Presumptive thoracic spine subluxation in a dog

An 8-years-old, male, Shih Tzu was presented with flaccid paraplegia, with flexor and patellar hyporeflexia. This episode began after the owners were not home. An MRI scan of thoracolumbar spine was performed.


There is a collapse of the intervertebral (IV) space of T8-T9 without clear visualization of the IV disc (orange arrows). At this level, there is a small gap between the vertebral bodies of T8 and T9, with ventral displacement of the vertebral body of T9 in comparison to T8 (green arrow). Associated, there is a slight stenosis of the vertebral canal in this IV space, with loss of visualisation of the subarachnoid and epidural space (both ventrally and dorsally), extending from the medial aspect of T7 to the cranial aspect of T10 (blue arrows). Along this vertebral bodies, the spinal cord is diffusely hyperintense on T2w (pink arrows) and slightly flattened at the level of the IV space of T8-T9, without any evident spinal cord compression. In addition, there is a diffuse increase of signal intensity on T2w in the paravertebral musculature surrounding the vertebral bodies of T7-T10 with moderate enhancement after contrast administration (yellow arrows).



T1w + C

In the abdomen (partially included in the study), there is a slight amount of hyperintense free peritoneal fluid visible on STIR (red arrows), mainly adjacent to the spleen (green arrows) and between the intestinal loops.


At the level of the tail of the spleen (green arrows), there is a round mass with well-defined margins (red arrows). This lesion has a mixed signal intensity on T2W, with small hyperintense areas within it.



  • Findings at the level of the IV space of T8-T9, consistent with a mild subluxation of the thoracic spine, possibly of traumatic origin, considering the patient’s history. Secondary to these changes, there is:
    • Focal stenosis of the vertebral canal at the level of T8-T9, causing a slight flattening of the spinal cord, without obvious compressive myelopathy.
    • Area of diffuse intramedullary hyperintensity, consistent with spinal cord contusion, most likely.
  • Changes in the adjacent paravertebral musculature, most likely secondary to trauma (associated myositis).
  • Scant amount of peritoneal fluid, consistent with mild hemoabdomen, considering the possible trauma. However, other types of effusion (inflammatory, among others), cannot be ruled out.
  • Splenic mass consistent with a neoplastic process, nodular hyperplasia, or hematoma.


Considering the high probability of a traumatic event and the possible very mild subluxation at the level of T8-T9, a CT scan should be considered for a more thorough evaluation of possible subtle fractures/osseous lesions. On the other hand, abdominal ultrasound with sampling of the free fluid and the splenic lesion, is recommended to reach a definitive diagnosis.