Laryngeal Paralysis in a Dachshund

Case Report
Cathy Welch, DVM

Reviewed by
Todd Deppe, DVM, DACVIM

Signalment
10 year female spayed Wirehaired Dachshund

History
Annie was presented to Veterinary Medical and Surgical Group (VMSG) for evaluation of progressive wheezing following home insulation removal about 6 weeks prior. Annie had a 2 year history of undefined sinus problems and snoring. Referral thoracic radiographs were consistent with bronchitis. Bloodwork (including a heartworm test) was unremarkable. Annie was treated for airway disease by her veterinarian with Clavamox, aminophylline, prednisone, and Tartephedreel and by the VMSG Internal Medicine Service with Flovent (fluticasone), albuterol, theophylline and a tapering dose of prednisone. Annie’s clinical signs remained static despite medical therapy. Subsequent evaluation suggested localization of stridorous breathing to the laryngeal region.

Clinical Exam
Annie’s abnormal exam findings consisted of intermittent inspiratory stridor and occasional increased respiratory effort on inspiration.

Laboratory Findings
Bronchoscopy was performed. Brush cytology from the bronchi showed no evidence of inflammation, malignancy or organisms. An aerobic culture sample from the bronchi yielded no growth.

Diagnostic Imaging
Thoracic radiographs showed diffuse bronchial opacity with no consolidation. Laryngeal structures were unremarkable. The cardiac silhouette was unremarkable. The thoracic radiographic findings were consistent with airway disease.

A laryngeal exam revealed bilateral laryngeal paralysis with no masses or other abnormalities noted.

Bronchoscopy showed a mildly flattened dorsal trachea with no dynamic tracheal collapse. The bronchi and nasopharnyx appeared normal.

Diagnosis
Laryngeal paralysis

Treatment/Management
Annie was admitted to the hospital. She was anesthetized, and a laryngeal exam performed at the time of induction confirmed laryngeal paralysis. Bronchoscopy was performed, and samples were obtained for cytology and culture. A unilateral laryngeal tie-back procedure was performed, and post-operative laryngeal exam showed appropriate left-sided lateralization. Annie recovered from surgery and anesthesia uneventfully. Post-operatively Annie was fed soft food made into small meatballs and offered water in small quantities elevated off the ground. Annie was walked with a chest harness. Her 2 week recheck showed Annie was doing great with no coughing or difficulty breathing. Her sutures were removed, and Annie was weaned off her medications including theophylline and Flovent inhaler. Her 4 week recheck showed Annie was doing well, and her breathing was normal. She was off all medications with no evidence of coughing, wheezing, or difficulty breathing. She was still being fed in meatballs. Continued monitoring and a slow transition to her regular kibble diet were recommended.

Prognosis
Annie’s prognosis is good, but she will have increased risk of aspiration pneumonia due to the inability to close her larynx completely. Annie will be monitored for any coughing or increased respiratory effort.

Discussion
Laryngeal paralysis occurs when the muscles (cricoarytenoides dorsalis) and/or the nerve (recurrent laryngeal nerve) of the larynx do not allow abduction of the arytenoid cartilage during inspiration. Laryngeal paralysis can be unilateral or bilateral. There is a congenital form affecting many breeds (Bouvier des Flanders, Bull Terrier, Dalmatian, Rottweiler, Huskies), and signs for this form occur before one year of age. Acquired laryngeal paralysis is more common than the congenital form, and the Labrador Retriever, Golden Retriever, St. Bernard and Irish Setter are overrepresented. Causes of acquired laryngeal paralysis include idiopathic, compression of the recurrent laryngeal nerve (neoplasia), trauma to the recurrent laryngeal nerve, iatrogenic with damage to the nerve (debarking, thyroidectomy), hypothyroidism, neuropathies or myopathies. The most common clinical signs are voice change, gagging, coughing and exercise intolerance. Physical exam findings vary from normal to acute respiratory collapse. Laryngeal paralysis is diagnosed under a light plane of anesthesia, and Dopram (2.2 mg/kg IV) is given to stimulate central respiratory function. Normally the vocal folds and arytenoids abduct during inspiration and passively relax during expiration. With laryngeal paralysis, vocal folds and arytenoids do not abduct during inspiration. Animals that present with cyanosis or collapse due to inflammation of the arytenoid cartilage are treated with oxygen, active cooling, acepromazine and dexamethasone; an emergency tracheostomy may need to be performed if the animal deteriorates despite medical therapy. Laryngeal paralysis is treated surgically. Most commonly a unilateral (left) arytenoid cartilage lateralization (tie-back) is performed. Complications associated with the surgery include failure of the tie-back suture, aspiration pneumonia, persistent coughing, noisy breathing, voice changes, and seroma formation at the surgery site. Factors that are significantly associated with a higher risk complications or death include age, temporary tracheostomy placement, concurrent respiratory tract abnormalities, concurrent esophageal disease, postoperative megaesophagus, concurrent neoplastic disease, and concurrent neurologic disease. Dogs appeared to have a life-long risk of developing respiratory tract complications following surgical correction. Significantly fewer owners of dogs under 10 kg than owners of dogs over 10 kg felt that their dog’s quality of life was improved by surgery (55% versus 93%).

Annie’s case is unusual because typically laryngeal paralysis is diagnosed in larger breed dogs, and Annie’s initial presenting signs and imaging were consistent with bronchitis – a common respiratory diagnosis in small breed dogs.

References

1. Broome C, Burbidge HM, Pfeiffer DU. Prevalence of laryngeal paralysis in dogs undergoing general anesthesia. Aust Vet J. 2000. 78:769-772.
2. Burbidge HM. A review of laryngeal paralysis in dogs. Br Vet J. 1995 Jan-Feb; 151(1):71-82.
3. MacPhail CM, Monnet E. Outcome of and postoperative complications in dogs undergoing surgical treatment of laryngeal paralysis: 140 cases (1985-1998). J Am Vet Med Assoc. 2001 Jun 15; 218(12):1949-56.
4. Schofield DM, Norris J, Sadanaga KK. Bilateral thyroarytenoid cartilage lateralization and vocal fold excision with mucosoplasty for treatment of idiopathic laryngeal paralysis: 67 dogs (1998-2005). Vet Surg. 2007 Aug;36(6):519-25.
5. Snelling SR, Edwards GA. A retrospective study of unilateral arytenoid lateralisation in the treatment of laryngeal paralysis in 100 dogs (1992-2000). Aust Vet J. 2003 Aug; 81(8):464-8.