What is laryngeal paralysis (LP)?
Normally, the voice box (the "larynx") opens as the dog inhales
and partially closes during exhaling. Laryngeal paralysis (LP) occurs
when the nerves controlling the voice box slowly but progressively lose
their function. When dogs normally breath, the voice box is opened
permitting inhaled air to pass to the lungs. LP diminishes that ability
when the tissue folds edging the sides of the voice box either do not move
at all or move out of time with the phases of breathing. One or both these
vocal folds may be affected. “This syndrome has been reported as a congenital
(present at birth) problem in the Bouvier des Flandres, Siberian Husky
and Dalmatian breeds,” according to the U. California at Davis Vet Medicine's
“Book of Dogs,” 1995 ed., pp. 289-290. Thus, LP slowly narrows the
dogs' airway making breathing progressively difficult. The condition
can occur in any breed and at any age but veterinarians report it to be
most common in older dogs of large breeds. I now definitely know
of two Dalmatians with LP - my own male and a bitch.
What are the early signs of LP?
Symptoms during early LP can be merely changes in the sound of barking
as if debarked or with laryngitis. Frequent coughing and clearing-of-the-throat
may be seen plus slight panting for no detectable reason. The dog's
breathing can sometimes sound like the wheezing of an asthmatic.
As LP worsens, the dog pants strenuously after the slightest exercise or
mildest excitement. (The normal reaction is to inhale more at these
times but becomes a drastic struggle as LP narrows the airway.)
What are late signs of LP?
In late-stage acutely severe stages of LP, the dog is intolerant
to exercise, heat and stress...anything which puts the slightest burden
on its lessening ability to take in air. When stressed, the animal
goes into seizure episodes of desperately gasping for air. Those
with fear of thunder and lightning show alarming LP symptoms during their
periods of anxiety. As the dog struggles to inhale, the limited intake
of air worsens its excitement and the dog can collapse and even die from
lack of oxygen. If the animal also has coexisting heart problems,
these episodes can be ominously stressful to those dogs' capacity to endure
them.
What causes LP? What are its treatments?
The California textbook states, “It was once thought that [LP] was
linked to... hypothyroidism...Instead it is now believed that [LP] probably
occurs as a component of a more serious inflammatory disease involving
either the neurologic system, the muscular system, or both.”
A specific cause rarely is confirmed and may be just the aging process
in some animals. Thyroid medication and tranquilizers have been tried
but surgery seems to be the only significant and lasting relief.
What type of surgery is showing the greatest success?
"Unilateral arytenoid lateralization" is the surgical procedure
most currently in favor. It involves tieing back one side of the
voice box so that a permanently open airway exists for the dog to breath
through even though the LP continues to progress. Tieing back both
sides proved to create too many complications after surgery, as did conducting
the surgery internally through the mouth. It now appears preferable
to surgically access the voicebox for the tie-back by opening up the neck
externally. Owners of dogs with LP, most 12 years or older, report
with a few exceptions that their dogs came out of the surgery rapidly,
were home within two to three days and rarely if ever had breathing difficulties
again. The choice of a surgeon experienced in the tie-back procedure
is of course critical. All dogs learned to drink and eat after the
surgical tie-back within a very few days.
Where can I obtain more information?
A very informative subscriber list and web site for owners of dogs
with LP exist. As this article was being written, the web site was
adding a linkage page with names, addresses, telephones of surgeons throughout
the U.S. who successfully performed the tie-back. Readers with computers
can access the following Internet webpage which will provide information
on how to subscribe:
http://www.geocities.com/Heartland/Plains/5102/LP_oldsters.html
A very informative subscriber list and web site for owners of dogs
with LP exist. Readers with computers can access the following Internet
webpage which will provide information on how to subscribe:
http://www.geocities.com/heartland/village/8335
A separate web page has been organized listing surgeons experienced in the special surgical technique this problem requires. It is:
http://www.geocities.com/Heartland/Village/8335/vets.html
I sincerely hope readers will find this article of information only and will never have to use it for their Dalmatians.
Carroll H. Weiss
carroll@usaccess.com
Portrait and case history of my Dalmatian successfully recovered
from laryngeal paralysis:
http://www.geocities.com/lplist/dazzle.html
Some LP information from the UC Davis School of Vet
Med Book:
Normally, the vocal folds open during inhalation and partially close
during exhalation. In laryngeal paralysis the vocal folds either do not
move at all or move out of time with the phases of respiration. One or
both vocal folds may be affected. This syndrome has been reported as a
congenital (present at birth) problem in the Bouvier des Flandres, Siberian
Husky and Dalmatian breeds. It also occurs commonly in older dogs of the
sporting breeds such as Labrador Retrievers.
It was once thought that laryngeal paralysis was linked to an underactive thyroid gland (hypothyroidism). Instead it is now believed that laryngeal paralysis probably occurs as a component of a more serious inflammatory disease involving either the neurologic system, the muscular system, or both. Clinical signs tend to develop gradually over a long period of time, and depend on the severity of the paralysis and the resulting obstruction to airflow through the larynx. The earliest sign is often a change in the quality of the bark. Affected dogs are easily fatigued, sensitive to heat, and pant excessively. In severe cases the condition can be life-threatening.
Confirmation of the diagnosis can be made by direct visualization of the vocal folds with the dog under light anesthesia. Because laryngeal paralysis commonly occurs as part of a generalized neuromuscular disorder, affected dogs should have a thorough neurologic evaluation performed by a veterinarian who is skilled in this type of procedure.
In general, treatment is similar to that for laryngitis or laryngeal edema. Correction may be attempted by surgically attaching one or both vocal folds to the outer sides of the larynx so that the larynx will remain open on inhalation and exhalation. While this often results in resolution of the clinical signs, it predisposes the dog to aspiration of foreign bodies and even food and water into the lungs. The prognosis often depends on the progression of the underlying inflammatory disorder.
UC Davis School of Veterinary Medicine Book of Dogs
HarperCollins Publishers, Inc., New York, NY
Part V: Canine Body Systems and Disorders
Chapter 29: The Respiratory System and Disorders, written by Philip
A. Padrid, DVM
“Laryngeal Paralysis,” pp. 289-90