Treatment of Tarlov Cyst

POLICY NUMBER

A.7.01.76

DESCRIPTION

Tarlov cysts (TC; perineural cyst, sacral perineural cyst, sacral meningeal cyst) are characterized as cerebrospinal fluid (CSF)-filled sacs that typically occur between the perineurium (the protective sheath that surrounds a bundle of nerve fibers) and endoneurium (a layer of connective tissue around the myelin sheath of a peripheral nerve), arising near the dorsal root ganglion but can be located anywhere along the spine and affect the nerve roots. TC are often asymptomatic; however, these cysts can present as chronic back pain in the sacral or coccyx area and individuals may have radiculopathy, leg weakness, bowel or bladder dysfunction, and/or sexual dysfunction. There is no specific, accepted therapy for individuals with symptomatic TC. Treatment is directed toward the specific symptoms and may include medication, surgery, or other techniques.

Tarlov Cysts

First identified in 1938, Tarlov cysts (TC) are fluid-filled sacs between the perineurium (the protective sheath that surrounds a bundle of nerve fibers) and endoneurium (a layer of connective tissue around the myelin sheath of a peripheral nerve), arising near the dorsal root ganglion, and affecting the nerve roots of the spine. While commonly found in the sacral region, they can occur anywhere along the spine. They may also be known as sacral perineural cysts, perineural cysts, or sacral, lumbar, thoracic, or cervical nerve root cysts. TC are an uncommon spinal column disease that has been associated with a wide range of debilitating pain, neurological disturbances, and dysfunctions with the condition being often overlooked or ignored as incidental findings of no clinical significance, particularly in the presence of other comorbid spinal pathologies. TC may be valved or non-valved and can be distinguished from other spinal lesions by the presence of spinal nerve root fibers within the cyst wall or in the cyst cavity itself. The exact cause of TC is unknown, but it is thought they are caused by inflammatory processes within the nerve root sheath or that trauma injures the nerve root sheath, causing leakage of cerebrospinal fluid (CSF) into the area where a cyst forms. Some researchers believe that an abnormal congenital connection (communication) exists between the subarachnoid space, which contains CSF, and the area surrounding the affected nerves (perineural region). The connection may remain or eventually close, after allowing cerebrospinal fluid to leak out and cause a cyst. As TC contain CSF, researchers have speculated that normal fluctuations in CSF pressure may lead to an increase in cyst size and a greater likelihood of developing symptoms. TC appear to be rare with women being at a higher risk of developing TC than men (7.01% vs. 4.05%). An estimated 4.27% of the global population has TC, while in the United States, it is estimated to be 3.82% of the population. Mostly asymptomatic, these cysts can present as chronic back pain in the sacral or coccyx area and individuals may have radiculopathy, leg weakness, bowel or bladder dysfunction, or sexual dysfunction. Furthermore, TC may cause neuropathic pain and may damage sensory and autonomic innervation of the penis/clitoris (via the dorsal nerve) and surrounding erogenous structures. TC is the leading cause of underrecognized pelvic syndrome known as persistent genital arousal disorder (i.e., PGAD). Approximately 15.6% of the cysts are symptomatic. Of note, inadequate knowledge due to the rarity of these cysts and gender bias by treating physicians has contributed to a significant delay or lack of treatment for individuals with TC.

Diagnosis

TC may be diagnosed through a detailed clinical history with identification of characteristic symptoms and a neurological examination. Diagnosis may be confirmed with either magnetic resonance imaging (MRI) or computed tomography (CT). A myelogram may also be used, with the dye allowing structures such as the nerve roots and spinal canal to be more clearly seen on x-ray. However, MRI without contrast is the preferred choice for image quality and patient safety. A comprehensive imaging panel consisting of a dedicated lumbar and sacral MRI is ideal as they are more sensitive imaging modalities than CT scans or routine lumbosacral MRIs. Furthermore, the sacral MRI should be performed in both the axial and sagittal plane with an emphasis on the field of view, matrix, slice thickness, and positioning to anatomic localization. It is important to differentiate the neck of the TC as "narrow- or wide-necked" with a high flow of CSF, as communication with the subarachnoid space can increase risk with any interventions in the sacral area. More specifically, a wide-necked cyst or a large communication pore with the subarachnoid space is contraindicated for percutaneous fibrin sealant injections as there is an increased possibility of fibrin sealant migration into the subarachnoid space. TCs usually appear as low-intensity intraspinal masses on T1-weighted and high-intensity on T2-weighted images, like CSF. About 1.5% of MRIs performed for low-back-pain reveal TCs, but as with herniated discs, not all are symptomatic at the time of imaging with most radiologists determining that TCs are incidental and lack clinical significance, and omit mention of TCs in their reports, obscuring the diagnosis. If MRI is inconclusive or fails to define this connectivity, CT myelography with delayed imaging is occasionally used to capture CSF filling from the spinal sac indicating a wide connection to subarachnoid space. CT is helpful to evaluate any bone erosion by the cysts, and axial and sagittal CT can assist with bone remodeling and plan interventions.

Once a cyst is identified with imaging modalities, it is paramount to distinguish from other similar conditions, such as dural ectasia, meningeal diverticula, or lipoma of the filum terminale and establish that the symptoms arise from the immediate anatomic region of the cyst and that radicular signs and symptoms are in the appropriate distribution of cyst-bearing nerve roots, with accurate dermatomal charting to ensure appropriate clinical management. If symptoms are still deemed uncertain, it may be feasible to perform diagnostic assessments with local anesthetic blockades of the nerve root or by aspirating cyst fluid to identify whether and which TCs are causing debilitating pain or other symptoms. Urodynamic testing and anorectal manometry can provide objective evaluation of bladder and bowel function.

Treatment

There is no specific accepted therapy for individuals with symptomatic TC. Treatment is directed toward the specific symptoms and may include conservative medical approaches including analgesic, anti-inflammatory, or neuropathic medications and physical therapy; minimally invasive image-guided percutaneous interventions; and/or various open and microsurgical approaches. More invasive interventions may be considered for symptomatic TC that are refractory to conservative treatment strategies. Asymptomatic TCs require no treatment, but rather cyst locations should be recorded and individuals educated on mitigating the risks of symptom onset, including lifestyle modifications.

Conservative

For chronic pain associated with TC, non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to treat nerve irritation and inflammation and medication for neuropathic pain (e.g., tricyclics, gabapentinoids, sodium channel blockers) may also be useful. Systemic corticosteroids can have a short-term benefit, although local injections are not indicated and repeated use can further exacerbate the pathophysiology of the cyst by weaking the walls leading to safety concerns. In some cases, oral acetazolamide may be prescribed to control CSF-induced hydrostatic pressure from the cysts but remains theoretical as there is no way to routinely monitor CSF pressure within TCs. Limited observational studies have reported that conservative management with physical therapy, anti-inflammatory medications, and drugs directed at neuropathic pain, fail to improve symptoms in as many as 75% of symptomatic cases.

Percutaneous

Minimally invasive percutaneous approaches to treating TCs involve aspirating or draining the CSF assisted with imaging modalities, such as CT or fluoroscopy, and are typically accompanied by an injection of fibrin gel. This non-surgical procedure uses a combination of substances that mimic blood clotting (i.e, fibrin glue) and after the cyst is drained, fibrin glue is used to seal or glue the cyst closed preventing it from filling with CSF again, however, results vary, and, in most cases, the cyst will eventually fill with CSF again, with symptoms returning within hours. Several cohort studies have reported results on this percutaneous intervention with high rates of symptom improvement greater than 70% after aspiration-fibrin sealant injection, albeit with varying definitions of treatment success with follow-up MRIs depicting that the cysts had disappeared or were substantially smaller in size. The largest cohort study (N=213) to date for any intervention performed for these cysts included a 5- to 10-year long-term follow-up where individuals underwent percutaneous cyst aspiration and fibrin-sealant injection for symptomatic sacral TCs and reported overall treatment success in 81.8% of patients at 1 year and 74% at 3 to 6 years. Treatment failures ranged from 14% to 25% with minor adverse events such as nausea, vomiting, low-grade fevers, cutaneous allergic reactions, headaches, allergic reactions to fibrin sealant, transient sciatica, and CSF leaks. Recurrence is possible after fibrin sealant injection as the material can gradually break down over time allowing for cyst recurrence. In the aforementioned study, 36 individuals (~17%) experienced cyst recurrence.

Surgical

Large cysts may necessitate surgical intervention with the primary objective to relieve nerve compression and/or stimulation, stop bone erosion, and relieve symptoms. There is no consensus on the optimal surgical method for TCs, and there have been numerous evolving surgical techniques. Treatment considerations for these cases are complex and best treated on a case by-case basis depending on a variety of factors including the patient's health status, characteristics of the sacral cyst, and adverse impacts in the sacral region and elsewhere. Current techniques for treating symptomatic sacral TC involve sacral laminectomy or laminoplasty combined with cyst obliteration by fenestration, imbrication, resection, or cyst wrapping with dural graft material, and sometimes free or pedicled autologous tissue transposition to fill the void. One technique is to expose the region of the spine where the cyst is located by removal of the overlying vertebral bone. The cyst is then sliced open with one or more thin cuts (fenestrations) and drained of fluid. The cyst wall is collapsed, then reinforced and sutured closed or the cavity is filled with another substance such as fat or tissue adhesive to prevent it from refilling with CSF. In another procedure, following exposure and drainage of the cyst, a flap of nearby muscle tissue is used to fill the cyst to prevent refilling. Other surgical techniques may include decompressive laminectomy. Less common procedures include CSF shunting (lumboperitoneal, cystoperitoneal, or cyst to subcutaneous port shunting), epiduroscopy with laser fenestration, and endoscopic occlusion of cyst ostia; however, limited to no success has been demonstrated for these techniques. The majority of the evidence for surgical intervention in TC come from cohort studies where high rates of treatment success have been reported with complete or partial symptom resolution in greater than 80 percent of patients. Of note, surgical interventions in the sacral region are both surgically and technically demanding leading to increased risk of ectasia and CSF leakage and may damage nerve roots within or near the cyst, and it is difficult to repair any anatomy. Other challenges include cyst recurrence, occurrence or progression of cysts on other untreated nerve roots, epineural scarring, and necrosis of the free tissue transfer grafts used to fill voids. When pain is intractable, despite a variety of interventions, or when other neurological symptoms become severe (ie bowel and bladder dysfunction, severe paraesthesias, etc.), and the sacrum is eroding and remodeling, surgery may be the treatment of choice. There are a small number of physicians in the world who have surgical expertise in the treatment for TCs, and the short-term and long-term outcome of surgery is improving but variable in individual patients at this time. Surgical interventions are typically reserved for patients with more advanced disease (including multiple cysts or wide-neck communication with the subarachnoid space) or have failed percutaneous procedures, in whom remnants and scarring now contribute to symptoms and complicate later procedures.

Neuromodulation

A transcutaneous electrical nerve stimulator (TENS) and electroacupuncture are possible intervention modalities that may be used to relieve nerve pain, albeit little to no evidence for these treatments have been generated. TENS devices deliver electrical impulses through the skin to the cutaneous (surface) and afferent (deep) nerves to control pain. Unlike medications and topical ointments, TENS does not have any known side effects, other than skin irritation from the electrodes seen in some patients. For patients with moderately or severely disabling pain, tonic and high-frequency subthreshold spinal cord or nerve root stimulation and intrathecal drug delivery may be considered if surgery is not possible or has been ineffective.

Treatment for Tarlov cysts is a surgical or percutaneous procedure and, as such, is not subject to regulation by the U.S. Food and Drug Administration (FDA). To date, the FDA has not approved any neuromodulation devices for the indication of Tarlov cysts.

POLICY

Treatment of Tarlov cysts (perineural cyst, sacral perineural cyst, sacral meningeal cyst) with surgical, percutaneous, and/or neuromodulation interventions is considered investigational.

POLICY EXCEPTIONS

None

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Management of Tarlov Cysts

No societal endorsements were found, but the following recommendations is provided for consideration. The focus of these recommendations is for the most common symptoms related to small-to-moderate sized cysts. No standard was found for categorizing cyst size; however, cysts over 2 cm might be considered large. There are other symptoms not included in these recommendations thought to be associated with Tarlov cysts (e.g., headache, abdominal pain) that might warrant earlier surgical intervention, and giant Tarlov cysts might prompt immediate surgical intervention.

The following key observations and recommendations are from Department of Medical Imaging, Toronto Western Hospital, University Health Network, based on their experience with over 1,000 patient referrals and treatment experience with cyst aspiration-fibrin sealant injections of symptomatic Tarlov cysts and on a review of the literature:

1. "Tarlov cysts are an uncommon finding, prevalence estimates have often been based on incidental radiographic findings and inconsistent reporting particularly from lumbar rather than dedicated sacral MRIs and likely contribute to an underestimation of the prevalence of this spinal disease.

2. There is extensive evidence that sacral Tarlov cysts are associated with a diverse range of pain and neurological symptoms. Workups of patients, particularly for women presenting initially with low back pain or coccygodynial pain, should include a careful history, neurological examination, and when appropriate electrodiagnostic testing or urodynamic studies to conduct more comprehensive multidisciplinary investigations.

3. Imaging investigations for Tarlov cysts should include a lumbar spine MRI and a sacral MRI with axial and sagittal planes of the entire sacrum and when identified radiologically should be reported in a differential diagnosis and in the appropriate clinical context, considered a potential pain generator and contributor to neurological symptoms.

4. A range of strategies can be employed to determine if sacral cysts are causative or contributing agents of symptoms: Tarlov disease specific quality-of-life questionnaires, patient-completed dermatome maps, and diagnostic tests including percutaneous anesthetic injection into the cyst or cyst fluid aspiration with a two-needle technique. Fluid aspiration can also assess whether rapid cyst refilling occurs indicating a wide-necked cyst, a contraindication to fibrin sealant injection.

5. Sacral Tarlov cysts can cause peripheral nerve fiber neuropathy through sacral nerve root stretching or compression, and electrodiagnostic tests can detect nerve conduction abnormalities and nerve fiber neuropathy, potentially responsible for a range of commonly reported Tarlov related pain, paresthesia and, bowel/bladder dysfunctions. Early intervention for nerve fiber neuropathy is preferred to ensure better neurological outcomes. As patients with Tarlov cysts have often reported experiencing symptoms for years, there is a concern that long-standing nerve damage may be unrecoverable.

6. Both percutaneous and open surgical approaches have resulted in high rates of rapid symptomatic relief, but percutaneous interventions have several advantages over open surgery. The cyst aspiration-fibrin injection is an uncomplicated technique performed as an outpatient procedure with rapid reductions in symptoms and recovery with no serious complications. In comparison, there is no consensus on the optimal surgical method, and surgeries are technically demanding. They also involve variable approaches with significantly higher complication rates, longer hospital stays, and recovery than percutaneous aspiration-fibrin sealant interventions."

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

05/15/2026: New policy added. Approved by the Medical Policy Advisory Committee.

SOURCE(S)

Blue Cross Blue Shield Association policy # 7.01.76

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

Investigational Codes

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