What is IVDD?
IVDD stands for intervertebral disc disease.
Discs sit between the bones of the spine. They help cushion the spine as a dog moves.
With IVDD, material from a disc can move into the spinal canal. This can press on the spinal cord.
Dogs with IVDD can have very different signs. Some dogs may have pain. Others may have trouble walking or moving their legs.
What did researchers want to know?
Researchers wanted to know if the amount of disc material or pressure on the spinal cord matched how serious a dog's nerve problems were.
It may sound simple:
More pressure should mean worse signs.
But the research shows that it is not always that simple.
What did the 2023 study find?
A 2023 study looked at 70 small-breed dogs with IVDD in the middle or lower part of the back.
All of the dogs had type I thoracolumbar IVDD that was confirmed during surgery.
Researchers used CT images to measure how much disc material had moved into the spinal canal.
They compared this with how serious each dog's nerve signs were.
Dogs with more disc material tended to have worse nerve signs.
However, the connection was weak.
This means the amount of disc material seen on an image did not fully explain how badly a dog was affected.
What did the other study find?
A 2008 study looked at 33 dogs with IVDD in the neck.
Researchers used MRI images to measure how much the spinal cord was being compressed.
More spinal cord compression was linked with worse nerve signs before surgery.
However, the amount of compression was not linked with the dogs' nerve status after surgery.
Again, the image told only part of the story.
Why can two dogs look different?
A scan can show what is happening inside the spine, but many things can affect how a dog looks and moves.
The amount of pressure on the spinal cord is only one part of the picture.
The dog's examination, history, movement, nerve function, imaging and other medical information all matter.
This is why veterinarians do not make decisions from one measurement on a scan alone.
What does this mean for dog owners?
An MRI or CT scan can provide very important information.
But a picture of the spine does not always tell you exactly how a dog will look, move or recover.
Two dogs with IVDD may have different signs even when their images seem similar.
The veterinary team looks at the whole dog, not just the image.
Why does this matter in rehabilitation?
Rehabilitation also begins with the individual dog.
A rehabilitation plan should consider the dog's medical history, veterinary examination, current movement, physical abilities, comfort and goals.
The amount of spinal cord compression seen on an image is useful information, but it does not tell the rehabilitation team everything they need to know.
What are the limits of this research?
These studies were not the same.
The 2023 study looked at 70 small-breed dogs with IVDD in the middle or lower back.
The 2008 study looked at 33 dogs with IVDD in the neck.
They also used different types of imaging and measured the spine in different ways.
Because of these differences, the studies should not be treated as if they asked exactly the same question.
They also do not mean that imaging is unimportant.
Instead, they show why imaging findings should be considered together with the dog's full veterinary examination.
The main takeaway
More spinal cord compression does not always mean a dog will have worse signs or a worse outcome.
Imaging is an important tool, but it is one part of a much larger clinical picture.
Every dog with IVDD should be evaluated as an individual.
Research used for this brief
Sakaguchi Y, Nishida H, Tanaka H, et al. (2023).
The volume of extruded materials is correlated with neurologic severity in small-breed dogs with type I thoracolumbar intervertebral disk herniation.
Journal of the American Veterinary Medical Association.
DOI: 10.2460/javma.22.07.0326
Ryan TM, Platt SR, Llabres-Diaz FJ, McConnell JF, Adams VJ. (2008).
Detection of spinal cord compression in dogs with cervical intervertebral disc disease by magnetic resonance imaging.
Veterinary Record.
DOI: 10.1136/vr.163.1.11
Further listening
This Research Brief was inspired by the Veterinary Rehabilitation Podcast episode “Spinal Cord Compression and Neurological Deficits in IVDD with Megan Doyle,” published March 17, 2026.
