Visiting Veterinarian : Visiting vet: The importance of the MRI
The dog in the video is leash-walked by a young woman in scrubs. He looks happy, but there's something off about his gait — hind legs wobbling, front legs taking short, choppy strides. "The first thing you need to determine," the speaker tells the roomful of veterinarians, "is whether this is a neurological problem."
Abnormal gaits are frequently caused by orthopedic or musculoskeletal issues like hip dysplasia or torn ligaments, but this is a neurology conference. The dog in question had a spinal cord tumor, diagnosed with MRI. "Cool science," I think, looking at the MRI image, "but not many of my clients can spring for MRI." Although advanced technologies are necessary to make definitive diagnoses of many spinal cord diseases, your local veterinarian can figure out a lot just watching an animal move, and talking to you. Yes, you.
You, the owner, are an essential diagnostic tool. You are the one who noticed your pet's problem. Your veterinarian will ask you questions. When did you first notice a change? Did it happen suddenly or was the onset gradual? Since it began, has it gotten better, worse, or stayed the same? Is one side worse than the other? What about front versus hind? Does he seem painful? Have you given medication? Did it help? This information gives important clues about the source of the dysfunction.
Take Frisbee, the young Labrador playing outside. Leaping to make a brilliant catch, she lands, yelps once, and falls to the ground. You run to her side as she struggles to get up. "Phew, looks like she's okay," you think momentarily. Her face looks relaxed. Other than that initial yip, she shows no signs of pain. But quickly, her expression changes to perplexed. Her legs won't work properly. She staggers around the yard. You feel her all over. Nothing hurts. She just can't walk.
Frisbee has fibrocartilaginous embolism (FCE). Typically affecting young large breed dogs, FCE occurs when a bit of gelatinous material from inside an intervertebral disc gets into an artery supplying the spinal cord. Exact symptoms depend on exact location of the embolism. Now, I know if you owned Frisbee, you would call your vet immediately, but should you perchance be stranded on a desert island with no medical care, you would find her symptoms do not get worse as you await rescue. In fact, there is a good chance over the next few weeks as she regains some function. There is no specific treatment other than supportive care. Definitive diagnosis requires MRI. But should your veterinarian be marooned along with you, he could easily make a presumptive diagnosis with nothing more than the history and physical examination. The key clues here are Frisbee's age and breed, the sudden onset, relative lack of pain, and the fact that symptoms do not progress, or even improve, with time.
Disco, the Dachshund, is another story. Like Frisbee, she experiences sudden onset of hind leg dysfunction, but Disco is in pain. She looks distressed, flinches if you try to lift her, and has a tender spot on her back that makes her tense up and cry if you touch it. Disco has intervertebral disk disease (IVD). These disks are small circular pads between the vertebrae that work like shock absorbers. Chondrodysplastic breeds, i.e., long, low-slung dogs like dachshunds, basset hounds, beagles, and corgis, have a genetic predisposition for disk degeneration, followed by spontaneous rupture. Symptoms can range from mild neck or back pain to total loss of sensation and paralysis, depending on location and severity of the pressure on the spinal cord. Radiographs may help support diagnosis but are often not definitive.
Back on that desert island, however, your veterinarian would feel pretty confident that a dachshund with acute onset of back pain and gait abnormalities probably has IVD. As long as Disco has feeling and some use of her legs, treatment consists of anti-inflammatories, pain medication, and rest. "If you can walk, you can wait," the neurologist says. Severe cases require immediate surgical intervention, as do milder cases that do not respond quickly to conservative medical treatment.
What about Gerry, the middle-aged German Shepherd? His signs came on extremely gradually. First his hind paws dragged a bit, then they knuckled over, now he doesn't seem to really know where his hind feet are when he walks. His front legs are strong and work perfectly. He has no pain, but symptoms are steadily worsening. Gerry has degenerative myelopathy, a slow progressive spinal cord degeneration of unknown cause but suspected to be genetic. No treatment has proven effective. Gerry's age and breed, combined with the gradual onset, lack of pain, and progressive dysfunction all point your veterinarian to the diagnosis.
Bumpy, the Boxer, also has a slow, progressive, non-painful loss of normal locomotion, but in her case, front legs are also affected, which means the problem is likely in her neck. Boxers have a high incidence of cancer, so spinal cord tumor is top on our list.
The neurologist presents case after case. The febrile pit bull with meningitis. The King Charles Cavalier with syringomyelia. The Doberman with Wobbler syndrome. The Yorkie whose congenitally malformed neck vertebrae led to traumatic dislocation. Most cases are accompanied with MRI images showing the exact location of the tumor, inflammation, abnormal disc, embolism, syrinx, and so on.
As I leave the conference and head home, I think how far veterinary medicine has come in recent years, yet how much it has stayed the same. Prognosis and appropriate treatment depend on an accurate diagnosis. MRI is an amazing technology that has only become routinely available to pets over the last decade, enabling us to get that previously elusive definitive diagnosis. But many owners still cannot take advantage of this level of diagnostics for their animals, whether due to finances or philosophy. Marooned together on our Island, local vets and pet owners can still work together to make presumptive diagnoses and empirical treatment plans using the time-honored tools of history, observation, and physical examination.