Analysis of Factors Associated with Occult Cerebrospinal Fluid Leak Following Lumbar Spine Surgery

Introduction: Durotomy-induced occult cerebrospinal fluid (CSF) leak is a common complication of posterior spine surgery. While intraoperatively identified dural tears have been widely reported, data on occult leaks resulting from missed dural injuries remain limited. Most existing studies focus on patient- and procedure-related factors, with few examining the correlation between laboratory findings and postoperative CSF leaks. This study aimed to determine the incidence and associated factors of CSF leak following posterior lumbar spinal surgery through perioperative factor analysis. Materials and methods: A single-institution retrospective study was conducted on patients who underwent posterior lumbar spinal surgery between January 2021 and December 2024. Medical records were reviewed to identify patients with postoperative CSF leaks. Perioperative variables were analyzed using univariate and multivariate regression to identify factors associated with CSF leakage. Results: Among 935 patients included, 46 (4.9%) developed postoperative CSF leaks, of which 12 (1.28%) were occult leaks. American Society of Anesthesiologists (ASA) grade and multiple fusion segments were identified as independent risk factors for occult CSF leak (P=0.033 and P=0.026, respectively). Patients with occult leaks exhibited significantly lower postoperative globulin and glycated serum protein levels, higher postoperative wound drainage volumes, longer drain retention times, longer surgical and anesthesia times, and greater estimated blood loss compared to those without leaks. Conclusion: In this large cohort, ASA grade and multiple fusion segments were independent risk factors for occult CSF leak following posterior lumbar surgery. Occult leak cases were associated with postoperative reductions in globulin and glycated serum protein levels.