Cervical vertebrae changes in foals

Equine Veterinary Journal 2024

Author

Obi Veterinary Education
September 25, 2025

Kristin Olstad, Mari Dahl Bugge, Bjørnar Ytrehus, Anne Selvén Kallerud

Background: The neuro-central synchondrosis (NCS) is a physis responsible for the growth of the dorsal third of the vertebral body and neural arches in horses. In pigs, experimental tethering of the NCS leads to stenosis, suggesting its potential role in equine spinal cord compression and ataxia (wobbler syndrome). This study aimed to describe the closure of the NCS and other physes in the cervical spine of foals using computed tomography (CT).

Methods: This was a post-mortem cohort study examining the cervical spine of 35 foals of various breeds and sexes, ranging from 153 gestational days to 438 days old. CT scans were used to evaluate physeal closure, scoring them from 6 (fully open) to 0 (fully closed). The mid-NCS was scored separately from the cranial and caudal portions, which were evaluated along with the respective vertebral body physes.

Results: The NCS was a pair of thin physes primarily oriented in a dorsal plane between the vertebral body and neural arches. The mid-NCS was closed in C1 from 115 days of age and in C2–C7 from 38 days of age. The dorsal physis closed later than the NCS in C1 but earlier in C2–C7. The physis of the dens was closed from 227 days. The cranial and caudal physes of the vertebral body were in the process of closing in the oldest cases but were not yet fully closed.

Limitations: The study population was drawn from a hospital setting, which may not represent a healthy, general foal population. Additionally, premature or dysmature cases were included, which could influence the results.

Conclusions: The NCS contributed primarily to height-wise growth but also to width- and length-wise growth of the vertebral body and neural arches. The mid-NCS was completely closed in all cervical vertebrae from 115 days of age. Further investigation into the role of the NCS in the pathogenesis of vertebral stenosis and spinal cord compression in horses is warranted.

Radiological maturity, early group. 3D volume-rendered CT images of the C1–C2–C3, left lateral views. (A) Case 1, 153 days of gestation. There are large primary ossification centres (asterisks) in the neural arches of C1 (slightly rotated) to C3, and smaller primary centres (arrows) in the bodies of C2–C3, but not C1. (B) Case 3, 244 days of gestation. In addition to the centres in (A), there is a large ossification centre in the dens (asterisk) and a small ossification centre in the ventral arch of C1 (dashed circle). The ventral crest (arrows) is present on the primary ossification centre of the vertebral bodies of C2–C3. (C) Case 6, 289 days of gestation. In addition to the centres in (A, B), there are large secondary centres (asterisks) cranially and smaller ossification nuclei (dashed circles) caudally in C2–C3. Unlike Cases 4–8 and 14p from 271 to 320 days of gestation, there is no secondary centre cranially in C2 and the cranial secondary centres are fused to the primary centres in the bodies of C3–C4. (D) Case 5, 280 days of gestation. There is a small secondary ossification centre (arrow) cranially in C2. There are regularly spaced, craniocaudally oriented grooves (dashed lines; likely vascular grooves) in the contours of the secondary centres cranially in C3–C4. (E) Case 4, 271 days of gestation. There is a properly formed secondary ossification centre cranially in C2 (arrow), and the secondary ossification centres cranially in C3–C4 are smoother than in Case 5 (D). (F) Case 14p, 0 days/16 h old, but 12 days premature, equivalent to 320 days of gestation. The secondary ossification centre cranially in C2 is almost as large and smooth as the ossification centres cranially in C3–C4.

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