A meningeal cyst is a fluid-filled sac that forms within the meninges, the three layers of protective tissue that surround the brain and spinal cord. The fluid contained inside these sacs is most often cerebrospinal fluid (CSF), the clear liquid that cushions the central nervous system. These cysts are nearly always benign, meaning they are not cancerous and do not spread to other parts of the body. Many individuals with meningeal cysts are unaware they have them, as they frequently do not produce any symptoms.
Types and Causes of Meningeal Cysts
Meningeal cysts are categorized based on their origin. Primary cysts are congenital, meaning they are present at birth due to abnormalities that occur as the brain and spinal cord develop. Secondary cysts are acquired later in life and can form as a result of head or spinal trauma, surgical procedures, inflammation, or infections that affect the meningeal layers.
Among the specific types, arachnoid cysts are the most common. These cysts form between the brain or spinal cord and the arachnoid membrane, one of the three meningeal layers. Another prevalent type is the Tarlov cyst, also known as a perineural cyst, which develops along the roots of spinal nerves and is most frequently found in the sacral region of the lower back.
Symptoms Based on Cyst Location
When symptoms do arise, their nature is entirely dependent on the cyst’s size and its precise location within the nervous system. A cyst that remains small and does not press on adjacent structures may never cause a problem. A larger cyst, however, can interfere with normal neurological function.
Cysts located along the spinal column, such as Tarlov cysts, can cause symptoms by compressing the spinal cord or nerve roots. This pressure may lead to localized pain in the back, or radiating pain that travels down the leg, a condition known as sciatica. Individuals might also experience numbness, tingling, or weakness in their legs. In more significant cases, compression in the lower spine can affect nerve control over the bladder or bowels.
When a cyst develops within the skull, it is referred to as a cranial or intracranial cyst. The symptoms are related to increased pressure on brain tissue. Common manifestations include persistent headaches, dizziness, and nausea. Depending on the affected brain region, some people may experience seizures, disturbances in vision or hearing, or difficulties with balance and coordination. In children, a cranial cyst can sometimes contribute to developmental delays if it impacts brain function.
Diagnosis and Monitoring
The primary tool for diagnosing a meningeal cyst is Magnetic Resonance Imaging (MRI). An MRI provides detailed images of soft tissues, allowing medical professionals to clearly visualize the cyst, its size, and its relationship to surrounding neural structures. In some instances, a Computed Tomography (CT) scan may also be utilized to offer additional perspectives on the cyst and adjacent bony anatomy.
Many meningeal cysts are “incidental findings,” discovered unintentionally while a patient is undergoing an MRI or CT scan for another reason. Because most of these cysts do not cause symptoms, the standard approach is often “watchful waiting.” This involves monitoring the cyst with periodic imaging scans to check for any changes in size or shape over time. This conservative strategy avoids unnecessary intervention unless the cyst begins to grow or cause problems.
Available Treatment Options
For cysts that do not cause symptoms, treatment is not required. When a cyst becomes symptomatic, the initial focus is on managing the discomfort through conservative methods. This can include pain relief medications or specialized physical therapy programs designed to alleviate pressure and strengthen surrounding muscles.
If symptoms are more severe or persistent, a procedure known as needle aspiration may be considered. This involves using a needle to drain the cerebrospinal fluid from the cyst, which can temporarily relieve the pressure on nearby nerves or brain tissue. However, the relief from aspiration is often short-lived, as the cyst can gradually refill with fluid over time.
Surgical intervention is reserved for cases where symptoms are significant and can be directly attributed to the cyst. One common surgical technique is fenestration, where a surgeon creates an opening in the cyst wall, allowing the fluid to drain into the surrounding CSF space and preventing it from accumulating again. In other cases, complete surgical removal of the cyst, known as excision, may be performed to resolve the issue permanently.