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In Reply: Growth of Lumbosacral Perineural (Tarlov) Cysts: A Natural History Analysis.

To the Editor: We would like to thank the author for their review and thoughtful discussion1 of our article “Growth of Lumbosacral Perineural (Tarlov) Cysts: A Natural History Analysis.”2 In the reported series of 42 Tarlov cysts (TC) in 28 symptomatic patients, a total of 7 cysts (17%) in 5 patients demonstrated growth. These findings suggest that TCs can commonly demonstrate growth. However, as the author noted,1 TC growth has only recently been documented, and the percentage of all TCs (symptomatic and non-symptomatic) that enlarge over time is unknown. As in all cases of suspected TCs, we agree with the author1 that alternative diagnoses such as neoplastic lesions should be considered. In the 5 patients with TC growth, post-contrast magnetic resonance imaging was available in 3. There was no evidence of a cystic tumor. Two of these patients underwent microsurgical resection. The gross intraoperative appearance was typical for TCs. Although initially in our experience, surgical specimens were sent on each patient, we subsequently have not routinely requested histological analysis.3 Of the remaining 23 patients in our cohort without TC growth, 14 underwent microsurgical resection. We have reported on our surgical experience on an earlier cohort of patients with symptomatic TCs.3 Finally, as the author noted,1 TCs have been associated with connective tissue disorders.4 None of the 5 subjects with TC growth had a diagnosis of Marfan disease or Ehlers-Danlos syndrome. However, the point made by the author1 is well taken and we have recently began collaborating with medical specialists in connective tissue disease at our institution to provide comprehensive care to all patients with suspected TCs.