IVDD or degenerative myelopathy? How vets tell them apart

IVDD or DM?

Your dog's back legs are weaker than they used to be. Maybe the feet scuff, the back end sways, or your dog stumbles on turns. Your vet has mentioned two possibilities you keep seeing online: IVDD (a disc problem) and degenerative myelopathy, often shortened to DM. They can look alike at first, and the difference matters, because the care paths are very different.

IVDD happens when a disc between the bones of the spine bulges or bursts and presses on the spinal cord. Degenerative myelopathy is a slow, inherited disease of the spinal cord itself. Nothing is pressing on the cord. The nerve tissue gradually stops working the way it should.

This page explains the clues vets use to tell them apart: pain, how fast things change, age and breed, what the DM gene test can and cannot tell you, and why imaging such as MRI matters. It does not diagnose your dog. Only a vet who examines your dog can do that.

Act now first if your dog suddenly gets worse

Whatever the cause turns out to be, some signs mean your dog needs a vet today, not a wait-and-see plan:

• Your dog suddenly cannot walk, or is much weaker than a few hours ago
• Your dog is crying out, trembling, or holding the back or neck stiffly in pain
• Your dog cannot pee, or is leaking urine without knowing
• Your dog does not react when you gently squeeze the toes

Go to your vet or an emergency hospital now. See IVDD emergency signs and herniated disc symptoms.

Side by side: the usual clues

These are general patterns, not rules. Many dogs do not fit neatly, and that is exactly why the exam and imaging matter.

Clue 1: pain

A disc that presses on the spinal cord often hurts. Dogs may cry out when picked up, hunch the back, refuse stairs, shiver, or hold the neck low. DM is usually not painful. Many caregivers describe a dog who seems happy and comfortable but whose back legs simply do not cooperate.

Pain is a strong clue, but not a perfect one. Slow disc bulges, sometimes called Type II IVDD, can cause mild or no obvious pain. Some dogs also hide pain well. See how to spot pain in a dog with IVDD.

Clue 2: sudden or gradual

Classic IVDD often shows up suddenly. Your dog was fine yesterday and is wobbly or down today. DM creeps in. Owners often notice it first as scuffed nails on the back feet, a swaying back end, crossing the back legs, or trouble getting up on slick floors. Over months, the weakness slowly increases.

A useful thing to bring your vet is a short timeline: when you first noticed a change, and whether it came on in a day or over weeks. Short phone videos of your dog walking help too.

Clue 3: age and breed

DM is mostly a disease of older dogs, and it is more common in certain breeds, including German shepherds, boxers, and Pembroke Welsh corgis. IVDD can affect dogs of many ages, and some breeds, such as dachshunds and French bulldogs, are known for disc problems earlier in life. For more on breed risk, see IVDD breeds and genetics.

Corgis are a breed where both conditions come up, so corgi owners often hear both names in the same visit.

What the DM gene test can and cannot say

DM is strongly linked to a change in a gene called SOD1. A DNA test, usually from a cheek swab or blood sample, shows how many copies of that change your dog carries.

What it can tell you:

• Two copies (often reported as "at risk"): your dog has a higher genetic risk of developing DM.
• One copy (a "carrier"): your dog is far less likely to develop DM, though it is not impossible.
• No copies (often "clear" or "normal"): DM from this gene change is unlikely.

What it cannot tell you:

• It does not diagnose DM. Many dogs with two copies never develop signs in their lifetime.
• It does not rule out IVDD or anything else. A dog can be "at risk" for DM and still have a disc problem causing today's signs.
• It does not say when signs might start.

In a dog that already has signs and has had other causes ruled out, an "at risk" result can support your vet's working diagnosis. On its own, it is a risk marker, not an answer.

Why MRI matters

There is no single test that confirms DM in a living dog. Vets usually reach a DM diagnosis by ruling out other causes that look similar, especially a disc or something else pressing on the spinal cord. That is why your vet or a veterinary neurologist may suggest MRI or another advanced scan.

• If MRI shows a disc pressing on the cord in the right place, IVDD may explain the signs.
• If MRI shows no compression that explains the signs, DM moves higher on the list, especially in an older dog of a typical breed with a matching gene result.
• Sometimes MRI shows a mild disc bulge that may or may not explain everything. Older dogs can have both a disc problem and DM. Your vet will weigh how much each one is likely contributing.

Imaging also checks for other look-alikes, such as tumors, inflammation, or other spinal problems. If you are deciding about MRI, see questions to ask before MRI or advanced imaging and how IVDD is diagnosed. For who to see, see regular vet or veterinary neurologist?

Very different care paths: strict rest vs keep moving

This is the main reason the difference matters.

IVDD: depending on severity, care often starts with strict crate rest so the disc and spinal cord can settle, or with surgery to remove the pressure. Activity is limited for weeks, then rebuilt step by step with your vet's guidance.

See crate rest and non-surgical IVDD plan.

DM: there is no cure, and rest does not fix it. Vets usually encourage dogs with DM to stay active within safe limits, because regular movement and physical therapy may help keep strength longer. Support often focuses on traction on floors, protecting the back feet, safe help on stairs and in the car, and planning ahead for mobility support as things change. See rehabilitation, mobility aids, and safe home setup.

Because the paths pull in opposite directions, do not switch from rest to more exercise, or the other way around, on your own. Ask your vet which path fits your dog right now.

Medicines are used differently, too. Pain and anti-inflammatory medicines are often part of IVDD care but usually do not slow DM. Your vet will explain what, if anything, fits your dog. See IVDD medications for medicine types, and do not start, stop, or change any medicine or supplement without your vet.

Questions to ask your vet

• Which do you think is more likely right now, a disc problem or DM, and why?
• Is my dog showing pain anywhere when you examine the spine?
• Would MRI or another scan change the plan for my dog?
• Should we do the DM gene test, and how would the result change what we do?
• Could my dog have both a disc problem and DM?
• Should my dog be resting right now, or staying active? What exactly is safe?
• What changes at home should make me call you?
• Would a rehabilitation vet or physical therapist help us?

If the news is DM

Hearing that your dog may have a progressive condition is hard. Many dogs with DM have good months of walks, sniffing, and time with their family, especially with an active routine and the right support at home. When you are ready, quality of life with lasting weakness and the caregiver guide can help you think ahead, at your own pace, with your vet.

Before you decide anything

This page is purely informational and is not perfect advice. Follow your vet's plan, and always check with your vet before changing, altering, or supplementing anything. If your dog suddenly cannot walk, is in pain you cannot settle, or cannot pee, go to your vet or an emergency hospital now.