Lumbosacral cerebrospinal fluid volume in humans using three-dimensional magnetic resonance imaging

BACKGROUND: The clinical response to spinal anesthesia is influenced by lumbosacral cerebrospinal fluid (CSF) volume, which is highly variable among patients. METHODS: Lumbosacral magnetic resonance images were obtained in 71 patients using a long echo time (TE = 198 msec), fast spin echo sequence with fat suppression. Three-dimensional images were created and lumbosacral CSF volume was estimated using a threshold-based region growing algorithm. RESULTS: A validation experiment using a water bath and cadaveric spinal cord demonstrated that the technique was accurate (1.4 ± 0.4% difference between estimated and measured). The coefficient of variance was 0.42% among the three estimated CSF values per subject. The mean calculated volume was 35.8 ± 10.9 mL with a range of 10.6-61.3 mL. Lumbosacral CSF volume was widely variable among patients and was inversely proportional to body mass index (r = -.276, P = 0.02). Mean calculated lumbosacral CSF volumes were smaller in the group of subjects that had radiographic diagnoses of spinal stenosis when compared with subjects with no diagnosis (mean difference -8.4 mL, 95% CI of the difference, -16.1 to -0.8 mL, P = 0.03) and were not different when compared with those with herniated disk disease (mean difference -6.4 mL, 95% CI of the difference -14.7 to 1.9 mL, P = 0.19). CONCLUSIONS: Application of this technique to clinical investigations may further enhance our understanding of spinal anesthesia.