Magnetic Resonance Imaging Characteristics of Suspected Vertebral Instability Associated With Fracture or Subluxation in Eleven Dogs

Abstract

The purpose of this study was to describe the magnetic resonance imaging (MRI) characteristics of suspected instability in dogs with vertebral fractures or subluxations. Eleven dogs that had MRI examinations of the spine prior to surgical stabilization of vertebral fractures and/or subluxations were included in the study. Nine dogs also had survey radiographs. Four dogs had cervical fracture or fracture-subluxation and presented with tetraplegia with intact nociception (n = 2) or nonambulatory tetraparesis (n = 2). Seven dogs had thoracolumbar fracture-subluxation or subluxation and presented with paraplegia with intact nociception (n = 5) or nonambulatory paraparesis (n = 2). A three-compartment model was applied to the interpretation of both the radiographic and MRI studies. Radiography identified compartmental disruption consistent with spinal instability in seven out of the nine cases radiographed. In MRI studies, rupture of the supportive soft tissue structures and/or fracture in at least two compartments could be visualized. Nine cases had spinal cord changes on MRI including signal intensity changes, swelling, compression, and intramedullary hemorrhage. Paravertebral muscle intensity changes were also visible at each trauma site. Magnetic resonance imaging provided helpful information on the location and extent of damage to supportive soft tissue structures and enabled assessment of spinal cord injury in this group of dogs with surgically confirmed vertebral fractures and subluxations.

Use of the T2*‐weighted Gradient Recalled Echo Sequence for Magnetic Resonance Imaging of the Canine and Feline Brain

“…In veterinary patients, the use of T2 * -weighted gradient recalled echo imaging to detect hemorrhage has been reported in cases of primary cerebral hemangioma, metastatic hemangiosarcoma, pituitary adenoma and adenocarcinoma, astrocytoma, oligodendroglioma, intravascular lymphoma, meningioma, Angiostrongylus vasorum infection, bacterial septicemia, hemorrhagic infarction, hemorrhagic stroke, cerebral microbleeds, subdural hematoma, spinal extradural hematoma associated with intervertebral disk herniation, hemorrhagic myelomalacia, traumatic intramedullary spinal cord hemorrhage, ischemic myelopathy, acute noncompressive nucleus pulposus extrusion, and necrotizing myopathy. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] However, the routine use of T2 * -weighted gradient recalled echo pulse sequences in a large series of canine and feline patients has not been reported.…”

MRI has limited agreement with CT in the evaluation of vertebral fractures of the canine trauma patient

“…We had hypothesized that structurally unstable vertebral fractures would be easier to identify since we had anticipated that a greater force would be required to fracture a vertebra severely enough to cause instability and that this force would cause other tissues to be damaged and rendered more visible on MRI. In prior studies, peri‐lesional T2‐weighted hyperintensity and disruption to paravertebral musculature was reliably associated with vertebral fracture on MRI in dogs which assisted in locating vertebral fractures . In addition, unstable vertebrae were often associated with spinal cord injuries including compression, swelling, intensity changes, and intramedullary hemorrhage, all of which can help localize the presence of unstable fractures .…”

“…In prior studies, peri‐lesional T2‐weighted hyperintensity and disruption to paravertebral musculature was reliably associated with vertebral fracture on MRI in dogs which assisted in locating vertebral fractures . In addition, unstable vertebrae were often associated with spinal cord injuries including compression, swelling, intensity changes, and intramedullary hemorrhage, all of which can help localize the presence of unstable fractures . These associated soft tissue changes have shown all useful for locating damaged vertebra even when the exact fracture morphology is poorly visible on MRI, but were not useful at differentiating structurally unstable vertebral fractures from all vertebral fractures in our study.…”

“…Most radiologists use the three‐compartment model to identify vertebral column instability . This method divides the osseous and structural soft tissues of the vertebral column into ventral, middle, and dorsal compartments; failure of at least two compartments predicts vertebral instability (Figure ) …”

“…MRI has the potential to be a single modality that could provide a comprehensive evaluation of both the soft tissue and osseous structures important in assessing spinal instability. To date, only a single study has evaluated vertebral column trauma in dogs using MRI . This study only described MRI findings associated with unstable vertebral fractures and subluxations, and did not assess the accuracy of detecting vertebral fractures with MRI …”