RETROSPECTIVE STUDIES

Outcome of 45 Dogs With Laryngeal Paralysis Treated by Unilateral Arytenoid Lateralization or Bilateral Ventriculocordectomy Katherine L. Bahr, DVM, Lisa Howe, PhD, DVM, DACVS, Carl Jessen, PhD, DVM, DACVS, Zachary Goodrich, VMD

ABSTRACT The purpose of this retrospective study was to assess risk factors and complications affecting postoperative outcome of dogs with laryngeal paralysis treated by either unilateral arytenoid lateralization (UAL) or bilateral ventriculocordectomy (VCC). Medical records of all dogs having either UAL or VCC between 2000 and 2011 were analyzed. Twenty-five dogs had VCC and 20 dogs had UAL. The overall postoperative complications rates for VCC and UAL were similar (52% and 60%, respectively; P ¼ .0887). Dogs that had UAL were more likely to have acute postoperative respiratory distress and aspiration pneumonia (P ¼ .0526). Dogs with VCC were more likely to have chronic postoperative respiratory distress and aspiration pneumonia (P ¼ .0079). Revision surgery was required in 6 dogs (24%) following VCC and 2 dogs (10%) following UAL. Sex, breed, presenting complaint, type of service provided, and concurrent diseases were not significantly associated with higher risk of either death or decreased survival time postoperatively with either procedure. Overall postoperative complication rates, required revision surgeries, and episodes of aspiration pneumonia were similar in dogs undergoing UAL and VCC surgeries. Dogs that had VCC appeared to have an increased risk of lifelong complications postoperatively compared with UAL; therefore, VCC may not be the optimal choice for treatment of laryngeal paralysis. (J Am Anim Hosp Assoc 2014; 50:264–272. DOI 10.5326/JAAHA-MS-6081)

Introduction

LP may be part of a generalized, progressive neuromuscular dis-

Laryngeal paralysis (LP) is a common upper respiratory disease

order referred to as “geriatric-onset LP polyneuropathy” syn-

that results in failure of abduction of the arytenoid cartilages.

drome.6–10 Previous studies have demonstrated degeneration of

Inherited and acquired forms exist, with acquired LP affecting

the distal part of the longest peripheral nerve fibers evidenced

predominantly older large-breed dogs of which Labrador retrievers

by electrophysiological changes and decreased motor nerve

and rottweilers may be predisposed. Clinical signs include respi-

conduction velocities. Nerve degeneration was present in tho-

ratory stridor, coughing, exercise intolerance, collapse, dyspnea,

racic and pelvic limbs in addition to recurrent laryngeal nerves,

and dysphonia. Acquired LP is most commonly considered idio-

which is consistent with a generalized polyneuropathy. Typically

pathic, but may also be caused by trauma, infection, neoplasia, may

the first obvious clinical sign of geriatric-onset LP polyneuropathy

be iatrogenic, or may be associated with systemic disorders such as

syndrome is LP, which is often accompanied by slowly pro-

hypothyroidism, diabetes mellitus, or myasthenia gravis.1–8 The

gressive pelvic limb weakness, esophageal motility disorders, and

most recent data suggests that the condition known as “idiopathic”

muscle atrophy.6–10

From the Department of Veterinary Small Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, TX (K.B., Z.G., L.H.); and the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN (C.J.).

LP, laryngeal paralysis; UAL, unilateral arytenoid lateralization; VCC, bilateral ventriculocordectomy

Correspondence: [email protected] (K.B.)

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Comparison of Two Surgeries for Laryngeal Paralysis in Dogs

Although medical treatment options exist for LP, surgical treatment is often required to alleviate clinical signs and decrease

of patients, and one study reported aspiration pneumonia in 15% of cases following transoral VCC surgery.22,24,28

the risk of either severe respiratory distress or dyspnea during daily

To the authors’ knowledge, no study has compared the

physical activity. The goals of surgical treatment are to allow free

postoperative outcome between UAL and VCC. The purpose of

air movement through the larynx while preserving its protective

this study was to assess risk factors and complications affecting

function. The ideal surgical procedure would be minimally in-

postoperative outcome of dogs with LP treated by UAL or VCC.

vasive, low in cost, last the lifetime of the patient, and result in

The hypotheses were that aspiration pneumonia occurs as

a return to normal activity for the patient. Common treatment

a complication with equal frequency in VCC and UAL and that

options for LP include arytenoid lateralization, bilateral ven-

VCC will have a higher overall complication rate and requires

triculocordectomy (VCC) performed via a transoral approach,

revision surgery more commonly than UAL, resulting in de-

VCC performed via a ventral approach, castellated laryngofissure,

creased owner satisfaction.

partial laryngectomy, permanent tracheostomy, and reinnervation.4,11–18 Unfortunately, none of those surgical procedures are

Materials and Methods

without risk of complication. Currently, the most commonly per-

Case Selection and Medical Records Review

formed surgery for treatment of LP is unilateral arytenoid lateral-

A retrospective search of the medical databasea was performed at

12,19

ization (UAL).

Texas A&M University to identify all dogs having either UAL or

The purpose of UAL is to abduct the entire arytenoid lat-

VCC surgery performed from 2000 to 2011. Cases were selected

erally and enlarge the rima glottidis both dorsally and ventrally to

for inclusion in the study if they met the following criteria: idi-

allow increased air passage. The UAL surgical procedure has the

opathic, acquired LP confirmed by laryngoscopy; documentation

disadvantage of being more invasive due to dissection through

in the medical record of the surgical procedure performed as

the neck musculature, which increases surgical time and is con-

determined by surgeon preference; surgical procedure performed

sidered a more advanced procedure that is typically performed

for the purpose of treating LP; and a known outcome at the time

by board-certified surgeons. It is commonly performed, however,

of follow-up (regardless if the patient was dead or alive). For cases

due to consistently good clinical results with comparative com-

in which postoperative follow-up and outcome information was

20

plications to other procedures. Complications with UAL include

not available in the medical record, owners were contacted by

aspiration pneumonia, seroma or hematoma formation at the

telephone to complete a client questionnaire (Table 1).

surgical site, inadequate lateralization, suture failure, and fragmentation of the arytenoid cartilage.3,12,19,21–27 Previous studies

Data Analysis

have reported postoperative complications rates of 10–28%

Patient data extracted from the medical records included signal-

with UAL, with aspiration pneumonia occurring in 8–19% of

ment, appointment type, history, primary complaint, physical

4,12,19

patients.

Variable definitions of postoperative complications

examination data, laboratory test results when available, concur-

and patient selection criteria, as well as duration of follow-up,

rent diseases, type of surgical procedure, postoperative outcome,

likely contribute to differing results.

and any follow-up appointments. The primary complaint was

Although UAL is currently the most common surgical

divided into one of the four following categories: difficulty

treatment of LP, VCC may offer a less-invasive and more cost-

breathing, dyspnea, voice change, and other. Difficulty breathing

effective alternative. The purpose of VCC is to remove the vocal

was defined as increased respiratory rate and effort that was not life

cords bilaterally to create a larger opening ventrally and allow

threatening. Dyspnea was defined as struggling to breathe and an

increased air passage through the rima glottidis. It has been

inability to oxygenate adequately that could become life threat-

suggested that a ventral opening may decrease the risk for aspi-

ening. Surgical records were reviewed for all dogs included in the

ration pneumonia by being physically located further away from

study and did not reveal any variations in the surgical technique

the esophageal opening. Because VCC is performed transorally,

for either procedure. Surgical procedures were performed by

it has decreased costs and can be performed with ease compared

multiple board-certified surgeons and surgery residents; however,

with other surgical procedures. Complications with VCC include

a board-certified surgeon was present at the time of all surgeries.

scar tissue formation (webbing or cicatrix formation), aspiration

Concurrent diseases were defined as diseases present on di-

pneumonia, and continued respiratory distress. Limited data are

agnosis of LP. Those concurrent diseases were divided into the

available regarding the postoperative outcome following VCC

categories of hypothyroidism, polyneuropathy, aspiration pneu-

surgery. Scar tissue formation has been reported in 12.5–37.5%

monia, megaesophagus, and other. A diagnosis of hypothyroidism

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biopsy were performed. A diagnosis of aspiration pneumonia

TABLE 1

and megaesophagus was made based on radiographic and clinical

Client Questionnaire Used in the Current Study 1. How did level of activity postoperatively compare with prior to surgery? 2. After surgery, how was exercise tolerance compared with prior to surgery?

findings. Complications were defined as an event occurring postop-

a. Greatly improved

eratively that likely would not have occurred had the surgical

b. Mildly improved

procedure not been performed or that could be attributed to

c. Same d. Worse

either the surgical procedure or concurrent disease at the time of diagnosis of LP. Excluded from the complications category

3. Did clinical signs recur after surgery? If clinical signs recurred, how long after surgery?

were events that occurred as an expected part of recovery from

a. , 4 wk

the surgical procedure (i.e., voice change, mild coughing). Events

b. 4–8 wk

were considered an expected part of recovery if they were either

c. . 8 wk 4. If clinical signs recurred, how did the clinical signs compare with prior to surgery?

self-limiting or did not clinically affect the patient as determined by examination of the records, which included follow-up eval-

a. Greatly improved

uations by veterinarians (in most cases) and client questionnaire.

b. Mildly improved

Complications were classified as either acute or chronic. An acute

c. Same

complication was one that occurred # 10 days postoperatively

d. Worse

and a chronic complication was one that occurred . 10 days

5. Was a revision surgery needed following the procedure? If so how many? a. 1 surgery b. 2 surgeries

postoperatively. Complications were divided into the following categories for comparison: scar tissue formation, aspiration pneumonia, respiratory distress, revision surgery required (perma-

c. . 3 surgeries 6. What type of revision surgery was performed if one was required?

nent tracheostomy, VCC, UAL, ventral laryngotomy), and death.

a. Resection of cicatrix

Death was regarded as a complication if it occurred acutely

b. UAL

following surgery and when the cause of death was related to

c. Permanent tracheostomy 7. Did dog develop aspiration pneumonia after surgery? If so when? a. , 6 mo postsurgically

the surgery. Scar tissue formation was confirmed by laryngoscopy, and respiratory distress was defined as owner-assessed

b. 6–12 mo postsurgically

breathing problems of the same or greater severity than prior

c. . 12 mo postsurgically

to surgery.

8. If dog developed aspiration pneumonia, how was it confirmed? a. Radiographs

Follow-up information was evaluated for complications (as previously defined), if the animal was still living, and cause of

b. Physical exam

death. Owners contacted by telephone provided information on

c. Both 9. If dog developed aspiration pneumonia, was hospitalization required? a. Yes

postoperative activity level, appetite, tolerance to exercise, recurrence of clinical signs, revision surgery if one was required, occurrence of aspiration pneumonia, cause of death, time of death

b. No 10. How many episodes of aspiration pneumonia did dog develop?

in relation to surgery, and overall owner satisfaction.

a. 1 episode b. 2 episodes c. . 3 episodes 11. Is your pet deceased? If so, what was cause of death? 12. When did dog die in relation to final surgery? a. , 6 mo

Surgical Procedures UAL All dogs were positioned in right lateral recumbency. A left lateral approach to the larynx was made ventral to the left jugular vein.

b. 6–12 mo

The thyropharyngeus muscle was incised along the dorsomedial

c. . 12 mo

edge of the thyroid cartilage, and the cricoarytenoideus dorsalis

13. Were you satisfied with the surgical procedure? Please provide reason why or why not.

was transected. Disarticulation of the cricoarytenoid articulation was performed. Two separate strands of either 0 or 3-0 polypropyleneb, depending on the size of the dog, were passed from

was made only if a thyroid panel was performed that included both

the caudodorsal aspect of the cricoid cartilage to the muscular

free thyroxine and thyroid-stimulating hormone. A diagnosis of

process of the arytenoid cartilage. Closure of the surgical site was

polyneuropathy was made only if electromyography and muscle

routine.

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Comparison of Two Surgeries for Laryngeal Paralysis in Dogs

Transoral VCC

the Emergency Service, 5 dogs (11.1%) presented to the Internal

All dogs were positioned in sternal recumbency with the maxilla

Medicine Service, and of the 4 remaining dogs, 1 dog (2.2%) each

propped open, suspended with gauze. The tongue was extended

presented to Cardiology, Neurology, Oncology, and Orthopedic

ventrally to expose the larynx. The vocal folds were grasped with

Services. Thirty-two dogs (71.1%) presented for difficulty breath-

Allis tissue forceps and transected with curved Metzenbaum

ing, 8 dogs (17.8%) for dyspnea, 2 dogs (4.4%) for voice change,

scissors at the ventral aspect of the cuneiform process, leaving

and 3 dogs (6.6%) for other reasons. LP was found to be bilateral

1–2 mm of mucosa at the ventral aspect of the vocal cord. The

in 41 cases (91.1%), left-sided in two cases (4.4%), and was not

same action was performed on the opposite side. Hemostasis

listed in the medical record in two cases (4.4%).

was achieved with digital pressure and the wounds left to heal

Eight of 45 cases (17.8%) had no documented concurrent diseases. Subsequently, 37 of 45 dogs (82.2%) had concurrent

by second intention.

diseases at the time of diagnosis. Aspiration pneumonia and hy-

Statistical Analysis

pothyroidism were the most common (n ¼ 6 for each), followed

Interactions between variables in different categories were calcu-

by polyneuropathy (n ¼ 3). The number of dogs tested for each

lated using the Independent x2 testc. Statistical significance for all

concurrent disease consistent with the definitions provided pre-

analyses was defined as the probability that the null hypothesis

viously is as follows: aspiration pneumonia (n ¼ 40), hypothy-

was rejected although true was , 5.0% (i.e., P , .05). A com-

roidism (n ¼ 19), and polyneuropathy (n ¼ 4). Twenty-two dogs

parison was made to test if the study sample (n ¼ 45) was

were placed into the “other” category for a variety of concurrent

a representative sample of the hospital’s breed database over the

diseases, including cervical pain, chronic bronchitis with bron-

exact same time period. The hospital’s breed values (n ¼ 65,535

chiectasis present on radiographs, bacterial laryngitis, vomiting,

as a percent) were used to calculate the x2 expected values for

lumbosacral disease, cranial nerve five deficits, thyroid adeno-

the breeds found in this study. The complications analysis used

carcinoma, heartworm disease, degenerative joint disease, and

a null hypothesis that stated that there was no difference be-

sinusitis.

tween the surgical techniques, UAL, and VCC, wherein the x

2

Follow-up data were available for 20 dogs with UAL that

expected values were equal (i.e., 50%) between the surgical

ranged in age from 8 mo to 10 yr, except in cases that either died

groups for the observed complications.

or were euthanized immediately postoperatively. Postoperative complications occurred in 12 dogs (60%). Of those, 9 dogs (45%)

Results

had acute complications and 3 dogs (15%) had chronic compli-

A total of 45 dogs met the inclusion criteria. Twenty-five dogs

cations. Aspiration pneumonia occurred in 5 dogs (25%) post-

had transoral VCC performed and 20 dogs had UAL performed.

operatively, with 3 of those episodes occurring as an acute

Breeds represented included 26 Labrador retrievers (57.7%),

complication and 2 as a chronic complication. Only 1 dog

3 mixed-breeds dogs (6.6%), and 1 each of the following breeds:

was suspected of having two episodes of aspiration pneumonia

Boston terrier, Weimaraner, giant schnauzer, wheaten terrier,

following the initial radiographically documented episode. Those

English springer spaniel, Bernese mountain dog, Doberman

two suspected episodes occurred , 6 mo following surgery;

pinscher, Siberian husky, Australian cattle dog, Chihuahua,

however, aspiration pneumonia was not confirmed by radiog-

Rhodesian ridgeback, Great Dane, German shepherd dog,

raphy in either episode.

Pekingese, cocker spaniel, and Yorkshire terrier. Comparison of

Respiratory distress also occurred in four dogs (20%) post-

this study sample to the hospital’s breed database over the

operatively following UAL. Revision surgery was required in two

same time period was not consistent with a random sample

of those dogs (10%). One dog was a Chihuahua that was noted

(P , .0001) because Labrador retrievers were overrepresented

to have an abnormally narrowed air passage before the initial

(57.7%). Patient ages at presentation ranged from 3 to 16 yr of

surgery, which did not widen following UAL. The other dog was

age with median and mean ages of 11 and 10.9 yr, respectively

a Pekingese that had a permanent tracheostomy performed 14 days

(standard deviation, 3.24 yr). Eighty percent of the animals in

postoperatively and was subsequently reoperated on 18 mo post-

this study were older than 9 yr. Twenty animals were spayed

operatively due to stenosis. That dog was noted to have concurrent

females, 1 was female, 17 were castrated males, and 7 were intact

laryngeal collapse at the time of the initial UAL. Of the two dogs

males.

that did not have revision surgeries, one dog did not have return

At Texas A&M University twenty-six dogs (57.7%) presented to the Soft-Tissue Surgery Service, 10 dogs (22.2%) presented to

of clinical signs until 2 yr after the procedure, and the other dog never seemed to improve following surgery.

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267

At the time of follow-up, 16 of 20 dogs (80%) were reported

transoral VCC and permanent tracheostomy in one dog, a ventral

to have died since UAL, and 4 of 20 dogs (20%) were reported alive.

laryngotomy for cicatrix resection and permanent tracheostomy

Of the 16 dogs that died, the presumed causes of death were listed

in the second dog, and transoral VCC and a ventral laryngotomy

in all 16 cases (Table 2). Four dogs died , 6 mo following surgery,

for cicatrix resection in the third dog. The first two dogs were

5 dogs died between 6 and 12 mo following surgery, and 7 dogs

Labrador retrievers and the third dog was a Siberian husky. Both

died . 12 mo following surgery. Seventeen dogs (85%) survived

dogs had permanent tracheostomies performed due to failure of a

to discharge, while 3 dogs (15%) did not survive to discharge.

second surgery to alleviate clinical signs (i.e., second transoral VCC

Death occurred as an acute complication in 2 dogs (10%), and 1

in the first case, and ventral laryngotomy for cicatrix resection in

dog was euthanized 1 day postoperatively when aspiration

the second case).

pneumonia occurred immediately following surgery. Eleven of the

Aspiration pneumonia occurred in four dogs (16%) post-

15 owners (73%) who completed the survey were satisfied with

operatively following transoral VCC. All of those episodes oc-

the UAL.

curred as a chronic complication. One dog died of complications

Follow-up data were available for 25 dogs with transoral VCC, ranging in age from 1.5 to 9.5 yr, except in cases that either

of aspiration pneumonia, and one dog was euthanized from severe aspiration pneumonia.

died or were euthanized immediately following surgery. Post-

At the time of follow-up, 19 of 25 dogs (76%) were reported

operative complications occurred in 13 dogs (52%). Only 1 dog

to have died since transoral VCC surgery, and 6 of 25 dogs (24%)

(4%) had an acute complication, and 12 dogs (48%) had chronic

were reported to be alive. Of the 19 dogs that died, the presumed

complications. Respiratory distress was the most common com-

causes of death are listed in all 19 cases (Table 3). Eight dogs died

plication that occurred in 9 dogs (36%) postoperatively, with all of

, 6 mo following surgery, 4 dogs died between 6 and 12 mo

those episodes occurring as a chronic complication.

following surgery, and 7 dogs died . 12 mo following surgery.

Six dogs (24%) following transoral VCC had revision sur-

Twenty-three dogs (92%) survived to discharge, and 2 dogs (8%)

geries performed, ranging from 6 wk to 1 yr after leaving the

did not survive to discharge. Both dogs that did not survive to

hospital. Three dogs (12%) required one revision surgery, and

discharge were euthanized, one because of progressive respira-

three dogs (12%) required two revision surgeries. All cases re-

tory distress and concurrent upper airway disease (brachycephalic

quiring revision surgery presented for examination of respiratory

syndrome, esophageal dysmotility, esophageal diverticulum, and

distress, and five of those dogs (20%) had cicatrix formation.

a hypoplastic trachea), and the other because of severe underlying

Cicatrix formation was similar in all cases and consisted of com-

gastrointestinal disease of unknown cause that was present before

plete fibrous scar tissue formation across the rima glottidis from

surgery. In total, 18 of the 21 owners (86%) that completed the

the mucosal surfaces of each vocal fold that had been previously

survey were satisfied with the VCC, while 3 owners (14%) were not

resected bilaterally. Of the three dogs that had only one revision

satisfied.

surgery, the revision surgery performed was UAL in two dogs

Sex, breed, appointment type, presenting complaint, and

and transoral VCC in one dog. All of those dogs were Labrador

concurrent diseases were not significantly associated with either

retrievers. Of the three dogs that had two revision surgeries, the

a higher risk of death or decreased survival time postoperatively

revision surgeries performed in their respective order were:

with either VCC or UAL. The presence of concurrent diseases

TABLE 2 Causes of Death in Dogs that had UAL Performed Cause of death

Details

Related to surgical procedure

Euthanasia due to aspiration pneumonia

3

Death due to complications from heatstroke

2

Presumed causes of death unrelated to surgical procedure

Euthanasia due to: Unknown causes

2

Neoplasia of type unknown Femur fracture

1 1

Tetraparesis Death due to unknown cause

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No. of dogs

1 6

Comparison of Two Surgeries for Laryngeal Paralysis in Dogs

TABLE 3 Causes of Death in Dogs that had VCC Performed Cause of death

Cause of death

Related to surgical procedure

Euthanasia due to aspiration pneumonia Euthanasia due to acute respiratory distress

No. of dogs 1 2

Death due to complications from aspiration pneumonia

1

Presumed causes of death unrelated to surgical procedure

Euthanasia due to: Unknown cause

1

Neoplasia from type unknown

2

Complications of anal gland abscess

1

Megaesophagus

1

Renal disease Tetraparesis

1 1

Death due to unknown cause

7

Hit by car

1

did not significantly affect the type of complication that occurred

etc. Only three dogs that were diagnosed with polyneuropathy

or whether animals presented with difficulty breathing or dyspnea

were included in this study, which may underestimate the true

for either procedure.

number of dogs with this condition due to lack of specific testing

The number of dogs with episodes of respiratory distress

for this condition and neurologic exams on all patients. The

and episodes of aspiration pneumonia was similar between both

aspiration pneumonia rate following VCC surgery in this study

surgical methods postoperatively and the differences were not sig-

was similar to previously reported results; however, limited in-

nificant (P ¼ .0877). Dogs that underwent UAL however, were

formation was available and case numbers in all studies were

significantly more likely to have dyspnea on initial presentation

small. The UAL aspiration pneumonia rate was higher in this

(P ¼ .004), have acute complications following surgery (P ¼

study (25%) than reported studies (8–19%).4,12,19 That difference

.001), and have acute postoperative respiratory distress and as-

may be due to either various definitions of aspiration pneu-

piration pneumonia (P ¼ .052). Dogs that underwent VCC were

monia among different studies or reflect the small case numbers

significantly more likely to have difficulty breathing on initial

in the current study. Owner satisfaction for UAL in this study

presentation (P ¼ .004), have chronic complications following

was lower (73%) than previously reported (88–90%) and may be

surgery (P ¼ .001), and have chronic postoperative respiratory

related to the higher incidence of aspiration pneumonia in the

distress and aspiration pneumonia (P ¼ .0079). Revision surgery

study population.3,4,12,19 Owner satisfaction for VCC (86%) in

was required in six dogs (24%) following VCC and two dogs

this study was similar to previously reported studies (83%).24

(10%) following UAL, but that difference was not significant (P ¼ .0877).

Interestingly, this study found that although both postoperative aspiration pneumonia and respiratory distress occurred with

There was no difference in the level of client satisfaction

similar frequencies following both procedures, they were both

between VCC and UAL (P ¼ .418), and there were no breed

significantly more likely to occur in the acute postoperative period

associations between procedures deemed either satisfactory or

after UAL surgery. Many studies exist that support this study’s

unsatisfactory for either procedure.

finding that there is low risk of long-term complications following UAL surgery. A study by MacPhail et al. assessed 109

Discussion

cases that had UAL surgery performed. In that series, 15 dogs

The overall postoperative complication rates, episodes of aspi-

(13.7%) had acute complications and 16 dogs (14.7%) had

ration pneumonia, and episodes of respiratory distress were

chronic complications following UAL. The complications that

similar in dogs undergoing UAL and transoral VCC surgeries. The

occurred chronically were not specified in that study. Their defi-

high rate of postoperative complications found in this study fol-

nition of a complication was a respiratory tract problem requiring

lowing both procedures may be attributable to both a broad defi-

either hospitalization or surgery, which was more specific than

nition of complications and inclusion of cases with preexisting

the definition provided in the current study. That difference may

conditions, such as neoplasia, hypothyroidism, polyneuropathy,

explain why our overall and acute complication rates were higher.4

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269

Another study by Hammel et al. evaluated the postoperative out-

only 3 dogs (7.5%) had postoperative complications acutely

come of 39 dogs with idiopathic LP after UAL surgery. They found

(, 10 days) following surgery. In the chronic postoperative

no correlation between signalment, pre- and postoperative clinical

period, 5 dogs (12.5%) had scar tissue formation requiring re-

signs, and development of pneumonia on postoperative survival in

vision surgery. In addition, 6 dogs (15%) developed aspiration

their study. Complications in that study were divided into major

pneumonia, and 5 of those occurred between 2 and 36 mo

and minor based on the need for hospitalization. That study did

following surgery. Follow-up in this study ranged from 5 to 52

not divide complications into acute or chronic categories; however,

mo.24 In a retrospective study by Petersen et al. that assessed the

only two dogs (5.1%) developed aspiration pneumonia . 6 mo

outcome following transoral VCC in 24 dogs, 9 dogs (37.5%)

after surgery and only one dog (2.5%) developed a complication . 12

had scar tissue formation and required revision surgery and 14

mo after surgery.19 Based on those results, this study suggested

dogs (58%) had complications occurring from 2 wk to 7 mo

that dogs, after an initial adjustment period following UAL,

postoperatively. Complications in that study included aspiration

become less likely to suffer from aspiration pneumonia as time

pneumonia, persistent cough, exercise intolerance, and increased

increases from surgery.

respiratory stridor.22

A study by Snelling et al. examining outcome after UAL in

Scar tissue formation following transoral VCC in the current

100 dogs found that 8% of dogs were diagnosed with aspiration

study was comparable to the reported rates in previous studies

pneumonia following surgery. Of those, half occurred as an acute

and was likely due to the use of an oral approach during VCC

complication (, 7 days) postoperatively and the other half oc-

that leaves the mucosal defect to heal by second intention. That

curred 120–870 days postoperatively. That study did not divide

technique was associated with a higher risk of scar tissue for-

all complications into acute and chronic categories; therefore,

mation.28 Cases with cicatrix formation often require revision

speculation about overall complications in this study cannot be

surgery to alleviate respiratory distress caused by blockage of

inferred.

12

A study by White that examined postoperative out-

the airway. In a recent study by Zikes et al., of 88 dogs that had

come in 62 dogs with LP following UAL, perioperative compli-

VCC performed via a ventral approach, the mucosal defect was

cations were found in seven dogs (11.3%). Long-term follow-up

sutured closed and no dogs postoperatively had cicatrix for-

was 1 yr in that study and chronic complications occurred in only

mation. In the short term, complications were divided into

3

four dogs (6.2%), and overall owner satisfaction was 91%. Based

major and minor, with a total of 6 dogs (6.8%) affected, which is

on the results of those studies and the current study, there is

comparable to the current study. Only 42 dogs included in

supporting evidence that most complications after UAL occur in

that study were available for follow-up. Of those, 3 dogs had

the acute postoperative period.3,4,12,19

long-term complications (7.1%). In total, 3 dogs developed

Transoral VCC was significantly more likely to have com-

documented aspiration pneumonia and 3 dogs had episodes of

plications occur chronically, many of which required revision

antibiotic-responsive coughing that occurred as both short- and

surgery due to respiratory distress and scar tissue formation.

long-term complications.29 That complication rate was lower than

In the current study, six cases (24%) required revision surgery

reported in the current study; however, aspiration pneumonia

postoperatively following VCC and only two cases (10%) required

rates postoperatively were similar. There were 9 dogs in the

revision surgery following UAL postoperatively; however, that

current study that developed respiratory distress, five of which

difference was not significant. Interestingly, both cases that had

had cicatrix formation postoperatively. It is possible that the

revision surgery following UAL had concurrent airway abnor-

postoperative chronic complications identified in the current study

malities along with LP. It is likely that those abnormalities led to

would have been more comparable to the study by Zikes et al. if

the need for revision surgery following UAL because none of the

the ventral approach was used to suture the mucosal defect

other dogs that had UAL performed had concurrent airway

closed thereby preventing cicatrix formation, postoperative re-

abnormalities other than LP or required revision surgery fol-

spiratory distress, and subsequent revision surgery.29 It seems

lowing UAL.

performing VCC via ventral laryngotomy and suturing the

Although there is limited data on postoperative outcome

mucosal defect closed may be effective in reducing the frequency of

following VCC surgery, the studies that exist support this study’s

cicatrix formation, but would consequently eliminate the min-

finding that complications occur more commonly in the late

imally invasive benefit of the transoral approach.29,30

postoperative period.22,24 In a study by Holt et al. assessing long

The authors of the current study did not find an association

term postoperative outcome of 40 dogs that had transoral VCC

with any of the risk factors included in this study on either death

in which the mucosal defect was left to heal by second intention,

or survival time with either surgical procedure. MacPhail et al.

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Comparison of Two Surgeries for Laryngeal Paralysis in Dogs

found an association between respiratory tract abnormalities,

UAL and VCC performed by the same surgeon, randomizing

neurologic disease, and esophageal disease on overall outcome,

what patient received either treatment, with follow-up evalua-

which was not a finding supported by the current study. It is

tion by the same surgeon, would be beneficial to provide a more

possible that significant associations may have become apparent

complete picture about risk factors, complications, and overall

4

outcome following each procedure.

had there been more cases in the current study.

There was an increased likelihood for dogs presenting with dyspnea to be treated with UAL, which may indicate that clini-

Conclusion

cians are more likely to perform UAL in cases that are perceived as

Based on past and present study results, it is likely that dogs

having an increased severity of clinical signs. Labrador retrievers

surviving the first 10 days after surgery will have a better overall

represented 57.8% of the sample population (26 dogs). The over-

outcome following UAL. The study authors conclude that dogs

abundance of Labrador retrievers in the study population agrees

that have transoral VCC have an increased risk of life-long

with previous studies that report the breed as commonly affected,

complications following surgery compared with UAL; there-

1–8

potentially indicating a genetic basis for LP in that breed.

There are several limitations of this study because of its

fore, transoral VCC may not be the optimal choice for treatment of LP in many dogs.

retrospective nature. As with any retrospective study, reliance on the written records and owner assessment for follow-up can influence conclusions drawn about postoperative outcome. Although a majority of cases in the current study had follow-up evaluations performed by a board-certified surgeon, that was not

FOOTNOTES a Veterinary Medical Information System, version 1.3.694; Java Virtual Machine, College Station, TX b Polypropylene; Ethicon Inc.; Cincinnati, OH c SPSS Inc., 18 (2011), IBM, Chicago, IL

always available, and owner assessment was relied upon. The authors considered a diagnosis of aspiration pneumonia only in cases with clinical signs and documentation, which may underestimate the total number in patients suffering from subclinical aspiration. The authors do not believe that had a significant impact on this study because the definition of a complication would not have included subclinical aspiration pneumonia due to the self-limiting nature and lack of clinically affecting the patient. Cases in which follow-up was not available beyond discharge after surgery were excluded from the study. It is, therefore, possible that the results of the study would be influenced with a higher number of cases with follow-up information. Another limitation of the study was that multiple surgeons with different levels of experience performed the surgeries over the span of the study, which could affect outcome in specific cases. Conversely, in the study by Hammel et al. that attempted standardization of the surgical procedure, the overall postoperative complication rate was comparable to previous studies in which surgical technique was not standardized.19 It is possible that because cases with UAL performed were more likely to present with dyspnea, the increased severity of clinical signs affected the number of complications that occurred postoperatively. Although that may have increased the number of acute complications postoperatively, the authors do not believe this influenced conclusions drawn about the chronic postoperative period. The decision to perform either UAL or VCC in a particular patient was surgeon preference, and further reasoning for the decision was not available in the medical records. Ideally, a prospective study investigating

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