Study suggests CT pathway can match MRI in acute canine IVDE

Version 2

A newly published Veterinary Surgery study is challenging one of the default assumptions in canine spinal imaging: that MRI should routinely lead perioperative decision-making in non-ambulatory chondrodystrophic dogs with acute thoracolumbar intervertebral disc extrusion. In a retrospective cohort analysis, Daniel Low and Andrea Markovic reported that conditional CT-myelography was non-inferior to MRI for recovery of ambulation, while also lowering imaging-related costs. (onlinelibrary.wiley.com)

That finding lands in a space where MRI has long held “gold standard” status. The 2022 ACVIM consensus statement describes MRI as highly sensitive, especially for identifying intramedullary injury, differentiating extrusion from protrusion, detecting residual compression, and helping with prognostication in severe cases. But the same consensus document also notes that CT is faster, less expensive, and can be recommended as a first-line advanced imaging modality when acute thoracolumbar IVDE is suspected in the typical chondrodystrophic dog, particularly when mineralized disc material is likely. (onlinelibrary.wiley.com)

The new study builds on that guidance by focusing not just on diagnostic capability, but on what imaging choice actually changes for the patient. According to the paper, MRI did not appear to alter rates of conservative management, surgical approach, extent of decompression, or use of adjunctive procedures compared with the CT-myelography pathway. The authors also reported comparable safety profiles between groups, while the cost advantage of CT-myelography was driven mainly by the imaging procedure itself rather than downstream differences in perioperative care. (onlinelibrary.wiley.com)

That cost angle is likely to resonate in referral practice. The authors explicitly frame their findings in terms of value-based care, arguing that a more expensive test is not automatically the more useful one if patient-centered outcomes are unchanged. Related commentary around Low’s broader imaging work has also highlighted interest in CT-first strategies for suspected IVDE, particularly when budget constraints shape decisions for pet parents and referring veterinarians. At the same time, discussion from specialists on professional channels shows the issue is not settled, with some clinicians emphasizing MRI’s role in identifying alternate differentials, spinal cord injury patterns, and medico-legal risk in atypical or high-stakes cases. (onlinelibrary.wiley.com)

The authors themselves are careful not to overstate the result. They note that the study does not prove MRI has no value, only that routine MRI did not improve aggregate outcomes in this specific population within their institutional setting. They also suggest MRI’s benefits may be concentrated in a smaller subset of dogs, including deep-pain-negative patients or those with a lower pretest probability of classic IVDE. That caution aligns with the ACVIM consensus statement, which says MRI can provide prognostic information in paraplegic dogs, especially deep-pain-negative dogs, and has superior ability to identify diagnoses other than IVDE. (onlinelibrary.wiley.com)

Recent IVDE studies in adjacent areas point in a similar direction: more intervention does not automatically mean better outcomes. In a prospective randomized pilot study of 32 dogs with paraplegia and absent pain perception undergoing decompressive surgery, adjunctive subarachnoid platelet-rich plasma and systemic erythropoietin did not produce a statistically significant overall clinical benefit. At 3 months, 75% of dogs regained ambulation, 21.8% did not, and one dog developed myelomalacia and was euthanized. The erythropoietin group showed only a non-significant trend toward less incontinence, suggesting that any benefit would need confirmation in a larger trial. Likewise, a randomized controlled trial of intraoperative IV magnesium sulfate in dogs undergoing thoracolumbar hemilaminectomy found no significant improvement in postoperative pain scores or inflammatory markers compared with placebo, although anesthesia recoveries were smoother and no adverse effects were reported. Taken together, those data reinforce the practical message from the imaging paper: in IVDE care, added complexity or biologic rationale alone is not enough—what matters is whether a strategy measurably improves patient-centered outcomes.

Another related issue is what happens after the imaging decision, particularly when prophylactic fenestration is part of the surgical plan. A recent Veterinary Surgery review on the biological and biomechanical effects of fenestration argues that the procedure should not be thought of as biologically neutral. Experimental models and limited canine data suggest fenestration triggers a strong reparative response marked by annular fibrosis, endplate sclerosis, and eventual ankylosis rather than restoration of normal disc architecture. Ex vivo work shows acute segmental laxity after fenestration, but in vivo healing appears to override that early destabilization, leading over time to marked stiffness and reduced range of motion. The review stops short of proving clinical harm in dogs with thoracolumbar IVDE, but it raises a plausible trade-off: prophylactic benefit against recurrence may come with longer-term changes in spinal loading that could shift stress to adjacent, non-fenestrated discs. For surgeons, that means the “extent of decompression” and use of adjunctive procedures mentioned in the imaging study sit within a broader conversation about how much intervention is actually optimal.

Why it matters: For veterinary professionals, this study may support a more selective imaging algorithm rather than a one-size-fits-all MRI-first approach. In practices where MRI access is limited, or where cost is a major barrier for pet parents, the paper offers evidence that CT-based pathways can still support good perioperative outcomes in the “classic” non-ambulatory chondrodystrophic IVDE case. That could help more teams move efficiently from diagnosis to decompression without assuming that the most information-rich scan always produces the best functional result. (onlinelibrary.wiley.com)

It also reinforces an important clinical distinction: imaging choice should reflect the question being asked. If the main goal is confirming a likely compressive thoracolumbar IVDE and planning surgery in a typical chondrodystrophic dog, CT may be enough. If the case is atypical, the neurologic injury is severe, prognostication is central, or alternative diagnoses remain in play, MRI still has clear advantages. And once surgery is underway, the same evidence-based lens applies to adjuncts and technique: current data do not show clear routine benefit for PRP, erythropoietin, or magnesium sulfate, while the longer-term consequences of fenestration deserve more deliberate consideration. (onlinelibrary.wiley.com)

What to watch: The next step is better stratification, ideally through prospective work that separates classic IVDE presentations from edge cases and tests whether MRI changes decisions or outcomes in deep-pain-negative dogs, unusual signalments, or dogs with equivocal CT findings. It will also be worth watching for larger trials of erythropoietin in severe spinal cord injury, confirmation or refutation of PRP’s lack of benefit, and whether magnesium sulfate’s smoother recoveries have any practical relevance despite the absence of analgesic or anti-inflammatory benefit. On the surgical side, more work is needed to determine the optimal extent of fenestration and whether fenestration-induced ankylosis meaningfully affects adjacent-disc disease risk over time. (onlinelibrary.wiley.com)