PAWSITIVE HAPPENINGS - April 2018 Veterinarian Newsletter

Posted April 27, 2018 in Articles
Clinic Updates
Degenerative Myelopathy
Our big sign was blown down during one of our last storms - and is still in the process of being replaced.  If any of your clients need directions - please have them call!.

MVER's hours of operation have changed! 
We are now open 
Monday - Thursday 5pm - 8am and 24 hours on weekends; 
5pm Friday through 8am Monday
Dr. Garrod is on medical leave until mid-May.  

Critical care, Cardiopulmonary medicine, Imaging:
Chris Rollings, DVM, DACVIM
Heather Jones DVM, MS, DACVIM (neuro)
Keith Montgomery DVM, DACVO
Kim Johnson DVM, DACVIM (onc)
Marlene Hauck DVM, PhD, DACVIM (onc)
Sean Kennedy DVM, DACVS
Stephanie Lister Grey DVM, MSc DACVS
April Chambers, DVM
Jessica Cioffi, DVM
Casey Cole, BVM
Gina Dinallo, DVM
Ashley Dunn, DVM
Ali Haghnazary, DVM 
Tricia Prine, DVM            
Amanda Profita, DVM

Degenerative myelopathy (DM) is the name given to a degenerative spinal cord disease of dogs similar to Lou Gehrig's disease (amyotrophic lateral sclerosis; ALS) in people. Any dog can get DM, but some of the breeds most implicated include the German shepherd, Pembroke Welsh corgi, Boxer, Chesapeake bay retriever, Bernese mountain dog, Rhodesian ridgeback, and Cavalier king charles spaniel. Although it is believed that DM has a heritable basis, the clinical signs of DM do not appear until later in an animal's life, typically around 7-11 years of age.

The first sign of DM is often scuffing of the hind toenails while walking, or slipping of the hind limbs on slick floors. These signs may be symmetric or asymmetric. Paraparesis progresses slowly over several months with the typical patient becoming nonambulatory 6-12 months after signs are first noted. Eventually, the front limbs also become affected and, if the disease is left to its natural course, brainstem signs follow. DM is not a painful condition and does not present acutely - this is a chronic, slowly progressive, nonpainful myelopathy.

Unfortunately, there is no effective treatment for reversing signs or halting progression of DM. Physical therapy and exercise is recommended to keep dogs with DM as strong as possible, but eventually all affected dogs will lose the ability to walk.

There is no test to diagnose DM in a living patient. Instead, the focus is to rule-out the presence of other, more treatable conditions such as intervertebral disc disease. This is done by performing an MRI and spinal tap.
What about the "DM test"?

A genetic test is available for a gene associated with the development of DM in some dogs. This gene, SOD1, is mutated in some dogs with DM and it is also mutated in one form of ALS in people. It is important to know that this is not a test for DM, but more an assessment of risk. There are dogs who test "at risk", meaning they have 2 copies of the mutation, who never develop DM, and there are dogs who test "clear", meaning they do not carry the mutation, who do indeed go on to develop DM. SOD1 mutation testing is a useful tool, but results must be used as one part of the entire clinical picture of a patient.

Heather Jones, DVM, MS, DACVIM (Neuro)

Laryngeal paralysis

Spring is here (while it may not feel much like it yet) - and with warmer weather -comes laryngeal paralysis dogs in crisis. Many of these patients have been developing slow progression in symptoms over even 6-12 months- but may have stayed relative static in symptoms through the colder months. With return of warmer days or more humidity - those patients that may have done ok through the winter- can present in acute respiratory crisis with little or no warning.

Laryngeal paralysis is most commonly diagnosed in older Labrador retrievers - between 9-13 years of age (especially black Labradors) - although any older dog (and even the occasional cat) can be diagnosed with the condition. There is a congenital / early onset / hereditary form seem in certain breeds - most notably Huskies and Dalmatians in the US - generally before 1 year of age. The acquired form is typically idiopathic- although it can be linked to chronic endocrine, infectious or immune mediated polyneuropathy. Up to 30% of patients can show concurrent peripheral neuropathy symptoms, either at the time of diagnosis, or within a year. This presents most typically as mild proprioceptive deficits, difficulty doing stairs, difficulty with slippery flooring. Some patients can have more significant symptoms - if there are reports of regular regurgitation, vomiting or swallowing changes - this can raise concerns about concurrent esophageal dysfunction and megaesophagus (up to 11% of dogs with laryngeal paralysis) - and is associated with increased risk of post-operative complications.

With older pets with a history of increased upper airway noise - even with no history of prior crisis - spring is a time to discuss this again with pet owners. Consider prescribing a sedative to be on hand in the event of stress or adverse excitement. Options would include oral acepromazine or trazodone. Doxepin is another drug option for regular use. Discussion should include events / activities to avoid - with avoidance of any exertion in warm weather, steering walks towards cooler parts of the day, and avoiding excess excitement / stress. Some pets (especially if owners would not do surgery) may do better with a low-dose steroid or non-steroidal anti-inflammatory to decrease airway swelling.

Surgery is generally recommended for dogs with moderate to marked symptoms. Surgery is generally not pursued yet for those pets with milder symptoms (or just suspicion of disease) - generally the cross-over point is where they can no longer take part in normal activities without showing respiratory stress, or after any crisis.

Diagnostics generally included for full evaluation include three view chest radiographs, full blood work including thyroid testing, neurologic examination, esophageal function testing if concerns are present and sedated airway examination. When performing airway examination - it is important not to give a variety of sedatives or anesthetics - as these can have affect on laryngeal function - even in normal dogs. I will generally perform airway examination under just propofol - keeping them light enough to maintain a swallow reflex. If needed - doxapram can be given to increase degree of inspiratory motion during this procedure. Finding of lack of inspiratory opening is considered diagnostic - although many will show paradoxical motion on maximum inspiration. Mild arytenoid redness / swelling / edema is also typically seen.

In the emergency presentation - with full respiratory crisis - full diagnostics often need to be put on a back burner - with focus on immediate stabilization. For moderate distress - this can involve sedation (generally acepromaxine 0.02-0.1mg/kg IV, max 3mg), cooling (to treat frequent hyperthermia), flow-by oxygen, +/- low-dose steroids (0.1-0.2mg/kg dexamethasone). In extreme presentation - emergency intubation is needed (try to evaluate quickly while intubating) - followed by the above. Generally intubation for even an hour will significantly improve function and allow extubation. If presenting with this type of crisis - if the owners will go for surgery- than arranging immediate referral for surgery while still sedated / calm is recommended. If not stable for transport, temporary tracheostomy can be performed - but this does generally increase complications rates following surgery, and surgery (if available) is often done in the emergency setting if unable to stabilize with normal care.

The surgery most commonly performed is unilateral arytenoid lateralization - with the goal to stabilize one of the arytenoids in a half open position, and prevent paradoxical motion, although not open so far as to dramatically increase risk of pneumonia. Generally - improvement is expected in 90% of animals undergoing surgery, and 70% of dogs are still alive 5 years after surgery (although this is generally an older population to start). Potential serious complications include airway swelling / intra-mural hematoma, aspiration pneumonia, suture breakage or cartilage fracture resulting in surgical failure. Factors associated with higher risk of complications include pre-operative pneumonia, post-operative megaesophagus and temporary tracheostomy. During recovery -they are often discharged to home as quickly as possible to minimize stress and all heavy sedation / opioids are avoided. It is important that pets are kept quiet for 4 weeks following surgery. Long-term - walking with the aid of a harness is recommended, and swimming is generally discouraged.

Stephanie A. Lister Grey, DVM, MSc, DACVS