Growth rate of a giant Tarlov (perineural) cyst with intrapelvic extension.

Background and importance: Giant Tarlov cysts (GTCs) are perineural cysts and their presacral intrapelvic extension are extremely rare entities. We present a case of GTC with intrapelvic extension who has preoperative Magnetic Resonance Imaging (MRI) follow-ups of 12 years, and we demonstrate the annual growth rate and the time-size correlation of a GTC.

Methods: Case report.

Clinical presentation: A 37-year-old woman was admitted with left gluteal pain radiating to left foot, left leg numbness, progressed over 12 years. On MRI, starting from the L5-S1 level, a giant Tarlov cyst with an atypical configuration, is observed. The patient had a known sacral Tarlov cyst, first discovered on MRI obtained 12 years before the surgery. She had 6 consecutive MRI follow-ups in 12 years preoperatively. The cysts diameters have been measured and the growth rate was estimated. We showed for the first time that presented GTC grows in in both Sagittal Diagonal (SD) and Sagittal Craniocaudal (SC) diameters over time with overall annual growth rates, 7.671% for RGR_SD and 6.237% for RGR_SC.

Conclusion: When the time-size correlation is observed, it becomes evident that the GTSs' growing speed increases over the years because of minimal resistance in the intrapelvic cavity. Early surgery may be considered to prevent rapid growth in the intrapelvic cavity and to reduce possible complications of the giant cyst.