Influence of laminectomy on the lumbosacral cerebrospinal fluid volume: A retrospective magnetic resonance imaging study.

The cerebrospinal fluid volume affects the block height of spinal anaesthesia. Laminectomy of the lumbar spine may result in increased lumbosacral cerebrospinal fluid volume. This study aimed to test the hypothesis that the lumbosacral cerebrospinal fluid volume of patients with a history of lumbar laminectomy would be larger than that of patients with normal lumbar spine anatomy using magnetic resonance imaging. Lumbosacral spine magnetic resonance images of 147 patients who underwent laminectomy at the L2 vertebrae or below (laminectomy group) and 115 patients without a history of spinal surgery (control group) were retrospectively reviewed. The lumbosacral cerebrospinal fluid volumes between the L1-L2 intervertebral disc level and the end of the dural sac were measured and compared between the two groups. The mean (standard deviation) lumbosacral cerebrospinal fluid volume was 22.3 (7.8) ml and 21.1 (7.4) ml in the laminectomy and control groups, respectively (mean difference 1.2 ml; 95% confidence interval -0.7 to 3.0 ml; P = 0.218). In the prespecified subgroup analysis according to the number of laminectomy levels, patients who underwent more than two levels of laminectomy exhibited slightly larger lumbosacral cerebrospinal fluid volume (n = 17, 30.5 (13.5) ml) compared with those who underwent two (n = 40, 20.7 (5.6) ml; P = 0.014) or one level of laminectomy (n = 90, 21.4 (6.2) ml; P = 0.010) and the control group (21.1 (7.4) ml; P = 0.012). In conclusion, the lumbosacral cerebrospinal fluid volume did not differ between patients who underwent lumbar laminectomy and those without a history of laminectomy. However, patients who underwent laminectomy at more than two levels had a slightly larger volume of lumbosacral cerebrospinal fluid than those who underwent less extensive laminectomy and those without a history of lumbar spine surgery. Further studies are warranted to confirm the subgroup analysis findings and elucidate the clinical implications of such differences in the lumbosacral cerebrospinal fluid volume.