Morphometric analysis of spinal cord termination in Cavalier King Charles Spaniels

Abstract

Background: There is an association between Chiari malformations, syringomyelia (CMSM) and tethered cord syndrome (TCS) in people, suggesting Cavalier King Charles Spaniels (CKCS) with CMSM could also have TCS. Currently there are no data on the position of the caudal spinal cord structures in CKCS.

Objective: To describe and compare location of spinal cord termination in CKCS with weight-matched controls and to examine the relationship between SM and spinal cord termination.

Animals: Thirty-nine CKCS and 33 controls with thoracolumbar MRIs; 34 of 39 CKCS also had cervical MRIs.

Methods: Blinded retrospective study. Spinal cord and dural sac termination were determined from T2-weighted sagittal and transverse images and half-Fourier acquisition single-shot turbo spin echo sequences. Intra-observer reliability was determined using kappa analysis. Presence of SM was compared with location of spinal cord and dural sac termination.

Results: Intra-observer reliability was moderate for identifying spinal cord termination (Kappa = 0.6) and good for dural sac termination (Kappa = 0.8). The spinal cord terminated at lumbar vertebra 6 (L6) in 1, 7 (L7) in 22, and sacrum in 16 CKCS versus 9 at L6, 23 at L7, 1 at sacrum in controls. Spinal cord (P < .001) and dural sac (P = .002) termination were significantly more caudal in CKCS compared to controls. The presence of thoracolumbar SM was associated with more caudal dural sac termination in CKCS (P = .03).

Conclusions and clinical importance: The relationship between TL SM and possible spinal cord tethering because of a more caudal dural sac termination should be investigated.

Keywords: conus medullaris; dural sac; filum terminale; syringomyelia.

Figure 1

Identification of A‐B, spinal cord termination and C, dural sac termination. Panels A and B show representative T2‐sagittal views (left) and transverse views (right). The yellow line is a reference line showing the corresponding location of the transverse slice. In panel A, the hypointense signal representing the spinal cord is still present and is seen within the red circle at L6. Panel B shows the next transverse slice where the spinal cord signal has disappeared at L6/L7 disc space. Dural sac termination is shown in C with a T2‐weighted sagittal view and a half‐Fourier acquisition single‐shot turbo spin echo (HASTE) sequence side‐by‐side. The red line indicates HASTE termination and the triangulation tool was used to identify the same location on the T2‐weighted sagittal view

Figure 2

Representative T2 sagittal MRIs from lumbar vertebrae 1 (L1) to the sacrum (S) in A, Cavalier King Charles Spaniel; B, brachycephalic control; and C, non‐brachycephalic control. Red line indicates spinal cord termination

Figure 3

Spinal cord and dural sac termination in Cavalier King Charles Spaniel (CKCS) and size‐matched controls. Each stacked bar shows the relative count for each breed terminating at every vertebral level. A, SC termination in CKCS and size‐matched controls. B, SC termination in CKCS, brachycephalic controls, and non‐brachycephalic controls. C, Dural sac termination in CKCS and size‐matched controls. D, Dural sac termination in CKCS, brachycephalic controls, and non‐brachycephalic controls. L6, lumbar vertebrae 6; L7, lumbar vertebrae 7; S, sacrum

Figure 4

Representative sagittal HASTE images showing termination of the dural sac in A, Cavalier King Charles Spaniel; B, brachycephalic control; and C, non‐brachycephalic control. The red line indicates dural sac termination in B and C, however, the dural sac extends beyond the sacrum in A. S, sacrum