Arachnoid Cyst
Arachnoid cysts are fluid-filled sacs that form between the layers of the arachnoid membrane, which surrounds the brain and spinal cord. They are most commonly found in the temporal lobe of the brain but can also occur in the third ventricle, suprasellar region, cerebellum, and brainstem areas.
Causes of Arachnoid Cysts
The exact cause of arachnoid cysts is not well understood, but possible reasons include:
- Congenital Factors: Some arachnoid cysts are present from birth and may result from developmental issues.
- Head and Spinal Cord Injuries: Arachnoid cysts can rarely form as a result of head or spinal cord trauma.
- Infections: Bacterial or fungal infections can lead to the development of arachnoid cysts.
- Tumors: Some brain or spinal cord tumors can cause arachnoid cysts. These cysts are usually benign and asymptomatic but can sometimes cause symptoms if they grow or exert pressure.
Symptoms of Arachnoid Cysts
- Headache: The cyst can affect the normal circulation of cerebrospinal fluid (CSF), leading to headaches. These headaches can intensify as the cyst grows or exerts pressure.
- Neurological Symptoms: When arachnoid cysts start pressing on surrounding nerve or brain tissue, neurological symptoms can occur, such as:
- Balance issues
- Difficulty walking
- Numbness in arms or legs
- Weakness or muscle atrophy
- Dizziness
- Coordination problems
- Vision Problems: Arachnoid cysts can press on the optic nerve or eye structures, leading to narrowed visual fields, double vision, or blurred vision.
- Urinary Dysfunction: Although rare, arachnoid cysts can cause urinary problems like incontinence or frequent urination.
The symptoms of arachnoid cysts depend on the cyst’s size, location, and the body’s response to it. Symptoms can become more noticeable as the cyst grows or exerts pressure.
Diagnosis
Many people with arachnoid cysts do not experience symptoms. For symptomatic cases, headaches or seizures might be present. Diagnosis is typically made through magnetic resonance imaging (MRI) or computed tomography (CT) scans. Sometimes, the cysts can block the pathways of cerebrospinal fluid (CSF), leading to hydrocephalus (an accumulation of CSF in the brain).
Treatment
Small, asymptomatic cysts may not require treatment. However, cysts that cause symptoms or show a tendency to grow might need surgical intervention. Surgery can involve removing or draining the cyst. Surgical options include open craniotomy and fenestration with ventriculoperitoneal shunt placement. In open craniotomy and fenestration, the skull bones are opened to access the cyst, and an opening is made in the cyst wall to allow the cyst’s CSF to drain into the subarachnoid space, where it can be absorbed like normal CSF. If there are cysts around the spinal cord, they are usually completely removed. This often resolves most symptoms. In cases where complete removal is not possible, the cyst may be connected to the subarachnoid space, or its contents may be drained using a shunt. Medications can be used to control headaches or other symptoms.
Frequently Asked Questions
Arachnoid cysts are fluid-filled sacs that form between the layers of the arachnoid membrane, which surrounds the brain and spinal cord. They are most commonly found in the temporal lobe of the brain but can also occur in the third ventricle, suprasellar region, cerebellum, and brainstem.
The exact cause of arachnoid cysts is not known, but possible causes may include:
Congenital Factors: Some arachnoid cysts are present from birth and may result from a developmental issue.
Head and Spinal Cord Trauma: Arachnoid cysts can rarely form as a result of head or spinal cord injuries.
Infections: Bacterial or fungal infections can lead to the development of arachnoid cysts.
Tumors: Certain brain or spinal cord tumors can cause arachnoid cysts. These cysts are usually benign and asymptomatic but can sometimes cause symptoms.
Symptoms of Arachnoid Cysts
Headache: Arachnoid cysts can disrupt the normal flow of cerebrospinal fluid (CSF), leading to headaches that may worsen as the cyst grows or exerts pressure.
Neurological Symptoms: When arachnoid cysts press on nearby nerve tissue or brain tissue, they can cause neurological symptoms such as:
Balance problems
Difficulty walking
Numbness in the arms or legs
Weakness or muscle weakness
Dizziness
Coordination issues
Vision Problems: Arachnoid cysts can press on the optic nerve or eye structures, causing issues such as narrowing of the visual field, double vision, or blurry vision.
Urinary Dysfunction: Though rare, arachnoid cysts can lead to urinary problems, including incontinence or frequent urination.
The symptoms of arachnoid cysts can vary depending on the size, location, and the body’s response to the cyst. Symptoms become more pronounced as the cyst grows or starts to exert pressure.
Diagnosis and Treatment
Diagnosis: Arachnoid cysts are often asymptomatic. In symptomatic cases, headaches or seizures might occur. Diagnosis is typically made through magnetic resonance imaging (MRI) or computed tomography (CT) scans. Sometimes, the cysts can block the circulation pathways of cerebrospinal fluid (CSF), leading to hydrocephalus, an accumulation of excess CSF in the brain.
Treatment: Small, asymptomatic cysts may not require treatment. However, cysts that cause symptoms or show growth may need surgical intervention. Surgery options include cyst removal or drainage. Open craniotomy and fenestration or ventriculoperitoneal shunting are common surgical methods. In open craniotomy and fenestration, the skull is opened to access the cyst, and an opening is made in the cyst wall to allow CSF to drain into the subarachnoid space, where it can be absorbed normally. If cysts are present around the spinal cord, they are usually completely removed to alleviate symptoms. In cases where complete removal is not possible, the cyst is connected to the subarachnoid space, or its contents are drained via a shunt. Medications may be used to control headaches or other symptoms.
