Equine wobbler syndrome affects young horses and can lead to serious neurologic defects. A Scandinavian research team recently started evaluating a structure that could provide new insights into identifying, treating, and preventing this condition: the neuro-central synchondrosis (NCS).

Growth Plates in Young Horses

The NCS is a growth plate in the horse’s neck (technically, a physis—or growth plate—in the cervical spine) responsible for height-wise growth of the vertebral canal through which the spinal cord runs, said lead researcher Kristin Olstad, BVSc, PhD, CertVR, associate professor at the Norwegian University of Life Sciences Faculty of Veterinary Medicine, in Ås. The growth occurs through endochondral ossification, a process in which bone replaces cartilage as the growth plates “close.”

“Researchers know, from multiple other sites in limbs, that the developmental orthopedic disease osteochondrosis can cause delayed endochondral ossification,” she explained. “If this occurred in the NCS, delayed growth due to osteochondrosis could potentially cause stenosis—a narrowed vertebral canal—and, thus, spinal cord compression and wobbler syndrome.”

But Olstad quickly discovered a problem when she investigated her hypothesis: While researchers have thoroughly described NCS and its role in stenosis in pigs, information about the structure in horses remains scarce.

“Personally, I was surprised to discover that there was a growth plate in the horse’s spine that I had never heard about and could not find in veterinary textbooks,” she said. “It’s only briefly mentioned in one German textbook and one German study. 

Studying the NCS in Horses

Olstad and colleagues carried out a study with the goal of describing the NCS so that ultimately, researchers can characterize its potential role in wobbler syndrome. “Before we can claim that something is abnormal, we must first know what is normal,” she said. “For immature animals, this includes knowing how the skeleton normally grows.” 

The team performed CT scans (the NCS isn’t visible on radiographs) on 35 foals of various breeds and sexes, ranging in age from 153 days of gestation to 438 days old, and they scored the physes on a scale of 0 (fully closed) to 6 (fully open). 

The team found that:

• The thinner middle portion of the NCS closed by Days 38 to 115 of age, but the thicker front (cranial, toward the head) and back (caudal, toward the tail) portions had not yet closed in the oldest foals in the study (about 14 months old). “This implies that disease would likely develop on different timelines in different portions of the NCS and between the different vertebral growth plates,” Olstad said, noting that additional work is underway to identify and confirm suspected lesions and define timelines for disease development.
  
• The NCS is a very thin growth plate, particularly in the middle. “This makes it somewhat unlikely that the middle portion will suffer osteochondrosis because osteochondrosis is caused by failure of the blood supply to growth cartilage,” Olstad said. “The NCS was thin enough in the middle to survive by diffusion if the blood supply fails.” She noted this doesn’t rule out the possibility of osteochondrosis occurring in the thicker portions of the NCS, which are the areas where researchers first identified spinal cord compression.
  
• Olstad also noted that researchers and veterinarians have, in some cases, associated the compression of the spinal cord or nerves exiting the vertebral canal with enlarged articular process or facet joints. “The NCS may explain the variability of the association,” she said, “Markedly enlarged facet joints could cause nerve compression regardless of vertebral canal height, whereas moderately enlarged facet joints might only cause compression if the height of the vertebral canal is also reduced.”

The Future of NCS and Wobbler Syndrome Research

This study represents not only the start of researchers’ and veterinarians’ understanding of the NCS itself but also first steps to identifying, treating, and preventing NCS-related wobbler syndrome.

“In some countries, pigs are routinely screened for osteochondrosis using whole-body CT (Topigs-Norsvin),” said Olstad. “In horses, it is more common to screen for osteochondrosis using radiography at 12 to 18 months of age, by which time the horse is too large to fit through a CT gantry. We are perhaps not ready for it just yet, but visualisation of the NCS requires CT or MRI scanning, and it is not entirely unfeasible that smaller foals may be CT-scanned for NCS osteochondrosis sometime in the future.”

Olstad thanked the owners of the foals included in the study and acknowledged the team’s funding source.

“This 2024 CT study is only a descriptive CT study of when the NCS is present in the neck of foals,” she said. “But we are extremely grateful to all participating foal owners and the Swedish-Norwegian Foundation for Equine Research. Without these basic studies, we would not have the knowledge of what is normal upon which to reach evidence-based diagnoses of disease.”

The study, “Closure of the neuro-central synchondrosis and other physes in foal cervical spines,” was published in the Equine Veterinary Journal in April 2024.