Laryngeal webs, both congenital and acquired, can result in airway obstruction and present a therapeutic challenge. In humans, congenital laryngeal webs are rare and occur in approximately 1 in 10,000 births.1 To the authors' knowledge, there is 1 case report2 of a congenital laryngeal web reported in the veterinary literature in a Quarter Horse filly. In human and veterinary patients, acquired laryngeal webs and laryngeal stenosis occur secondary to mucosal injury, either as a result of neck trauma or iatrogenically. Iatrogenic trauma is the most common cause of acquired laryngeal webs in humans, which can occur from surgical damage or as a consequence of long-term airway intubation.3
In veterinary patients, ventriculocordectomy is associated with a substantial risk for development of laryngeal web formation. Ventriculocordectomy performed by use of an oral approach is more likely to result in web formation because the mucosal defect is allowed to heal by secondary intention, compared with a ventral laryngotomy with primary closure of the mucosal defect.4
A number of surgical treatments for laryngeal webs have been described in dogs. Simple resection of the laryngeal web often results in transverse regrowth of scar tissue and recurrence of clinical signs. Web resection with mucosal flap coverage and placement of an intraluminal stent for 2 weeks after surgery has been reported in 4 dogs.5 Follow-up information in that study5 revealed no recurrence of clinical signs associated with upper airway obstruction after intraluminal stent removal, although 1 dog was reported to have inspiratory stridor at exercise. In another report, Schmidt et al6 used a CO2 laser for management of acquired laryngeal webs in 19 research dogs and reported that total excision of the scar resulted in recurrence and, possibly, worsening of the laryngeal scar, whereas preservation of the mucosa with flaps improved airway size. Lastly, Holt and Harvey7 reported on 9 dogs that developed glottic stenosis after vocal fold resection or partial laryngectomy treated via perioral scar resection and highdose corticosteroids; most of those dogs were breathing normally at follow-up examination.
The purpose of the study reported here was to determine short- and long-term outcome in dogs treated for laryngeal web formation by use of web resection with mucosal apposition. We hypothesized that web resection with mucosal apposition is an effective treatment for laryngeal web formation in dogs.
Materials and Methods
Criteria for selection of cases—Medical records of all dogs that had laryngeal examination performed for diagnosis of laryngeal web and all dogs that received surgery for laryngeal web formation at the Veterinary Medical Teaching Hospital of the University of California, Davis, between 1992 and 2006 were reviewed. Cases were included if the laryngeal web was treated by use of a single surgical procedure of web resection and mucosal apposition without stent placement and performed via ventral laryngotomy. Exclusion criteria included dogs with laryngeal webs treated by use of surgery with an oral approach, electrocautery, or laser lysis; or if a laryngeal stent was placed at the time of surgery; or if mucosal flaps were not used to close the defect after web resection.
Presurgical evaluation—Preoperative data collected included age at time of surgery, sex, breed, weight, and pertinent medical history. All dogs were treated by use of a similar diagnostic and therapeutic protocol. The laryngeal web was diagnosed via laryngoscopy performed under a light plane of anesthesia, and a laryngeal web was defined as a band of scar tissue spanning the ventral larynx (Figure 1).
Laryngoscopic view of a laryngeal web in a dog. Notice the laryngeal web (defined as a band of scar tissue) expanding the ventral aspect of the larynx (arrow).
Citation: Journal of the American Veterinary Medical Association 233, 5; 10.2460/javma.233.5.738
Surgical procedures—In each dog, a ventral laryngotomy was performed through a midline incision through the cricothyroid ligament and thyroid cartilage. The thyroid laminae were gently retracted with skin hook retractors to expose the laryngeal web without tearing the web. A sharp No. 11 blade was used to transect the web on midline. The scar tissue was then cored out or removed with iris scissors or rongeurs, leaving a rim of mucosa intact. The mucosa rostral and caudal to the web was undermined with iris scissors and cotton-tipped applicators to elevate the mucosa without tearing it to create mucosal flaps that could be apposed without tension (Figure 2). On each side, the mucosal flaps were apposed in a continuous or simple interrupted suture pattern with 4-0 to 6-0 polyglactin 910 depending on the size of the patient, beginning at the dorsal aspect of the mucosal defect and suturing ventrally. This procedure was then repeated on the contralateral side. Additional surgical procedures were then performed if indicated (eg, arytenoid lateralization). All dogs received dexamethasone sodium phosphate (0.25 mg/kg [0.11 mg/lb], IV) during the procedure, and acepromazine maleate (0.01 to 0.05 mg/kg [0.005 to 0.023 mg/lb], SC) was given for sedation after surgery if indicated.
Illustration of the surgical approach used for treatment of a laryngeal web in a dog. A—A ventral laryngotomy is performed, and the thyroid laminae are retracted laterally. B—The laryngeal web is transected on midline. C—The fibrous tissue within the web is cored out, and the mucosal edges are sutured.
Citation: Journal of the American Veterinary Medical Association 233, 5; 10.2460/javma.233.5.738
Postoperative care and evaluation— Postoperative medical treatments, postoperative complications, and postoperative hospitalization time were recorded. Follow-up information was collected via telephone interview with the owner or referring veterinarian 6 months to 6 years after surgery. Owners were interviewed regarding their dog's progress since surgery and were asked specifically if they considered their dog to be clinically normal; whether they had noticed any complications after surgery and, if so, whether the dog required veterinary care; whether they had noticed a change in exercise tolerance; whether the dog received any special treatments; whether any additional surgical procedures had been performed since the laryngeal web surgery; whether the dog was receiving any other medical treatment; whether the dog had died or was euthanized; whether they knew the cause of death; and what clinical signs the dog had prior to death. On the basis of the information obtained from owners, clinical outcome was categorized as excellent, good, or poor. Excellent outcome included dogs that owners considered to be clinically normal, that were not receiving any form of medical or special treatment, and for which the owners reported no clinical signs of exercise intolerance. Good outcome included dogs that owners considered to be clinically normal but required special care or medications, such as reduced activity in hot weather, or dogs that had treatable clinical signs of exercise intolerance (by use of sedatives or anti-inflammatory medication or by reducing the amount or degree of activity). For example, those owners reported their dogs to have a good quality of life but were unable to run with their dog in warm weather. Poor outcome included dogs with continued clinical signs or dogs that died from upper airway obstruction.
Results
Selection of cases—Twenty-two dogs had a diagnosis of laryngeal web between 1992 and 2006. Records of 15 dogs with laryngeal web formation treated by mucosal flaps were included in the study. Seven dogs were excluded from the study; 4 dogs were treated by creation of mucosal flaps and intraluminal silicone keel stent placement, 2 dogs did not undergo a surgical procedure for treatment of the web, and 1 dog had mucosa that could not be apposed following failure of previous scar resection and keel stent placement.
Presurgical evaluation—Mean ± SD age at the time of diagnosis was 5.7 ± 3.4 years and ranged from 9 months to 13 years. Four of the 7 male dogs were castrated, and 5 of the 8 female dogs were spayed. Mean ± SD body weight at the time of surgery was 23.5 ± 17.7 kg (51.7 ± 38.9 lb), with a range of 3.8 to 53 kg (8.4 to 116.6 lb). Breeds included Pug (n = 2 dogs); Labrador Retriever (2); and Australian Cattle Dog, Belgian Shepherd Dog, Cairn Terrier, Cocker Spaniel, Malamute, Newfoundland, Miniature Schnauzer, American Eskimo, Poodle mixed breed, Toy Poodle, and Samoyed (1 each).
Thirteen dogs had a history of laryngeal surgery, and in 2 dogs, the history was not available. Ten dogs had a history of an oral ventriculocordectomy, most often performed when the dog was < 1 year of age. Two dogs had laryngeal paralysis and had undergone previous procedures of arytenoid lateralization; in both dogs, the tissue associated with the arytenoid lateralization subsequently broke down, and in 1 dog, this was followed by a unilateral arytenoidectomy. The last dog with historical information available had everted saccules and an elongated soft palate, and during surgery, inadvertent damage to the vocal cords occurred during the bilateral sacculectomy procedure.
Mean ± SD duration of clinical signs that occurred after laryngeal surgery (oral ventriculocordectomy, arytenoidectomy, or sacculectomy) was 2.8 ± 1.1 months, with a range of 1 to 4 months. All owners reported a worsening of clinical signs. Six of 15 dogs had previous surgical treatment of their laryngeal webs, including surgical excision, balloon dilation, resection with electrocautery, cryosurgery, or a combination of these surgical procedures performed multiple times.
Clinical signs included exercise intolerance (n = 11 dogs), dypsnea (8), stridor (6), collapse (2), heat intolerance (3), and tachypnea (1). A light plane of anesthesia was induced to evaluate airway function and diagnose laryngeal webbing, and in 4 dogs, laryngeal paralysis was identified at the time of laryngeal web diagnosis.
Anesthesia—Anesthetic premedication consisted of an opioid drug (oxymorphone, methadone, morphine, or butorphanol) and an anticholinergic drug (atropine or glycopyrrolate). Anesthesia was induced after administration of thiamylal, thiopental, or propofol. A benzodiazepine drug (midazolam or diazepam) was administered at the time of induction in most dogs to decrease the dose of the induction agent. Anesthesia was maintained with isoflurane in oxygen via a circle or a Bain system, according to the patient's weight. Intermittent positive-pressure ventilation was used as needed. After surgery, analgesics were given as needed.
Surgical procedures—A ventral laryngeal web was identified at surgery in all 15 dogs, and in 1 dog, the laryngeal web extended to include a dorsal laryngeal web. Five dogs had tube tracheostomies. A temporary tracheotomy tube was placed immediately before surgery (n = 1 dog), 1 day prior to surgery (2), or during the immediate postoperative period (2). In the 3 dogs that had tracheotomy tubes placed prior to surgery, the overseeing clinician deemed the procedure necessary for emergency stabilization. In the 2 dogs that had temporary tracheotomies performed after surgery, 1 dog was a Pug and the clinician anticipated upper airway swelling, and the second dog's (Miniature Schnauzer) record did not indicate why the dog received a temporary tracheotomy. Intraoperative complications were not detected in any dogs.
Four dogs had laryngeal paralysis at the time of laryngeal web resection with mucosal apposition. Two of the 4 dogs had unilateral arytenoid lateralization at the time of web resection. The third dog had laryngoscopy performed 5 days after surgery, which revealed persistent laryngeal paralysis. Bilateral arytenoid lateralization was then attempted, but because of fibrosis and fracture of the arytenoids, a permanent tracheotomy was performed. The last dog with laryngeal paralysis and a laryngeal web only had web resection with mucosal apposition performed. One month after web resection in that dog, a unilateral arytenoid lateralization and soft palate resection were performed.
Postoperative care—Postoperative complications were observed in 4 of 15 dogs and included dypsnea in 3 dogs and bradycardia in 1 dog. One dog had continued inspiratory dypsnea and stridor after surgery. This was the dog in which laryngoscopy was performed 5 days after surgery and laryngeal paralysis was detected; after a failed attempt of arytenoid lateralization, a permanent tracheostomy was done. Another dog that was dypsneic after surgery was treated by placement of a larger temporary tracheotomy tube and IV administration of a corticosteroid (dexamethasone, 0.25 mg/kg, IV), and the third dog with dyspnea responded to administration of corticosteroids and sedation (dexamethasone, 0.25 mg/kg, IV, and acepromazine maleate, 0.2 mg/kg [0.4 mg/lb], IV) but required a unilateral arytenoid lateralization 1 month after surgery. The dog with bradycardia responded to administration of atropine (0.02 mg/kg [0.04 mg/lb], IV). Mean duration of hospitalization after surgery was 2.5 ± 1.9 days.
Follow-up examination—Laryngoscopy under a light plane of general anesthesia was performed in 4 dogs after discharge. In 2 dogs that the owners reported to be clinically normal at rest and during activity, laryngoscopy was performed 4 and 16 months after surgery and revealed no regrowth of the laryngeal web. The third dog was examined 4 years after web resection surgery for increased panting and respiratory noise; endoscopic examination revealed no regrowth of scar tissue in the larynx, but bronchi were erythematous, and a diagnosis of mild suppurative and eosinophilic bronchitis was made. The fourth dog developed a cough 6.5 years after web resection surgery, and thoracoscopy with lung biopsy was performed. Regrowth of the laryngeal web was not reported in the medical record, and the lungs had interstitial fibrosis, intra-alveolar histiocytosis, and mild interstitial neutrophilia and eosinophilia.
Telephone follow-up—The owners of 10 of 15 dogs were contacted by telephone, and 5 dogs were lost to follow-up. Mean ± SD follow-up period was 2.7 ± 4.6 years. All owners reported their dogs to have a good to excellent outcome from surgery. Seven owners reported that their dogs had an excellent outcome and were completely free of clinical signs; 1 dog in this group had a permanent tracheotomy performed 1 month after web resection because of complications associated with arytenoid lateralization. Three dogs had good outcomes, although they had some clinical signs of exercise intolerance at higher activity levels. One of these dogs had eosinophilic bronchitis 4 years after web resection, and prednisone treatment was initiated, and 1 Pug had a unilateral arytenoid lateralization procedure performed 1 month after web resection but still had stridor with vigorous activity. Both of those dogs had laryngoscopy performed 1 month and 4 years after surgery, and neither dog had regrowth of the laryngeal web. The third dog in the good outcome group became less active after surgery, and a diagnosis of hypothyroidism was made by the referring veterinarian; after thyroid supplementation treatment was started, the owners reported that the dog had only minor improvement in activity.
Discussion
Laryngeal web formation is a potential complication of airway surgery in humans and dogs and is more likely to occur with surgical procedures in which the mucosal defect is allowed to heal by secondary intention.8 Resection of the web with mucosal apposition via a ventral laryngotomy is an effective technique for treatment of laryngeal web formation in dogs.
Most dogs in this study had a history of bilateral oral ventriculocordectomy that created 2 opposing ventrolateral mucosal defects that healed together, bridging the larynx. Perhaps staging the procedure by doing a unilateral oral ventriculocordectomy, instead of a bilateral procedure, would prevent disruption of the ventral commisure of the vocal folds and reduce the potential complication of laryngeal web. Alternatively, a ventral laryngotomy and bilateral ventriculocordectomy with apposition of the laryngeal mucosa may avoid laryngeal web formation as well.
Most dogs had multiple procedures performed in attempts to remove the laryngeal web prior to referral, which included excision, cauterization, cryosurgery, laser, and balloon dilation. Many of these techniques create a defect in the mucosa, whereby incised mucosal edges, submucosa, and muscle are exposed, allowing granulation tissue to fill the defect and leading to scar tissue spanning the ventral larynx. Although these techniques resulted in temporary relief of the upper airway obstruction, recurrence of more exuberant scar tissue can potentially increase the difficulty of web resection with mucosal apposition. Web resection with mucosal apposition can be challenging because the laryngeal mucosa is friable, and in small dogs, access to the ventrolateral aspect of the larynx can be difficult. Excessive scar tissue resulting from previous surgeries can further increase the difficulty of this procedure.
Surgical treatment of a laryngeal web involves a precise midline incision of the web to permit elevation of the mucosal flaps. Inadvertent tearing of the web during intubation can prevent creation of these mucosal flaps. Therefore, gentle intubation techniques are needed to avoid damaging the laryngeal web or tearing the mucosa. In suspected laryngeal web cases, a difficult intubation should be anticipated and a selection of endotracheal tubes of various sizes as well as stylets should be available.
Six dogs in this study had a diagnosis of laryngeal paralysis, historically or at the time of the laryngeal web diagnosis. Two Labrador Retrievers were historically diagnosed with laryngeal paralysis and had been treated via arytenoid lateralization or arytenoidectomy, which led to laryngeal web formation. Two other large-breed dogs had arytenoid lateralization performed at the time of web resection, and 2 small-breed dogs had laryngeal paralysis at the time of web resection. This association between laryngeal web formation and laryngeal paralysis may be attributable to the laryngeal web preventing abduction of the arytenoids, although one would expect that resection of the laryngeal web would result in normal abduction of the arytenoids. In 2 dogs, after resection of the laryngeal web, laryngeal paralysis persisted as a clinical problem and arytenoid lateralization led to a good to excellent outcome.
Long-term clinical outcome was classified as excellent in 7 dogs and good in 3 dogs. The good outcome classification included 3 dogs that had concurrent medical problems: 1 dog had hypothyroidism, 1 dog had brachycephalic syndrome and laryngeal paralysis, and 1 dog had eosinophilic bronchitis. This categorization system, therefore, may overestimate the number of dogs classified as having good outcomes. Additionally, 1 dog in the excellent outcome category had a permanent tracheostomy performed. Furthermore, the owners of 5 dogs could not be contacted for follow-up information to determine clinical outcome.
The major limitation of this study was its retrospective nature. Although diagnostic and therapeutic protocols were similar, complete data were not available for every dog. Another limitation of the study was that outcome was based on owner assessment, rather than on follow-up laryngeal examinations.
Airway procedures that leave exposed mucosal edges are at risk of leading to laryngeal web formation. A single surgical procedure of web resection with mucosal apposition for treatment of laryngeal web formation in dogs was associated with good to excellent outcome.
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