Arytenoid Lateralization for Treatment of Laryngeal Paralysis by Salah EL MOUSTAGHFIR

Veterinary Surgery 38:445–451, 2009

Arytenoid Lateralization for Treatment of Laryngeal Paralysis in 10 Cats ROBERT J. HARDIE, DVM, Diplomate ACVS & ECVS, JESSICA GUNBY, DALE E. BJORLING, DVM, MS, Diplomate ACVS

DVM,

and

Objective—To describe the signalment, history, clinical signs, surgical technique, and outcome for cats with laryngeal paralysis that had arytenoid lateralization. Study Design—Case series. Animals—Cats with laryngeal paralysis (n ¼ 10). Methods—Medical records (1996–2002) for cats with laryngeal paralysis that had arytenoid lateralization were reviewed for signalment, history, clinical signs, degree of paralysis, cause, concurrent medical conditions, surgical technique, and outcome. Follow-up information was obtained from owners or referring veterinarians. Results—Of 10 cats, 9 had bilateral and 1 had unilateral laryngeal paralysis. Arytenoid lateralization were unilateral (n ¼ 7), bilateral (1), and staged bilateral procedures (2), 10 days and 3 years apart, respectively. Postoperatively, 1 cat had persistent inspiratory noise because of minimal enlargement of the rima glottidis and 2 cats required a temporary tracheostomy for management of laryngeal swelling. Three cats developed aspiration pneumonia and died 4, 7, and 150 days after surgery; all 3 had bilateral (simultaneous or staged) procedures. Of the 7 remaining cats, 4 were alive at follow-up and 3 had died of causes unrelated to arytenoid lateralization. The calculated mean survival time for all 10 cats was 406 days (median, 150 days; range, 4–1825 days). Conclusions—Arytenoid lateralization was effective at enlarging the rima glottidis and reducing signs of airway obstruction in most cats. Clinical Relevance—Unilateral arytenoid lateralization is a feasible option for the surgical management of cats with marked clinical signs; however, bilateral procedures should be avoided or at least performed with considerable caution because of the apparent risk for aspiration pneumonia. r Copyright 2009 by The American College of Veterinary Surgeons

muscular, metabolic or toxic diseases, congenital, and idiopathic causes.1,2 The causes, treatment, and outcome for horses and dogs with laryngeal paralysis are well described3–14; however, there is relatively little information available on this disorder in cats and few reports have described the outcome of various medical and surgical treatments including anti-inﬂammatory therapy, partial arytenoidectomy, castellated laryngoﬁssure, ventriculocordectomy, and arytenoid lateralization.15–21 Our purpose was to describe the signalment, history, clinical signs, surgical technique, and outcome for cats that had

INTRODUCTION

ARYNGEAL PARALYSIS is characterized by impaired abduction of the arytenoid cartilages and obstruction of the rima glottidis during respiration. Common clinical signs of laryngeal paralysis include increased inspiratory noise, inspiratory stridor, dysphonia, exercise intolerance, inappropriate respiratory effort, coughing, and aspiration pneumonia. Some causes of laryngeal paralysis include trauma or injury to the recurrent laryngeal nerve, cervical or thoracic masses, neuro-

From the Department of Surgical Sciences, School of Veterinary Medicine, The University of Wisconsin, Madison, WI. Presented at the European College of Veterinary Surgeons Meeting, Prague, Czech Republic, July 2–4, 2004. Address reprint requests to Dr. Robert J. Hardie, DVM, Diplomate ACVS & ECVS, Department of Surgical Sciences, School of Veterinary Medicine, The University of Wisconsin, 2015 Linden Drive, Madison, WI 53706. E-mail: hardier@svm.vetmed.wisc.edu. Submitted February 2008; Accepted January 2009 r Copyright 2009 by The American College of Veterinary Surgeons 0161-3499/09 doi:10.1111/j.1532-950X.2009.00547.x

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arytenoid lateralization as the sole treatment for laryngeal paralysis. MATERIALS AND METHODS Inclusion Criteria Medical records (1996–2002) were reviewed for cats with laryngeal paralysis that had arytenoid lateralization. Signalment, history, clinical signs, degree of paralysis, proposed cause, concurrent medical conditions, surgical technique, and outcome were retrieved from the record. Laryngeal examinations were performed under a light plane of anesthesia using various protocols. Diagnosis of laryngeal paralysis was made by directly observing impaired abduction of one or both arytenoid cartilages during multiple respiratory cycles. Follow-up information was obtained by telephone conversation with the owners or referring veterinarians.

RESULTS Ten cats (3 neutered males, 7 spayed females; mean age, 8.8 years; range, 1–18 years) were identified (Table 1). Breeds were 7 domestic short-hair and 3 domestic long-hair cats. Significant historical and clinical examination findings at initial examination included dysphonia, increased upper respiratory noise, inspiratory stridor, exercise intolerance, inappropriate respiratory effort, openmouthed breathing, occasional coughing and choking when eating, dysphagia, and weight loss. One cat had had left arytenoid lateralization 3 years earlier but the specific details of the surgical procedure were not available in the medical record. This cat developed aspiration pneumonia immediately after surgery but recovered and was doing well for 3 months after which it developed recurrent signs of upper respiratory obstruction and periods of inappropriate respiratory effort that persisted until referral 2 years and 9 months later. None of the other cats had previous treatment for laryngeal paralysis. Duration of clinical signs ranged from 1 day to 3 years. Concurrent medical problems were present in 7 cats including hyperthyroidism and previous unilateral thyroidectomy for thyroid adenoma (2), renal insufficiency (2), congestive heart failure (1), hypertension (1), thyroid adenocarcinoma (1), and mycoplasma pneumonia (1). Laryngeal paralysis was bilateral in 9 cats and unilateral (left) in 1 cat. In the cat that had previous left arytenoid lateralization, the left arytenoid cartilage was fixed in an abducted position, but the right arytenoid cartilage was deviated medially obstructing the glottis and failed to abduct during inspiration so the cat was considered to have bilateral laryngeal paralysis. The cause of laryngeal paralysis was considered idiopathic in 7 cats and iatrogenic in 3 cats. For the 3 cats with iatrogenic, bilateral laryngeal paralysis, injury to the recur-

rent laryngeal nerves was presumed to have occurred during thyroidectomy. One cat had a thyroid adenocarcinoma removed and 2 cats had unilateral thyroid adenomas removed. Onset of clinical signs occurred immediately after thyroidectomy for all 3 cats. The precise reason for the bilateral laryngeal paralysis in the 2 cats that previously had unilateral thyroidectomy was not specifically described in the medical records. Arytenoid lateralization was performed immediately after thyroidectomy in the cat that had the thyroid adenocarcinoma and 1 and 2 years later, respectively, in the 2 cats that had thyroid adenomas. Seven cats had unilateral arytenoid lateralization (6 left sided and 1 right sided), 1 cat had bilateral lateralization, and 2 cats had 2 separate unilateral (staged bilateral) arytenoid lateralization procedures 10 days and 3 years after the 1st procedure, respectively, resulting in bilateral lateralization. Surgical Technique Cats were positioned in either dorsal or lateral recumbency with the larynx elevated. A skin incision was located over the larynx ventral to the jugular vein and the subcutaneous tissues dissected to the level of the thyropharyngeus muscle that was transected to expose the lateral aspect of the thyroid cartilage. The thyroid cartilage was retracted to expose the cricoid and arytenoid cartilages. The cricoarytenoideus dorsalis muscle was identified and transected at the insertion on the muscular process of the arytenoid cartilage. The cricoarytenoid articulation was separated by incising the joint capsule and the arytenoid cartilage mobilized from the cricoid cartilage. Nine cats had sutures placed between the cricoid and arytenoid cartilages and 1 cat had sutures placed between the thyroid and arytenoid cartilages. For placement of the cricoarytenoid suture, the suture was passed through the caudal aspect of the cricoid cartilage in a medial to lateral direction and then through the muscular process of the arytenoid cartilage in a medial to lateral direction (Fig 1). Two sutures were placed in 8 cats and 1 suture was placed in 2 cats. The suture(s) were tied under tension to abduct the arytenoid cartilage; however, the precise degree of tension applied was not described. Suture material was either 3-0, 4-0, or 5-0 monofilament nylon or polypropylene. The thyropharyngeus muscle was reapposed with absorbable suture material in a simple continuous pattern. The subcutaneous tissue and skin were closed routinely. For the 1 cat that had simultaneous, bilateral arytenoid lateralization, the same procedure was performed on the opposite side. After completing the procedure, cats were extubated, and the larynx was examined to assess the degree of arytenoid lateralization. In 9 cats, the rima glottidis was considered enlarged because of abduction of the

11 years F/S, DSH

3 years F/S, DLH

18 years F/S, DSH

8 years F/S, DLH

1 year F/S, DSH

2 years 7 months M/N, DLH

13 years F/S, DSH

8 years 3 months M/N, DSH

6 years M/N, DSH

Duration (months)

2 days

Side of Surgery

Bilateral

Unilateral thyroidectomy 2 years earlier Left arytenoid lateralization 3 years earlier

L; R side, 10 days later

Bilateral, R side sutures removed 3 days postoperatively L

Thyroid adenocarcinoma

Immediately after thyroidectomy

Bilateral

Unilateral—left

Paralysis

Bilateral

None

Hypertension, renal insufﬁciency Hyperthyroidism

Mycoplasma pneumonia

Hyperthyroidism, unilateral thyroidectomy 1 year earlier Congestive heart failure, chronic renal insufﬁciency

Concurrent Conditions

Since a kitten

24 Inspiratory noise, increased respiratory effort, occasional cough and choking when eating Persistent upper respiratory 36 noise, wheezing, lethargy and inappropriate respiratory effort

Upper respiratory noise, inappropriate inspiratory effort, open-mouthed breathing Inappropriate respiratory effort after thyroidectomy (large thyroid adenocarcinoma)

Inspiratory stridor, exercise 24 intolerance, weight loss Inappropriate inspiratory 36 effort, change in vocalization, dysphagia Upper respiratory noise, 5 wheezes, high pitched squeaks, abdominal breathing effort, openmouthed breathing

Inspiratory stridor, weight loss

2 Inappropriate respiratory effort, change in vocalization

Inspiratory stridor, open-mouthed breathing, weight loss

Clinical Signs

F/S, female spayed; M/N, male neutered; DSH, domestic short hair; DLH, domestic long hair.

18 years F/S, DSH

Signalment

Cat

Complications

Still alive 24 months after surgery

Died of aspiration pneumonia 150 days after surgery

Still alive 3 months after surgery Died of unknown cause 8 days after surgery

Died of aspiration pneumonia 4 days after surgery

Died of anemia, congestive heart failure 5 months after surgery

Died of unknown cause 12 months after surgery

Outcome

Aspiration pneumonia

Died of aspiration pneumonia 7 days after surgery

Still alive 24 months Persistent airway after surgery obstruction and respiratory distress from laryngeal swelling, tracheostomy tube in place for 48 hours after surgery None Still alive 60 months after surgery

Persistent airway obstruction and respiratory distress, tracheostomy tube placed 48 hours after surgery None

None

Minimal abduction of left arytenoid cartilage, persistent harsh inspiratory noise Aspiration pneumonia

None

Table 1. Summary Data for 10 Cats with Laryngeal Paralysis that had Arytenoid Lateralization

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Fig 1. (A) Illustration of the feline larynx demonstrating the arytenoid lateralization technique. The thyroid cartilage (T) has been retracted with a stay suture. Two sutures have been placed from the caudal aspect of the cricoid cartilage (C) through the muscular process of the arytenoid cartilage (MP). (B) Close-up photograph of 2 arytenoid lateralization sutures placed in a feline cadaver. T, thyroid cartilage; MP, muscular process of arytenoid cartilage; C, cricoid cartilage.

arytenoid cartilage and in 1 cat, the rima glottidis was considered minimally enlarged to unchanged. After surgery, the cats were monitored in the intensive care unit and administered anti-inﬂammatory and analgesic medications at the discretion of the attending surgeon. Outcome All cats recovered from surgery. The cat that had simultaneous, bilateral arytenoid lateralization developed aspiration pneumonia immediately after surgery. The right cricoarytenoid lateralization sutures were removed 72 hours after surgery in an effort to reduce risk of further aspiration, but the cat died of progressive aspiration pneumonia 4 days after the initial procedure. Two cats

required a temporary tracheostomy after unilateral arytenoid lateralization for management of persistent laryngeal swelling and airway obstruction. The cause of the persistent laryngeal swelling was not speciﬁcally described. For 1 cat, a tracheostomy tube was placed immediately after surgery and removed 48 hours later; the cat had no further problems. The 2nd cat had a tracheostomy tube placed 48 hours after surgery for management of persistent airway obstruction. The tube was removed after 48 hours, but the cat had persistent airway obstruction. A 2nd arytenoid lateralization procedure was performed on the opposite side 10 days after the 1st procedure. The cat recovered from this procedure but died of aspiration pneumonia 150 days later. For the cat that had undergone the left arytenoid lateralization procedure 3 years earlier, a 2nd arytenoid lateralization procedure was performed on the right side. The cat recovered from surgery but developed aspiration pneumonia 48 hours after surgery and died 7 days later because of progressive complications from the pneumonia. The cat that was considered to have had minimal enlargement of the rima glottidis on inspection of the larynx, immediately after surgery, had persistent harsh inspiratory noise but no further treatment was pursued. Overall, 3 cats died because of aspiration pneumonia, 4, 7, and 150 days after bilateral (simultaneous or staged) procedures. Of the remaining 7 cats, 4 were still alive at time of follow-up and 3 had died of causes unrelated to arytenoid lateralization on days 8, 150, and 365. The calculated mean survival time for all 10 cats was 406 days (median, 150 days; range, 4–1825 days).

DISCUSSION Results of this study indicate that arytenoid lateralization is effective at enlarging the rima glottidis and relieving signs of airway obstruction in most cats with laryngeal paralysis. Unilateral arytenoid lateralization is a feasible option for the surgical management of cats with marked clinical signs; however, bilateral procedures should be avoided or at least performed with considerable caution because of the apparent risk for aspiration pneumonia. The exact reason for the aspiration pneumonia in 3 cats was not known, but it was most likely because of inadequate protection of the enlarged or deformed rima glottidis by the epiglottis during swallowing. Use of arytenoid lateralization for treatment of laryngeal paralysis has been described in 2 separate reports involving 8 cats.19,21 The surgical techniques were not described in detail; however, unilateral arytenoid lateralization was performed in 6 cats and bilateral arytenoid lateralization combined with bilateral ventriculocordectomy was performed in 2 cats. Complications related to

HARDIE, GUNBY, AND BJORLING

the lateralization procedures included transient Horner’s syndrome and dysphonia in 1 cat, and failure of the procedure and recurrence of clinical signs in 3 cats (1 unilateral and 2 bilateral), 4, 12, and 24 months after surgery. The reasons for failure in these cats were not described in those reports; however, all 3 cats had a ‘‘successful’’ 2nd surgical procedure involving either unilateral arytenoid lateralization on the opposite side, bilateral arytenoidectomy, or left-side ‘‘laryngoplasty.’’ None of the 8 cats were reported to have developed aspiration pneumonia. Other surgical procedures that have been reported for treatment of laryngeal paralysis include castellated laryngofissure with bilateral ventriculocordectomy (2 cats) and partial arytenoidectomy (6 cats).16,18–21 Complications related to the surgical procedures occurred in 3 cats. One cat that had castellated laryngofissure developed obstruction of the glottis from medial collapse of the right arytenoid cartilage 4 months after surgery.18 The right arytenoid cartilage was subsequently resected (partial arytenoidectomy) and the cat recovered without further problems. Of the cats that had partial arytenoidectomy, 1 developed severe laryngeal stenosis and was euthanatized 3 days after surgery and 1 developed complications from progressive pneumonia and was euthanatized 1 month after surgery.19,21 Because of the small number of cases reported in cats, it is difficult to make a generalized comment regarding the risks for complications with a particular procedure; however, of the 26 cats treated surgically (including 10 cats from our report) 14 cats (54%) developed some type of postoperative complication and 4 cats (15%) developed aspiration pneumonia and died as a result. The surgical technique used in these cats was similar to that described for dogs although the cricothyroid articulation was not disarticulated nor was the transverse arytenoid ligament transected in any of the cats.22 The procedure is technically more demanding in cats compared with dogs because of the small size and fragility of laryngeal cartilages. In all cats, the lateralization sutures were placed through the muscular process of the arytenoid cartilage in a ‘‘simple interrupted’’ pattern. This pattern appears adequate for abducting the arytenoid cartilage in most cats and none of the sutures were reported to have pulled through the arytenoid or cricoid cartilages at surgery. Other suture patterns have been described in dogs to increase holding strength and minimize the risk of suture pull-out that may also be appropriate for use in cats.23 Likewise, for the 2 cats that had only 1 suture (3-0 and 4-0 polypropylene) placed to lateralize the arytenoid cartilage, the single suture appeared adequate for maintaining abduction. The potential benefits of placing a 2nd suture through the fragile arytenoid cartilage in cats should be balanced against the risk of fragmenting the cartilage. Also, cutting needles should be

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avoided to reduce the risk of accidentally cutting through the fragile cartilages and suture material should be of adequate size relative to the size of the laryngeal cartilages (generally 3-0 or 4-0). The cats in this study had many of the clinical signs typically seen in dogs with bilateral laryngeal paralysis (dysphonia, exercise intolerance, inspiratory stridor, coughing, gagging, respiratory distress, and inappropriate respiratory effort); however, the clinical presentation was more varied compared with dogs, presumably because of differences in activity levels and interaction with owners.9 For the 1 cat with unilateral laryngeal (left) paralysis, it was not clear why it had such severe clinical signs despite the unilateral nature of the disease. One possible explanation is that excessive medial deviation or collapse of the left arytenoid cartilage occurred during inspiration leading to a greater degree of airway obstruction than would be expected with unilateral paralysis. However, it is important to note that of the 27 cats (not including those in our study) previously reported, 7 were diagnosed with unilateral paralysis, and all had varying degrees of clinical signs similar to those described above. This suggests that cats may be more susceptible than dogs to the effects of unilateral paralysis, and that the decision to treat them should be based on the severity of clinical signs and quality of life, rather than the just the degree of paralysis. The cause of laryngeal paralysis was considered idiopathic in 7 cats and iatrogenic in 3 cats. The cause for iatrogenic paralysis in 3 cats was presumed to be injury to the recurrent laryngeal nerves that occurred during thyroidectomy. For the other 7 cats, no obvious cause was identified on physical examination, hematology or serum biochemical profile, or survey thoracic and cervical radiographs, and the cause was considered idiopathic. However, it was not possible to definitively exclude focal manifestations of a polyneuropathy or polymyopathy as the cause for laryngeal paralysis. Two cats were relatively young (12 months, 2 years 7 months), and both cats had developed clinical signs at an early age (7 months, as a kitten) suggesting that the condition may have been congenital in these 2 cats. Similarly, 12 of the 27 cats reported in the literature were 3 years of age at the time of diagnosis, also raising the possibility that laryngeal paralysis may be a congenital disorder in some cats.16,18–21 To date, no breed predisposition has been reported in cats. Diagnosis of laryngeal paralysis was made by direct observation of larynx under light anesthesia. When examining the larynx in cats, it is important to avoid stimulating the larynx and causing laryngeal spasm that would affect accurate assessment of laryngeal function. Use of intravenous doxapram as a respiratory stimulant to facilitate assessment of laryngeal function has been reported in both dogs and cats; however, it should be

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used cautiously and patients monitored closely for adverse reactions such as acute collapse of the glottis because of increased depth of respiration, tachycardia, hypertension, and cardiac arrhythmias.24–27 Limitations of our study include those inherent with any retrospective study involving a relatively few number of cases spanning many years. The surgical procedures were performed by different surgeons, at 2 different teaching hospitals, and it is possible that the experience level of the surgeons may have affected technique and clinical outcome in some way. More speciﬁcally, the degree of tension applied to the lateralization sutures was not described in detail and it is possible that excessive tension may have distorted the larynx to such a degree that the epiglottis was not able to completely cover the glottis, therefore increasing the risk for aspiration. However, the goals of our study were to describe the outcome of a single procedure (arytenoid lateralization) for the treatment of laryngeal paralysis in cats and provide some degree of baseline information from which other surgical techniques can be compared. The decision to surgically treat laryngeal paralysis in cats, as well as the type of procedure should be made carefully based on the severity of clinical signs and the condition of the larynx at the time of visual examination. Arytenoid lateralization appears to be a feasible option for management of upper airway obstruction caused by laryngeal paralysis in most cats; however, based on our ﬁndings, bilateral (simultaneous or staged) procedures should be avoided or at least performed with considerable caution because of apparent increased risk for aspiration pneumonia. Further studies are needed in cats to document the degree of distortion of the larynx caused by arytenoid lateralization sutures, as well as correlate the clinical outcome with various surgical procedures to better determine the most appropriate technique for treating cats with laryngeal paralysis. ACKNOWLEDGMENTS The authors would like to thank Vicky Lipscomb, MA, VetMB, Dipl. ECVS, MRCVS for assistance with this study.

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