Perineural cysts, also known as Tarlov cysts, are fluid-filled sacs that form along nerve roots, most commonly in the lower spine. These cysts are relatively common, affecting an estimated 5 to 9 percent of the population, and are typically benign. While many individuals have these cysts without knowing, a small percentage may experience symptoms.
What Perineural Cysts Are
Perineural cysts are fluid-filled sacs that develop on spinal nerve roots, most frequently in the sacral region at the base of the spine. They contain cerebrospinal fluid (CSF), the clear fluid surrounding the brain and spinal cord. A distinguishing feature is the presence of spinal nerve root fibers within their walls or cavity, classifying them as type II spinal meningeal cysts. While they can occur anywhere along the spine, the sacral area is the most common location.
Cysts form as dilations of the nerve root sheath within the perineural space. They can vary in size, with some remaining small and others growing larger over time. Most perineural cysts are asymptomatic and are often discovered incidentally during imaging scans for other medical reasons.
When Perineural Cysts Become Symptomatic
Perineural cysts can cause issues if they enlarge and compress surrounding nerve roots. This compression leads to symptoms, with pain being the most frequently reported. Pain often manifests as radicular pain, similar to sciatica, radiating down the legs, buttocks, or lower back. Other potential symptoms include numbness, tingling, or weakness in the legs.
Larger cysts may cause changes in bowel or bladder function, such as incontinence or constipation. Sexual dysfunction can also occur. These symptoms can fluctuate, sometimes flaring up and then subsiding. Only a small percentage, estimated between 1% and 8%, of people with perineural cysts experience symptoms. Untreated, symptomatic cysts can rarely lead to permanent nerve damage.
How Perineural Cysts Are Identified
Perineural cysts are often discovered incidentally during imaging tests for other health concerns. Magnetic Resonance Imaging (MRI) is the primary diagnostic tool for visualizing these fluid-filled structures, providing detailed images of the cyst’s size, location, and relationship to nearby nerve roots.
A Computed Tomography (CT) myelography may also be recommended. This involves injecting a contrast dye into the spinal canal to determine if there is a communication between the cyst and the subarachnoid space. A medical professional considers a patient’s reported symptoms and conducts a neurological evaluation with imaging findings to confirm a diagnosis.
Addressing Symptomatic Perineural Cysts
Treatment for perineural cysts is considered when they cause significant symptoms. For mild discomfort, conservative approaches are the first line of management. These include pain management, physical therapy, and medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) or oral steroids to reduce inflammation and pain.
If conservative methods do not provide sufficient relief, or if symptoms are severe, other interventions are explored. Temporary relief can be achieved through cyst aspiration, where fluid is drained from the cyst, though refilling is common. Definitive treatments for persistent symptoms may involve surgical procedures like microsurgical cyst fenestration, which creates an opening in the cyst wall to reduce nerve pressure. Other surgical options include cyst excision or shunting procedures. Surgical intervention is typically reserved for cases with significant neurological problems, such as severe pain or bladder and bowel dysfunction.
Outlook for Perineural Cysts
For the vast majority of individuals, perineural cysts remain asymptomatic throughout their lives and do not require intervention. Many people will never even be aware they have them. For the small percentage who experience symptoms, appropriate management can lead to relief.
While symptomatic cases can be challenging, perineural cysts are not considered life-threatening. The outlook for those with symptoms improves with tailored treatment strategies, ranging from conservative care to surgical options. Even with intervention, some patients may experience residual symptoms, but the aim is to enhance comfort and function.