Laryngeal Paralysis Is First Sign of General Neurological Paralysis
Debby Handler knew something was wrong when "Will," her 10-year-old yellow Labrador Retriever, began breathing heavily and his bark became hoarse. "He was not gasping for breath, but it was obvious his airway was starting to close down a bit," says Handler of Ann Arbor, Mich.
Will was diagnosed with idiopathic laryngeal paralysis, a condition in which the muscles of the larynx become paralyzed. When paralysis sets in, the larynx cannot expand, which restricts a dog's ability to breathe deeply. Most dogs with laryngeal paralysis exhibit loud, labored breathing and throat clearing, as Will did. The disease can cause life-threatening breathing obstruction if left untreated.
Laryngeal paralysis is a well-known upper respiratory problem first diagnosed in the 1970s. It affects older, large-breed dogs, most commonly Labrador Retrievers and Newfoundlands, but also other breeds and mixed breeds. A congenital form, affecting younger dogs, is seen in Bouvier des Flandres, Dalmatians, white-coated German Shepherd Dogs, Leonbergers, Pyrenean Shepherds, Rottweilers, and Siberian Huskies.
Bryden J. Stanley, B.V.M.S., M.Vet.Sc., DACVS, associate professor of surgery at Michigan State University College of Veterinary Medicine in East Lansing, Mich., began researching laryngeal paralysis in 2005. Her research showing that paralysis of the larynx is the first sign of slow-developing, generalized paralysis was published last February in Veterinary Surgery.
Similar conclusions were made in a case study published in the May/June issue of the Journal of the American Animal Hospital Association. The research, conducted at the University of Tennessee, found that 11 dogs diagnosed with laryngeal paralysis also had signs of generalized neuromuscular dysfunction.
Stanley's research showed that many dogs suffering from laryngeal paralysis experience esophageal problems. In time, they exhibit generalized neurological deterioration, initially noticeable in their hind limbs.
"We discovered that something we thought was unique to the larynx is not," Stanley says. "Laryngeal paralysis is an early sign of a more general neurological degeneration."
Looking Beyond the Larynx
Stanley's study followed 32 dogs suffering from laryngeal paralysis and 34 healthy dogs in a control group. Seventy percent of the laryngeal paralysis cases Stanley studied were in Labrador Retrievers. The dogs in the control group were selected to match the age, sex and breed of the diagnosed dogs. The dogs ranged in age from 6 to 14 years old, with an average age of 11 years.
All dogs received esophageal radiographs, or esophagrams. Those diagnosed with laryngeal paralysis underwent laryngeal tieback surgery, the most common corrective surgery for the disease. The procedure involves using permanent sutures to hold open arytenoid cartilage so air can easily pass through the larynx.
The dogs returned for five follow-up examinations during the next year. Though the dogs' exercising and breathing abilities improved after surgery, Stanley found some dogs appeared to experience more swallowing problems. Additionally, 75 percent of the dogs diagnosed with laryngeal paralysis demonstrated esophageal dysfunction, though only 28 percent had a history of regurgitating or gagging.
Stanley also found that after surgery, 18 percent of dogs developed aspiration pneumonia, an inflammation of the lungs due to regurgitating gastric acid or food aspirating into the airway. These dogs had worse esophageal function than the other diagnosed dogs. Neither a dog's neurological status nor history of regurgitation was an accurate predictor of aspiration pneumonia.
Stanley's study also showed a general deterioration of neurological function in all dogs within a year of the initial laryngeal paralysis diagnosis. At the time of diagnosis, 31percent of the dogs had abnormal neurological examinations, particularly related to their hind legs. Muscle wasting, weakness, unsteadiness, gait problems, and abnormal spinal reflexes were among the problems.
Within six months of the initial diagnosis, 58 percent of the dogs were abnormal. After one year, all dogs diagnosed with laryngeal paralysis showed signs of other nerves being affected. Some were unable to walk. Others experienced marked muscle wasting of hind limb muscles, spinal muscles and muscles on top of the head.
One such dog is "Bailey," a 13-year-old yellow Labrador Retriever owned by Philip Baron of Cadillac, Mich. When Bailey was 10, Baron noticed the dog wheezed and coughed after walks. "I called it an old man's hack," Baron says. "I noticed that Bailey had a significant drop in energy during our daily walks, and he would have to rest several times during a relatively slow walk through the woods."
Baron also noticed Bailey's tongue and gums were discolored after exercise. "His tongue was a deep purple color, and he would essentially collapse when we got home," Baron says.
Bailey was diagnosed with laryngeal paralysis and had laryngeal tieback surgery. The surgery greatly improved his quality of life, particularly when the dog and owner went for walks.
"It was noticeable within days after the surgery," Baron says. "His age affected the distance that we walked, but the quality of the walk was much better. He could prance and run, whereas before he was sluggish. His tongue and gums were back to their normal color even during a walk."
After the surgery, Bailey's breathing improved, but over the next two years, he began dragging his hind legs more. "Now, you can see some atrophy in the hindquarters, and because he is losing muscle mass, you can see his bone structure more," Baron says.
While tieback surgery has improved Will's quality of life, general neurological deterioration has been slow but gradual. "He has started to lose some muscle in his hind end," Handler says. "You notice it in the way he stands. It's as though he's sometimes unaware of where his hind end and legs are."
As a result of that weakness and ongoing battles with arthritis, Will no longer jumps onto the bed. However, the corrective surgery has enabled him to take long walks several times a week.
"Will has bursts of ability and strength," Handler says. "Last winter, he trudged with us through eight inches of snow on the golf course. He will suddenly lapse though. One night he attempted to go upstairs, and I think if I hadn't encouraged him, he would have gone down right there."
Subsequently, the veterinarian prescribed medication for Will's arthritis, which has enabled him to once again climb stairs. The tieback surgery combined with the arthritis medication has greatly improved Will's quality of life, Handler says.
Managing Laryngeal Paralysis
Stanley hopes her research can help prepare owners for the gradual nerve degeneration that follows a laryngeal paralysis diagnosis. "I think we can manage laryngeal paralysis, the swallowing issues and the resulting neurological progression better now because we know what to expect," she says.
Baron has found that frequent exercise helps manage Bailey's condition. "The less active he is, the more work he must exert to move around and walk," Baron says. "However, if he gets out and stays active, he has more mobility."
Handler has found that elevating the food bowl helps avoid aspiration pneumonia. She noticed Will fares better during feeding when she elevates his bowl, causing him to raise his front end higher than his rear.
While Bailey and Will are fairly active dogs living with the disease, not all laryngeal paralysis cases are so manageable. "Some dogs seem to progress more quickly," Stanley says. "Occasionally, they deteriorate markedly within a year."
Owners whose dogs have more immediate and degenerative cases of laryngeal paralysis are often distressed. Support networks dedicated to helping others cope provide understanding.
"Once they've had a dog that suffered from laryngeal paralysis, people become committed to the disease," Stanley says. "After they've nursed one through, they want to help others."
With the help of those owners, Stanley is pursuing additional research to identify genetic causes of the disease. Researchers are also collecting pedigrees and blood samples to extract DNA. The goal is to determine the mode of inheritance and find a gene mutation in Labrador Retrievers and Newfoundlands.
"The real breakthrough will be characterizing what exactly this disease is and finding the underlying genetic mutations," Stanley says. "We still have another 10 years of research, but it would be wonderful for the owners and the dogs if we can breed away from the disease."
GOLPP More Accurately Defines Condition
Research conducted at Michigan State University shows that idiopathic laryngeal paralysis, a condition in which the muscles of the larynx become paralyzed, is actually part of a progressive general neuropathy. The condition eventually affects esophageal function and leads to generalized neurologic dysfunction, particularly in the hind legs.
As a result of the findings, Bryden J. Stanley, B.V.M.S., M.Vet.Sc, DACVS, associate professor of surgery, and her colleagues at Michigan State University suggest renaming the condition geriatric onset laryngeal paralysis polyneuropathy (GOLPP) to more accurately define the progressive disorder.
To further investigate GOLPP, Michigan State has formed a study group made up of surgeons, neurologists, diagnostic imaging specialists, internists, pathologists, anesthesiologists and molecular geneticists. They have recently received funding from the AKC Canine Health Foundation to investigate GOLPP. The goal is to provide more information about the disease and help for managing dogs that suffer from the condition.
To participate in the ongoing research, please contact Michele C. Fritz at [email protected] or 517-432-9902. For more information about GOLPP, visit http://cvm.msu.edu/golpp. You may also contact the researchers by sending an e-mail to [email protected]