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

The clinical response to spinal anesthesia is influenced by lumbosacral cerebrospinal fluid (CSF) volume, which is highly variable among patients.

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.

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).

Application of this technique to clinical investigations may further enhance our understanding of spinal anesthesia.