent dizziness or balance problems
- Vision changes
- Weakness or numbness
- Difficulty walking
- Persistent nausea or vomiting
- Developmental concerns in a child
- New bladder or bowel problems
If an arachnoid cyst has already been diagnosed, follow-up with a neurologist or neurosurgeon may be recommended depending on its location and symptoms.
Sudden severe headache, loss of consciousness, a new seizure, sudden weakness or numbness, significant confusion, repeated vomiting, or other sudden neurological changes require urgent medical evaluation, particularly following a head injury.
A person with an arachnoid cyst may need evaluation by a:
- Neurologist
- Neurosurgeon
- Pediatric neurologist or pediatric neurosurgeon for children, when appropriate
The specialist can determine whether the cyst is responsible for the symptoms and whether observation or treatment is appropriate.
No. An arachnoid cyst is generally a benign, fluid-filled sac and is not a brain tumor. However, its location and size can sometimes cause pressure on nearby brain structures.
Most arachnoid cysts are not dangerous and never cause symptoms. A cyst can become clinically important if it grows, causes pressure, blocks normal CSF circulation, or affects the brain, spinal cord, or nearby nerves.
Yes. Headaches can occur when an arachnoid cyst causes pressure or affects the normal circulation of cerebrospinal fluid. However, headaches are common and an arachnoid cyst found on an imaging scan may not necessarily be the cause.
Some intracranial arachnoid cysts can be associated with seizures, particularly when they affect or compress certain areas of the brain. A person experiencing seizures should be evaluated by a healthcare professional.
No. Many arachnoid cysts require no treatment. Surgery is generally considered when the cyst causes significant symptoms, pressure, obstruction of CSF flow, or other complications.
Some arachnoid cysts can enlarge, although many remain stable. Children may require follow-up imaging because cyst behavior can vary during growth.
A large or strategically located cyst may sometimes interfere with normal brain development or function and may be associated with developmental problems. However, an arachnoid cyst does not automatically cause developmental delay.
Yes. Depending on its location, a cyst can put pressure on structures involved in vision and may cause visual symptoms. New or worsening vision problems should be medically evaluated.
Yes. A spinal arachnoid cyst may compress the spinal cord or nerve structures and can cause back pain, weakness, abnormal sensations, walking difficulties, or bladder problems.
Rupture is uncommon, but it can occur. Bleeding or rupture, particularly following trauma, can produce sudden neurological symptoms and requires prompt medical assessment.
Yes. Many people with arachnoid cysts have no symptoms and live normal lives. The outlook depends mainly on the cyst’s location, size, symptoms, and whether it affects surrounding structures.
A neurologist can evaluate neurological symptoms and coordinate care. A neurosurgeon may be consulted when the cyst causes significant pressure or symptoms and surgical treatment needs to be considered.
Medical Disclaimer -The information provided on MyMediLand is intended for general educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. An arachnoid cyst may be harmless in one person but clinically significant in another, depending on its size, location, and effect on surrounding structures. Do not diagnose or treat yourself based solely on information found on this website. Always consult a qualified healthcare professional for appropriate evaluation and advice regarding symptoms, imaging findings, diagnosis, or treatment. If you experience sudden or severe neurological symptoms, seek immediate medical attention.
