Giant Tarlov Cyst and the Importance of Advanced Imaging Before Interventional Spine Injections.

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A 23-yr-old man with a 1.5-yr history of progressive lumbosacral back pain presented as a direct referral to an interventional pain provider for consideration of an injection. He described the pain as a “pressure” in his sacrum. Prolonged activity aggravated the pain and rest alleviated it. He denied any radicular symptoms or any changes in bowel or bladder function. Over-the-counter anti-inflammatory medications and physical therapy for discogenic pain provided minimal relief. On examination, the patient exhibited tenderness to palpation at the sacrum and pain with extension and lateral rotation of his lumbar spine. He displayed normal strength, sensation, and reflexes in bilateral lower limbs. His pain was not reproducible with straight leg raise, log roll, hip scour, FABER (flexion, abduction, and external rotation of the hip), or FADIR (flexion, adduction and internal rotation of the hip). The provider determined that a magnetic resonance imaging (MRI) of the lumbar spine was indicated before any procedure to further evaluate the etiology of pain. Magnetic resonance imaging of the lumbar spine revealed an 8.8 × 7.2 × 3.7-cm perineural cyst filling nearly the entirety of the sacral spinal canal with associated canal expansion (Figs. 1–3).FIGURE 1: Sagittal MRI revealing a Tarlov cyst filling nearly the entirety of the sacral spinal canal with associated canal expansion.FIGURE 2: Axial T2 MRI revealing a Tarlov cyst filling nearly the entirety of the sacral spinal canal with associated canal expansion.FIGURE 3: Coronal T2 MRI revealing a Tarlov cyst filling nearly the entirety of the sacral spinal canal with associated canal expansion.Perineural cysts, also known as Tarlov cysts, are meningeal dilatations of the posterior nerve root sheath that most frequently occur in the sacral region and communicate with the cerebrospinal fluid.1 These cysts are usually asymptomatic and are discovered incidentally. However, sometimes, the cyst can enlarge via net inflow of cerebrospinal fluid resulting in distortion, stretching, or compression of adjacent nerve roots, which can cause a progressively painful radiculopathy as well as localized pain via mass effect. Treatment is usually not required for asymptomatic Tarlov cysts. Approximately 20% of these cysts are symptomatic, and the role of specific surgical and nonsurgical interventions remains controversial.2 In a retrospective study by Elsawaf et al.,3 15 patients who were experiencing symptomatic Tarlov cysts underwent surgical excision, and all of the patients had either complete or substantial resolution of their pain after surgery. Risks of surgical intervention include worsening neurologically deficits.4 Unintentional needle insertion of these cysts during an interventional procedure may lead to serious and unwanted outcomes, including cerebrospinal fluid leak and postdural puncture headache. The necessity of obtaining advanced imaging before interventional spine procedures for back pain is often debated.5–7 This case demonstrates that advanced imaging can be of great use for chronic low back pain refractory to conservative care both to identify potentially rare etiologies of pain and to identify pathology that may render the considered intervention contraindicated because of increased risk of complication, such as a Tarlov cyst. It is also worth noting the importance of an accurate diagnosis before any therapeutic interventional procedure and that the correct pathology paired with the correct intervention leads to the highest probability of the procedure being successful. Ultimately, the patient preferred to not undergo surgery at this time but rather underwent a L4-L5 interlaminar steroid injection. Epidural steroid injections are not a known treatment for Tarlov cysts nor for axial back pain; however, this was discussed with the patient, and given the lack of other treatment options, the patient wished to proceed with the injection. The patient obtained 40% pain relief from this, which he was satisfied with. The patient will be followed by neurosurgery and get a repeat MRI in a year, and if symptoms were to worsen, a repeat injection or surgical intervention would be considered.