Mae Comes Home – with Degenerative Myelopathy

Mae makes herself at home

Some of you might recall Mae – she’s our big boned cream girl, also famous for being mom to the uber cute Solo. Mae was placed into a retirement home, but when things got rough for her adoptive mom, she thought it was best for Mae to come back to us. We’re always ready to take back any of our placed dogs, so of course we arranged to pick Mae Mae up.

We knew she’d been experiencing some rear end weakness, and that her vet had been having a hard time coming up with a definitive diagnosis for what was causing it. I’d assumed it was likely arthritis – her vet had speculated it was first stage degenerative disk disease, but in my (thanfully limited) experience with that, it usually comes as a ‘bolt from the blue’. One day, your dog goes to sleep completely normal, the next day, they wake up paralyzed.

Mae’s condition, on the other hand, was slowly progressive.

Knowing Mae was coming home, I made a vet appointment for the following day. Once I’d seen Mae, I was even more glad I’d made the appointment.

Mae’s hind end weakness is very pronounced – she knuckles over when she walks, and on slick surfaces she comes close to dragging her rear. She also has some difficulty bending forward to reach a water dish – an elevated feeding platform seems to have alleviated some of this.

Mae is also now fecally incontinent – she does not seem to realize when she needs to defecate, until after she’s already done so.  Basically, she’ll be walking past you, and poop will just sort of fall out of her. A few seconds later, she’ll seem to think “Oh, hey. I think I have to go outside and poop”, at which time she’ll head over to the door to ask to go outside. Pickle, who has developed the disturbing habit of poop eating, is currently regarding Mae as a kind of walking gumball machine.

Because Mae isn’t pushing when she defecates, her anal glands aren’t getting expressed, so she’s developed a rather nasty abcess. Poor baby! Nothing says ‘welcome home’ like having someone wrestle you down and clean out your butt abcess.

I realize that all of this sounds rather horrible. Mae, however, is still her happy, playful, joyful self, and she’s obviously in no pain (well, other than the butt squeezing).

I had a bad idea that I knew what all of these symptoms added up to – degenerative myelopathy. I wanted the veterinarian to help me to determine if I was right, and what the prognosis was.

Degenerative Myelopathy, for those lucky enough to have never encountered this horrid condition, is a progressive auto immune disease. It affects all dogs, of all breeds including mixes, and is thought to be similar to Lou Gehrig’s Disease in people.

The Canine Genetic Disease Network has a brief overview of DM –

Degenerative myelopathy is a progressive disease of the spinal cord in older dogs. The disease has an insidious onset typically between 8 and 14 years of age. It begins with a loss of coordination (ataxia) in the hind limbs. The affected dog will wobble when walking, knuckle over or drag the feet. This can first occur in one hind limb and then affect the other. As the disease progresses, the limbs become weak and the dog begins to buckle and has difficulty standing. The weakness gets progressively worse until the dog is unable to walk. The clinical course can range from 6 months to 1 year before dogs become paraplegic. If signs progress for a longer period of time, loss of urinary and fecal continence may occur and eventually weakness will develop in the front limbs. Another key feature of DM is that it is not a painful disease.

As you can tell, this pretty much sums up Mae’s symptoms. But what causes Degenerative Myelopathy?

Degenerative myelopathy begins with the spinal cord in the thoracic (chest) region. If we look under the microscope at that area of the cord from a dog that has died from DM, we see degeneration of the white matter of the spinal cord. The white matter contains fibers that transmit movement commands from the brain to the limbs and sensory information from the limbs to the brain.

This degeneration consists of both demyelination (stripping away the insulation of these fibers) and axonal loss (loss of the actual fibers), and interferes with the communication between the brain and limbs. Recent research has identified a mutation in a gene that confers a greatly increased risk of developing the disease.

The PNAS website has this side by side comparison view of thoracic spinal cords, showing the clinical changes which DM causes:

Fig. 2.

Spinal cord histopathology. (A) Luxol fast blue-periodic acid Schiff staining of a thoracic spinal cord cross-section from a DM-affected 13-year-old Pembroke Welsh corgi. The white matter degeneration is depicted by regions of pallor where there has been loss of nerve fibers. (B) A similarly stained spinal cord cross section from an unaffected 13-year-old Labrador retriever. Note there is no evidence of nerve fiber loss. The bar in the lower right of the photomicrograph indicates the magnification.

Until recently, diagnosis of Degenerative Myelopathy was, in the words of the CGD website, a “diagnosis of elimination”. In other words, look for other causes, rule them out, and when you run out of options you can assume it’s DM.

Now, thankfully, we have a DNA test which can identify the genetic marker for DM (thank you, Canine Genome Project).

The DNA test is offered, free of charge, to French Bulldogs, Chesapeake Bay Retrievers,  Boxers, Pembroke Welsh Corgis and Rhodesian Ridgebacks, thanks to donations made by the AKC Canine Health Foundation, American Boxer Charitable Foundation, Pembroke Welsh Corgi Club of America, Rhodesian Ridgeback Club of the United States, French Bulldog Club of America, and French Bulldog Rescue League. However, it is only free to dogs age ten years and older. Mae doesn’t make this cut off, so we’ve ordered hers for $65.

Data is collected via OFA (Orthopedic Foundation for Animals).

When it arrives we’ll have Mae’s blood collected, and use the kit to send her samples to OFA for definitive diagnosis. This won’t help us to treat her condition – there is no treatment or cure for Degenerative Myelopathy. It will, however, allow us to help to contribute to on going research into the condition.

Mae’s prognosis isn’t great. DM is, I’ve mentioned, a progressively worsening condition. She’ll lose more and more of her co ordination, and her rear limb weakness will steadily worsen. Eventually, her rear will cease to be functional at all, at which time she’ll only be able to get around if we obtain a mobility cart for her. After a time, the paralysis will spread to her front limbs, and finally to difficulty in swallowing. Thankfully, there is no pain associated with DM.

For now, we’ll wait for a definite diagnosis, and continue to enjoy Mae’s presence. She’s happy to be here, and she really seems to enjoy once more having other dogs for company. Pickle has adopted Mae as the mommy she’s always wanted, while Delilah is fairly certain we’ve hired Mae as a live in nanny to care for that pesky kid of hers.

In other words, it’s business as usual over at Casa Bullmarket.