1-year-old male intact Standardbred

History:

A yearling Standardbred colt was found down in a muddy portion of his paddock but no trauma was witnessed. The colt was prompted to stand once briefly but then went down again and was unable to rise from lateral recumbency thereafter.

Based on the initial exam by the referring veterinarian, the colt was treated presumptively for colic but did not respond to medical therapy. The colt was referred for further colic workup and presented down in the trailer with hind limb paraplegia.

Physical Exam:

Cranial nerve function and tail and anal tone were normal and there was an intact panniculus response, however thorough neurological exam was limited due recumbency. The horse was quiet, alert, and responsive with moderate tachycardia (52 bpm) and demonstrated vague signs of pain. Rectal examination was normal.

Abdominal ultrasound showed mild to moderate small intestinal distention with a moderate amount of peritoneal effusion that was slightly serosanguinous when sampled. Based on the horse’s persistent discomfort and the inability to rule out abdominal pathology, exploratory laparotomy was pursued, revealing a feed-distended right dorsal colon.

Following surgery, the colt remained recumbent.

Post-laparotomy, radiographs of the cervical, thoracic, and lumbar spine were performed stall-side due to persistent paraplegia.

Imaging Findings:

There is a fracture of the T1 lamina with moderate caudodorsal displacement of the spinous process.

There is dorsal displacement of the T2 spinous process relative to the vertebral body and subsequent widening of the spinal canal and T2-3 articular process joint. There is amorphous mineral superimposed over the region of the pedicles of the T2 vertebral body. There is moderate dorsal displacement of the T3 vertebral body relative to T2, resulting in a reduction in the diameter of the spinal canal at this site. The caudoventral epiphysis of the T3 vertebral body is caudally angulated with associated widening of the physis. There is a similar, although less severe, appearance at T2. There is a mildly caudally displaced oblique fracture of a mid-thoracic spinous process.

A moderate amount of gas is within the peritoneum, resulting in outlining of the abdominal viscera.

Summarized Imaging Diagnosis:

1. T2-3 subluxation with multiple thoracic fractures, including the T1 and T2 vertebral laminae/pedicles and caudoventral Salter-Harris type III fractures, likely secondary to trauma.
2. Mid-thoracic spinous process fracture, likely secondary to trauma.
3. Pneumoperitoneum, consistent with recent laparotomy.

The horse was anesthetized and a myelogram was performed by injecting 40 ml Iohexol (300 mg I/ml) in the subarachnoid space at the level of the atlanto-occipital joint. The head was maintained in an elevated position for 5 minutes and then radiographs were made at 5 and 10 minutes post-injection with the horse in left lateral recumbency.

Myelogram Findings:

There is complete attenuation of the dorsal and ventral subarachnoid contrast columns beginning at the level of caudal C6 and extending through the level of cranial T3. At the level of mid-T3 extending caudally, the dorsal and ventral contrast columns are faintly visible.

Final Imaging Diagnosis:

C6-T3 extra-dural compressive myelopathy, likely secondary to the presence of multiple vertebral fractures and spinal subluxation. Concurrent spinal cord edema or hemorrhage are possible. The lesions identified radiographically and via myelography correlated well with the horse’s clinical presentation. Due to the grave prognosis, the horse was humanely euthanized.

Although axial skeletal trauma is most common within the cervical region, especially in foals, injuries to the thoracic spine do occur and the range of severity is wide.

Consequences can be relatively innocuous, such as spinous process fractures, or life-threatening to grave in the case of vertebral body fractures.

A survey of neurological diseases in horses. Tyler CM, Davis RE, Begg AP, et al. Aust Vet J 1993; 70(12): 445-449

Cervical vertebral fracture in three foals. Pinchbeck G, Murphy D. Equine Vet Educ 2001; 13(1): 8-12

“Fractures of the vertebrae” Equine Fracture Repair. Nixon AJ, Wiley Blackwell 2020, p734-769 Traumatic injury to the central nervous system in horses: