Computed tomographic myelography of the cranial cervical spine in Warmblood horses with no spinal pathology—Inter‐ and intravertebral ratios and distribution of contrast columns in neutral and flexed cervical spine

Background: Computed tomographic myelography (CTM) and radiographic myelography (RxM) are diagnostic for extradural spinal cord compression, but knowledge about the contrast distribution in flexion and normal position of nonaffected horses is lacking. Objectives: (1) To determine the inter‐ and intravertebral ratios at C3–C4 of CTM in neutral and flexed positions in Warmbloods. (2) To compare the diameters of the spinal cord and the contrast columns at C3–C4 between neutral and flexed positions in CTM and RxM. (3) To evaluate the variability of measurements. Study Design: Terminal in vivo method–comparison study with histological confirmation of absence of spinal pathology. Methods: RxM and CTM were performed in 13 neurologically normal Warmbloods in neutral and flexed cervical spine positions. Inter‐ and intravertebral ratios, the sagittal diameters of the spinal cord, the dorsal (dcc) and ventral contrast column (vcc) were calculated (in mm) and compared between the cervical spine positions. Results: The flexion angle was 24° in both modalities. Flexion of the cervical spine led to a significant reduction of the diameter of the spinal cord in CTM (sc_inter2: 9.2 ± 1.1 (mean ± standard deviation) and 8.0 ± 1.4, p = 0.02; sc inter 3: 9.2 ± 1.3 and 7.7 ± 1.7, p = 0.007) and of the heights of the contrast columns in both modalities (dcc inter2: RxM: 10.2 ± 1.9 and 8.5 ± 2.1, p = 0.005; CTM: 8.8 ± 1.4 and 7.2 ± 2.0, p = 0.004; vcc inter3: RxM: 2.7 ± 1.3 and 0.9 ± 0.7, p < 0.001; CTM: 2.2 ± 1.2 and 0.0 ± 0.1, p < 0.001) at intervertebral locations. Main Limitations Small group size, no calibration of radiographs. Conclusions: Flexion of the cervical spine decreased the diameter of the spinal cord and the dorsal and ventral myelographic contrast columns in Warmbloods with no spinal pathology.