Recurrent Laryngeal Neuropathy Research Articles

Dynamic respiratory endoscopic findings pre- and post laryngoplasty in Thoroughbred racehorses.

To investigate laryngeal function in cases of recurrent laryngeal neuropathy pre- and post laryngoplasty (LP) using dynamic respiratory endoscopy (DRE). To compare the rima glottidis area during DRE pre- and post LP; document all forms of dynamic upper airway obstruction (DUAO) pre- and post LP and investigate the relationship between post operative abduction at rest and exercise. Prospective case series. Thoroughbred racehorses with pre- and post LP DRE were included. Left-to-right arytenoid cartilage angle ratios and rima glottidis area ratios were used to quantify laryngeal function during rest and exercise, pre- and post LP. In 35 horses, mean pre-LP ratios were greater during rest (left-to-right quotient angle ratio [LRQ] 0.76 ± 0.13; left-to-right arytenoid ratio [LRR] 0.72 ± 0.14; rima glottidis area ratio [RGA] 0.40 ± 0.10) than exercise (LRQ 0.39 ± 0.16, P < 0.001; LRR 0.38 ± 0.16, P < 0.001; RGA 0.15 ± 0.05, P < 0.001). Exercising ratios were larger post LP (LRQ 0.61 ± 0.13; LRR 0.60 ± 0.12; RGA 0.30 ± 0.08) than pre-LP (LRQ 0.39 ± 0.16, P < 0.001; LRR 0.38 ± 0.16, P < 0.001; RGA 0.15 ± 0.05, P < 0.001). A positive linear relationship was found between post LP resting and exercising ratios (R(2) = 0.48; P < 0.001) and post operative abduction grades (R(2) = 0.63; P < 0.001). Pre-LP all horses demonstrated left arytenoid cartilage collapse with bilateral vocal cord collapse and 37% had aryepiglottic fold collapse. Post LP 13 horses (37%) developed additional DUAOs and these horses had smaller RGAs (0.25 ± 0.08) than horses that did not develop DUAOs (0.32 ± 0.07, P = 0.01). Multiple forms of DUAO occurred pre-LP and additional forms often developed post LP. Post LP the degree of arytenoid cartilage abduction at rest was useful to predict the degree of abduction during exercise.

Association Between ‘Wind‐Test’ Findings and Resting Endoscopic Assessment of Laryngeal Function at Thoroughbred Public Auction in the UK

Reasons for performing studyDespite ongoing advances in diagnostic imaging, ‘wind‐testing’ remains the most common screening test for upper respiratory tract obstructions and is an important condition of sale at Thoroughbred public auctions in UK/Europe. Correlations between abnormal respiratory noise and resting laryngeal function have been incompletely investigated to date.ObjectivesTo determine whether associations exist between respiratory noise at lunge and subsequent diagnosis of recurrent laryngeal neuropathy (RLN).Study designRetrospective analysis of records for all post sale wind‐testing undertaken by a single veterinary practice at Tattersalls Newmarket yearling, breeze‐up and horse‐in‐training sales between 2009 and 2013.MethodsDescriptions of abnormal respiratory noise were categorised as ‘inspiratory whistle’, ‘inspiratory harsh’ or ‘pan‐respiratory harsh’, and included lunge direction during which noise was evident. Concurrent examination by 2 veterinary surgeons was a criterion for inclusion of cases. All horses making abnormal respiratory noises underwent resting endoscopy with a consensus score (Lane scale) given for laryngeal function.Results2972 horses underwent post sale wind‐testing and 418 horses (14.1%) underwent resting endoscopic examination due to abnormal respiratory noise. Likelihood of making an abnormal respiratory noise differed significantly between groups (yearlings 10.8%, ‘breeze‐up’ 2‐year‐olds 20.6%, horses‐in‐training 30.1%). Yearlings were significantly more likely (P&lt;0.0001, Chi‐squared/Bonferroni test) to make a ‘harsh’ respiratory noise than horses‐in‐training. Type of noise (whistle) was significantly associated with resting endoscopic evidence of RLN in yearlings (P = 0.009); specificity of ‘whistle’ for RLN in this group was 38.6%. There was no association between lunge direction noise (left, right or both) and RLN.ConclusionsThese results support the widespread belief that harsh respiratory noise when lunged of presumed ‘palatal/pharyngeal’ origin is more likely in yearlings than horses‐in‐training, possibly due to upper respiratory inflammation or immaturity. Inspiratory whistle in both lunge directions is no stronger an indicator of RLN than unidirectional whistle.Ethical animal research: Ethical committee oversight not currently required by this congress: retrospective study of clinical records. Explicit owner informed consent for participation in this study was not stated. Sources of funding: None. Competing interests: None.

Use of Laryngeal Computed Tomography for Noninvasive Assessment of Laryngeal Function in Horses with Recurrent Laryngeal Neuropathy

Reasons for performing studyRecurrent laryngeal neuropathy (RLN) is a common equine distal axonopathy associated with neurogenic atrophy of intrinsic laryngeal muscles (particularly the left) causing laryngeal paresis and poor performance. An objective, reliable method of assessing changes in structure that correlates with laryngeal muscle function in vivo is necessary to determine response to novel treatments, including functional electrical stimulation. This study aimed to determine whether laryngeal muscle and nerve morphology (determined by CT and histopathology) correlated with laryngeal function.Study designProspective cohort study.MethodsResting (grades 1–4) and exercising (grades A–C) laryngeal function was graded in adult Thoroughbred horses. Standing CT of the larynx was performed to compare volume, cross‐sectional area (XSA) and tissue density between left and right cricoarytenoideus dorsalis (CAD) muscles in 22 horses. CAD muscles and recurrent laryngeal nerves were collected in a subgroup of 10 horses and analysed for fibrosis, fat infiltration and nerve fibre density (axons/μm2).ResultsHorses with grade C RLN on exercising endoscopy had significantly (P&lt;0.005) smaller left CAD muscles and reduced nerve fibre density than horses with grades A or B. Horses with grade 4 RLN on resting endoscopy had significantly (P&lt;0.005) smaller left CAD muscles than horses with grades 1 or 2. Left CAD muscles had significantly more collagen than the right in horses with grade C RLN. CT measurements of the CAD muscles were significantly associated with % collagen/fat and nerve fibre density (P&lt;0.05).ConclusionsLaryngeal CT results correlate with laryngeal function at rest and exercise in the horse and provide a noninvasive method of monitoring changes in CAD morphology in response to novel treatments. CAD CT appearance is dependent on % collagen and fat in the muscle and is associated with nerve fibre density.Ethical animal research: Horses destined for euthanasia were recruited for this study with approval of the Institutional Ethical Committee and under UK Home Office Licence. Sources of funding: Med‐El Elektro‐medizinische Geräte GmbH, Innsbruck, Austria. Competing interests: None.

A Single Nucleotide Polymorphism (BIEC2‐808543) on Eca3 Is Associated with Recurrent Laryngeal Neuropathy Independent of Height in Thoroughbred Horses

IntroductionRecurrent laryngeal neuropathy (RLN) is considered height‐linked in Thoroughbreds. A SNP (BIEC2‐808543) proximal to the LCORL/NCAPG gene significantly influences height variation in horses. It has been suggested that the C‐allele of this SNP is associated with RLN risk. Our objective was to investigate the association between the BIEC2‐808543 C‐allele, RLN and height in a cohort of Thoroughbreds.MethodsResting and exercising upper respiratory tract endoscopic videos, laryngeal ultrasonograms, wither height, age and sex were recorded in 79 Thoroughbreds (age 34 ± 11 months). The Havemeyer grading scale was used to characterise RLN cases (Grade B or C at exercise) and controls (Grade 1.1 or 2.1 at rest, Grade A at exercise, normal laryngeal ultrasound). All horses were genotyped for the BIEC2‐808543 SNP using a custom TaqMan SNP Genotyping assay. Logistic regression was performed measuring additive effects of allele dosage with sex, age and height as covariates (P≤0.05). Horses were subcategorised into tall (T,≥162 cm) and short (S,&lt;162 cm) groups for C‐allele frequency determination, with data presented as mean ± SD.ResultsThere were 16 RLN cases (height 164.5 ± 4 cm) and 32 controls (height 156.2 ± 4 cm). With sex and age as covariates, a significant association between the C‐allele and RLN cases was observed (P = 0.01). With height included as a covariate, a strong trend of association between the C‐allele and RLN remained (P = 0.06). C‐allele frequency was 41.7% for the T‐RLN group (n = 12, height 166.2 ± 3 cm), 12.5% for the S‐RLN group (n = 4, height 159.5 ± 2 cm), 13% for the T‐Control group (n = 16, height 165.1 ± 2 cm) and 14% for the S‐Control group (n = 16, height 156.2 ± 4 cm).ConclusionsThe association between the BIEC‐808543 C‐allele and RLN appears to be independent of height.Ethical Animal ResearchInstitutional Animal Research Ethics Committee approval was obtained. Explicit owner informed consent for participation in this study is not stated. Sources of funding: Science Foundation Ireland under Grant Number 11/PI/1166. Competing interests: Dr Hill is a co‐founder and Chairman of Equinome Ltd.

Genetics of upper and lower airway diseases in the horse.

Genetic predispositions for guttural pouch tympany, recurrent laryngeal neuropathy and recurrent airway obstruction (RAO) are well documented. There is also evidence that exercise-induced pulmonary haemorrhage and infectious diseases of the respiratory tract in horses have a genetic component. The clinical expression of equine respiratory diseases with a genetic basis results from complex interactions between the environment and the genetic make-up of each individual horse. The genetic effects are likely to be due to variations in several genes, i.e. they are polygenic. It is therefore unlikely that single gene tests will be diagnostically useful in these disorders. Genetic profiling panels, combining several genetic factors with an assessment of environmental risk factors, may have greater value, but much work is still needed to uncover diagnostically useful genetic markers or even causative variants for equine respiratory diseases. Nonetheless, chromosomal regions associated with guttural pouch tympany, recurrent laryngeal neuropathy and RAO have been identified. The association of RAO with other hypersensitivities and with resistance to intestinal parasites requires further study. This review aims to provide an overview of the available data and current thoughts on the genetics of equine airway diseases.

Genomic analysis establishes correlation between growth and laryngeal neuropathy in Thoroughbreds

BackgroundEquine recurrent laryngeal neuropathy (RLN) is a bilateral mononeuropathy with an unknown pathogenesis that significantly affects performance in Thoroughbreds. A genetic contribution to the pathogenesis of RLN is suggested by the higher prevalence of the condition in offspring of RLN-affected than unaffected stallions. To better understand RLN pathogenesis and its genetic basis, we performed a genome-wide association (GWAS) of 282 RLN-affected and 268 control Thoroughbreds.ResultsWe found a significant association of RLN with the LCORL/NCAPG locus on ECA3 previously shown to affect body size in horses. Using height at the withers of 505 of these horses, we confirmed the strong association of this locus with body size, and demonstrated a significant phenotypic and genetic correlation between height and RLN grade in this cohort. Secondary genetic associations for RLN on ECA18 and X did not correlate with withers height in our cohort, but did contain candidate genes likely influencing muscle physiology and growth: myostatin (MSTN) and integral membrane protein 2A (ITM2A).ConclusionsThis linkage between body size and RLN suggests that selective breeding to reduce RLN prevalence would likely reduce adult size in this population. However, our results do not preclude the possibility of modifier loci that attenuate RLN risk without reducing size or performance, or that the RLN risk allele is distinct but tightly linked to the body size locus on ECA3. This study is both the largest body size GWAS and the largest RLN GWAS within Thoroughbred horses to date, and suggests that improved understanding of the relationship between genetics, equine growth rate, and RLN prevalence may significantly advance our understanding and management of this disease.

Racing performance following prosthetic laryngoplasty using a polyurethane prosthesis combined with a laser-assisted ventriculocordectomy for treatment of recurrent laryngeal neuropathy in 78 Thoroughbred racehorses.

Recurrent laryngeal neuropathy (RLN) causes airway obstruction and adversely affects racing performance in Thoroughbred racehorses. Prosthetic laryngoplasty (PL) is the preferred treatment of RLN as it returns variables of airway mechanics to baseline. A number of materials have been evaluated as prostheses; however, the application of Lycra has not been rigorously investigated. To evaluate the efficacy of PL using a Lycra prosthesis, in combination with transendoscopic, laser-assisted ventriculocordectomy, to restore racing performance in Thoroughbred racehorses with RLN. Retrospective case series. Medical records, preoperative and post operative racing performance indices from 78 Thoroughbred racehorses that underwent surgical treatment for RLN were evaluated. Medical records, preoperative and post operative racing performance indices were evaluated. Case history, postoperative complications and PL failure were recorded. Racing performance was analysed using Beyer Speed Figures (BSF), earnings and a performance index (PI), with comparisons made between the 3 races before and after surgery. Factors associated with return to racing and racing performance were analysed. Eighty-two per cent (46/56) of horses that raced prior to surgery and 75% (15/20) of horses that had not raced prior to surgery competed in at least one race post operatively. Horses had a lower BSF and PI in the final race before surgery. Following surgery, PI and BSF values were restored to preoperative values in 73% and 78% of horses respectively. Surgical failure rate and immediate post operative complication rate were lower than, or comparable with,other reported prosthesis materials. Thoroughbred racehorses with RLN have a good prognosis for racing successfully after PL using a Lycra prosthesis. The described surgical technique is associated with a low post operative complication rate and an increase in indicators of racing performance (PI and BSF) post operatively. Lycra offers an attractive option for application as a prosthetic for PL with a low complication rate and similar efficacy to reported rigid prostheses.

Simulation of the Electrical Field in Equine Larynx to Optimize Functional Electrical Stimulation in Denervated Musculus Cricoarythenoideus Dorsalis.

Distribution of the electrical field is very important to activate muscle and nerve cells properly. One therapeutic method to treat Recurrent Laryngeal Neuropathy (RLN) in horses can be performed by Functional Electrical Stimulation (FES). Current method to optimize the stimulation effect is to use implanted quadripolar electrodes to the musculus cricoarythenoideus dorsalis (CAD) and testing electrode configuration until best possible optimum is reached. For better understanding and finding of maximum possible activation of CAD a simulation model of the actual entire setting is currently in development. Therefore the geometric model is built from CT-data of a dissected larynx containing the quadripolar electrodes as well as fiducials for later data registration. The geometric model is the basis for a finite difference method containing of voxels with corresponding electrical conductivity of the different types of tissue due to threshold segmentation of the CT-data. Model validation can be done by the measurement of the 3D electrical potential distribution of a larynx positioned in an electrolytic tray. Finally, measured and calculated results have to be compared as well as further investigated. Preliminary results show, that changes of electrode as well as conductivity configuration leads to significant different voltage distributions and can be well presented by equipotential lines superimposed CT-slices – a Matlab graphical user interface visualizes the results in freely selectable slices of the 3D geometry. Voltage distribution along theoretically estimated fiber paths could be calculated as well as visualized. For further calculation of nerve or denervated muscle fiber activation and its optimization, real fiber paths have to be defined and referenced to the potential- and the CT-data.

A review of equine laryngoplasty complications

SummaryProsthetic laryngoplasty is a common treatment for equine recurrent laryngeal neuropathy (RLN). Complications of this surgery include immediate post operative problems, such as dysphagia, seroma formation, wound infection and sudden loss of arytenoid abduction. Longer term complications include gradual loss of arytenoid abduction, chronic coughing, arytenoid granulomas and dynamic upper airway collapse unrelated toRLNsuch as palatal dysfunction, and aryepiglottic fold or vocal fold collapse. However, the benefit of this procedure greatly outweighs these potential post operative complications, especially if appropriate surgical and post operative management practices are employed.

Vagal and recurrent laryngeal neuropathy following stereotactic ablative radiation therapy in the chest

PurposeTo identify clinical and dosimetric factors associated with vagus nerve (VN) and recurrent laryngeal nerve (RecLN) injury following stereotactic ablative radiation therapy (SABR) in the chest. Methods and MaterialsWe examined the clinical courses and SABR plans of 67 patients treated for T1 or T2 non-small cell lung cancer of the upper right or left lung, including 2 who developed vocal cord paresis (VCP) following treatment. After developing a contouring atlas for the VN and RecLN in the thorax, dose to those structures was retrospectively determined for each patient, and we identified 12 patients whose treatment imparted significant dose to either nerve and who were assessable for more than 12 months follow-up. Biologically effective doses using linear-quadratic (LQ) and linear quadratic-linear (LQ-L) modeling were correlated with VN and RecLN toxicity. ResultsOf 12 patients, 2 developed VCP. The first underwent repeat SABR and received a cumulative single fraction equivalent dose (alpha/beta = 3; SFED3) of 37.4 or 64.5 Gy to the VN and 13.7 or 15.3 Gy to the RecLN (by LQ or LQ-L modeling, respectively). This was the highest VN dose and fifth highest RecLN dose in the cohort. The second had rheumatoid arthritis and connective tissue disease and received a SFED3 of 16 Gy to the VN and 19.5 Gy to the RecLN (by both LQ and LQ-L modeling). This was in the upper tertile of VN and RecLN doses for the cohort. ConclusionsFollowing SABR for non-small cell lung cancer, VCP was associated with high cumulative dose to the VN in 1 patient and a moderately high dose to the VN and RecLN in another patient with rheumatoid arthritis and connective tissue disease. Particularly in the setting of reirradiation or connective tissue disease, potential toxicity to the VN or RecLN should be considered.

Ultrasound-guided biopsy of thecricoarytenoideus lateralismuscle: Technique and safety in horses

Current diagnosis of recurrent laryngeal neuropathy (RLN) depends upon disease recognition in the clinically affected horse. Biopsy of the intrinsic laryngeal muscles may provide a method to identify the changes in fibre-type composition that occur in RLN before clinical signs become apparent. To develop an ultrasound-guided biopsy technique of the left cricoarytenoideus lateralis muscle (CALM) and evaluate its efficacy and safety in vivo. A longitudinal descriptive study. Six standing horses underwent ultrasound-guided biopsy of the left CALM. Frozen muscle cores were obtained with a breast biopsy tool. Serial endoscopic, ultrasonographic and physical examinations before and for 8 weeks after the biopsy were assessed for iatrogenic trauma. Histologies of representative muscle core cross-sections were analysed for the total number of muscle fibres obtained with each biopsy. There were no immediate complications of the procedure and the left CALM was harvested in all instances. Biopsy samples had an average weight of 0.043 g (range = 0.023-0.077 g) and contained 3418 fibres in cross-section (range = 711-7143). Laryngeal endoscopic grade did not change significantly between prebiopsy and the end of the 8 week follow-up. The left CALM had significantly greater echogenicity than the right throughout the study (P<0.001), but there was no difference between the prebiopsy CALM echogenicity and that at completion of the study. Ultrasound-guided biopsy of the left CALM is safe and well tolerated, providing a minimally invasive method to obtain muscle from healthy horses. This new technique may be applicable in research and clinical settings.

Anatomic and neuromuscular characterisation of the equine cricothyroid muscle

As part of investigation into laryngeal stability and reanimation using functional electrical stimulation, the cricothyroid muscle might be utilised to increase laryngeal cross-sectional area in horses with recurrent laryngeal neuropathy. For optimal electrode placement and muscle recruitment, the neuroanatomy and excitability of the equine cricothyroid muscle needs to be defined. To describe the anatomy, innervation and function of the equine cricothyroid muscle and its contribution to laryngeal diameter. Seventeen equine larynges were collected at necropsy and 12 were grossly dissected. Seven larynges (five grade 1, two grade 4) were prepared for immunohistochemistry following gross dissection and 5 larynges were prepared for special staining: acetylcholinesterase staining of motor endplates (n = 3) and Sihler's staining (n = 2). Three larynges were stimulated following in situ cadaver dissection and 2 larynges were removed and stimulated ex vivo. Three neuromuscular compartments, each innervated by a primary nerve branch of the external branch of the cranial laryngeal nerve, were identified in all larynges. Stimulation of each neuromuscular compartment resulted in ventral displacement of the thyroid cartilage with respect to the cricoid cartilage, thereby increasing dorsoventral height of the rima glottis. The equine cricothyroid muscle has 3 distinct neuromuscular compartments with discrete innervation, fibre type distribution and muscle fibre sizes. All neuromuscular compartments tense the vocal cords by increasing dorsoventral height of the rima glottis through ventral displacement of the thyroid cartilage with respect to the cricoid cartilage. Simultaneous functional electrical stimulation of the cricothyroid and dorsal cricoarytenoid muscles may enhance laryngeal cross-sectional area in horses with recurrent laryngeal neuropathy.

DIAGNOSTIC SENSITIVITY OF SUBJECTIVE AND QUANTITATIVE LARYNGEAL ULTRASONOGRAPHY FOR RECURRENT LARYNGEAL NEUROPATHY IN HORSES

Recurrent laryngeal neuropathy (RLN) is the most common cause of laryngeal hemiplegia in horses and causes neurogenic atrophy of the intrinsic laryngeal muscles, including the cricoarytenoideus lateralis muscle. Recurrent laryngeal neuropathy results in paresis to paralysis of the vocal fold and arytenoid cartilage, which limits performance through respiratory compromise. Ultrasound has previously been reported to be a useful diagnostic technique in horses with RLN. In this report, the diagnostic sensitivity of subjective and quantitative laryngeal ultrasonography was evaluated in 154 horses presented for poor performance due to suspected upper airway disease. Ultrasonographic parameters recorded were: cricoarytenoideus lateralis echogenicity (subjective and quantitative), cricoarytenoideus lateralis thickness, vocal fold movement, and arytenoid cartilage movement. Ultrasonographic parameters were then compared with laryngeal grades based on resting and exercising upper airway endoscopy. Subjectively increased left cricoarytenoideus lateralis echogenicity yielded a sensitivity of 94.59% and specificity of 94.54% for detecting RLN, based on the reference standard of exercising laryngeal endoscopy. Quantitative left cricoarytenoideus lateralis echogenicity values differed among resting laryngeal grades I-IV. Findings from this study support previously published findings and the utility of subjective and quantitative laryngeal ultrasound as diagnostic tools for horses with poor performance.

UPPER AIRWAY EVALUATIONS OF THOROUGHBRED RACEHORSES IN A PRIVATE CLINIC IN CURITIBA, BRAZIL – RESTING ENDOSCOPIC FINDINGS IN 587 HORSES

Obstructive upper airway diseases are an important cause of poor performance in athletic horses. The present study aimed to determine the prevalence of common URT abnormalities (pharyngeal lymphoid hyperplasia - PLH, dorsal displacement of the soft palate - DDSP and recurrent laryngeal neuropathy - RLN) in a population of Thoroughbred racehorses in training submitted to resting endoscopy in a private clinic in Curitiba, Paraná, Brazil. 587 URT resting endoscopies, 385 2-year-old and 202 3-year-old-plus horses, were performed during the period of the study and the clinical records of all the examinations were reviewed and analysed. 340 (57.9 %) horses were evaluated for routine athletic follow up, 15 (2.6%) were pre-purchase examinations, 83 (14.1%) were examined as an investigation for cough, 58 (9.9%) horses had poor performance, 48 (8.2%) had abnormal respiratory noise, 35 (6.0%) had epistaxis and 8 (1.4%) had nasal discharge. Pharyngitis (Grades III, IV PLH) was diagnosed in 198 (33.7%) horses and was more prevalent in the 2-year-old group than in the older horses (40.5% vs. 20.8%, P&lt;0.05). DDSP was identified in 185 (31.5%) horses, Grade III RLN in 13 (2.2%) and Grade IV was seen in 21 (3.6%) horses. The present study gives a prevalence of upper airway abnormalities in resting endoscopic evaluation in a racehorse population in Brazil.

Using Quarterly Earnings to Assess Racing Performance in 70 Thoroughbreds after Modified Laryngoplasty for Treatment of Recurrent Laryngeal Neuropathy

To validate and then use quarterly earnings to assess racing performance of Thoroughbreds after modified laryngoplasty for treatment of recurrent laryngeal neuropathy Retrospective cohort study. Thoroughbred racehorses after modified laryngoplasty (N = 70), and untreated cohorts (N = 210). Medical (2005-2008) and race records of 70 Thoroughbred racehorses treated by modified laryngoplasty were reviewed. Postsurgery data were collated as the number of starts and the dollar race winnings for each quarter after the date of surgery. Comparisons were made to an untreated cohort population. Initial comparisons were made between subgroups of the untreated cohort to ensure that one randomly selected group of untreated horses would not differ significantly from another untreated group. In the last race before surgery, treated horses performed significantly (P < .001) worse than untreated horses. When data were examined by quarter, with the exception of the first quarter after surgery, there were no significant differences in race starts or dollars earned between treated horses and untreated cohorts. All treated horses had at least 1 race after surgery and there was no difference in cumulative survival up to 40 races after surgery between treated and untreated groups Quarterly earnings can be used to provide a more detailed longitudinal assessment of a racehorse's performance. Horses treated by modified laryngoplasty for recurrent laryngeal neuropathy return to similar level of performance as their untreated cohorts by the second quarter after surgery, and continue to compete as long as their cohorts.

Detection of copy number variants in the horse genome and examination of their association with recurrent laryngeal neuropathy

We used the data from a recently performed genome-wide association study using the Illumina Equine SNP50 beadchip for the detection of copy number variants (CNVs) and examined their association with recurrent laryngeal neuropathy (RLN), an important equine upper airway disease compromising performance. A total of 2797 CNVs were detected for 477 horses, covering 229kb and seven SNPs on average. Overlapping CNVs were merged to define 478 CNV regions (CNVRs). CNVRs, particularly deletions, were shown to be significantly depleted in genes. Fifty-two of the 67 common CNVRs (frequency≥1%) were validated by association mapping, Mendelian inheritance, and/or Mendelian inconsistencies. None of the 67 common CNVRs were significantly associated with RLN when accounting for multiple testing. However, a duplication on chromosome 10 was detected in 10 cases (representing three breeds) and two unphenotyped parents but in none of the controls. The duplication was embedded in an 8-Mb haplotype shared across breeds.

P27 Does resting laryngoscopy accurately predict severity of muscle histopathology in equine recurrent laryngeal neuropathy?

P27 Does resting laryngoscopy accurately predict severity of muscle histopathology in equine recurrent laryngeal neuropathy?

Quantitative electromyography improves prediction in vocal fold paralysis

Quantitative laryngeal electromyography (LEMG) using turns analysis can differentiate acute vocal fold paralysis from normal controls. The objective of this study is to determine if using both traditional qualitative LEMG measurements in addition to turns analysis improves prognostic accuracy in patients with acute vocal fold paralysis who demonstrate voluntary motor activity. Retrospective review of LEMG data (qualitative and quantitative) and charts of patients with vocal fold paralysis on flexible laryngoscopy, recurrent laryngeal neuropathy, and varying degrees of motor unit recruitment. Laryngeal EMG using a standardized protocol involving qualitative (evaluation of recruitment, motor unit configuration, detection of fibrillations, synkinesis) and quantitative (turns analysis) measurements was performed. Prognosis was correlated with vocal fold motion recovery status (minimum of 6 months following onset) using positive and negative predictive values (PPV, NPV). Twenty-three patients underwent LEMG for acute recurrent laryngeal neuropathy. All four patients with excellent LEMG prognosis recovered motion, whereas 17/19 patients with fair/poor LEMG prognosis were without motion at least 6 months following onset, resulting in a 100% PPV and 89.5% NPV. Integrating both qualitative and quantitative LEMG data improves prognostic accuracy in vocal fold paralysis patients who demonstrate voluntary motor unit activity.

Ultrasonographic evaluation of Cricoarytenoideus lateralis muscle in Standardbred horse

The cricoarytenoideus lateralis muscle (CALM) is an adductor of the arytenoid cartilages but is not directly involved in the pathogenesis of recurrent laryngeal neuropathy (RLN) as the abductor cricoarytenoideus dorsalis muscle (CADM) is. Nevertheless, the CALM is the first muscle to experience a neurogenic atrophy in the course of RLN and this feature explains its potential importance in RLN diagnosis. On 30 gelding and 30 female Standardbred horses weighing about 500 kg and aged between 3 and 9 years, an ultrasound examination of the larynx was performed in order to assess shape, size, and echogenicity of the CALMs. The mean width, thickness, and area of the muscle were respectively 1.42 cm, 1.23 cm, and 1.36 cm^2 for the right side and 1.40 cm, 1.21 cm, and 1.34 cm^2 for the left side. No differences were found in relation to sex, age, or difference between right and left muscle. Focal calcifications of thyroid cartilage prevented visualization of the muscles, especially in females.

Evaluation of Dysphagia After Cervical Surgery Using Laryngeal Electromyography

The purpose of this study was to investigate the causes of dysphagia after cervical surgery using laryngeal electromyography (LEMG), and the effect of laryngeal neuropathy on the severity of dysphagia. Seventeen patients with dysphagia evident after cervical surgery were included. Video fluoroscopic swallow study (VFSS) parameters evaluated included the volume of residue in the vallecular pouch and the pyriform sinus, the Rosenbek penetration-aspiration scale (PAS), and the swallowing function scoring system (SFSS). By VFSS findings, patients were classified into a mild or severe dysphagia group. Nine of 17 patients showed voice change. SFSS scores were 0 in 2 patients, 3 in 1 patient, 4 in 1 patient, 5 in 1 patient, and 6 in 12 patients. PAS scores were 1 in 8 patients, 2 in 5 patients, 7 in 3 patients, and 8 in 1 patient. Laryngeal neuropathy was evident in seven patients (41.2%). Of these, all patients exhibited recurrent laryngeal neuropathy and 28.6% had superior laryngeal neuropathy. When we evaluated LEMG findings with respect to the severity of dysphagia, the severe dysphagia group showed significant association with the presence of laryngeal neuropathy (p=0.006). Although the level of residue in the vallecular pouch was not associated with the presence of laryngeal neuropathy (p=0.442), the amount of residue in the pyriform sinus did show a significant association (p=0.020).