FRANK J. MILNE STATE-OF-THE-ART LECTURE


Table 2. Laryngeal Grade on Resting Endoscopy From the Summary of the Havermeyer Meeting held 7–10 September 2003 in Strafford-Upon-Avon, United Kingdom


Grade I II Description


All arytenoid cartilage movements are synchronous and symmetrical and full arytenoid cartilage abduction can be achieved and maintained.


Arytenoid cartilage movements are asynchronous and/or larynx asymmetric at times but full arytenoid cartilage abduction can be achieved and maintained.


III


Arytenoid cartilage movements are asynchronous and/or asymmetric. Full arytenoid cartilage abduction cannot be achieved and maintained.


1. Transient asynchrony, flutter or delayed movements are seen. 2. There is asymmetry of the rima glottidis much of the time due to reduced mobility of the affected arytenoid and vocal fold but there are occasions, typically after swallowing or nasal occlusion, when full symmetrical abduction is achieved and maintained.


1. There is asymmetry of the rima glottidis much of the time due to reduced mobility of the arytenoid and vocal fold but there are occasions, typically after swallowing or nasal occlusion, when full symmetrical abduction is achieved but not maintained.


2. Obvious arytenoid abductor deficit and arytenoid asymmetry. Full abduction is never achieved.


3. Marked but not total arytenoid abductor deficit and asymmetry with little arytenoid movement. Full abduction is never achieved.


IV


Complete immobility of the arytenoid cartilage and vocal fold.


Description generally refers to the left arytenoid cartilage in reference to the right. However, this grading system can apply to the right side (i.e., right Grade III-1).


Sub-Grade


there was histopathological evidence of left RLN even in horses with resting laryngeal Grade I and exercise Grade A.50,53 Collins et al, 2009 demon- strated a statistically significant correlation be- tween the severity of the histopathological muscle assessment of the left CAD and the Havemeyer la- ryngeal grade and sub-grades.50 In summary, the well-defined, and universally adopted Havermeyer resting laryngeal grade (Table 2) allows a fair and validated description of the status of a given horse’s respiratory laryngeal function at the time of exam- ination. It broadly and ipsilaterally correlates with the RLN disease process (with the caveat that all horses may have the disease), and has fair predic- tion of laryngeal collapse during exercise. It is worth noting that the laryngeal ultrasound dichoto- mized assessment (i.e., normal vs abnormal) of the echogenicity of the cricoarytenoid lateralis (CAL) muscle has a better sensitivity and specificity and is therefore likely a predictive value of laryngeal col- lapse during exercise.54,55 However, laryngeal ul- trasound should not replace the resting assessment of the larynx given that the luminal side of the larynx is not well evaluated with laryngeal ultra- sound.56 Small or localized luminal side arytenoid chondromas, arytenoid subluxation, and abnormal movements of the arytenoid cartilage are likely to be missed on laryngeal ultrasound, not to mention all other important anomalies such as DDSP, epiglotti- tis, epiglottic abscess, sub-epiglottic ulceration, post- surgical assessment, etc.


90 2016  Vol. 62  AAEP PROCEEDINGS


Generic Deglutitive Examination


Resting evaluation of the protective mechanism of the larynx is another important value of endos- copy. Dysphagia is observed in neonatal foals with apparent nasopharyngeal “immaturity,”57 with congenital or acquired cleft palate,34,38 fol- lowing guttural pouch diseases with extension of the disease or surgical trauma to adjacent periph- eral nerves.27,58–62 Dysphagia is also reported as a complication of various upper-airway surgical procedures such as staphylectomy,63–65 arytenoid- ectomy,66–69 and laryngoplasty (Table 3).15,70–75 Dysphagia is broadly described as nasal regurgi-


tation of feed material or water and tracheal aspi- ration of feed material. Equine practitioners have been increasingly frequently asked to treat horses with swallowing disorders/dysphagia. Its true def- inition is passage of food, saliva, secretions, and/or liquids past the vocal folds into the extrathoracic tra- chea.76 The author has observed (no doubt as have others) that the site of aspiration is different in horses with a cleft palate compared with that seen after a laryngoplasty or arytenoidectomy. Furthermore,dys- phagia after laryngoplasty may be in our estimation due to the following:


1. Failure of the arytenoid cartilages and vocal fold to meet on the midline to protect the trachea


2. Predominant scarring of the left dorsolaryn- geal area that prevents laryngeal elevation


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