MRI-Based Estimation of Lumbar CSF Volume and Its Clinical Impact on Spinal Anaesthesia

Spinal anesthesia is a widely used and effective alternative to general anesthesia for surgeries performed below the L₁-L₂ level, where the spinal cord ends. However, the distribution and duration of local anesthetics in spinal anesthesia are often unpredictable due to factors such as anesthetic dose, injection speed and location, patient position, age, and body habitus. One important yet less predictable factor is the individual variability in cerebrospinal fluid (CSF) volume, especially in the lumbosacral region. Since CSF dilutes the intrathecally administered anesthetic, differences in CSF volume can significantly impact drug concentration and, consequently, block level and duration. Advancements in imaging techniques such as ultrasound and MRI have contributed to more accurate estimations of CSF volume. While most studies have used ultrasound-based estimations, MRI-based evaluations remain limited. In this study, we aimed to investigate the effect of lumbosacral CSF volume, measured via 3D T₂-weighted MRI, on the duration and extent of spinal anesthesia. Understanding this relationship could improve predictability in spinal anesthesia and enhance personalized anesthetic planning.