Partial laryngectomy for the management of laryngeal masses in six cats

OBJECTIVES

Partial laryngectomy is an organ-sparing surgical procedure for the removal of laryngeal masses which has not been described in cats. The aim of this study was to report on the surgical procedure and the short- and long-term clinical outcomes of cats that underwent partial laryngectomy.

METHODS

Medical records were retrospectively collected over a 4-year period in two institutions. The following data were retrieved: signalment, history, clinical signs, diagnostic test results, surgical procedure, postoperative management, complications and outcome.

RESULTS

Six cats underwent partial laryngectomy. The most common clinical signs in cats with laryngeal masses were stridor (n = 4) and dyspnoea (n = 4). In all cats, a full-thickness portion of one or several laryngeal cartilages was resected, including thyroid cartilage alone (n = 2), thyroid cartilage and arytenoid (n = 2), and arytenoid cartilage and epiglottis (n = 2). The resected laryngeal masses were reported to be lymphoma (n = 3), carcinoma (n = 1), laryngeal cyst (n = 1) and inflammatory laryngeal disease (n = 1). All cats survived the surgical intervention of partial laryngectomy. Four cats showed varying degrees of respiratory distress in the short-term postoperative period. A temporary tracheostomy tube was placed in two cats. No other postoperative complications were noted in the short- or long-term. Four cats were still alive at the time of writing. These cats survived at least 252 days.

CONCLUSIONS AND RELEVANCE

In a small number of cases, our results show that successful long-term outcomes after partial laryngectomy are achievable, with longer survival times than previously reported. Therefore, partial laryngectomy should be considered as a viable treatment option in cats with laryngeal masses.

Ex vivo evaluation of arytenoid corniculectomy, compared with three other airway interventions, performed on cadaveric equine larynges with simulated recurrent laryngeal neuropathy

OBJECTIVE

To compare laryngeal impedance, in terms of air flow and pressure, following arytenoid corniculectomy (COR) versus 3 other airway interventions (left-sided laryngoplasty with ipsilateral ventriculocordectomy [LLP], LLP combined with COR [LLPCOR], and partial arytenoidectomy [PA]) performed on cadaveric equine larynges with simulated left recurrent laryngeal neuropathy (RLN) and to determine whether relative laryngeal collapse correlated with the interventions performed.

SAMPLE

28 cadaveric equine larynges.

PROCEDURES

Each larynx in states of simulated left RLN alone and with airway interventions in the order LLP, LLPCOR, COR, and PA was evaluated in a box model construct that replicated upper airway flow mechanics consistent with peak exercise in horses. Results for impedance, calculated from airflow and pressure changes, were compared between states for each larynx. Multivariable mixed-effects analysis controlling for repeated measures within larynx was performed to calculate the predicted mean impedance for each state.

RESULTS

Results indicated that tracheal adapter diameter, individual larynx properties, airway intervention, and relative laryngeal collapse affected laryngeal impedance. The LLP and LLPCOR interventions had the lowest impedance, whereas the COR and PA interventions did not differ substantially from the simulated left RLN state. Residual intraclass correlation of the model was 27.6 %.

CONCLUSIONS AND CLINICAL RELEVANCE

Although impedance was higher for the simulated left RLN with the COR intervention state than with the LLP intervention state, given the clinical success of PA for treating RLN in horses and the similar results for the COR and PA intervention states in the present study, the use of COR warrants further investigation. The residual interclass correlation suggested that individual laryngeal variation affected impedance and may have a clinical effect.

Total laryngectomy for management of chronic aspiration pneumonia in a myopathic dog

A 5-month-old female pit bull terrier dog evaluated for ataxia, progressive regurgitation, and recurrent aspiration pneumonia had markedly elevated creatine kinase activity, non-inflammatory generalized myopathy, and severe esophageal dysmotility. A narrow-field total laryngectomy was performed. The dog is doing well 30 months after surgery, and no longer has episodes of aspiration pneumonia, despite intermittent regurgitation. This case represents the first application of total laryngectomy for the prevention of chronic recurrent aspiration pneumonia in the dog.

Effect of laryngoplasty on respiratory noise reduction in horses with laryngeal hemiplegia

REASONS FOR PERFORMING STUDY

Laryngoplasty is the technique of choice for treatment of laryngeal hemiplegia, with the aim of improving airway function and/or eliminating respiratory noise. However, there are no quantitative data in the literature describing the effect of laryngoplasty on upper airway noise or its relationship to upper airway mechanics in horses with laryngeal hemiplegia.

OBJECTIVES

To determine whether laryngoplasty reduces respiratory noise in exercising horses with laryngeal hemiplegia; and to establish whether the degree of upper airway obstruction can be predicted by upper airway noise, or the degree of arytenoid abduction correlated with airway obstruction and noise production.

METHODS

Six Standardbred horses with normal upper airways during maximal exercise were used. Respiratory sounds and inspiratory transupper airway pressure (Pui) were measured in all horses before and after induction of laryngeal hemiplegia and 30, 60 and 90 days after laryngoplasty. Inspiratory sound level (SL) and the sound intensity of the 3 inspiratory formants (F1, F2 and F3, respectively) were measured using a computer-based sound analysis programme. The degree of abduction was graded by endoscopic visualisation 1, 30, 60 and 90 days post operatively. Linear regression analysis was used to determine correlations between Pui, sound indices and grades of arytenoid abduction.

RESULTS

In laryngeal hemiplegia-affected horses, Pui, inspiratory SL and the sound intensity of F1, F2 and F3 were significantly increased. At 30 days following laryngoplasty, the sound intensity of F1 and Pui returned to baseline values. The sound intensities of F2, F3 and SL were significantly improved from laryngeal hemiplegia values at 30 days post operatively, but did not return to baseline at any measurement period. Sound level, F2 and F3 were significantly correlated with Pui (P<0.05), but the correlations were weak (r2 = 0.26, 035 and 0.40, respectively). Grade of abduction and F2 were positively and significantly correlated (P<0.006, r2 = 0.76). Grade of arytenoid abduction and Pui were not correlated (P = 0.12).

CONCLUSIONS

Laryngoplasty reduced inspiratory noise in laryngeal hemiplegia-affected horses by 30 days following surgery, but did not return it to baseline values. While upper airway noise and Pui were correlated, this relationship was insufficiently strong to predict Pui from noise in individual animals. The degree of arytenoid abduction was not correlated with Pui, but was positively correlated with noise production.

POTENTIAL RELEVANCE

Laryngoplasty reduces upper airway noise in horses with laryngeal hemiplegia, but is not as effective as bilateral ventriculocordectomy in this regard, although respiratory noise reduction occurs more rapidly than with bilateral ventriculocordectomy. Residual noise during exercise cannot be used as a predictor of improvement in upper airway function in individual horses following laryngoplasty. The degree of arytenoid abduction obtained following surgery does not affect upper airway flow mechanics. Interestingly, we found that the greater the arytenoid abduction, the louder the respiratory noise.

Effects of unilateral laser-assisted ventriculocordectomy in horses with laryngeal hemiplegia

REASONS FOR PERFORMING STUDY

Recent studies have evaluated surgical techniques aimed at reducing noise and improving airway function in horses with recurrent laryngeal neuropathy (RLN). These techniques require general anaesthesia and are invasive. A minimally invasive transnasal surgical technique for treatment of RLN that may be employed in the standing, sedated horse would be advantageous.

OBJECTIVE

To determine whether unilateral laser-assisted ventriculocordectomy (LVC) improves upper airway function and reduces noise during inhalation in exercising horses with laryngeal hemiplegia (LH).

METHODS

Six Standardbred horses were used; respiratory sound and inspiratory transupper airway pressure (Pui) measured before and after induction of LH, and 60, 90 and 120 days after LVC. Inspiratory sound level (SL) and the sound intensities of formants 1, 2 and 3 (Fl, F2 and F3, respectively), were measured using computer-based sound analysis programmes. In addition, upper airway endoscopy was performed at each time interval, at rest and during treadmill exercise.

RESULTS

In LH-affected horses, Pui, SL and the sound intensity of F2 and F3 were increased significantly from baseline values. At 60 days after LVC, Pui and SL had returned to baseline, and F2 and F3 values had improved partially compared to LH values. At 90 and 120 days, however, SL increased again to LH levels.

CONCLUSIONS

LVC decreases LH-associated airway obstruction by 60 days after surgery, and reduces inspiratory noise but not as effectively as bilateral ventriculocordectomy.

POTENTIAL RELEVANCE

LVC may be recommended as a treatment of LH, where reduction of upper airway obstruction and respiratory noise is desired and the owner wishes to avoid risks associated with a laryngotomy incision or general anaesthesia.

Ventriculocordectomy reduces respiratory noise in horses with laryngeal hemiplegia

REASONS FOR PERFORMING STUDY

Show and performance horse with laryngeal hemiplegia (LH) often present for excessive respiratory noise rather than significant exercise intolerance. Therefore, the goal of surgery in these horses is to reduce respiratory noise but there are no quantitative studies evaluating the effect of any upper-airway surgery in LH-affected horses.

OBJECTIVE

To determine whether bilateral ventriculocordectomy (VC) reduces respiratory noise in exercising horses with laryngeal hemiplegia.

METHODS

Six Standardbred horses with normal upper airways were used in this study. Respiratory sounds and inspiratory trans-upper airway pressure (Pui) were measured in all horses before and after induction of LH, and 30, 90 and 120 days after VC. In horses with LH, spectrogram analysis revealed 3 inspiratory sound formants centred at approximately 400, 1700 and 3700 Hz. Inspiratory sound levels (SL) and the sound intensity of the 3 inspiratory formants (F1, F2, F3 respectively) were measured using a computer-based sound analysis programme.

RESULTS

In LH-affected horses, Pui, inspiratory SL and the sound intensity of F2 and F3 were significantly increased compared to baseline values. At 90 and 120 days after VC the sound intensities of F2 and F3 returned to baseline values. The Pui and SL, were significantly decreased compared to LH values, but remained different from baseline.

CONCLUSIONS

VC effectively reduces inspiratory noise in LH-affected horses by 90 days following surgery. Inspiratory trans-upper airway pressures are improved 30 days following VC, but do not return to baseline values.

POTENTIAL RELEVANCE

VC can be recommended as a surgical treatment of LH-affected horses if reduction of respiratory noise is the primary objective of surgery. Further studies are required to determine if variations of the surgical technique used in this study will have similar results.

Racing performance after combined prosthetic laryngoplasty and ipsilateral ventriculocordectomy or partial arytenoidectomy: 135 Thoroughbred racehorses competing at less than 2400 m (1997-2007)

REASONS FOR PERFORMING STUDY

The success of combined prosthetic laryngoplasty with ipsilateral ventriculocordectomy (LPVC) has not been compared to that of partial arytenoidectomy (PA) in a clinical population.

HYPOTHESES

In Thoroughbred (TB) racehorses: (1) earnings after LPVC are unaffected by the severity of recurrent laryngeal neuropathy (RLN) (laryngeal grade III vs. grade IV); (2) LPVC and PA yield similar results in the treatment of grade III RLN; (3) performance outcome following PA is independent of diagnosis (RLN vs. unilateral arytenoid chondritis [UAC]); and (4) neither LPVC nor PA returns horses to the level of performance of controls.

METHODS

Medical and racing records of 135 TB racehorses undergoing LPVC or PA for the treatment of grade III or IV RLN or UAC were reviewed. Racing records of age and sex matched controls were also reviewed.

RESULTS

After LPVC, horses with grade III RLN performed better compared to those with grade IV RLN. Furthermore, horses treated for grade III RLN by LPVC showed post operative earnings comparable to controls. Rate of return to racing were similar for PA and LPVC, although LPVC resulted in higher post operative earnings. Performance after PA was similar regardless of diagnosis (UAC or RLN). Finally, neither LPVC when performed for grade IV RLN, nor PA performed for either diagnosis restored post operative earnings to control levels.

CONCLUSIONS

Thoroughbred racehorses treated by LPVC for grade III RLN show significantly better post operative earnings compared to horses treated for grade IV disease. In grade III RLN, LPVC returns earning potential to control levels. PA and LPVC lead to similar success in terms of rate of return to racing, but PA leads to inferior earnings after surgery.

POTENTIAL RELEVANCE

Laryngoplasty should be recommended for all TB racehorses with grade III RLN to maximise return to racing at a high level. This contradicts the common approach of waiting for complete paralysis.

Histological evaluation of the equine larynx after unilateral laser-assisted ventriculocordectomy

REASONS FOR PERFORMING STUDY

Trans-endoscopic laser surgery, such as unilateral laser-assisted ventriculocordectomy (LVC), has gained popularity in the treatment of RLN because a laryngotomy incision or general anaesthesia are not required. However, removal of the vocal fold and ventricle takes considerable laser energy and could cause collateral tissue damage, including injury to the adjacent laryngeal cartilages.

OBJECTIVES

To document the histological effects of laser surgery on laryngeal tissues in horses that have undergone LVC for the treatment of laryngeal hemiplegia (LH).

METHODS

Six horses were used: 4 with experimentally induced LH that had subsequently undergone LVC 6 months prior to euthanasia; and, 2 horses were used as controls. One of the control horses with naturally occurring LH was used to study the effect of neuropathy alone, whereas the other was subjected to euthanasia immediately following LVC to evaluate the acute effect of laser surgery. Using a band saw, each larynx was sectioned transversely at 5 mm intervals and evaluated histologically.

RESULTS

Acutely, LVC caused thermal damage to adjacent soft tissues but did not affect the histology of the laryngeal cartilages. Six months after LVC, laryngeal cartilages were histologically normal and there was squamous metaplasia of the repaired laryngeal mucosa, resulting in restitution of the mucosal integrity.

CONCLUSIONS

Using a diode laser in contact fashion at 20 W, LVC can be used to remove the laryngeal vocal fold and ventricle without causing laryngeal cartilage damage.

POTENTIAL RELEVANCE

Laryngeal chondritis is an unlikely consequence of LVC.

The Saanen goat as an animal model for post-laryngectomy research: practical implications

A modern way of voice rehabilitation after total laryngectomy includes the use of shunt valves and tracheostoma valves. Problems of fixation to the surrounding tissue are a major drawback in the use of the shunt valve, heat and moisture exchange (HME) filters and, especially, the tracheostoma valve. To solve these problems different tissue connectors were developed. The main objective was to test the feasibility of these prototypes in a new animal model. Here we discuss the results, problems and complications of the selected Saanen goat model. In this prospective laboratory study, 19 healthy adult female Saanen goats (Capra hircus) were used and observed post-surgically for 12 weeks. Selection criteria such as comparable anatomy to humans and easy handling were used for animal model development. Also a literature search using the Medline and the ISI Web of Science databases was performed. The anatomy of the Saanen goat was investigated in a separate postmortem study. Surgery consisted of a laryngotracheal separation and implantation of a tracheo-oesophageal and tracheostoma tissue connector with fibrin tissue glue. Postoperative care consisted of frequent stoma care, monitoring appetite, weight, vital signs and administration of antibiotics, analgesics and mucolytic agents. All animals survived the surgical procedure. However, postoperative care was extensive, labour intensive and was accompanied by several complications. Eleven animals died spontaneously before the end of the experiment. The tracheostoma tissue connector caused signs of local infection in all cases. There was no evidence of infection around the tracheo-oesophageal tissue connector in 18 cases. It was concluded that the use of goats in this tracheostoma model was associated with major complications and should, therefore, only be used for short-term experiments with intensive care. Additional research is needed to see if clinical application of the tissue connectors is possible in the future.

Ventriculocordectomy as the Sole Treatment for Recurrent Laryngeal Neuropathy: Long-Term Results from Ninety-Two Horses

OBJECTIVE

To evaluate the effect ventriculocordectomy (VC) for treatment of recurrent laryngeal neuropathy (RLN) on exercise performance and owner satisfaction in a mixed-breed population of horses.

STUDY DESIGN

Retrospective study.

ANIMALS

Adult horses (n=92) with a history of abnormal respiratory noise and RLN.

METHODS

Retrospective analysis of horse that had unilateral VC (and contralateral ventriculectomy in 63 horses) for treatment of idiopathic RLN. Owners/trainers completed a questionnaire about complications and outcome at least 1 year after surgery. Performance index was determined using race records for previously raced Thoroughbreds to evaluate outcome.

RESULTS

Clinical signs included abnormal exercise-induced respiratory noises (noises; 52%), poor performance (11%), and noises and poor performance (37%). The median preoperative resting endoscopic grade of laryngeal function was Havemeyer grade III.1 (mild asymmetry). No discharge from the laryngotomy 1 week postoperatively occurred in 62% horses, 22% coughed after surgery, 66% made no noises, 9% continued to make noises at the canter, 21% made noise at the gallop, and 4% of owners were unsure whether noises were present. Ninety-three percent of horses returned to full work after surgery. Overall, 86% of owners considered the surgery worthwhile, 3% did not consider it worthwhile, and 11% were unsure. Surgery had a significantly beneficial effect on the racing performance index in Thoroughbreds (P=.004).

CONCLUSIONS

VC is a useful alternative to laryngoplasty for selected cases of RLN and is associated with a positive effect on exercise performance, a low postoperative complication rate, and a high rate of owner satisfaction.

CLINICAL RELEVANCE

Unilateral VC should be considered as a sole treatment in horses with low grades of RLN.

A Comparison of Laryngoplasty and Modified Partial Arytenoidectomy as Treatments for Laryngeal Hemiplegia in Exercising Horses

OBJECTIVE

To compare upper airway mechanics, arterial blood gases, and tracheal contamination in horses with induced left laryngeal hemiplegia (recurrent laryngeal neuropathy [RLN]) treated by laryngoplasty/vocal cordectomy (LPVC) or modified partial arytenoidectomy (MPA).

STUDY DESIGN

Repeated measures under the following conditions: Control, RLN, LPVC, and MPA.

ANIMALS

Six horses.

METHODS

Two trials were conducted under all conditions at 80% and 100% of maximal heart rate (HR(max)). In Trial 1, arterial blood gases, tracheal and pharyngeal pressures, and laryngeal videoendoscopy were recorded. In Trial 2, upper airway pressure and airflow were determined. Tracheobronchial aspirates were performed after exercise to quantify airway contamination.

RESULTS

Compared with control, RLN significantly increased inspiratory impedance and worsened exercise-induced hypoxemia. At 80% HR(max), LPVC restored most variables to control values. At 100% HR(max), LPVC improved all variables, but did not restore minute volume, arterial pH, and PaCO(2). At 80% HR(max), MPA restored all variables except bicarbonate to control values. At 100% HR(max), MPA improved all variables, but did not statistically restore minute ventilation or bicarbonate level. Only minor differences were noted between LPVC and MPA. Both resulted in equivalent tracheal contamination.

CONCLUSIONS

Airway mechanics and arterial blood gas values were not restored to normal after either LPVC or MPA in horses exercising at HR(max). This does not affect ventilation at sub-maximal exercise, but has clinical implications at HR(max). Both procedures diminish normal laryngeal protective mechanisms.

CLINICAL RELEVANCE

At sub-maximal exercise intensities both LPVC and MPA restore airway ventilation to normal. At maximal exercise the superiority of LPVC over MPA is slight.

Performance after Partial Arytenoidectomy without Mucosal Closure in 27 Thoroughbred Racehorses

OBJECTIVE

To examine the effect of partial arytenoidectomy without mucosal closure on postoperative racing performance and long-term complications in Thoroughbred racehorses treated for laryngeal hemiplegia, arytenoid chondropathy, or failed laryngoplasty.

STUDY DESIGN

Retrospective study.

ANIMALS

Twenty-seven Thoroughbred racehorses.

METHODS

Medical records of Thoroughbred racehorses that had partial arytenoidectomy without mucosal closure between 1992 and 2002 were reviewed. Horses were divided into groups: horses that had not raced (Group 1) and those that had raced (Group 2) before surgery. Lifetime race records were compared between groups. A standard starts index (SSI) and performance index (PI) were used for Groups 1 and 2, respectively, to objectively evaluate each horse's postoperative performance. Telephone interviews of owners and trainers were used for subjective performance evaluation and to determine prevalence of long-term complications.

RESULTS

Eleven (61%) Group 1 and 7 (78%) Group 2 horses raced and earned money after surgery. All Group 1 horses that raced performed at a level lower than the national average. Only 1 Group 2 horse had an improved PI score postoperatively.

CONCLUSIONS

Thoroughbred racehorses have a fair prognosis for racing successfully after partial arytenoidectomy without mucosal closure.

CLINICAL RELEVANCE

This technique may be a practical alternative to primary mucosal closure, would decrease surgical time, and avoid some problems reported with primary mucosal closure.

Long-term survey of laryngoplasty and ventriculocordectomy in an older, mixed-breed population of 200 horses. Part 1: Maintenance of surgical arytenoid abduction and complications of surgery

REASONS FOR PERFORMING STUDY

Laryngoplasty (LP) is currently the most common surgical treatment for equine laryngeal paralysis, however, there have been no reports quantifying the degree of retention of arytenoid abduction following LP. Additionally, the complications of LP have been poorly documented.

OBJECTIVES

To record the degree of arytenoid abduction retention following LP and to accurately document all complications of surgery.

METHODS

A study (1986-1998) of 200 horses of mixed breed and workload, median age 6 years (prospective 136 cases and retrospective 64 cases) undergoing LP (using 2 stainless steel wires) and combined ventriculocordectomy was undertaken; 198 owners completed questionnaires, a median of 19 months following surgery. The degree of arytenoid abduction achieved was endoscopically, semi-quantitatively evaluated using a 5-grade system, at 1 day, 7 days, and 6 weeks after surgery.

RESULTS

On the day following LP, 62% of horses had good (median grade 2) arytenoid abduction, 10% had excessive (grade 1), and 5% had minimal (grade 4) abduction (overall-median grade 2). Due to progressive loss of abduction, moderate (median grade 3, range 1-5) abduction was present overall at 1 and 6 weeks after LP. Further surgery was required to re-tighten prostheses in 10% of cases with excessive loss of abduction, or to loosen prostheses in 7% of horses which had continuing high levels of LP abduction and significant post operative dysphagia. LP wound problems (mainly seromas and suture abscesses) were reported to last < 2 weeks in 9% of cases, < 4 weeks in 4% and > 4 weeks in 4%. The (partially sutured) laryngotomy wounds discharged post operatively for < 2 weeks in 22% of cases, < 4 weeks in 7% and for > 4 weeks in 2%. Coughing occurred at some stage post operatively in 43% of cases and its presence correlated significantly with the degree of surgical arytenoid abduction. This coughing occurred during eating in 24% of cases and was not associated with eating (or dysphagia) in the other 19% of cases. Chronic (> 6 months duration) coughing occurred in 14% of cases, but appeared to be due to intercurrent pulmonary disease in half of these horses.

CONCLUSIONS

Suturing the cricotracheal membrane allows most laryngotomy wounds to heal quickly. Laryngoplasty wound problems were of little long-term consequence when stainless steel wire prostheses were used.

POTENTIAL RELEVANCE

A significant loss of LP abduction occurs in most horses in the 6 weeks following surgery and efforts should be made to find ways to prevent such loss. However, excessive LP abduction is associated with post operative dysphagia and coughing.

Long-term survey of laryngoplasty and ventriculocordectomy in an older, mixed-breed population of 200 horses. Part 2: Owners' assessment of the value of surgery

REASONS FOR PERFORMING STUDY

There is continuing debate on the clinical benefit of laryngoplasty (LP) in the treatment of equine laryngeal paralysis. In particular, there is little information available on the clinical value of this surgery in older horses, in non-Thoroughbreds or in sports or pleasure horses; nor on the relationship between the degree of LP abduction achieved and the clinical value of LP.

OBJECTIVES

To evaluate the owner's assessment of the value of LP (and combined ventriculocordectomy) in an older, mixed breed and mixed workload population of horses and to also assess the relationship between the degree of LP abduction present and the clinical value of this surgery.

METHODS

A study (1986-1998) of 200 horses of mixed breed and workload, median age 6 years (prospective 136 cases and retrospective 64 cases) undergoing LP and ventriculocordectomy was undertaken. The degree of laryngoplasty abduction achieved and maintained was semiquantitatively evaluated using a 5-grade system.

RESULTS

A survey of 198 owners, a median of 19 months after LP surgery, showed that 91% of cases had returned to full work and 3% to reduced work, including 95% of horses with good (Grade 2) laryngoplasty abduction at 6 weeks after surgery, 91% with moderate (Grade 3) abduction, 88% of cases with minsimal (Grade 4) abduction and just 25% of cases with total loss of surgical abduction (Grade 5). Once back in work, 73% of cases were reported to make no abnormal exercise-related noises ('noises') at exercise, with reduced 'noises' reported in some of the 21% of horses that still made 'noises'. In the other 6% of cases, owners were unsure if 'noises' were present. The absence or presence of 'noises' once back at work correlated significantly with the degree of surgical arytenoid abduction present at 6 weeks after LP. Once back in work, 'noises' were less commonly detected in sports and pleasure horses (absent in 76% of cases) than in racehorses (absent in 60%) of cases. Exercise performance following surgery was reported to be markedly increased in 75% of cases, with 10% showing no difference in exercise performance, 3% showing worse performance, and owners unsure of any effect on exercise performance in 13% of cases. Improved work was reported in 70% of sports and pleasure horses and in 67% of racehorses. Overall, 86% of owners believed LP was worthwhile, 7% believed it was not worthwhile and 6% were unsure of its value. Surgery was reported to be of most benefit to sports horses (e.g. reported worthwhile for 100% of show jumpers) and of least benefit to National Hunt (long distance) racehorses where 71% of owners believed it to be worthwhile.

CONCLUSIONS AND POTENTIAL RELEVANCE

Most horse-owners believe that LP and combined ventriculocordectomy are of clinical value, especially in sports and pleasure horses. Large scale physiological studies on clinical cases, pre- and post operatively, are required to examine more critically the value of such surgery.

Outcome of and postoperative complications in dogs undergoing surgical treatment of laryngeal paralysis: 140 cases (1985-1998)

OBJECTIVE

To compare outcomes of various surgical techniques for treatment of laryngeal paralysis in dogs and determine incidence and risk factors for development of postoperative complications.

DESIGN

Retrospective study.

ANIMALS

140 dogs undergoing surgical treatment for laryngeal paralysis at a veterinary teaching hospital between 1985 and 1998.

PROCEDURE

Data were analyzed to determine outcome and factors influencing outcome and development of complications. Kaplan-Meier curves were constructed for survival analysis.

RESULTS

Postoperative complications were documented in 48 (34.3%) dogs; 20 (14.3%) dogs died of related causes. Aspiration pneumonia was the most common complication (33; 23.6%). Seven dogs died of aspiration pneumonia > 1 year after surgery. Dogs that underwent bilateral arytenoid lateralization were significantly more likely to develop complications and significantly less likely to survive than were dogs that underwent unilateral arytenoid lateralization or partial laryngectomy. Factors that were significantly associated with a higher risk of dying or of developing complications included age, temporary tracheostomy placement, concurrent respiratory tract abnormalities, concurrent esophageal disease, postoperative megaesophagus, concurrent neoplastic disease, and concurrent neurologic disease.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that surgical repair of laryngeal paralysis may be associated with high postoperative complication and mortality rates. Surgical technique and concurrent problems or diseases increased the risk of complications. Dogs appeared to have a life-long risk of developing respiratory tract complications following surgical correction.

Procedure for laryngotracheal separation in the goat: development of a new animal model for analysis of craniofacial growth

Most animal models used to study the process of postnatal craniofacial growth require direct manipulation of the craniofacial area, a growth period, then evaluation of the area. However, the scar tissue associated with direct manipulation of the craniofacial structures can produce growth abnormalities that are unrelated to the manipulation itself. To avoid this confounding variable in the study of craniofacial growth, we developed an animal model that involves laryngotracheal separation in a young animal. Our procedure completely separates the trachea from the upper aerodigestive tract and removes the site of scar tissue formation from the region of investigation. The tracheal stomas of the goats we describe were maintained for as long as 9 months. Unlike human patients, goats with laryngotracheal separation require laryngectomy tubes to prevent life-threatening stenosis of the tracheal stoma. Here we describe the operative procedure and post-operative care required for this new animal model.

Efficacy of prosthetic laryngoplasty with and without bilateral ventriculocordectomy as treatments for laryngeal hemiplegia in horses

OBJECTIVE

To evaluate the efficacy of prosthetic laryngoplasty with and without bilateral ventriculocordectomy for treatment of experimentally induced left laryngeal hemiplegia (LLH).

ANIMALS

15 adult Standardbreds.

PROCEDURE

Horses were allotted to 3 equal groups. Sham operation (group 1), prosthetic laryngoplasty (group 2), or prosthetic laryngoplasty with bilateral ventriculocordectomy (group 3) was performed after induction of LLH. Upper airway function testing was performed prior to left recurrent laryngeal neurectomy (LRLN), 14 days after LRLN, and 60 and 180 days after surgical treatment. Measurements were obtained at rest and at treadmill speeds corresponding to 75 and 100% of maximal heart rate. Videoendoscopy was performed at rest and during exercise in all horses prior to LRLN and 60 and 180 days after surgical treatment. Upper airway endoscopy was performed immediately after LRLN to document induction of grade-IV LLH. Also, horses in group 3 were endoscopically examined at 7, 14, 21, 28, and 120 days after surgical treatment to evaluate healing of the ventriculocordectomy sites.

RESULTS

When horses were at rest, significant differences were not apparent between groups at any period or between periods for any measured variable. LRLN induced airway obstruction in all horses during exercise. In sham-operated horses, this obstruction was unaffected by time. In contrast, 60 and 180 days after surgical treatment, inspiratory flow limitations induced by LRLN were reversed in horses of groups 2 and 3. There were no significant differences between the 2 treatment groups. Endoscopy revealed the left arytenoid cartilage abducted beyond the intermediate position, but not touching the pharyngeal wall in all horses with a laryngeal prosthesis. After surgical treatment, 4 group-2 horses had filling of both ventricles with air during exercise. There was moderate to marked swelling of the ventriculocordectomy sites immediately after surgery, and this swelling resolved by 7 days after surgery. The ventriculocordectomy sites looked best at 14 and 180 days.

CONCLUSIONS

60 and 180 days after prosthetic laryngoplasty, upper airway function returned to pre-LRLN values in horses with experimentally induced LLH exercising at 100% of maximal heart rate. Combining ventriculocordectomy with prosthetic laryngoplasty does not further improve upper airway function in these horses.

Total laryngectomy and permanent tracheostomy for treatment of laryngeal rhabdomyosarcoma in a dog

An extensive, laryngeal tumor was identified in a nine-year-old, spayed female, mixed-breed dog. Clinical staging of the tumor included computed tomography. Six days prior to surgery, a percutaneous gastrostomy tube was placed under endoscopic guidance. Surgical treatment included total laryngectomy and permanent tracheostomy. The histologic diagnosis of the tumor was rhabdomyosarcoma. There were no major postoperative complications, and there have been no signs of local recurrence, metastatic disease, or long-term complications associated with the surgical procedure during an 18-month follow-up period.

Complications and long-term results after partial laryngectomy for the treatment of idiopathic laryngeal paralysis in 45 dogs

Forty-five dogs with severe respiratory signs caused by idiopathic, acquired laryngeal paralysis were treated by partial laryngectomy. The predominant postoperative complications were coughing in 28 dogs and pneumonia in 15 dogs. Eight dogs required a second operation to alleviate persistent or recurrent upper airway obstruction. Results of surgery were considered excellent in 11 dogs (25%), good in 18 dogs (40%), fair in 6 dogs (13%), and poor in 10 dogs (22%). Poorer results were obtained by surgical residents than by more experienced surgeons. Death in the immediate postoperative period was related to pneumonia (8 dogs) and laryngeal collapse (1 dog). Nine dogs died later of respiratory disease. Although partial laryngectomy is effective for the treatment of laryngeal paralysis, it is not recommended because of the high incidence of postoperative complications.

Development of hypoparathyroidism after excision of laryngeal rhabdomyosarcoma in a dog

An uncommon neoplasm of the larynx, rhabdomyosarcoma, was diagnosed in a 6-year-old 14-kg neutered female Spitz. In addition to the progressive onset of expected clinical signs of the tumor (exercise intolerance, respiratory stridor, inability to bark), the dog experienced hyperthermic crisis. Laryngectomy was successful in eradicating the local neoplastic tissue; however, unusual postoperative complications developed and included acute complications of pharyngotracheal fistula and hypoparathyroidism, and long-term complications of periodic collapse of the tracheal stoma and intolerance to heat. Probable causes and successful management of these complications are described. At 22 months after laryngectomy, the dog was admitted for a solitary hepatic metastasis. While hospitalized, the dog died of apparent asphyxiation attributable to stoma collapse.

Neodymium (Nd):YAG laser surgery in the equine larynx: a pilot study

Laryngeal surgery in the equine is customarily and routinely performed by means of a ventral laryngotomy incision. Such procedures are usually performed under deep general anesthesia with the horse in dorsal recumbency. The objective of this work was to determine the efficacy of an endoscopic approach coupled to a Nd:YAG laser fiber in performing arytenoidectomy. Arytenoidectomy is commonly indicated in the treatment of arytenoid chondritis and in the failure of prosthetic implantation for left laryngeal hemiplegia. This preliminary study was undertaken to determine the feasibility of the endoscopic laser approach to ablate the most difficult of the structures of the larynx, considering tissue structure and density. This procedure was accomplished by using heavy sedation and local anesthesia and was performed in the standing position. This approach appears to be feasible and makes other adjacent structures accessible via the endoscope coupled to a surgical laser. Indications for future pilot applications of laser surgery in the equine larynx are entrapment of the epiglottis, dorsal soft palate displacement, and the ablation of laryngeal cysts and polyps. This pilot study appears to offer a new modality for discrete surgical ablation of this structure, with minimal postoperative complications and a reduced or equivalent convalescent period in this valuable species of animal.