Bilateral Ventriculocordectomy via Ventral Laryngotomy for Idiopathic Laryngeal Paralysis in 88 Dogs
Bilateral ventriculocordectomy through a ventral median laryngotomy was performed for the treatment of idiopathic laryngeal paralysis in 88 dogs. The purpose of this retrospective analysis was to provide long-term follow-up for a large number of dogs surgically managed with this technique. A combination of medical record and completed client questionnaire information provided short-term (14 days) follow-up for 88 dogs and long-term (>6 mo) follow-up for 42 dogs. Major short-term postoperative complications were identified in 3 of 88 (3.4%) patients. Major long-term complications were identified in 3 of 42 (7.1%) patients. The results of surgery were considered to be very satisfactory in 93% and unsatisfactory in 7%. Three dogs in this series developed aspiration pneumonia. Bilateral ventriculocordectomy through a ventral median laryngotomy is associated with a low incidence of both short- and long-term complications. Due to the ease of this procedure, the minimal surgical trauma to the patient, and the satisfactory results, this surgery should be considered an option for the treatment of idiopathic laryngeal paralysis in the dog.
Introduction
Laryngeal paralysis has been recognized as a significant clinical syndrome for more than 4 decades. This disorder has been thoroughly described in the literature. Surgery is the treatment of choice for dogs with clinical evidence of respiratory distress due to laryngeal paralysis. A surgical approach that provides alleviation of upper airway obstruction with the least potential for complications is the ultimate goal.
Over the last 40 yr, multiple surgical options for laryngeal paralysis have been developed and evaluated with this goal in mind. Treatment options include numerous variations of thyroarytenoid and cricoarytenoid cartilage lateralization, arytenoidectomy, ventriculocordectomy (vocal fold resection, vocal cordectomy), castellated laryngofissure, abductor muscle prosthesis, muscle-nerve pedicle transposition, permanent tracheostomy, and combinations thereof.1–7 Recently, a video-assisted left partial arytenoidectomy by diode laser photoablation has also been described.8 Numerous studies evaluating the various techniques have revealed a wide variety of surgical and postsurgical complications in 10–58% of cases.7,9–14 The reported results have been mixed, but the most common and most serious complication has been aspiration pneumonia.7,13–15
Unilateral arytenoid lateralization (UAL) is currently considered the surgical technique of choice for laryngeal paralysis in dogs and is the most commonly performed procedure.7,13,15 However, the complication rate is still high. Complications have been reported in 10–28% of dogs undergoing this procedure. For example, the reported rate of aspiration pneumonia is 8–33%, and 14% of dogs die from respiratory tract-related diseases.7,13–15
Other reported surgical treatments have failed to gain favor for a variety of reasons. For example, bilateral arytenoid lateralization is rarely performed due to the excessive widening of the laryngeal lumen, resulting in an increased risk of aspiration pneumonia (reported in up to 88% of cases).7,12
Partial laryngectomy is an alternative surgical approach still in use by some surgeons today, but there are numerous variations associated with varying degrees of success and complications. Partial laryngectomy involves performing either a uni- or bilateral ventriculocordectomy with a unilateral partial arytenoidectomy. The partial arytenoidectomy, as previously described, involves removal of the medial two-thirds of the corniculate process of the arytenoid cartilage, leaving the cuneiform cartilage intact.11,16 Several retrospective studies report that the postoperative complications in dogs undergoing partial laryngectomy are too high for it to be considered an appropriate treatment.11,16
Transoral bilateral ventriculocordectomy has also been described. Satisfactory results were reported for 83% of dogs in one study; however, 5 of 40 dogs developed postoperative granulation and scar tissue formation with stenosis of the rima glottidis that required a second surgery.10
Variations of the castellated laryngofissure have also been described that reportedly provide satisfactory results, but this surgical procedure is rarely performed.4,5,17 This might be because the castellated laryngofissure has been described as being more technically demanding, time consuming, and traumatic than arytenoid abduction techniques.18 In addition, castellated laryngofissure can lead to severe postoperative bleeding and edema, requiring a temporary tracheostomy for several days.19 Finally, the rima glottidis is opened to the same degree as the bilateral arytenoid lateralization, leaving the airway similarly susceptible to aspiration pneumonia.18
In 2001, outcomes of various surgical approaches for the treatment of 140 dogs with laryngeal paralysis were compared. It was concluded that, although UAL is considered the surgical treatment of choice, high complication and death rates still exist. 7,13The authors of the current study therefore suggest a need to re-examine surgical goals and alternative surgical techniques that would yield better results with fewer complications.
In 2007, Schofield et al. described the combined bilateral thyroarytenoid cartilage lateralization, vocal fold excision, and mucosoplasty technique through a ventral median laryngotomy.20 This alternative to the UAL was developed to yield better results with fewer complications by addressing both the structural and soft tissue components of canine laryngeal paralysis. Although the risk of aspiration pneumonia in that report did appear to be lower than previously described techniques, glottic narrowing required additional surgery and/or permanent tracheostomies in 19.4% of cases. This led to the conclusion that UAL should remain the treatment of choice for laryngeal paralysis.
The authors of this study propose that a bilateral ventriculocordectomy with mucosal closure performed through a ventral laryngotomy approach is an alternative surgical technique that meets the goals of better surgical results with fewer complications. The authors have been utilizing this technique for >2.5 decades and, to their knowledge, this approach has not been evaluated and reported in the literature to date. The purpose of this retrospective analysis was to provide long-term follow-up for a large number of dogs surgically managed by a single experienced surgeon performing a bilateral ventriculocordectomy for the treatment of laryngeal paralysis.
Materials and Methods
Inclusion Criteria
Medical records of 104 patients undergoing bilateral ventriculocordectomy over a 26 yr period (1982–2008) were reviewed. Those patients included 5 cats and 99 dogs. Only dogs diagnosed with idiopathic, acquired laryngeal paralysis were included in this study. All dogs with this diagnosis requiring surgical treatment underwent ventriculocordectomy by one surgeon (T.M.). No other surgical treatment of laryngeal paralysis was performed. For the dog to be included, the medical records had to include the method of diagnosis, a description of the surgical procedure, and a minimum of short-term (14 day) follow-up information. Age, breed, sex, history, clinical signs, and preoperative evaluation (including a thorough physical examination, complete blood count, serum biochemical profile, urinalysis, thoracic radiographs, and electrocardiogram) were obtained from the medical records for all dogs included in the study.
Diagnosis
Laryngoscopy was performed in every patient (either under heavy sedation or a light plane of general anesthesia) to confirm the diagnosis of laryngeal paralysis. The diagnostic evidence of laryngeal paralysis was either minimal abduction of the arytenoid cartilages or complete failure of the arytenoid cartilages and vocal folds to abduct during inspiration (Figure 1). Inflammation and edema of surrounding soft tissues and paradoxical vocal fold and arytenoid motion were also noted (Figure 2). Surgery was recommended when clinical symptoms of airway obstruction (i.e., inspiratory dyspnea and stridor, respiratory distress, cyanosis, collapse, exercise intolerance, coughing, gagging) were negatively impacting the patient’s quality of life.
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Surgical Procedure
Following the confirmation of laryngeal paralysis, each patient was intubated, and anesthesia was induced and maintained with gas anesthetic in oxygen. Each dog was positioned in dorsal recumbency with the head and neck extended. Temporary tracheotomy tubes were not used. A ventral midline skin incision was made from the level of the caudal mandible to the midcervical trachea. The paired sternohyoideus muscles were separated along the median raphe using blunt dissection. This provided exposure to the thyroid and cricoid cartilages on the ventral surface of the larynx. The cricothyroid membrane and thyroid cartilage were incised on the ventral midline to expose the laryngeal lumen and both vocal folds. Weitlaner retractors were used to maintain the opening of the laryngotomy incision by placing stay sutures through the cartilage edges and around the retractor on either side (Figure 3). The endotracheal tube was left in place and gently retracted, as needed, to expose the vocal folds on either side. First, the right vocal fold and vocalis muscle were identified, sharply dissected (using full-curve Thorek scissors), and completely excised. The ventriculocordectomy site mucosa was closed with a variety of different absorbable suture materials (e.g., 4-0 or 5-0 polyglactin 910, polyglyconate, polyglycolic acid, or poliglecaprone 25) in a ventrodorsal-dorsoventral continuous cruciate suture pattern (Figure 4). The lateral wall mucosa of the lateral saccule was freely moveable, which allowed tension-free closure of the defect without requiring undermining of the adjacent mucosa. Hemorrhage was minimal. The same procedure was performed on the left side. The thyroid cartilage was closed with nonabsorbable material (2-0 or 3-0 polyamide or polypropylene), providing alignment and apposition of the thyroid cartilages without overlap. The cricothyroid membrane and muscular layers were closed with absorbable suture material (3-0 or 4-0 polyglactin 910, polyglycolic acid, polyglyconate, or polydioxanone) in a simple continuous pattern. The subcutaneous and subcuticular layers were closed with absorbable 5-0 polyglycolic acid or poliglecaprone 25 in a simple interrupted pattern. In some cases, the skin was closed with either polyamide or staples.
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Figures 5 and 6 illustrate the larynx immediately after bilateral ventriculocordectomy. Figure 7 is an exemplar photo of the surgical site 1 yr postsurgically.
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Citation: Journal of the American Animal Hospital Association 48, 4; 10.5326/JAAHA-MS-5751
Outcome
The medical records were examined for descriptions of immediate postoperative complications that could be associated with the bilateral ventriculocordectomy or any complications that developed during the long-term follow-up period. For the purpose of this study, a complication was considered major if it required either surgical intervention or hospitalization. Aspiration pneumonia requiring hospitalization, respiratory distress, surgical failure, and death were considered major complications. Persistent cough, respiratory stridor, exercise intolerance, and mild seroma development were considered minor complications. Patients were carefully monitored in the immediate postoperative period for dyspnea, vomiting, pyrexia, hemorrhage, and coughing.
The operating surgeon reassessed every patient 14 days postsurgically. The assessment included a detailed postoperative history from the owners and a physical examination. The owners were questioned about exercise tolerance, coughing, noisy respiration, and any perceived or observed postoperative complications. As part of a complete physical examination, the incision was evaluated for appropriate healing. The patient was evaluated for any evidence of postoperative aspiration pneumonia. Second-look laryngoscopy was not performed unless indicated by either history or physical examination findings suggestive of upper airway obstruction or surgical complication.
The owners were contacted again by mail for long-term (>6 mo) follow-up information. Contact information was available for 70 of 88 of the dogs; therefore, 70 survey questionnaires were mailed (Table 1). Based on owner responses, results of surgery regarding patient condition were graded as poor, fair, good, or excellent. Owner responses regarding overall satisfaction with surgical results were categorized as very dissatisfied, dissatisfied, satisfied, or very satisfied. Information regarding complications encountered at any time after surgery was requested. In cases where the owners could not be located, medical record information was reviewed. Based on questionnaire responses and medical record information, surgical success and owner satisfaction were determined by resolution of respiratory distress, improvement in exercise tolerance, diminished upper airway stridor, and a paucity of major postoperative complications, particularly aspiration pneumonia.
Results
Signalment
Of the 88 dogs included in this study, the most common breeds were the Labrador retriever (n=31), Brittany spaniel (n=6), Irish setter (n=5), Saint Bernard (n=4), golden retriever (n=4), cocker spaniel (n=3), springer spaniel (n=3), beagle (n=3), and basset hound (n=2). No other purebreed dog was represented more than once. There were eight mixed-breed dogs affected. Mean patient age was 10.7 yr (median, 12 yr). Forty-nine were female (44 spayed) and 39 were male (31 castrated), with a female:male ratio of 1.3:1.
Clinical Findings
Clinical signs prior to examination were recorded for 73 dogs. Clinical signs had been present for variable periods of time, ranging from 1 day to 36 mo (mean, 8.7 mo). The number of dogs affected by each clinical symptom and their degree of severity are summarized in Table 2. Most patients had a gradual onset of a variety of respiratory symptoms with intermittent episodes of dyspnea that increased in severity over time. Presenting clinical signs included the following: dyspnea (n=68), increased upper airway noise/wheezing/inspiratory stridor (n=50), exercise/excitement/stress and/or heat intolerance (n=17), coughing/gagging/choking with eating or drinking (n=14), varying degrees of respiratory distress with occasional progression to hyperventilation/severe respiratory distress/cyanosis/collapse (n=14), excessive panting (n=8), change in voice/bark (n=5), pelvic limb weakness (n=3), vomiting (n=1), and anxiety expressed as either pacing or an inability to settle (n=1). Twelve (13.6%) dogs were either being treated for hypothyroidism or were newly diagnosed with hypothyroidism based on subnormal thyroid function profiles at the time of treatment of laryngeal paralysis.
Physical Examination
A physical examination was performed on every patient. In addition to thoracic auscultation, the laryngeal region was auscultated both before and during mild laryngeal compression. Any abnormal characteristics of facial and nasal anatomy were recorded. Tracheal sensitivity was subjectively evaluated by applying gentle pressure to the trachea in an attempt to elicit a tracheal cough. Orthopedic and neurologic examinations were also performed. Body condition and skeletal muscle mass were noted. Detailed physical examination findings were available for 77 of 88 dogs. Relevant physical findings included the following: laryngeal stridor (n=49), obesity (n=12), increased tracheal sensitivity (n=10), orthopedic abnormalities (n=9), increased bronchovesicular sounds (n=7), hyperthermia (n=5), stenotic nares (n=1), and facial/nasal mass (n=1).
Neurologic examination findings suggestive of generalized neuromuscular disease included generalized or focal muscle weakness, muscle atrophy, and/or depressed spinal reflexes. Those signs were noted in six dogs.
Concurrent Disease
Fourteen (16%) of the 88 dogs had no other documented concurrent diseases. In contrast, 74 of 88 (84%) dogs had a variety of concurrent medical conditions (both major and minor) at the time of laryngeal paralysis diagnosis. Hypothyroidism was the most common concurrent disease (n=10). Other concurrent diseases (n=1 for each) included the following: hyperadrenocorticism, gastrointestinal disease (gastroesophageal reflux, esophagitis), caudal tongue abscess, perineal hernia, flea allergy dermatitis, atopy, severe bilateral otitis externa, chronic dermatitis caused by Malassezia spp., degenerative joint disease, idiopathic epilepsy, intervertebral disk disease, cauda equina, lymphoplasmacytic urethritis, vaginitis, estrogen-responsive urinary incontinence, microvascular dysplasia, chronic hepatopathy, heart disease, benign splenic mass, apocrine gland adenocarcinoma, facial hemangiopericytoma, and mast cell tumor. Twenty-seven (36.5%) of the 74 dogs had a variety of other airway diseases concomitantly with the laryngeal paralysis, including stenotic nares, nasopharyngeal stenosis, everted lateral saccules, elongated soft palate, tracheal collapse, bronchitis, pulmonary adenocarcinoma, and undifferentiated nasal carcinoma. One dog had tracheal stenosis from a previous tracheal laceration, and another dog had multicentric tracheal calcinosis circumscripta. One dog had an undefined solitary pulmonary mass.
Presurgical Laryngoscopy, Cytology, and Bacteriology Results
Bilateral laryngeal paralysis (i.e., failure of both arytenoid cartilages and vocal folds to abduct during inspiration) was identified at laryngoscopy and documented in 84 of 88 patient records. Three dogs had unilateral left paralysis with right-sided paresis, and one dog had variable laryngeal function that ranged from no abduction on inspiration to mild/moderate abduction with increased inspiratory effort. In addition to laryngoscopy, 80 of 88 dogs also underwent tracheobronchoscopy for a complete airway evaluation at the time of surgery. Bronchial brush cytology was submitted for cytologic analysis in 37 of 80 dogs. Thirteen dogs had evidence of mild chronic inflammation consisting of a mixed population of neutrophils and macrophages. Seven dogs had normal cytologic results. Six dogs had respiratory epithelial cell and goblet cell hyperplasia with hypersecretion of mucus. Four dogs had septic samples with no evidence of inflammation. One dog had evidence of chronic eosinophilic inflammation. Results for the remaining six dogs were unavailable for review.
Bronchoalveolar lavage samples were submitted for bacterial culture in 27 dogs. Twelve cultures were negative. Isolated organisms identified included the following: Pseudomonas aeruginosa (n=5), Klebsiella pneumoniae (n=3), and one each of Staphylococcus aureus, Streptococcus spp., Pasturella multocida, Alcaligenes faecalis, and Citrobacter freundii. One culture revealed Candida albicans with evidence of oral contamination of the sample. Results of four cultures were unavailable. Of the 11 positive cultures, cytology revealed no evidence of inflammation in half of the samples. Two cytology samples revealed bacteria, but the corresponding cultures were negative. Appropriate postoperative medical therapy was determined according to results. Culture-positive dogs were treated with antibiotics based on sensitivity results. Additional diagnostics, including allergy testing, were recommended in one dog with eosinophilic inflammation.
Several dogs in this study had undergone previous upper respiratory tract surgeries. Four dogs (one English bulldog, one beagle, one cocker spaniel, and one English pointer) required surgical correction of an elongated soft palate and excision of everted lateral saccules. The English bulldog was a 2 yr old spayed female with a history of two soft palate resections prior to referral for continued dyspnea. Laryngoscopy revealed severe laryngeal paralysis with no abduction of the arytenoids during the inspiratory phase of respiration. Lateral saccule eversion did not extend beyond the vocal folds. The beagle, cocker spaniel, and English pointer all had bilateral laryngeal paralysis with the arytenoid cartilages in a fixed paramedian position and no movement on inspiration. Another dog included in this study had undergone surgery for a tracheal laceration in the midcervical region 1 yr before presenting for progressively worsening dyspnea. That dog was referred for a possible tracheal resection and anastomosis. Laryngoscopy and tracheoscopy were performed, and severe bilateral laryngeal paralysis was diagnosed. The site of previous tracheal surgery was only minimally stenosed, and resection was not deemed necessary. Another dog had tracheal resection and anastomosis for mineralized densities in the midcervical tracheal rings with segmental tracheal deformity and collapse without a fixed stricture. Finally, one dog required surgery (i.e., lance and drain) for a caudal lingual abscess. That dog had complete lack of arytenoid movement identified bilaterally. Increased laryngeal noise, but no dyspnea, persisted after bilateral ventriculocordectomy and complete resolution of the abscess.
Surgery
Mean surgical time for ventriculocordectomy (including tracheo-bronchoscopy) with no other surgical procedures was 49 min (range, 45–75 min). There were no reported complications during recovery from anesthesia in any of the dogs. Mean hospitalization time was 24 hr.
Postsurgical Laryngoscopy
One dog required additional laryngoscopy evaluations at 1 wk, 1 mo, and 2 yr postoperatively, and additional laryngectomy surgical procedures were required. No other patients required additional laryngoscopy examinations either on or before 14 days postsurgically. One patient was doing well 2 wk after surgery, but developed progressive symptoms of upper airway obstruction 5–6 wk later. Laryngoscopy was repeated in that dog, which revealed that the surgery site had healed appropriately. Medical management for allergic airway disease resulted in resolution of clinical signs. The dog went on to do well for an additional 3 yr. One dog underwent laryngoscopy 4 wk after surgery due to recurrence of upper airway symptoms. Findings revealed development of a subepiglottic, high-grade, squamous cell carcinoma. Five dogs underwent subsequent second-look laryngoscopy examinations during anesthesia and/or surgery for other disease conditions or procedures, including the following: lung lobectomy, insulinoma excision, pyometra, gastric dilatation, and axillary infiltrative carcinoma excision. Appropriate healing of the ventriculocordectomy surgery sites was confirmed in all five dogs.
Short-Term Results
Six of the 88 dogs included in this study experienced minor (n=3) or major (n=3) complications within the first 14 days postsurgically. One of those dogs developed aspiration pneumonia that responded to oral antibiotic therapy without hospitalization. That dog had a prior history of pneumonia that had been treated successfully as an outpatient several months prior to surgery. Two dogs developed incisional seromas. One seroma resolved without intervention and the other required centesis for resolution.
Of the three dogs experiencing major complications, one was a 9 yr old female Saint Bernard that had multiple preoperative medical conditions in addition to laryngeal paralysis. Specifically, hypothyroidism, acute gastritis, an undefined dermatopathy, a ruptured right cranial cruciate ligament, hyperglobulinemia consistent with chronic inflammation, and an increased pulmonary interstitial pattern were present at the time of diagnosis. That dog continued to exhibit signs of upper airway obstruction after ventriculocordectomy, and an additional transoral, bilateral, partial laryngectomy was performed 1 wk later. That dog required a third surgery for more aggressive laryngeal tissue resection 1 yr later and went on to do well. A second dog died suddenly 2–3 days postsurgically with severe aspiration pneumonia. That dog had a solitary pulmonary mass identified on preoperative thoracic radiographs. The mass was located in the left caudal lung lobe. Mass excision was to be performed after recovery from the ventriculocordectomy procedure. The third dog with major complications was a 14.5 yr old springer spaniel that developed acute, severe neurologic symptoms (circling and head pressing) 4 days postsurgically.
Long-Term Results
If the patients were doing well at the 14 day follow-up appointment, no additional rechecks were scheduled with the primary surgeon unless indicated by the patient’s clinical condition or if specific concerns arose. Patients who were doing well were referred back to their primary veterinarian for continued case management. Long-term follow-up information (>6 mo) was available for 42 of 88 (48%) dogs. The median duration of long-term follow-up for those patients was 13 mo (mean, 16.4 mo).
Clients that maintained a client-patient-doctor relationship with the primary surgeon for continued monitoring of the respiratory condition or for additional unrelated surgeries provided follow-up information ranging from 24 wk to 208 wk.
Of the 42 dogs for which long-term follow-up information was available, the outcome was considered satisfactory in 39 (93%) dogs, including 1 dog with a documented episode of aspiration pneumonia that resolved with outpatient treatment.
The outcome was considered unsatisfactory in three dogs. The latter three dogs had major complications contributing to their deaths or the owner’s decision to have them euthanized. In the first dog, the patient reportedly had repeated infections of unknown body system and unknown etiology that were treated by the local veterinarian for several months until the owners elected euthanasia. No additional details were available. The second dog was examined at an emergency hospital for acute respiratory distress (presumptive pulmonary thromboembolism) 6 mo after ventriculocordectomy. That dog was treated in the hospital for 3 days, diagnosed with multiorgan failure, and euthanized. The second dog had reportedly done very well until a sudden deterioration in condition. Additional details were not available, and a necropsy was not performed. The third dog reportedly did well for the first 2 mo postsurgically, but gradually developed repeated episodes of coughing, gagging, dysphagia, and aspiration, and the owners eventually elected euthanasia due to concerns surrounding quality of life.
Results of Client Survey
In total, 24 of 70 client surveys were returned. Fifteen (63%) clients felt the results of surgery were excellent, with minimal or no respiratory abnormalities after surgery. Seven (29%) clients felt the results were good, with some respiratory changes after surgery that did not negatively impact either quality of life or exercise tolerance. Those changes were reported as mild coughing (n=5), gagging (n=2), and continued audible laryngeal noise (n=2). Two (8%) clients felt the results were fair with some functional abnormalities and respiratory changes that persisted after surgery; however, they still felt there was improvement over the patient’s presurgical condition. Those owners reported frustration with attempts to bark (n=1) and persistent coughing, gagging, and retching when eating and drinking (n=1). Although those two clients felt the surgery results were fair, they both indicated they felt the surgery was satisfactory in resolving their pets’ respiratory distress, leaving them with minimal postsurgical symptoms. Overall, 14 owners were very satisfied and 10 were satisfied.
Discussion
The signalment, history, and presenting clinical signs were similar to previous reports. The Labrador retriever was the most commonly breed affected (35%). All dogs included in this study were diagnosed with the idiopathic form of laryngeal paralysis. However, none of the dogs underwent electrodiagnostic studies or pathologic evaluation for generalized neuromuscular disease. Therefore, laryngeal paralysis as one component of a generalized peripheral neuropathy, as opposed to an isolated clinical problem, was not established in this study. Six dogs displayed clinical weakness, subtle muscle atrophy, or depressed spinal reflexes on initial physical examination.
Overall, short-term and long-term results were similar. Satisfactory outcome was reported for 85 of 88 dogs at the 14 day follow-up evaluation. Long-term follow-up information was available for 42 of 88 dogs, and the outcome was considered satisfactory in 39 of 42 dogs.
The majority of dogs in this study had concurrent diseases. Previous studies have established that concurrent disease (particularly respiratory disease, neurologic disease, esophageal disease, and neoplasia) increases the risk of complication and death after surgery for laryngeal paralysis.7 This fact emphasizes the importance of a thorough assessment of every patient presented for a respiratory distress and diagnosed with laryngeal paralysis. Identifying and treating concurrent diseases may have a significant impact on long-term prognosis and outcome.
The one dog that required repeat laryngoscopy evaluations at 1 wk, 1 mo, and 2 yr developed progressive laryngeal collapse. That dog ultimately required additional partial laryngectomy procedures to maintain a functional upper airway.
Dogs in this study had few reported complications. Three of the 88 dogs developed documented aspiration pneumonia. Three additional dogs experienced an episode of antibiotic-responsive cough, one dog was euthanatized for dyspnea 1 yr postsurgically, and one dog suffered from repeated infections of unknown etiology. It is impossible to know how many of the included dogs may have suffered subclinical aspiration, clinical aspiration pneumonia treated medically to resolution, and episodes of aspiration pneumonia that were never reported to the primary surgeon. Of the 24 clients that provide long-term follow-up information in the form of a completed client survey, all 24 reported they were either satisfied or very satisfied with the results of surgery and the improved quality of life provided.
The current study had a number of limitations inherent in large retrospective studies. This study included records that spanned 25 yr in a private practice. A case series, over such a long time period, risks biases that may not be accounted for. However, in this series, the same surgeon performed a standardized ventriculocordectomy procedure and was available for long-term follow-up at the same location throughout the study period. This could help limit the number of uncontrolled variables. If patients had suffered surgical complications any time after surgery, the owner of the dog or the referring veterinarian would have been able to notify the primary surgeon.
Bilateral ventriculocordectomy was the only procedure performed by the primary surgeon for laryngeal paralysis both during and after the study period. The clinical results were found to be excellent compared with results for alternative surgical procedures reported in the literature. There was a lack of evidence to support a more effective or safer surgical approach. Gas anesthetic agents and suture materials used for the procedure changed over time based on improved products and availability. None of the suture materials caused a known tissue reaction or complication.
The use of information from client questionnaires is another potential shortcoming of this study. Results of the questionnaires may have been affected by altered recollections of the dog owners. A limited number of responses made substantial conclusions difficult. Questions on client surveys must be clear and concise to increase potential for solid data. Owners could have been dissatisfied with surgical outcome for reasons other than either additional surgery or death. Several locations on the survey for additional client comments were provided, which may have minimized the shortcomings associated with questionnaires.
UAL is currently the most frequently performed surgery for the treatment of idiopathic laryngeal paralysis in dogs.7,13,15 However, reported complication rates remain high, and several different complications have been associated with this technique. Seroma formation, fragmentation of the arytenoid cartilage, avulsion of the suture, inadequate or overzealous lateralization, intralaryngeal hematoma, coughing and gagging, respiratory distress, sudden death, and aspiration pneumonia have all been reported.7,13–15 The UAL technique requires experience with more extensive and intricate dissection of tissues, appropriate placement of lateralizing sutures, and appropriate degree of suture tensioning. In contrast, the ventriculocordectomy procedure allows clear visualization of the surgical field and is technically simpler to perform.
Aspiration pneumonia remains the most common and most serious postoperative complication associated with surgical management of laryngeal paralysis. High complication rates (from 10% to 33% of cases) from UAL procedures have been attributed to the variable degree of permanent enlargement of the rima glottidis, increasing the susceptibility of the airway to laryngotracheal aspiration. 7,13–15,21 In addition, the UAL procedure alters the ability of the epiglottis and extrinsic laryngeal muscles to protect the airway during swallowing. Although the risk of aspiration pneumonia is increased for the remainder of the dog’s life, the biggest risk is during the immediate (≤14 days) postoperative period.22 In the current study, all 88 dogs were available for evaluation during that time period, and only 2 dogs developed aspiration pneumonia.
The low incidence of documented aspiration pneumonia in this study may be due to several factors. For example, there was a lack of periodic postoperative thoracic imaging and airway sampling, as well as the potential for undetected subclinical episodes of aspiration. The low incidence may also have been due to improved protection of the upper airway by laryngeal musculature and arytenoid cartilages that were left undisturbed during the surgical procedure.
Postoperative thoracic radiographs and tracheobronchial washes were not performed routinely in this study. Therefore, there is no way to know what total number of dogs may have had episodes of aspiration pneumonia during the long-term follow-up period. In the dogs that developed recurrence of respiratory symptoms, it would have been ideal to establish whether recurrence was either related to progressive neurologic disease or was a result of complications related to the surgical procedure.
Follow-up laryngoscopy was only performed in patients either with clinical symptoms suggestive of airway compromise or in patients undergoing anesthesia for other procedures. Laryngoscopy is not recommended to evaluate for potential postoperative laryngeal stenosis or collapse unless clinically warranted.
Bilateral ventriculocordectomy creates no disruption to either the thyropharyngeus or cricoarytenoideus dorsalis muscles in the described surgical approach. Thus, if a particular patient is considered at increased risk for developing postoperative aspiration pneumonia (e.g., due to gastrointestinal disease, progressive neuromuscular disease) then this procedure may actually leave the airway better protected than it would be after UAL. A controlled, prospective comparison study of pre- and postoperative respiratory function that also assesses swallowing function could provide objective data to assess this theory.
One study looking at experimentally induced laryngeal paralysis compared the effectiveness of both the UAL and the bilateral ventriculocordectomy by the ventral laryngotomy approach for improving respiratory function.23 That study compared clinical improvement and improvement in tidal breathing flow volume loop and upper airway resistance measurements. No statistical differences in upper airway mechanics were identified between the surgical procedures. Both procedures provided comparable improvement in upper airway obstruction.
Ideally, surgical treatment of laryngeal paralysis would result in minimal trauma to the patient, would be both simple and cost-effective to perform, and would produce excellent outcomes with few to no complications. The procedure would meet the goal of improving airflow through the upper respiratory system while maintaining a functional level of airway protection normally provided by the larynx.
Conclusion
The authors conclude that bilateral ventriculocordectomy via a ventral laryngotomy approach requires less extensive and intricate dissection than UAL. The ventral laryngotomy approach with sharp dissection and suturing of mucosa allows for less tissue trauma, swelling, scarring, and fibrosis that could otherwise contribute to postoperative complications.10 Due to the ease of this procedure, the minimal surgical trauma to the patient, and the satisfactory end results, bilateral ventriculocordectomy through a ventral laryngotomy approach should be considered for the treatment of all degrees of idiopathic laryngeal paralysis in the dog.
Photograph showing a paralyzed larynx with flaccid vocal folds (A) the corniculate processes of the arytenoid cartilages, (B) the cuneiform processes of the arytenoid cartilages, (C) the thin arrow points to the laryngeal ventricle, and (D) the thick arrow identifies the vocal folds.
Photograph of the canine larynx with bilateral paralysis and paradoxical movement of the vocal folds on inspiration prior to surgery. Ventrally, the vocal folds are visualized paradoxically drawn to midline during inspiration (arrow). The paralyzed arytenoid cartilages are seen dorsally with the resultant symmetrically narrowed glottic lumen.
Intraoperative photograph showing the Weitlaner retractor (yellow arrow) and stay sutures (black arrows).
Intraoperative photograph showing primary closure of the laryngeal mucosa with a ventrodorsal-dorsoventral suture pattern (arrows). Note the placement of the stay suture (yellow arrow).
Photograph of the canine larynx immediate postoperatively. Note the ventriculocordectomy site (arrows), corniculate processes of the arytenoid cartilages (A), and the cuneiform processes of the arytenoid cartilages (B).
Photograph of the canine larynx 3 wk postoperatively.
Photograph of the canine larynx 1 yr postoperatively. Note the site of the ventriculocordectomy (arrows), the corniculate processes of the arytenoid cartilages (A), and the cuneiform processes of the arytenoid cartilages (B).
Contributor Notes
