Tarlov cysts are fluid-filled sacs that develop along the nerve roots of the spine, often discovered incidentally on spinal imaging. While most cysts remain asymptomatic, a smaller subset can expand and place pressure on nearby nerves, leading to debilitating pain and neurological symptoms. Understanding the anatomy and available treatments is a necessary first step. The management approach is highly individualized, progressing from observation to complex microsurgery based on the severity of the presentation.
Anatomical Definition and Causes
A Tarlov cyst, also known as a perineural cyst, is a thin-walled sac most frequently located in the sacral region of the spine, specifically around the S1 to S5 nerve roots. These cysts are filled with cerebrospinal fluid (CSF), the clear fluid that surrounds the brain and spinal cord. A defining characteristic is the presence of spinal nerve root fibers embedded within the cyst wall or cavity, differentiating it from other spinal cysts.
The exact reason these cysts form remains unclear, but several theories exist. One mechanism involves a one-way valve effect: CSF enters the nerve root sheath but becomes trapped, causing the sac to inflate. This accumulation can be triggered by trauma or injury to the spine, which may increase the pressure of the CSF and lead to cyst enlargement. Other proposed factors include congenital predisposition or inflammation within the protective sheath surrounding the nerve root.
Clinical Presentation
Most Tarlov cysts are small and remain completely asymptomatic, often discovered incidentally during imaging for an unrelated condition. Only about 5% to 20% of affected individuals will experience symptoms, which arise when the cyst grows large enough to compress the adjacent sacral nerve roots or erode the surrounding bone. This nerve compression can lead to chronic, localized pain in the sacral or coccygeal area.
Patients frequently report radicular pain, often described as sciatica, which is a shocking or burning sensation that travels down the buttocks and legs. As the compression worsens, it can cause sensory changes like numbness, tingling (paresthesia), or weakness in the lower extremities. In more severe cases, large cysts can exert pressure on the entire bundle of nerves at the base of the spine, leading to significant neurological deficits such as bowel or bladder dysfunction.
Identifying Tarlov Cysts
The diagnostic process begins with a detailed patient history and a thorough neurological examination to assess the distribution of pain, muscle strength, and sensory changes. Since the symptoms can mimic other conditions, such as a herniated lumbar disc, imaging is necessary to confirm the presence of the cyst and rule out other spinal pathology. Magnetic Resonance Imaging (MRI) is the most effective tool for visualization.
An MRI provides clear, detailed images that show the fluid-filled cyst as a bright signal on T2-weighted sequences, matching the signal of CSF. This allows physicians to determine the cyst’s exact size, location, and its relationship to the nerve roots and the surrounding bone. In certain situations, a CT myelography may also be used, which involves injecting a contrast dye into the spinal canal. This technique helps confirm if the cyst is communicating with the subarachnoid space, which is useful when planning a surgical approach.
Management and Treatment Options
Treatment for Tarlov cysts is determined by the presence and severity of symptoms; asymptomatic cysts typically require only observation. For patients with mild or intermittent pain, the first step involves conservative management to alleviate discomfort. This approach includes pain medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) or medications targeting neuropathic pain, along with physical therapy to improve function and manage symptoms.
Minimally Invasive Procedures
When conservative methods fail to provide lasting relief, minimally invasive procedures may be considered to reduce the cyst’s size and pressure. One technique is CT-guided aspiration, where a needle is used to drain the CSF from the cyst. However, aspiration alone frequently results in a high rate of recurrence, as the cyst often refills with fluid shortly after being drained.
A more advanced minimally invasive technique combines aspiration with the injection of a fibrin glue sealant. After the CSF is removed, the fibrin glue is injected to seal the opening, preventing the cyst from refilling and offering a more durable solution. This procedure is also valuable as a diagnostic tool; if the patient experiences temporary relief after the cyst is drained, it strongly supports the cyst as the source of their pain.
Surgical Intervention
Surgical intervention is reserved for patients suffering from severe, debilitating pain, progressive neurological deficits, or significant bowel and bladder dysfunction. The primary goal of surgery is to decompress the compressed nerve root and permanently seal the cyst to prevent refilling. This is often performed as a microsurgical procedure, which allows the surgeon to work with high magnification and precision.
Common surgical techniques include cyst fenestration, where a small window is created in the cyst wall to drain the fluid, followed by imbrication, which involves folding and suturing the redundant cyst wall tissue. Crucially, the surgeon must identify and carefully repair the dural defect where the CSF enters the cyst, often using a patch or fibrin glue to reinforce the area. While surgery offers the possibility of long-term relief for many patients, it carries risks, with a postoperative CSF leak being the most common complication.