Transnasal laryngoscopy for the diagnosis of laryngeal paralysis in dogs

Four dogs with clinical signs of laryngeal paralysis and three normal dogs were evaluated with transnasal laryngoscopy. Six of these dogs subsequently underwent standard laryngoscopy. For transnasal laryngoscopy, a video endoscope was passed through the left nasal passage after intramuscular sedation and topical anesthesia. The laryngeal opening was observed during spontaneous ventilation. Laryngeal paralysis was diagnosed in four dogs and was confirmed with traditional laryngoscopy in three dogs. Normal motion of the arytenoid cartilages was present in the other three dogs; however, two required mechanical stimulation of the laryngeal mucosa for full evaluation. Transnasal laryngoscopy provided a means for diagnosing laryngeal paralysis in dogs without general anesthesia.     

Assessment of survey radiography as a method of diagnosing bilateral laryngeal paralysis in dogs

The gold standard for diagnosis of laryngeal paralysis is laryngoscopy under light anesthesia. This prospective analytical cross-sectional study aimed to determine whether a radiographic assessment of the larynx could be used as a non-invasive screening tool for diagnosing laryngeal paralysis in non-sedated animals, as the laryngeal ventricles may appear wider in affected animals. The laryngeal ventricles of 18 dogs with bilateral laryngeal paralysis composing the affected group and 25 non-sedated dogs presenting no respiratory abnormality composing the control group were evaluated using right lateral radiography of the larynx. Three observers measured the ratios of the maximal ventricular length and surface to the body length of the third cervical vertebra (MVL/LC3 and VS/LC3, respectively). They also subjectively assessed the ventricular shape as either normal or rounded. The most accurate criterion was found to be MVL/LC3, as the respective areas under the ROC curves were 0.96 (95% confidence interval [CI]: 0.95–0.97), 0.89 (95% CI: 0.87–0.91), 0.80 (95% CI: 0.65–0.95) for MVL/LC3, VS/LC3, and ventricular shape evaluation, respectively. Based on ROC curve analysis, two thresholds of clinical interest were set for the MVL/LC3; bilateral laryngeal paralysis was very unlikely for values < 0.3 and very likely for values > 0.5. The findings of this study support the use of lateral laryngeal radiography as a screening tool for diagnosing bilateral laryngeal paralysis. However, further diagnostic tests remain required if MVL/LC3 lies between these threshold values or if clinically indicated. Further studies are warranted to explore the use of laryngeal radiography in unilateral paralysis and other laryngeal or oropharyngeal diseases.     

THE ROLE OF ULTRASOUND IN THE ASSESSMENT OF LARYNGEAL PARALYSIS IN THE DOG

Forty dogs with clinical signs suggestive of upper respiratory tract disease underwent echolaryngography and laryngoscopy. Laryngoscopy was used as the definitive technique to diagnose laryngeal paralysis. The ultrasound investigation accurately indicated the presence of the paralysis and confirmed the uni- or bilateral nature of the disorder. Findings indicative of laryngeal paralysis included asymmetry or absence of motion of the cuneiform processes (30/30), abnormal arytenoid movement (16/30), paradoxical movement (9/30), caudal displacement of the larynx (2/30) and laryngeal collapse (1/30). Thirty dogs were found to be afflicted with laryngeal paralysis and ten had normal laryngeal motility.     

Bilateral thyroarytenoid cartilage lateralization and vocal fold excision with mucosoplasty for treatment of idiopathic laryngeal paralysis: 67 dogs (1998-2005)

Objective— To evaluate combined bilateral thyroarytenoid cartilage lateralization, vocal fold excision, and mucosoplasty technique (BTAL) through ventral median laryngotomy for treatment of laryngeal paralysis in dogs.
Design— Retrospective study.
Animals— Dogs (n=67) with laryngeal paralysis.
Methods— Medical records were reviewed for dogs with idiopathic laryngeal paralysis that had BTAL between January 1998 and March 2005. Retrieved data included signalment, history, physical and laryngoscopic examination findings, clinicopathologic tests, and results of recheck examination findings.
Results— BTAL was performed by a single surgeon. Short-term (<6 months) follow-up information was available for 67 dogs and long-term (>12 months) for 40 dogs. Major postoperative complications were surgical failures (13; 7 short term, 6 long term) and aspiration pneumonia (1). Mean recurrence of clinical signs was at 19 weeks (range, 2–30 weeks). Minor complications occurred in 22 (33%) dogs including occasional coughing or gagging, stridorous breathing during exercise, panting, noisy or heavy breathing, and aspiration pneumonia (3 dogs) that did not require hospitalization. All owners reported an improved quality of life and had no regrets with surgical outcome.
Conclusions— BTAL is seemingly an effective procedure for treatment of laryngeal paralysis.
Clinical Relevance— BTAL is associated with a low incidence of aspiration pneumonia; however, there is substantial risk of recurrence of clinical signs associated with narrowing of the glottis. Consequently, unilateral arytenoid lateralization currently represents the accepted approach to the treatment of laryngeal paralysis.     

The effect of two modifications of unilateral arytenoid lateralization on rima glottidis area in dogs

OBJECTIVES: To evaluate the clinical outcome and percentage increase in rima glottidis area achieved using a combined technique of cricoarytenoid and thyroarytenoid cartilage lateralization compared with cricoarytenoid cartilage lateralization alone in live anesthetized dogs clinically affected with bilateral laryngeal paralysis. STUDY DESIGN: Randomized prospective clinical study. ANIMALS: Twenty dogs with bilateral laryngeal paralysis. Methods-Bilateral laryngeal paralysis was diagnosed by direct laryngoscopy. Each dog was allocated randomly to 1 of 2 surgical groups: CAL (cricoarytenoid lateralization) and CTAL (cricoarytenoid and thyroarytenoid lateralization). Photographs were taken of each larynx before and after surgery, the images were digitized, and the preoperative and postoperative areas of each rima glottidis were measured. The percentage increase in rima glottidis area produced by each of the arytenoid lateralization procedures was compared. Follow-up was obtained by telephone survey of owners and referring veterinarians. RESULTS: There was no significant difference in mean (+/- SD) percentage increase in rima glottidis area for the CAL group (241.5 +/- 42.9%) or the CTAL group (236.4 +/- 44.5%). Clinical follow-up (median, 18 months postoperatively) indicated 60% of the dogs were still alive and only 1 dog had died as a result of complications related to surgery. CONCLUSIONS: CTAL for the treatment of canine laryngeal paralysis does not significantly increase rima glottidis area compared with CAL alone. The mean percentage increase in rima glottidis area obtained with both procedures was comparable to previously reported mean increases with CAL in live anesthetized dogs. Both procedures resulted in good long-term clinical outcome. CLINICAL RELEVANCE: CTAL is as effective as CAL in providing an increased rima glottidis for the treatment of bilateral laryngeal paralysis in dogs.     

A comparison of thiopental,propofol, and diazepam-ketamine anesthesia for evaluation of laryngeal function in dogs premedicated with butorphanol-glycopyrrolate

Thiopental, propofol, and diazepam-ketamine were compared for evaluation of laryngeal function in dogs. There was no significant difference among the three protocols in time to observation of normal function after drug administration or in the occurrence of swallowing, laryngospasm, or breathing. Jaw tone was significantly greater with diazepam-ketamine. Exposure of the larynx was excellent in five dogs and moderate in three dogs, each receiving thiopental or propofol. Exposure was excellent in one dog, moderate in six dogs, and poor in one dog receiving diazepam-ketamine. Exposure of the larynx for laryngeal function evaluation is more readily accomplished with thiopental or propofol than with diazepam-ketamine.     

Juvenile laryngeal paralysis in three Siberian husky x Alaskan malamute puppies

Three three-month-old Siberian husky x Alaskan malamute crossbreds had suffered episodic inspiratory dyspnoea and stridor for four to eight weeks and their endurance had decreased. In two of them bilateral, and in the other unilateral, laryngeal paralysis was diagnosed by laryngoscopy. In the nucleus ambiguus of the dogs there was a depletion of motor neurons, neuronal degeneration and mild gliosis, but there were no lesions in the root and peripheral segments of the recurrent laryngeal nerves.     

An experimental evaluation of castellated laryngofissure and bilateral arytenoid literalisation for the relief of laryngeal paralysis in dogs

The aim of this study was to compare the efficacy of 2 surgical procedures for providing an adequate laryngeal airway in dogs after surgically induced laryngeal paralysis. The laryngeal function of 10 healthy, adult experimental dogs was assessed by clinical examination, laryngoscopy, arterial blood gas measurement and analysis of tidal breathing flow-volume loops before, and after, bilateral recurrent laryngeal neurectomy. A castellated laryngofissure with vocal fold resection was done on 5 dogs and bilateral arytenoid cartilage lateralisation performed on the remaining 5 dogs. Six weeks later, the laryngeal function of the 10 dogs was reassessed, before the dogs were killed and a necropsy performed. The visible changes in laryngeal structure were recorded. Both surgical procedures alleviated some of the airway obstruction caused by the bilateral recurrent laryngeal neurectomy, but bilateral arytenoid cartilage lateralisation produced more consistent clinical improvement, a wider rima glottidis, increased inspiratory air flow and a significant increase in post-operative arterial oxygen tension.     

Effects of various anesthetic agents on laryngeal motion during laryngoscopy in normal dogs

OBJECTIVE: To evaluate the effects of various drugs and drug combinations conventionally used for anesthesia on arytenoid cartilage motion during laryngoscopy in normal dogs. STUDY DESIGN: Experimental study. ANIMALS: Six large breed healthy dogs with no previous history of respiratory dysfunction. METHODS: Each dog was randomly assigned to a different injectable anesthetic protocol once weekly for 6 weeks, then in the 7th week all dogs were anesthetized with isoflurane. Videolaryngoscopy was performed and recorded starting immediately after induction until dogs could no longer be safely restrained for endoscopy. Video was digitized and 3 still images of maximal inspiration and expiration from the first 15 seconds (induction) and the last 15 seconds (recovery) were captured and imported into an image analysis software program. The height and area of the laryngeal ostium were measured in pixels. Normalization of the glottal gap area was performed using the formula (normalized glottal gap area (NGGA)=area in pixels/height(2)). ANOVA was performed on the NGGA of images collected at inspiration and expiration during induction and recovery. Fischer's exact test was performed when significance (P<.05) was found. RESULTS: Within each protocol, laryngeal motion (defined as change in NGGA) at induction was not significantly different from laryngeal motion measured at recovery. Additionally, no significant differences were found in arytenoid motion immediately after induction when anesthetic protocols were compared. Arytenoid motion before recovery was significantly greater with thiopental when compared with propofol (P=.046), ketamine+diazepam (P=.0098), acepromazine+thiopental (P=.0021), and acepromazine+propofol (P=.0065). No significant difference in arytenoid motion was seen immediately after induction or before recovery when acepromazine+butorphanol+ isoflurane and thiopental were compared. CONCLUSION: We concluded that intravenous thiopental given to effect is the best choice for assessing laryngeal function in dogs. Dogs premedicated with acepromazine with or without opioids that require further anesthetic restraint for laryngoscopy should be anesthetized with isoflurane administered by mask. CLINICAL RELEVANCE: Misdiagnosis of laryngeal paralysis during laryngoscopy can be avoided by selecting the anesthetic regimens with the least effect on arytenoid motion.     

Laryngeal paralysis in immature and mature dogs as one sign of a more diffuse polyneuropathy

Six dogs with laryngeal paralysis had clinical, electrophysiologic, and pathologic evidence of a more generalized polyneuropathy. Three of the dogs were young Dalmatians, one was a young Bouvier des Flandres, and two were older, large-breed dogs. The results of this study suggest that laryngeal paralysis in dogs may frequently be one clinical sign of an underlying, more generalized polyneuropathy. Two forms of this generalized polyneuropathy may exist: an early form, as seen in young dogs with congenital or hereditary disease, and a delayed-onset form that is usually found in older dogs with so-called idiopathic laryngeal paralysis, some of which may have hypothyroidism.     

Effects of doxapram HCl on laryngeal function of normal dogs and dogs with naturally occurring laryngeal paralysis

OBJECTIVES: To compare the effects of IV doxapram on glottic size and arytenoid motion in normal dogs and in dogs with laryngeal paralysis. STUDY DESIGN: Prospective experimental and clinical trials. ANIMALS: Six healthy dogs weighing 24.5 +/- 3.9 kg and six dogs weighing 27.4 +/- 11.5 kg suspected of having laryngeal paralysis. METHODS: Dogs were pre-medicated with acepromazine and butorphanol, and a light plane of anesthesia was induced with isoflurane by mask. Videoendoscopic examination of laryngeal function was recorded before (baseline) and after IV doxapram administration. Normalized glottal gap area (NGGA) at maximal inspiration and expiration, and percentage change in height, width, area, and NGGA were calculated with measurements from digitized images of the glottal gap. RESULTS: Active arytenoid motion was present in all normal dogs at baseline. After doxapram administration, depth of respiration appeared greater, but arytenoid motion, as measured by percentage change in NGGA, and in area and width, did not significantly increase in normal dogs. No arytenoid motion was detected in dogs with laryngeal paralysis at baseline; however, rima glottidis NGGA of dogs with laryngeal paralysis was greater at inspiration and expiration than normal dogs. After doxapram administration, dogs with laryngeal paralysis developed paradoxical arytenoid motion and significant, negative percentage change in area (-61%) and NGGA (-145%) because of inward collapse of the arytenoids during inspiration. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of doxapram during laryngeal examination is useful for differentiating normal dogs from dogs with laryngeal paralysis. Dogs with laryngeal paralysis may suffer extreme glottic constriction with vigorous respirations, and may require intubation during examination.     

Comparison of unilateral arytenoid lateralization and ventral ventriculocordectomy for the treatment of experimentally induced laryngeal paralysis in dogs.

This study evaluated changes in respiratory function in dogs with experimentally induced laryngeal paralysis treated with either unilateral arytenoid lateralization or ventral ventriculocordectomy, and compared the effectiveness of these procedures. Evaluation consisted of clinical assessment and tidal breathing flow volume loop and upper airway resistance measurements. Carbon dioxide and doxapram hydrochloride were used as respiratory stimulants. Initially, all dogs improved clinically after corrective surgery. However, by the end of the study, laryngeal collapse had developed in 2 of 5 dogs corrected by ventral ventriculocordectomy. No statistical differences in upper airway mechanics testing were seen between the surgical procedures. With both groups combined, many measurements of upper airway obstruction improved after surgical correction. Based on this study, these surgical procedures yield comparable results, although additional studies are needed to evaluate both the cause of laryngeal collapse and the role of upper airway mechanics testing in the evaluation of canine laryngeal paralysis.     

Laryngeal silicone stent as a treatment option for laryngeal paralysis in dogs: a preliminary study of 6 cases

BackgroundLaryngeal paralysis is a common idiopathic degenerative neurological disease in older medium-to-large breed dogs, with surgical correction of the obstruction being the treatment of choice.ObjectivesThis study evaluated the use of laryngeal silicone stents to treat canine laryngeal paralysis in dogs where classic surgical treatment was not accepted by the owners.MethodsDogs diagnosed with laryngeal paralysis, for which the owners refused arytenoid lateralization surgery as a first-line treatment, were treated with laryngeal silicone stents.ResultsSix dogs with bilateral laryngeal paralysis were included in the study. All dogs showed improvement in clinical signs immediately after the procedure. No clinical signs or radiographic changes were noted in four out of six dogs in the follow-up visit performed 1 wk later. One dog was suspected of aspirating water while drinking, but the signs disappeared after repositioning the stent. Another dog had a relapse of stridor due to caudal migration of the stent. This dog underwent arytenoid lateralization surgery because larger stents are not commercially available. At the time of writing, between seven and 13 mon after stent placement, no significant incidents have occurred in four dogs, and all owners report a satisfactory quality of life.ConclusionsLaryngeal silicone stenting is an interesting alternative for treating dogs with acquired laryngeal paralysis when the owners refuse classic arytenoid lateralization surgery. Furthermore, stent placement can be a temporary solution to stabilize these dogs until a permanent surgical treatment can be performed.     

Experimental crush of the equine recurrent laryngeal nerve: a study of normal and aberrant reinnervation

Experimental reinnervation of the equine larynx in healthy ponies was studied after the recurrent laryngeal nerve was crushed, using endoscopic, electromyographic, and microscopic techniques. In 12 ponies, the recurrent laryngeal nerve was crushed unilaterally in the midcervical area. All showed postoperative paralysis of the larynx on the operated side. In 8 ponies, recovery of movement of the vocal folds occurred at different times (2.5 to 8 months) after surgical operation was done. These movements, which were often abnormal, included trembling and asynchronism. In 2 of these ponies, complete return of normal vocal fold function occurred. Return of function was due to reinnervation, as determined by electromyographic examination of the laryngeal muscles and microscopic evaluation of these muscles and the recurrent laryngeal nerves. In the muscles, there was evidence of fiber-type grouping, and the nerves showed regenerative activity. In 3 ponies, there was evidence of aberrant reinnervation, with adductor or abductor muscles discharging during an inappropriate phase of the respiratory cycle. Further evidence that reinnervation occurred in the larynges of these ponies was determined in microscopic sections of the recurrent laryngeal nerves and muscles, which showed regenerative activity and muscle fiber-type grouping, respectively. The endoscopic abnormalities in these ponies were compared with those seen in horses with spontaneous subclinical laryngeal paralysis. However, the possibility that the abnormal endoscopic findings in this latter group of horses are due to aberrant reinnervation is thought to be unlikely.     

Laryngeal carcinoma in a cat

Laryngeal neoplasia was diagnosed in a 5-year-old domestic shorthair cat examined for cough and gagging episodes. Resection of the mass revealed a squamous carcinoma which had invaded the deep floor of the larynx. Primary neoplasia of the feline larynx is a rare condition but needs to be distinguished from other obstructive laryngeal conditions, using radiography, laryngoscopy and biopsy.     

Upper airway obstruction in canine laryngeal paralysis

The type and the severity of airway obstruction in 30 dogs with bilateral laryngeal paralysis was assessed, using tidal breathing flow-volume loop (TBFVL) analysis. The dogs had clinical evidence of mild-to-severe upper airway obstruction (ie, respiratory distress, exercise intolerance, stridor). Seventeen dogs had TBFVL consistent with a nonfixed (inspiratory) obstruction, 10 had TBFVL indicative of a fixed (inspiratory/expiratory) obstruction, and 3 had normal TBFVL. Analysis of TBFVL confirmed that dogs with laryngeal paralysis have upper airway obstruction that differs in type and severity. Use of TBFVL provided a quantitative evaluation of airway obstruction and demonstrated the effects of bilateral laryngeal paralysis on the breathing patterns of dogs.     

A study of an electrodiagnostic technique for the evaluation of equine recurrent laryngeal neuropathy

The electrodiagnostic measurement of the thoracolaryngeal reflex (TLR) ('slap test') latency was compared to 5 other diagnostic techniques used for evaluation of laryngeal function, namely laryngeal muscle palpation, resting and immediately postexercise endoscopic examinations, and palpable and endoscopic responses to the TLR. Compared to resting endoscopy, the electrodiagnostic measurement of TLR latency was not found to be an accurate test for the evaluation of recurrent laryngeal neuropathy (RLN), nor was laryngeal muscle palpation or the endoscopic response to the TLR. Twenty-five (71%) of 35 Clydesdale horses examined were affected by RLN; 16 (46%) had mild, 5 (14%) moderate, 3 (9%) severe hemiparesis and 1 (3%) had total laryngeal paralysis. Within these 35 horses, physical traits such as height or neck length did not correlate with the incidence or severity of RLN. Ten control ponies showed no evidence of abnormal laryngeal function.     

The effects of doxapram hydrochloride (dopram-V) on laryngeal function in healthy dogs

Laryngeal dysfunction is assessed most accurately by direct visualization of the larynx under a light plane of anesthesia. If the plane of anesthesia used is too deep, laryngeal structures may appear paralyzed and remain in a paramedian position. Doxapram hydrochloride is a known respiratory stimulant. We hypothesized that doxapram would significantly increase intrinsic laryngeal motion in healthy anesthetized dogs. The goal of this study was to evaluate the effect of doxapram on the area of rima glottidis (RG) in healthy dogs. Thirty healthy dogs were studied. Dogs were premedicated with butorphanol tartrate (0.22 mg/kg IV), acepromazine maleate (0.05 mg/kg SC), and glycopyrrolate (0.005 mg/kg SC), followed by induction with propofol (4 mg/kg IV). Intrinsic laryngeal motion observed in each dog was recorded on videotape after induction. Doxapram then was administered (2.2 mg/kg IV) and respirations again were recorded. Representative breaths for each dog were photographed during 4 phases of respiration (inspiration at rest, inspiration with doxapram, expiration at rest, and expiration with doxapram). The area of the RG then was calculated by using a computer-assisted analysis program. Results of each category were compared by using a 1-way analysis of variance; P < or = .05 was considered significant. Doxapram visibly increased respiratory effort, and was associated with increased intrinsic laryngeal motion. Compared to the resting state, the area of the RG was significantly increased after doxapram administration during both inspiration and expiration. We propose the routine use of doxapram during laryngoscopy to increase intrinsic laryngeal motion and aid in the diagnosis of laryngeal dysfunction.     

Sound signature for identification of tracheal collapse and laryngeal paralysis in dogs

The aims of this study were to investigate whether upper airway sounds of dogs with laryngeal paralysis and tracheal collapse have distinct sound characteristics, compared with unaffected dogs. The sounds of 5 dogs with laryngeal paralysis and 5 dogs with tracheal collapse were recorded. Honking sound appeared as predominant clinical signs in dogs with tracheal collapse. Laryngeal stridors appeared as predominant clinical signs in dogs with experimentally produced laryngeal paralysis by resection of laryngeal nerve, in which two types of stridor, I and II, were recorded. All these sounds were analyzed using sound spectrogam analysis. There were significant differences in duration (sec), intensity (dB), pitch (Hz), first formant (Hz), second formant (Hz), third formant (Hz), fourth formant (Hz) of sounds between the normal bark and two types of stridor or honking sound, indicating that the sound analysis might be a useful diagnostic modality for dogs with tracheal collapse and laryngeal paralysis.     

Clinical and laryngoscopic findings in a Swiss Alpine goat with left grade 4 laryngeal hemiplegia

This case report describes the diagnostic trial of an inspiratory wheeze in a 1.5-year-old Swiss Alpine goat. Left grade 4 laryngeal hemiplegia was diagnosed via laryngoscopy, whereas the severity of the hemiplegia was assessed according to the grading system used in horses.The results of clinical, radiographic, sonographic and endoscopic examinations as well as haematological, biochemical and serological analyses did not reveal the cause of the hemiplegia. Treatment with an antibiotic and vitamin B complex resulted in only slight improvement. A postmortem examination four months later revealed no gross lesions in the left laryngeal nerve, larynx and intrinsic laryngeal musculature. Histological examination of the nerve, arytenoid cartilage and intrinsic laryngeal musculature also showed no lesions. Therefore, the cause of the disease in this goat is suspected to be on the cellular or molecular level of the intrinsic laryngeal musculature.