Arachnoid Cyst

Arachnoid cysts are sac-like structures filled with cerebrospinal fluid (CSF) that develop between the brain or spinal cord and the arachnoid membrane, one of the layers surrounding the brain and spinal cord. These cysts are mostly congenital and are generally benign. However, in some cases, they can grow and put pressure on surrounding tissues, potentially causing various neurological problems. The symptoms of arachnoid cysts vary depending on the size, location, and the pressure they exert on adjacent structures. On this information page, you can learn more about arachnoid cysts in detail.

An arachnoid cyst is a benign sac filled with cerebrospinal fluid (CSF) that develops in the brain or spinal cord. It usually forms in one of the membranes surrounding the brain and spinal cord, called the arachnoid membrane. Most arachnoid cysts are present at birth (congenital) and do not cause any symptoms. However, in some cases, the cyst can grow and put pressure on the brain, leading to various neurological problems.

These cysts are classified based on their location. Here are the main types of arachnoid cysts:

• Cerebral Arachnoid Cysts (Brain Arachnoid Cysts): Located between the brain hemispheres or on the surface of the brain. This is the most common type.
• Posterior Fossa Arachnoid Cysts: Located behind the cerebellum, in the lower and back part of the brain.
• Suprasellar Arachnoid Cysts: Located at the base of the brain, above the pituitary gland. These cysts may cause hormonal disorders.
• Spinal Arachnoid Cysts (Spinal Cord Arachnoid Cysts): Found within the membranes surrounding the spinal cord.

Suprasellar arachnoid cysts are arachnoid cysts located at the base of the brain, positioned above the pituitary gland (a small gland that controls the secretion of many hormones in the body) and the optic chiasm (the point where the optic nerves cross). The arachnoid membranes are thin layers surrounding the brain and spinal cord, and cerebrospinal fluid (CSF) is found between these membranes.

The characteristics of these cysts are as follows:

• Location: Due to their proximity to critical structures in this region of the brain (such as the hypothalamus, optic pathways, pituitary gland, etc.), they have a higher potential to cause symptoms compared to other types of arachnoid cysts.
• Effects: As the cysts grow, they can exert pressure on these important structures, potentially leading to various hormonal, visual, and neurological problems.

Posterior fossa arachnoid cysts are cerebrospinal fluid (CSF)-filled sacs that develop in the thin membrane called the arachnoid membrane, located behind the cerebellum, in the lower and back part of the brain. The posterior fossa houses the brain structures located in this region of the skull. These cysts are typically benign, similar to arachnoid cysts found in other brain regions.

Important Facts About Posterior Fossa Arachnoid Cysts:

• Tendency to Be Congenital: Posterior fossa arachnoid cysts are generally present at birth. These cysts form during fetal development due to abnormal formation of the arachnoid membranes.
• Prevalence: Posterior fossa arachnoid cysts account for approximately 20-30% of intracranial arachnoid cysts (arachnoid cysts within the brain).
  Most Common Locations: The most frequently observed areas in the posterior fossa include the cerebellopontine angle and the vermis (the midline of the cerebellum).

Cerebral arachnoid cysts (brain arachnoid cysts) are cerebrospinal fluid (CSF)-filled sacs that develop in the arachnoid membrane, one of the layers surrounding the brain and spinal cord. These cysts can occur in different parts of the brain and are among the most common types of brain cysts.

Cerebral arachnoid cysts can be located in various regions of the brain, but they are most commonly found in the following areas:

• Middle fossa: The area where the temporal lobe of the brain is located.
• Cerebellar regions: Around the cerebellum.
• Suprasellar region: Above the pituitary gland.
• On the surface of the brain: Outside the cerebral hemispheres.

Spinal arachnoid cysts are fluid-filled sacs that develop within the arachnoid membrane, one of the three protective layers surrounding the spinal cord and its structures. These cysts can occur at any level within or around the spinal cord.

Important facts about spinal arachnoid cysts:

• The arachnoid membrane is the middle layer of the three membranes covering the brain and spinal cord. It has a thin and transparent structure.
• Spinal arachnoid cysts form when a sac develops between the layers of the arachnoid membrane and fills with cerebrospinal fluid (CSF).
• They are generally benign (non-cancerous) and, in most cases, grow slowly.

The causes of arachnoid cysts can be classified into two main categories: primary (congenital) and secondary (acquired).

Developmental Anomalies: The vast majority of these cysts are congenital. They form as a result of abnormalities in the development of the arachnoid membranes—thin, membrane-like structures surrounding the brain and spinal cord—during fetal development. These abnormalities may include:

• Problems in the folding or separation of the arachnoid membrane.
• Separation or adhesion between the layers of the arachnoid membrane.
• Disorders in the circulation of cerebrospinal fluid (CSF).

Genetic Predisposition: Some studies suggest that genetic factors may play a role in the formation of certain arachnoid cysts. However, this genetic link is not yet fully understood.

Completely Unknown Causes: In some cases, the causes of congenital arachnoid cysts cannot be fully explained.

• Head Trauma: Head traumas, especially severe impacts, falls, or traffic accidents, can cause tears or damage to the arachnoid membrane. This damage may lead to fluid accumulation between the membranes and the formation of a cyst.
• Infections: Infections affecting the central nervous system, such as meningitis, can cause inflammation in the arachnoid membrane and trigger cyst formation.
• Surgical Procedures: Rarely, arachnoid cysts may develop after brain surgeries or other surgical interventions.
• Other Rare Causes: Tumors or hemorrhages may also very rarely lead to the formation of arachnoid cysts.

The symptoms of arachnoid cysts vary depending on their location, size, and whether they exert pressure on surrounding tissues. In some individuals, arachnoid cysts cause no symptoms and are often incidentally discovered during brain or spinal imaging performed for other reasons. These types of cysts are called "asymptomatic."

However, if the cyst grows or presses on sensitive brain structures, various symptoms may arise.

The most common symptoms of arachnoid cysts include:

• Headache: Headaches that can be severe, especially in the mornings, and worsen over time.
• Dizziness and Balance Problems: Loss of balance, dizziness, and coordination disorders.
• Nausea and Vomiting: Especially in cysts located in the brainstem or cerebellum regions.
• Chronic Fatigue: Persistent weakness and feeling of tiredness.

• Seizures: Cysts located especially in the temporal lobe or cerebral hemispheres can cause epilepsy.
• Visual Disturbances: Double vision, blurred vision, and visual field loss (especially with cysts near the pituitary gland).
• Hearing Problems: Hearing loss or tinnitus (ringing in the ears).
• Hormonal Disorders: Cysts near the pituitary gland can cause hormonal imbalances (e.g., precocious puberty, growth hormone issues).
• Cognitive Dysfunction: Difficulty concentrating, memory problems.
• Behavioral or Psychological Changes: Mood swings, personality changes.
• Enlarged Head in Infants (Hydrocephalus): If the cyst obstructs cerebrospinal fluid flow.

• Back and Lower Back Pain: Pain localized to the area where the cyst is located.
• Weakness in Legs and Arms: Muscle weakness and involuntary movements.
• Numbness and Tingling: Numbness and tingling sensations in the legs and arms.
• Bladder and Bowel Problems: Issues with urine or stool control (rare).

Important Warnings:

Many of these symptoms can also indicate other health problems. Therefore, it is important to consult a doctor for accurate diagnosis and treatment.
Since most arachnoid cysts are asymptomatic, especially if you have these symptoms and your doctor has diagnosed a cyst, it is crucial to work closely with your doctor to determine whether your symptoms are related to the cyst.

Arachnoid cysts are fluid-filled sacs that form in the arachnoid membranes surrounding the brain and spinal cord. Most of the time, they cause no symptoms and are found incidentally. However, when they grow or are located in certain areas, they can lead to various complications.

Potential complications of arachnoid cysts:

A. Hydrocephalus (Fluid Accumulation in the Brain):
Arachnoid cysts can block the normal flow of cerebrospinal fluid (CSF). This can cause CSF to accumulate in the brain, leading to hydrocephalus. Hydrocephalus may increase intracranial pressure and cause serious neurological damage.

B. Increased Intracranial Pressure:
A growing cyst can press on brain tissue, increasing intracranial pressure. Elevated intracranial pressure can result in severe headaches, vomiting, visual disturbances, loss of consciousness, and in extreme cases, death.

C. Neurological Disorders:
Pressure from arachnoid cysts can impair the function of specific brain or spinal cord regions, causing various neurological symptoms:

• Seizures: Especially cysts near the cerebral cortex can cause seizures.
• Movement Disorders: Coordination problems, imbalance, or muscle weakness.
• Sensory Loss: Numbness or tingling sensations.
• Visual or Auditory Impairments: Double vision, blurred vision, hearing loss.
• Paralysis: Spinal cord cysts may compress the spinal cord, causing paralysis.
• Speech Disorders.

D. Developmental Delays (in Children):
In children, arachnoid cysts can affect brain development and lead to developmental delays.

E. Cyst Rupture and Bleeding:
In rare cases, arachnoid cysts can rupture spontaneously or due to trauma. This can cause bleeding in or around the brain and requires urgent medical intervention.

The diagnosis of arachnoid cysts is generally made through a combination of neurological evaluation and imaging techniques.

Key steps in diagnosing an arachnoid cyst:

A. Neurological Examination:

• The doctor thoroughly reviews the patient’s symptoms and medical history, specifically asking about potential arachnoid cyst symptoms such as headaches, dizziness, seizures, vision or hearing problems.
• During the neurological exam, the patient’s reflexes, muscle strength, sensory functions, balance, and coordination are tested. This exam can provide clues about which part of the brain or spinal cord the cyst might be affecting.

B. Imaging Methods:
Imaging is the most important tool for diagnosing arachnoid cysts.

• Magnetic Resonance Imaging (MRI): MRI is considered the gold standard for diagnosing arachnoid cysts. It provides highly detailed images of the brain and spinal cord soft tissues, clearly showing the cyst’s size, location, contents, and effects on surrounding tissues. MRI is especially effective at differentiating arachnoid cysts from other fluid-filled structures (e.g., epidermoid cysts).
• Computed Tomography (CT): CT scans can also be used to detect and locate arachnoid cysts. However, CT is not as good as MRI at showing soft tissues. CT is preferred when a better evaluation of the cyst’s relationship to bone structures is needed or in emergency situations (e.g., after trauma).

C. Diagnostic Process:

• Incidental Discovery: Most arachnoid cysts are found incidentally during brain or spinal cord imaging performed for other reasons. If the patient has no symptoms, periodic monitoring of the cyst may be sufficient.
• Presence of Symptoms: In symptomatic patients, the doctor carefully evaluates imaging results and neurological exam findings to determine whether the symptoms are related to the cyst.

and overall health condition. Most arachnoid cysts are asymptomatic and are detected incidentally; in such cases, treatment is generally not required, only regular monitoring is recommended.

A. Treatment for Asymptomatic Arachnoid Cysts:
Observation and Monitoring: For cysts that do not cause symptoms and show no tendency to grow, regular MRI or CT scans are performed at intervals. The size of the cyst and its relation to surrounding tissues are monitored.

B. Treatment for Symptomatic Arachnoid Cysts:
If the cyst causes severe headaches, seizures, vision or hearing problems, balance issues, motor/sensory loss, or increased intracranial pressure (hydrocephalus), treatment may be necessary.

Treatment Options:

• Surgical Intervention:
  • Cyst Fenestration: Small holes are made in the cyst wall to allow the fluid inside to communicate with cerebrospinal fluid circulation. This can be done endoscopically (through the nose with a camera) or via craniotomy (opening the skull).
  • Cyst Excision: Surgical removal of the entire cyst, but rarely preferred due to risk of damage to brain tissue.
  • Shunt Placement: A thin tube is placed to divert the cyst fluid to another body cavity (usually the abdominal cavity); especially used in the treatment of hydrocephalus.
• Medication:
  The arachnoid cyst itself is not treated with medication; however, antiepileptic or pain-relief drugs may be prescribed to control symptoms like seizures or headaches.

In summary, monitoring is sufficient if there are no symptoms; if symptoms exist, surgical methods and symptomatic medication can be applied. Treatment decisions must be made by a neurology or neurosurgery specialist.

At A Life Health Group, we provide services to our patients using the most advanced technology and a multidisciplinary approach in the diagnosis and treatment of arachnoid cysts. We prepare personalized treatment plans according to the size, location, and symptoms of the arachnoid cysts and ensure the most appropriate intervention with our experienced neurosurgery team.

• Detailed Diagnostic Process:
  • The size, location, and relation of the cyst to surrounding tissues are thoroughly evaluated with Computed Tomography (CT) and Magnetic Resonance Imaging (MRI).
• Personalized Treatment Approach:
  • The most effective treatment method is determined and applied according to our patients' symptoms and cyst characteristics.
  • Continuous monitoring is performed, and the treatment plan is updated when necessary.
• Surgical Treatment Options:
  • Cyst Fenestration: Opening the cyst content into the cerebrospinal fluid circulation to reduce pressure.
  • Cyst Excision: Complete removal of the cyst, applied when possible.
  • Shunt Application: Placement of a shunt to transfer the cyst fluid to another part of the body.

At A Life Health Group, we aim for the best results with the expertise and technological infrastructure we provide in arachnoid cyst treatment. For detailed information and appointments, you can contact us.