Laryngeal paralysis-polyneuropathy complex in young related Pyrenean mountain dogs

OBJECTIVES: To characterise clinical, electrophysiological and histopathological findings. To analyse pedigree information in six young related Pyrenean mountain dogs with laryngeal paralysis-polyneuropathy complex (LP-PNC). METHODS: A retrospective study of clinical records and pedigrees of six young related Pyrenean mountain dogs with LP-PNC was carried out. RESULTS: All dogs were presented with laryngeal paralysis and concurrent megaoesophagus. Electrodiagnostic testing was performed in three dogs and showed electrophysiological abnormalities in the distal appendicular muscles. Histopathological findings of peripheral nerve samples were dominated by distal axonal degeneration. Clinical, electrophysiological and histopathological findings were supportive of a diagnosis of degenerative, sensorimotor LP-PNC, similar to that reported in young dalmatians and rottweilers. All dogs died or were euthanased by two years of age. An autosomal recessive mode of inheritance was suspected based on pedigree analysis. CLINICAL SIGNIFICANCE: Congenital LP-PNC should be suspected in any young dog presenting with laryngeal dysfunction and other concurrent neurological abnormalities. The prognosis is usually poor.     

Cricopharyngeal-laryngeal dysplasia in a horse with sudden clinical onset idiopathic laryngeal hemiparesis

A 7-year-old Thoroughbred racehorse developed loud exercise-related respiratory noises and exercise intolerance over a short period. Examination showed congenital cricopharyngeal-laryngeal dysplasia (rostral displacement of the palatopharyngeal arch) and also left sided idiopathic laryngeal hemiparesis, the latter appearing to be of recent clinical onset. The animal developed colic some months after laryngeal surgery and a nephrosplenic entrapment was surgically corrected. Aerophagia and regurgitation worsened after surgery and, after developing inhalation pneumonia, the animal was destroyed. Post-mortem examination confirmed the presence of idiopathic laryngeal hemiparesis and of cricopharyngeal-laryngeal dysplasia which had some previously undescribed laryngeal muscle abnormalities.     

Cricopharyngeal-laryngeal dysplasia in a horse with sudden clinical onset idiopathic laryngeal hemiparesis

A 7-year-old Thoroughbred racehorse developed loud exercise-related respiratory noises and exercise intolerance over a short period. Examination showed congenital cricopharyngeal-laryngeal dysplasia (rostral displacement of the palatopharyngeal arch) and also left sided idiopathic laryngeal hemiparesis, the latter appearing to be of recent clinical onset. The animal developed colic some months after laryngeal surgery and a nephrosplenic entrapment was surgically corrected. Aerophagia and regurgitation worsened after surgery and, after developing inhalation pneumonia, the animal was destroyed. Post-mortem examination confirmed the presence of idiopathic laryngeal hemiparesis and of cricopharyngeal-laryngeal dysplasia which had some previously undescribed laryngeal muscle abnormalities.     

Endoscopic findings in the upper respiratory tract of 678 Thoroughbred racehorses

The frequency of upper respiratory tract abnormalities was determined in a selected population of racing Thoroughbreds. The prevalence of pharyngeal lymphoid hyperplasia was 34.2%; left laryngeal hemiplegia was 1.8%; and epiglottic entrapment was 0.74%. Excluding pharyngeal lymphoid hyperplasia and tracheal exudate, 3.7% of the population examined had upper respiratory tract abnormalities.     

Equine laryngeal hemiplegia part II: Some clinical observations

Some clinical features of laryngeal hemiplegia in 127 horses are described. Possible aetiologic factors were found in only 11% of affected animals. The onset of clinical signs was either sudden or insidious. The majority of cases were presented because of an abnormal respiratory noise made at exercise. Other clinical signs, particularly those usually attributed to laryngopalatal dislocation, were observed in a substantial proportion of affected animals. In all cases surveyed the left arytenoid was affected, although in 3 animals a bilateral laryngeal dysfunction was noted. Thirty of 65 animals examined with a fibreoptic endoscope had other upper respiratory tract abnormalities in addition to abnormal arytenoid movements. Electrocardiographic examination of 45 affected horses did not reveal a significantly higher incidence of abnormalities than that observed in the racing population. The majority of haemograms taken from affected animals were also within normal limits.     

Laryngeal Paralysis-Polyneuropathy Complex in Young Rottweilers

Five Rottweiler puppies from 3 unrelated litters developed inspiratory stridor at 11–13 weeks of age. Physical examination disclosed tetraparesis in all dogs, and bilateral lenticular cataracts in 4 dogs. Laryngeal examination under light anesthesia showed laryngeal paralysis in all dogs. Electrodiagnostic testing revealed denervation potentials in the distal appendicular muscles of 4 dogs tested and in the intrinsic laryngeal muscles of 2 dogs tested. Motor nerve conduction velocity was slightly low in 1 dog. Neurogenic muscular atrophy was found in distal appendicular muscles (n = 3) and intrinsic laryngeal muscles (n = 2), and degenerative changes were found in peripheral nerves (n = 3) and recurrent laryngeal nerves (n = 2). No abnormalities were detected in the spinal cord, spinal nerve roots, or ganglia of 3 dogs autopsied. The clinical, electrophysiologic, and histopathologic findings support a diagnosis of polyneuropathy and resemble the finding reported in young Dalmatians. Young dogs with laryngeal paralysis should be evaluated neurologically to rule out a more generalized polyneuropathy. The condition is suspected to be hereditary in nature and the prognosis is poor.     

Correlation of resting and exercising endoscopic findings for horses with dynamic laryngeal collapse and palatal dysfunction

Reasons for performing study: To correlate resting and exercising endoscopic grades of laryngeal function in horses undergoing high‐speed treadmill endoscopy (HSTE) using the Havemeyer grading system. To correlate dorsal displacement of the soft palate (DDSP) seen at rest with palatal function during exercise. Methods: Records of horses that underwent HSTE examination (1999–2009) were reviewed. Resting laryngeal function score and other abnormalities noted on resting endoscopy were recorded as were results of HSTE. Results of resting and exercising endoscopic findings were correlated. Results: 281 horses underwent HSTE. There was significant correlation between grade of laryngeal function at rest (grades 1–4) and exercise (ρ= 0.53, P<0.001) and between resting subgrades 3.1, 3.2 and 3.3 and exercising grades of laryngeal function (ρ= 0.43, P = 0.0017). DDSP was observed at rest significantly more often in horses that developed DDSP during HSTE than those without DDSP during HSTE (RR = 4.1, P<0.001). The sensitivity and specificity of DDSP seen during resting endoscopy as a test for DDSP occurring during exercise were 25.5 and 95.1% respectively (positive predictive value 0.57, negative predictive value 0.83). Conclusions and potential relevance: The results of the current study support the use of the Havemeyer system for grading laryngeal function in the resting horse, and corroborate findings of previous studies correlating resting and exercising palatal abnormalities. Studies that use the presence of spontaneous DDSP during resting endoscopic examination as an inclusion criterion for investigating efficacy of treatments for DDSP are likely to have a low proportion of horses with false positive diagnoses.     

Laryngeal dyskinesia in a horse

A 3-year-old Warmblood gelding was evaluated for intermittent respiratory distress and an inspiratory noise. These signs were mainly observed at exercise but sometimes occurred at rest as well. At the age of 2 months, a severe episode of respiratory distress had necessitated a temporary tracheotomy, which had then healed uneventfully. Examination of the patient and resting endoscopy revealed no structural laryngeal alterations. Exercise endoscopy revealed episodes of active bilateral laryngeal adduction during inspiration. Spirometrically, a corresponding impairment of inspiratory airflow was identified. These abnormalities were most pronounced at the trot but they occurred at magnitudes of inspiratory airflow lower than those inducing dynamic arytenoid collapse in horses with recurrent laryngeal neuropathy. Therefore, the diagnosis of a laryngeal dyskinesia characterised by an active bilateral arytenoid adduction during inspiration was made. No specific treatment was implemented. Three years later, the owner reported that the condition was markedly improved and the horse was used for pleasure riding.     

IMAGING DIAGNOSIS—NASAL SEPTAL AND LARYNGEAL CYST‐LIKE MALFORMATIONS IN A THOROUGHBRED WEANLING COLT DIAGNOSED USING ULTRASONOGRAPHY AND MAGNETIC RESONANCE IMAGING

A foal was examined for abnormal upper airway noise. Endoscopically, there were narrowed nasal passages and an extralumenal mass of the cranial trachea. Using ultrasonography and magnetic resonance (MR) imaging of the larynx and cranial cervical trachea, irregular margins of the laryngeal cartilages and first tracheal ring containing areas consistent with fluid were identified. In MR images, a widened nasal septum was seen that contained material consistent with fluid. Postmortem examination confirmed the diagnosis of nasal septal, laryngeal, and cranial cervical tracheal cyst‐like lesions. This is a unique congenital condition, in which premortem imaging was instrumental in defining the abnormalities.     

ECHOLARYNGOGRAPHY IN CATS

Twenty-five cats with clinical signs of upper respiratory tract disease and five cats without upper respiratory signs underwent echolaryngography. Direct inspection of the larynx under general anesthesia was undertaken in all cats and used as the 'gold standard' for the diagnosis of laryngeal diseases. The aims were to: (a) establish which anatomic structures of the larynx are visible ultrasonographically in cats without upper respiratory tract disease, (b) establish which laryngeal abnormalities can be detected and accurately localised using ultrasonography and (c) evaluate in which conditions the technique may provide complementary information or an alternative method of investigation. The ultrasound investigation accurately indicated the presence and location of cysts and masses. Abnormal laryngeal movements were also detected, although it was difficult to confirm whether these were unilateral or bilateral. Vocal cord thickening was seen but the underlying cause could not be established with this technique.     

Laryngoscopy

The larynx normally functions in vocalization, deglutition, and respiration. There is no substitute for direct laryngoscopy in animals suspected of having laryngeal disease. Clinical signs that should alert the veterinarian include cough, choking while eating or drinking, exertional cyanosis and syncope, noisy breathing, inspiratory dyspnea, stridor, and significant change in sound production. Controlled anesthesia is mandatory for animals with suspected laryngeal disease because many of these patients have compromised respiratory function. Laryngoscopy is used to note abnormalities in the shape, color, and motility of the larynx with special attention to correlating the movement of the arytenoid cartilages and vocal folds with the respiratory cycle.     

Disorders of the larynx.

The upper respiratory tract is a frequent cause of exercise intolerance in horses, particularly in racing horses. There are a myriad of laryngeal abnormalities that may restrict airflow at the rima glottidis. Careful endoscopic examination is a crucial part of the examination of any racing horse suffering from poor performance. There has recently been interest in spectrum analysis of respiratory sounds. It has been determined that laryngeal hemiplegia and dorsal displacement of the soft palate have unique sound patterns. Therefore, spectrum analysis of respiratory sounds may prove to be useful in the diagnosis of laryngeal disorders in horses. Accurate diagnosis and appropriate surgical intervention are necessary to provide the horse the best chance of returning to its full athletic potential.     

Partial Laryngectomy in the Dog I. Healing and Swallowing Function in Normal Dogs

Laryngeal paralysis was created in normal dogs by sectioning the recurrent laryngeal nerves. The dogs were treated with bilateral vocal fold resection and unilateral partial arytenoidectomy, and sacrificed from 6 hours to 28 days following surgery. Swallowing abnormalities were not found in any of the dogs. Healing by granulation-epithelialization was complete by 14 days.     

ULTRASONOGRAPHY OF THE EQUINE LARYNX

Nasopharyngeal and laryngeal evaluation is important when examining horses with upper airway signs for poor performance. Currently endoscopy is the most common method to evaluate the equine upper airway. Ultrasonography of the equine larynx has not previously been described. Using six cadaveric specimens and four standing horses, the ultrasonographic appearance of the equine larynx was established. A scanning technique, including useful acoustic windows and the normal ultrasonographic appearance at each site, is described. Ultrasound allowed visualization of portions of the hyoid apparatus, laryngeal cartilages, associated soft tissues, and intrinsic and extrinsic laryngeal musculature, that are not seen using endoscopy. Additionally, real-time ultrasound allowed observation of the movement of the vocal folds and the arytenoid cartilages during respiration. In three horses with arytenoid chondritis, ultrasonography aided in the diagnosis and localization of arytenoid abcessation and perilaryngeal inflammation. The establishment of this technique will serve as the basis for future investigations in the evaluation of clinical patients with upper airway abnormalities.     

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.     

Equine laryngeal dysplasia

Equine 4th and 6th branchial arch defects are not uncommon in the equine population at large but can be challenging to diagnose and treat. An understanding of the anatomical structures that can be involved and how structural abnormalities may affect laryngeal function is important for clinicians faced with such cases. Diagnosis is often made using resting endoscopic examination alone but, in many cases, laryngeal ultrasound, radiography and 3‐dimensional (3D) imaging techniques can be useful in confirming a diagnosis and for detecting which structures are abnormal. Exercising endoscopy is an important tool when ascertaining whether treatment is an option, for guiding treatment choice and making a prognosis for athletic function.     

Prevalence of pharyngeal and laryngeal abnormalities in Thoroughbreds racing in Australia, and their association with performance

REASONS FOR PERFORMING STUDY: Little information is available regarding the prevalence of abnormalities of the upper airway and their association with performance in the general population of Thoroughbred racehorses. OBJECTIVES: To describe the prevalence of selected abnormalities of the upper airway and their association with performance in Thoroughbred racehorses in Australia. HYPOTHESIS: That abnormalities of the upper airway of Thoroughbred racehorses are associated with poor race performance. METHODS: Rhinolaryngoscopy was performed after racing and presence and characteristics of abnormalities of the larynx and pharynx were recorded in a prospective cross-sectional study of Thoroughbred horses racing in Victoria, Australia. RESULTS: Rhinolaryngoscopy was performed once on each of 744 horses over 35 months. Fifty abnormalities of the upper airway were detected in 47 horses (6.3%, 95% confidence interval [CI] 4.7-83%). Epiglottic entrapment was detected in 7 horses (0.9%, 95% CI 0.4-1.9%) and was significantly (P = 0.015) associated with superior performance. Grade 2 asymmetry (4 grade scale) of the left arytenoid cartilage was detected in 9 horses (1.2%, 95% CI 0.5-2.4%) and was also associated with superior performance (P<0.001). Ulceration or erosion of the mucosa of the axial surface of one or both arytenoids was detected in 18 horses (2.4%, 95% CI 13-3.8%) and was not associated with alterations in exercise performance (P = 0.31). CONCLUSIONS: Epiglottic entrapment, Grade 2 laryngeal asymmetry and mucosal erosions detected in Thoroughbred racehorses were not associated with impaired performance; therefore, surgical correction and concern over laryngeal function in horses with Grade 2 asymmetry may not be necessary in individuals performing to expectation.     

Management of arytenoid chondropathy and failed laryngoplasty in horses: 75 cases (1979-1985)

By use of endoscopy, 75 horses with respiratory noise and/or exercise intolerance were determined to have structural arytenoid cartilage abnormalities (60 primary, 11 after previous laryngeal surgery), or failed left laryngoplasty (4 horses) for laryngeal hemiplegia in which the arytenoid cartilage still appeared normal. Eighty-eight percent of the horses were either Thoroughbred (54 horses; 72%) or Standardbred (12 horses; 16%) racehorses; only 9 horses (12%) had occupations not related to racing. Seventy-six percent of the racehorses were 2 to 4 years old; all non-racehorses were greater than 4 years old. The male:female ratio was approximately 2:1. Of the horses with cartilage abnormalities, 28 had left-sided involvement, 22 had right-sided involvement, and 21 had bilateral involvement. Sixty-two arytenoidectomies were performed, 58 for cartilage abnormalities (22 left, 19 right, 17 bilateral), and 4 for failed left laryngoplasties. Overall, 45% of the Thoroughbred racehorses that returned to racing after arytenoidectomy raced successfully (50% left, 75% right, 22% bilateral); only 20% of the Standardbreds were able to race. Seventy-five percent of non-racehorses were able to return to their previous use. Many horses were retired intentionally after surgery.     

Radiographic assessment of laryngeal reflexes in ketamine-anesthetized cats

The competence of the laryngeal closure reflexes of cats anesthetized with ketamine was assessed. Radiographic evaluations of the respiratory and digestive tracts were made after colloidal barium suspension was instilled into the pharynges of conscious and ketamine-anesthetized cats. There was a significant ketamine dose-related response of spread of contrast medium into the supraglottic laryngeal area and into the stomach 2 minutes after contrast medium was instilled into the pharynx (P less than 0.05). Cats did not aspirate contrast medium into the lower respiratory tract. Three ketamine-anesthetized cats aspirated contrast medium into the subglottic area of the larynx, and 2 of these cats also aspirated the material into the cranial part of the trachea. This material was coughed up and swallowed within 5 minutes. Transit time of contrast medium into the stomach seemed to be increased in 11 of the 15 cats given the larger dosages of ketamine (24, 36, 48 mg/kg of body weight), compared with that in conscious cats and those given ketamine at 12 mg/kg. Competent laryngeal protective reflexes in cats can be maintained with ketamine anesthesia. Contrast radiography could be used as a diagnostic aid in ketamine-anesthetized cats suspected of laryngeal reflex abnormalities.