Pug Myelopathy: a new understanding of “weak rear”


  • March 28, 2019
  • by Kathleen L. Smiler, DVM, DACLAM

From the March 2019 issue of ShowSight. Click to subscribe.

By Kathleen L. Smiler, DVM, DACLAM, Pug Dog Club of America Health Committee Chair

Pug Myelopathy is a recently recognized spinal condition believed unique in purebred Pugs. It is called by several terms (e.g., constrictive myelopathy, facet hypoplasia), and it is most often referred to as “Pug Myelopathy.” With an average age of onset of ~nine years, the rear limb incoordination (ataxia) may progress to paralysis of the rear limbs over a period of one to four years. Originally referred to as “weak rear,” this has become a widespread problem in Pugs. Although the rear legs appear to be weak, the cause is a neurological deficit that develops in the spine. Affected dogs may initially drag their feet, stagger, have trouble jumping and can have fecal and urinary incontinence. It usually affects just the rear limbs, unlike a very different disease, Degenerative Myelopathy (DM), which can have similar initial signs, but slowly progresses tragically to complete paralysis and usually euthanasia. In Pug Myelopathy, we are learning there is usually a complex of spinal abnormalities that involve both the vertebral bones, and the spinal cord. Spinal cord compression—often near the last pair of ribs—can be caused by one or more syndromes that may include chronic multiple moderate Hansen’s Type II intervertebral disc disease (IVDD) and spinal arachnoid diverticulum (SAD) “pouch”, with fibrous thickening of the arachnoid (a layer of the spinal cord membranes – meninges - surrounding the spinal cord) and spinal cord atrophy. Unraveling the relationships between these conditions is one goal of the research at Michigan State University, led by Dr. Jon Patterson, which is funded by the Pug Dog Club of America. Although little is published about this condition, Pug Myelopathy may be the most common cause of mid-back spinal cord problems in Pugs.

Many veterinarians are not yet knowledgeable about this condition, and affected dogs may have had a previous diagnosis that was incomplete or inaccurate. Since so little is known, there is no consensus among neurologists about the best way to treat it. Surgery may be appropriate for a limited number of individual cases, but it must be considered as soon as possible after symptoms first occur, and may only delay progression of paralysis.

The most important palliative treatment appears to be consistent physical therapy using rehabilitation exercises to preserve muscle strength and enhance development of a “spinal walk.” A therapeutic wheeled cart, carefully fitted by a knowledgeable professional, may exercise the rear legs to assist, improve, and extend the ability to remain mobile. Other forms of integrative medicine can enhance the ability and interest to stay active. Pugs affected with Pug Myelopathy are usually pain free and can lead enriched long lives with good nursing care despite their disability. All senior Pugs require periodic wellness exams to detect and alleviate other problems of aging; including those of the dog’s front legs, shoulders, and neck; including using medication and/or supplements. It is critical that affected Pugs be carefully monitored for the ability to completely empty the urinary bladder several times a day. If your dog develops signs of “weak rear” or ataxia, it is important to have your primary care veterinarian arrange a referral for an examination by a board-certified veterinary neurologist or surgeon as soon 
as possible.

In Pug Myelopathy, both bony (vertebral) and spinal cord abnormalities are found in most cases. Almost all purebred Pugs have hypoplastic (underdeveloped) or aplastic (absent) facet articulations between the vertebrae of the mid to lower back. These are best seen with a CT scan, but to understand lesions potentially compressing the spinal cord, an MRI is the preferred diagnostic test.

Currently there is no way to predict which Pugs will develop a neurological disease at 7-12 years of age, long after a successful show and breeding career has occurred. Using state-of-the art canine genetic tools, scientists at Purdue University will begin to investigate the genetic variants underlying these canine spinal abnormalities, hopefully leading to the development of genetic tests. Such tests would allow breeders to screen for clinically relevant spinal abnormalities, and examine possible inheritance, while selecting for desired breed characteristics. A genetic test may also identify individual dogs “at risk” for Pug Myelopathy syndromes, be used to aid in diagnosis of an affected dog, and/or supplement a prognosis after spinal injury or trauma. Genetic screening would improve the welfare and well-being of purebred Pugs, and provide direction in reducing other inherited disorders in purebred dogs. To submit case history and medical records, test results and images, and pedigrees and DNA samples from affected Pugs please contact Dr. Smiler. A clinical study to examine the benefits of rehabilitation and physical therapy for long term nursing care is also in development.

To obtain more information on Pug Myelopathy please contact:

Kathleen L. Smiler, DVM, DACLAM (click to email).

Our websites: http://pugrearataxiaparalysis.com/ and http://www.pugdogclubofamerica.com/pug-myelopathy.html.

Our Facebook Page: https://www.facebook.com/Pug-Dog-Health-Rear-AtaxiaParalysis-218123938233440/.

Wonderful Wheelie Pugs Support Group: https://www.facebook.com/groups/wheeliepugs/

About the Author

Dr. Kathleen Smiler’s Pug, 7-year-old Lily (pictured above), was affected in 2005 by an almost unknown rear limb weakness first recognized at Auburn University. In the past 12 years Kathleen has increased awareness, promoted research, and developed resources for Pug owners to provide long term home nursing care for their own disabled dogs. Dr. Smiler is a 1970 graduate of the Michigan State University, College of Veterinary Medicine. Her work experience in research combines purebred dog practice with basic investigative science. She has held offices in many veterinary medical organizations, and is currently the Michigan Delegate to 
the AVMA.

 

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