Characterising spinal cerebrospinal fluid flow in the pig with phase-contrast magnetic resonance imaging

Abstract

Background: Detecting changes in pulsatile cerebrospinal fuid (CSF) fow may assist clinical management decisions, but spinal CSF fow is relatively understudied. Traumatic spinal cord injuries (SCI) often cause spinal cord swelling and subarachnoid space (SAS) obstruction, potentially causing pulsatile CSF fow changes. Pigs are emerging as a favoured large animal SCI model; therefore, the aim of this study was to characterise CSF fow along the healthy pig spine. Methods: Phase-contrast magnetic resonance images (PC-MRI), retrospectively cardiac gated, were acquired for fourteen laterally recumbent, anaesthetised and ventilated, female domestic pigs (22–29 kg). Axial images were obtained at C2/C3, T8/T9, T11/T12 and L1/L2. Dorsal and ventral SAS regions of interest (ROI) were manually segmented. CSF fow and velocity were determined throughout a cardiac cycle. Linear mixed-efects models, with post-hoc comparisons, were used to identify diferences in peak systolic/diastolic fow, and maximum velocity (cranial/caudal), across spinal levels and dorsal/ventral SAS. Velocity wave speed from C2/C3 to L1/L2 was calculated. Results: PC-MRI data were obtained for 11/14 animals. Pulsatile CSF fow was observed at all spinal levels. Peak systolic fow was greater at C2/C3 (dorsal: − 0.32±0.14 mL/s, ventral: − 0.15±0.13 mL/s) than T8/T9 dorsally (− 0.04±0.03 mL/s; p<0.001), but not diferent ventrally (− 0.08±0.08 mL/s; p=0.275), and no diference between thoracolumbar levels (p>0.05). Peak diastolic fow was greater at C2/C3 (0.29±0.08 mL/s) compared to T8/T9 (0.03±0.03 mL/s, p<0.001) dorsally, but not diferent ventrally (p=1.000). Cranial and caudal maximum velocity at C2/C3 were greater than thoracolumbar levels dorsally (p<0.001), and T8/T9 and L1/L2 ventrally (p=0.022). Diastolic velocity wave speed was 1.41±0.39 m/s dorsally and 1.22±0.21 m/s ventrally, and systolic velocity wave speed was 1.02±0.25 m/s dorsally and 0.91±0.22 m/s ventrally. Conclusions: In anaesthetised and ventilated domestic pigs, spinal CSF has lower pulsatile fow and slower velocity wave propagation, compared to humans. This study provides baseline CSF fow at spinal levels relevant for future SCI research in this animal model.