Video-Assisted Left Partial Arytenoidectomy by Diode Laser

Photoablation for Treatment of Canine Laryngeal Paralysis

MASSIMO OLIVIERI, DVM, PhD, SIMONA G. VOGHERA, DVM, and THERESA. W. FOSSUM, DVM, PhD, Diplomate ACVS

Objectives—To evaluate the clinical outcome of left partial arytenoidectomy by video-assisted laserdiode photoablation as a surgical treatment for canine laryngeal paralysis (LP).Study Design—Case series.Animals—Dogs with bilateral LP (n¼ 20).Methods—After endoscopic diagnosis of bilateral LP, left partial arytenoidectomy was performedby photoablation of arytenoid cartilage tissue using a diode laser (600mm diameter, 15W power,980 nm wave length) to increase the width of the rima glottidis. Outcome was evaluated endo-scopically (1 and 6 months) and clinically (1, 6, and 12 months).Results—No substantial complications occurred during photoablation or in the immediate post-operative period. Postoperative width of the rima glottidis ranged from 6 to 10mm at its widestaspect. At 1 month, respiratory function after walking and short running appeared good. Clinicaland endoscopic examination revealed good outcome at 1 and 6 months. At 6 months, there was noevidence of hypertrophic scar, hypertrophic granulation tissue, or stricture of the laryngeal glottis inany dog. Two dogs developed aspiration pneumonia after 12 months.Conclusions—Partial arytenoidectomy using video-assisted diode laser photoablation appears to bean effective technique for treating LP.Clinical Relevance—Partial arytenoidectomy by diode laser photoablation should be considered asan alternative technique for treatment of canine LP.r Copyright 2009 by The American College of Veterinary Surgeons

INTRODUCTION

IN CANINE laryngeal paralysis (LP), there is bilat-eral loss of abduction of the arytenoid cartilages and

vocal folds during inspiration1 because of recurrentlaryngeal neuropathy and dysfunction of the intrinsic la-ryngeal muscles.2 LP may be congenital or acquired;the former being diagnosed in dogs o1 year of age.3–5

Acquired LP is often seen in adult, older, large-breeddogs. Labradors, Great Danes, Chesapeake Bay Retriev-ers, Afghan Hounds, Irish Setters, and Saint Bernards aremost commonly affected, and males are more commonlyaffected than females.5–7 Acquired LP may be caused by

traumatic or surgical lesions of the cervical region result-ing in secondary nerve damage; by intra- or extrathoracicmasses that cause compression of the recurrent laryngealnerves; or by generalized polyneuropathy or hypothy-roidism5–7; however, in many dogs the cause is unclearand LP is considered idiopathic.5–7

The most frequently observed clinical signs areexercise intolerance, inspiratory stridor, inappropriateinspiratory effort, loss or alteration in phonation,coughing (mainly after food and water ingestion), cy-anosis, and collapse.1,6 These signs worsen with obe-sity, exercise, excitement, and high environmentaltemperatures.1,6

This work was done at the Clinica Veterinaria Malpensa.

Address reprint requests to Dr. Theresa W. Fossum, DVM, Phd, Dipolmate ACVS Michael E. DeBakey Institute for Comparative

Cardiovascular Studies, Texas A&M University, College Station, TX 77843-4474. E-mail: tfossum@cvm.tamu.edu.

Submitted December 2007; Accepted February 2009

From the Clinica Veterinaria Malpensa, Samarate—Varese, Italy and the Michael E. DeBakey Institute for Comparative Cardio-

vascular Studies, Texas A&M University, College Station, TX.

r Copyright 2009 by The American College of Veterinary Surgeons

0161-3499/09

doi:10.1111/j.1532-950X.2009.00546.x

439

Veterinary Surgery

38:439–444, 2009

Unilateral lateralization of the arytenoid cartilage orpartial arytenoidectomy have been recommended fortreatment of LP in dogs. The latter technique is subject tocomplications including aspiration pneumonia, submu-cosal hematoma, and seroma development.1,8,9 We reporta technique for, and outcome after, video-assisted partialleft arytenoidectomy performed by photoablation with adiode laser in 20 dogs.

MATERIALS AND METHODS

Inclusion Criteria

Medical records (2004–2006) of dogs with bilateral LP thathad partial arytenoidectomy with a diode laser were reviewed.Inclusion criteria were an endoscopic diagnosis of LP and� 6 months follow-up clinically and endoscopically. Laryn-geal movement, was evaluated using a 5mm rigid endoscopepositioned caudal to the tip of the epiglottis10 with the dog insternal recumbency, premedicated with atropine (0.03mg/kgintramuscularly), during light, general anesthesia with prop-ofol (1mg/kg intravenously [IV] as needed to facilitate theexamination). The same procedure was used to evaluate out-come 1 and 6 months after partial arytenoidectomy. Thoracicradiographs were taken before surgery and at 15 days, 1–6,and 12 months after surgery. All dogs had complete hemato-logic and serum biochemical profile analysis before surgery.

Surgical Technique

After endoscopic diagnosis, dogs were immediately takento surgery. They were intubated and anesthesia was main-tained with isofluorane in oxygen. Cefazolin (25mg/kg IV)and dexamethasone (1mg/kg IV) were administered at anes-thetic induction. Partial left arytenoidectomy was performedusing a 600mm diameter, 15W power, and 980nm wavelengthdiode laser (easylase 980 nm; Team laser, Padova, Italy). Theenergy used during surgery was 4–6 J over 50 seconds in con-tinuous mode. Cartilage vaporization was achieved with atriangulation technique between the laser and the endoscope.

During the procedure, the endotracheal tube was protectedby using a straight malleable retractor, 4–5mm wider than theendotracheal tube, which prevented contact of the tube withthe laser beam. Photoablation of the arytenoid cartilage wasperformed under constant endoscopic observation and con-sisted of photovaporization of a portion of the corniculateprocess of the left arytenoid cartilage with char removal by useof a gauze sponge. The portion of laser-vaporized cartilageextended from the interarytenoid band to the cuneiform pro-cess of the arytenoid cartilage (Fig 1A). The interarytenoidband was preserved to prevent collapse of the arytenoid car-tilage and stricture formation. Caudally, photovaporizationwas limited to the laryngotracheal junction (Fig 1B). At theend of the procedure, the final width of the rima glottidis wasmeasured at its widest portion from the medial aspect of theleft corniculate process to the corresponding medial aspect ofthe right corniculate process (Fig 1E). Straight malleable re-

tractors of differing diameters were used to make the mea-surements (Fig 1C).

Postoperative Care

Cephalexin (25mg/kg, orally twice daily for 5 days) wasadministered to prevent infection, prednisone (0.5mg/kgorally every 6 hours for 7 days) to decrease postoperativeedema, and omeprazole (0.7mg/kg orally once daily for30 days) to treat the potential gastric ulcers were administered.All dogs were discharged 48 hours after surgery.

Outcome

Dogs were reevaluated on day 15, and again at 1, 6, and12 months, or as needed, and complications (aspiration pneu-monia, formation of hypertrophic granulation tissue, or la-ryngeal strictures) recorded. At � 1 month, dogs wereevaluated after 15 minutes walking and 5 minutes running.Owners were also asked to rate their dog’s activity level asimproved, no change, or worse than before surgery.

RESULTS

Left partial arytenoidectomy was performed in20 dogs. There were 4 large mixed-breed dogs (weigh-ing430kg), 4 medium mixed-breed dogs (weighing419–24 kg), 3 Labrador Retrievers, 2 Maremmano Shep-herds, 2 Newfoundlands, and 1 each of Cocker Spaniel,Saint Bernard, Irish Setter, Springer Spaniel, and Pit Bull(Table 1). All 20 dogs had pronounced inspiratorystridor, cough, exercise intolerance, and alteration inphonation. Three dogs (1 Maremmano Shepherd, 1 Lab-rador Retriever, 1 Newfoundland) also had cyanosis andsyncopal episodes. Eleven dogs had arytenoid cartilage‘‘kissing lesions’’ and 9 had ‘‘paradoxical motion’’ of thearytenoid cartilages.

During laser photovaporization no major complica-tions occurred. Some hemorrhage occurred in all dogsbut was easily controlled with the laser. At the end ofsurgery, width of the rima glottidis ranged from 6 to10mm; 6mm for dogs weighing o30kg; 7–8mm fordogs 30–50 kg; and 10mm for dogs 450kg. No compli-cations were observed in the immediate postoperativeperiod. At 1 month, respiratory function after 15 minuteswalking and 5 minutes running appeared good and allowners noted that dogs had improved exercise tolerance.There was no evidence of aspiration pneumonia on fol-low-up radiographs at 15 days or at 1, 6, and 12 monthsafter surgery in 16 dogs; however, 2 dogs (dogs 9 and14) developed aspiration pneumonia after 12 months.One of the 2 Maremmano Shepherds (dog 12) developeda peripheral neuropathy and was euthanatized after10 months. One mixed breed dog died from gastric di-latation-volvulus, 9 months after surgery (dog 3) and had

440 VIDEO-ASSISTED DIODE LASER TREATMENT OF CANINE LARYNGEAL PARALYSIS

no evidence of abnormal respiratory effort after laryngealsurgery.

Endoscopy at 1 and 6 months revealed completehealing of the arytenoid cartilage by 1 month (Fig 1D–F). No hypertrophic scars, hypertrophic or polypoidgranulation tissue, or stricture formation of the glottiswas observed.

DISCUSSION

Partial arytenoidectomy using video-assisted diode la-ser ablation appears to result in minimal tissue trauma inhuman patients.11–15 Observation of laryngeal structurescan sometimes be impaired, especially in the latter part ofthe surgery, because the vaporized mucosa and cartilagetend to become dark, making it difficult to recognize thelimits of the cricoid cartilage; however, these darkenedportions of the vaporized cartilage have been shown tohave a preserved histologic cellular organization in manand horses.16,17

In humans, laser arytenoidectomy is an intralaryngealsurgery that results in acceptable air passage through theglottis while preserving vocal quality.11,13,15,18–23 Thistechnique is also associated with a reduced incidence ofaspiration pneumonia in humans, because it does not re-quire that temporary tracheotomy be performed after theprocedure.11,13,15,18–23 Formation of hypertrophic granu-lation tissue resulting in dyspnea has been reported as acomplication in human patients.11–13,22 This tissue can beeasily removed with diode laser.14,21,24 Another reportedcomplication is stricture formation, but these do notnormally require surgical treatment.13,14,22

Preliminary results of the use of the diode laser forunilateral partial arytenoidectomy for treatment of LP indogs appears to compare favorably with our experiencewith intraoral partial arytenoidectomy. Our experiencesuggests that it may allow for surgical resolution of ob-struction caused by LP with fewer complications thanoccur with intraoral partial arytenoidectomy. Further,our experience suggests that use of video-assisted diodelaser enhances precision of arytenoid cartilage resection

Fig 1. (A) Initial photovaporization of the left corniculate process of the arytenoid cartilage; (B) view of the larynx after

photovaporization; (C) final measurement of the glottis with a malleable retractor (R; 10mm width) in 1 large mixed breed dog;

(dog 2); (D) 1-month follow-up after photovaporization in a Cocker Spaniel (dog 19); (E) 1-month follow-up of dog 10; (F) 1-month

follow-up of dog 4. Note complete healing of the laryngeal mucosa.

441OLIVIERI, VOGHERA, AND FOSSUM

because of the magnification afforded by the endoscope.This, in turn, reduces the total amount of vaporizationperformed, which may reduce the risk of aspirationpneumonia.15,22 The risk of surgical trauma is low andthere appears to be a reduced incidence of marked post-operative edema, in humans as well as in the 20 dogswe report, which may reduce the need for intubationor temporary tracheotomy in the early postoperativeperiod.11–15

The diode laser promotes coagulation from local ther-mal action created over the cartilaginous tissue duringphotovaporization,11,14,15,22,25–27 which dramatically de-creases the risk of intramural hematoma forma-tion.11,14,15,22,25–27 Intramural edema and hematomaformation are potential complications of standard intra-oral techniques and generally occur during the earlypostoperative period28 as dyspnea, inspiratory stridor,and occasional cough.29–31 In the worst-case scenario,edema and hematoma formation, if marked, can be lifethreatening.29–31

CO2 lasers are commonly used for laryngeal surgery inpeople in conjunction with microlaryngoscopy.27 Re-ported advantages are improved accuracy, rapid re-epithelialization, prevention of scar or granulation tissueformation, and a low incidence of aspiration pneumo-nia.11–13,15,19 Hemostasis is generally good with a CO2

laser, unless the arytenoid artery is incised; the lattervessel requires electrocautery because of its size.11,27

Electrocautery is not needed when a diode laser is used.Despite the relatively small number of the dogs treated,

the risk of aspiration pneumonia (2/20 dogs) is similar

to other studies and it is an acknowledged commonand potentially fatal complication noted after standardsurgical techniques.7,30,32,33 In 1 report,28 aspiration pneu-monia occurred in 15 of 45 (33%) dogs treated with vent-riculocordectomy and partial arytenoidectomy during theearly postoperative period, and in 7 of 45 (16%) dogsit was a long-term complication. Aspiration of foodcan occur because the laryngeal aperture at the level ofthe corniculate process of the arytenoid cartilage is toolarge creating difficulty in closure during deglutition, es-pecially if the LP is associated with a neuromuscularproblem.6,30,34–36

Another serious medium- to long-term complicationthat can occur after intraoral arytenoidectomy is glotticstenosis, which may occur as a direct consequence of theformation of hypertrophic granulation or scar tissues af-ter resection of oral tissues. Clinically, affected dogs ap-pear to have reduced exercise tolerance and markedlaryngeal inspiratory stridor.28–31,34,37 In our study, glot-tic stenosis did not occur within 6 months.

Partial arytenoidectomy by diode laser photoabla-tion is a relatively quick technique taking 25–30 min-utes11,15 with a maximum of 60 minutes in large dogs.To be successful, the surgeon must have good knowl-edge of endoscopic laser technique and video-assistedprocedures. Lasers may also be used to remove thehypertrophic tissue that occurs after other surgicalprocedures.14,21,24

Our results suggest that unilateral partial arytenoidec-tomy by diode laser photoablation is a safe and prom-ising technique for treatment of LP in dogs.

Table 1. Summary Data for 20 Dogs with Bialteral Laryngeal Paralysis Treated by Unilateral Partial Arytenoidectomy with Photoablation by Diode

Laser

Dog Breed Sex Age (Years) Weight (kg)

Final Aditus

Diameter (mm) Concurrent Conditions

1 Mixed breed Male 11 32 7

2 Mixed breed Male 10 74 10

3 Mixed breed Female 11 33 7

4 Mixed breed Male Castrate 12 65 10

5 Mixed breed Female spayed 11 24 6

6 Mixed breed Female 14 22 6

7 Mixed breed Female spayed 12 21 6

8 Mixed breed Male 13 19 6

9 Labrador Male 13 35 7 Hiatal hernia

10 Labrador Male 13 31 7

11 Labrador Male 9 41 7

12 Maremmano Shepherd Female 11 49 8 Peripheral neuropathy

13 Maremmano Shepherd Male 11 41 7

14 Newfoundland Female 3 43 8

15 Newfoundland Male 9 45 8

16 Irish Setter Male 14 23 6

17 Springer Spaniel Male Castrate 13 25 6

18 Pit Bull Male 8 26 6

19 Cocker Spaniel Male 10 10 6

20 Saint Bernard Male 4 67 10

442 VIDEO-ASSISTED DIODE LASER TREATMENT OF CANINE LARYNGEAL PARALYSIS

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