Mucopurulent respiratory secretions in nasopharynx

Usually from the lungs i.e. not a sign of nasopharyngeal disease. Occasionally from guttural pouch or tracking caudally from sinus drainage angle. 

Pharyngeal lymphoid hyperplasia 

Multiple large lymphoid follicles in nasopharynx are very common in young horses. Follicle size regresses with maturity, normal adult horses usually have small follicles. Pharyngeal lymphoid hyperplasia once believed to cause "poor performance" – THIS HAS BEEN DEFINITIVELY DISPROVEN. With respiratory infections (in all age groups) these follicles enlarged, especially in dorsal pharyngeal recess. 

Nasopharyngeal Collapse 

Dynamic endoscopy will occasionally show airflow obstruction and noise due to nasopharyngeal collapse of unknown aetiology. No specific treatment. 

Cleft palate 

Is a rare developmental disorder; usually affecting the caudal aspect of the soft palate, occasionally hard palate. Signs include nasal discharge containing food (milk), cough immediately after suckling +/- signs of aspiration pneumonia to being asymptomatic with smaller defects. Endoscopy will show defect in caudal soft palate. If hard palate involved, see by direct oral examination. Surgical correction is v. difficult, often unsuccessful and poor prognosis for athletic career. 

Intermittent dorsal displacement of the soft palate (DDSP), “gurgling" 

Affects horses at very strenuous exercise e.g. racehorses, eventers, up to 20% prevalence in racehorses. The horse is an obligate nasal breather and the caudal (free) margin of the soft palate should normally be positioned tightly underneath the base of the epiglottis. If the soft palate displaces dorsally to epiglottis, this will cause airflow obstruction (mainly expiratory) with the production of loud abnormal gurgling expiratory and inspiratory noises (but up to 30% of DDSP horses are ‘silent’ displacers) and reduced exercise performance – horses may slow down or even pull up.

The only way to definitively diagnose DDSP is by dynamic (overground or high speed treadmill) endoscopy. Displacing palate transiently during resting endoscopy is NOT a good indicator that DDSP occurs at exercise (unless permanently displaced). Some DDSP affected horses may have endoscopically visible ulceration of caudal border of soft palate, induced by abnormal epiglottic - soft palate contact during work. 

Proposed aetiologies and associated treatments for DDSP:

1. Primary dysfunction of intrinsic palate muscles (palatinus, palatopharyngeus)o Try to fibrose (stiffen) palatal tissue e.g. thermal cautery of oral aspect of palate, laser cautery of nasal side of palate, oral palatoplasty (‘Ahern’ procedure)

predisposed to by unfitness or lack of ability, e.g. a horse running outside its distance or class. o Conservative tx e.g. rest, improve fitness.

Permanent DDSP 

Permanent DDSP is very rare compared to intermittent DDSP. Often secondary to other disease e.g. epiglottic entrapment, or, sub-epiglottic cysts. Others are due to congenital or acquired neuromuscular dysfunction of the soft palate or epiglottic muscles. Affected horses make loud and continuous gurgling noises at rest or at low level of exercise and may be mildly dysphagic. Endoscopy shows the soft palate permanently displaced above the epiglottis. Use oropharyngeal endoscopy and/or digital examination to examine epiglottic area. If not secondary to epiglottic entrapment - perform a tie- forward +/- staphylectomy. 

Epiglottic entrapment 

Seen particularly in Standardbreds (high incidence epiglottic hypoplasia) and occasionally in Thoroughbreds. The rostral (free) aspect of the epiglottis becomes trapped in a pouch of mucosa that develops from the mobile sub-epiglottic mucosa. Entrapment may be permanent/intermittent/exercise induced. If permanent, entrapping membrane and possibly the epiglottic cartilage may be swollen and ulcerated. Permanent or intermittent DDSP often occurs secondary to epiglottic entrapment. Airflow obstruction and abnormal expiratory noises occur as air fills the pouch during expiration. Endoscopy: an entrapped epiglottis loses normal flat, serrated appearance and become rounded, thickened, reddened or ulcerated. Additionally, the normally prominent blood vessels on its dorsal aspect of epiglottic cartilage are now not visible. If DDSP is present, oral endoscopy or digital oral examinations under sedation of value and lateral pharyngeal radiography can be used to assess epiglottic length. Treat by sectioning the entrapping membrane per nasum or per os using hooked bistoury (long curved hook knife) per nasum or per os or transendoscopic laser, standing or under GA. Alternatively, resection or midline division of entrapping membrane via laryngotomy under GA 

Subepiglottic cysts 

Rare congenital structures, mainly in Standardbreds. They can deviate epiglottis dorsally causing airflow obstruction and possibly dysphagia, depending on the degree of epiglottic distortion. On endoscopy may see cyst or just epiglottic tip at an abnormal angle, (cyst may be hidden under soft palate). Surgical excision per os or via nasopharyngeal laser surgery. 

Epiglottic retroflexion 

Occasionally, an abnormally dorsally angled epiglottis may be observed in resting horses, without the presence of a subepiglottic cyst. Rarely seen as dynamic disorder during high speed treadmill endoscopy where epiglottis sucked back towards laryngeal lumen. Causes abnormal resp noise +/- poor performance. Currently no effective treatment available. 

Aryepiglottic fold dispalcement 

The mobile folds between the arytenoids and epiglottis will sometimes become diplaced medially into airway during fast work and cause turbulence and noise. They can be partially resected by transendoscopic laser or trans-laryngeal surgery – good prognosis 

Recurrent laryngeal neuropathy (RLN), idiopathic laryngeal hemiplegia (LH), idiopathic laryngeal hemiparesis, "roaring", “whistling”, laryngeal paralysis.

This is the most important URT airway obstruction of the larger breeds, especially TB's, TB crosses, Warmbloods and draught horses and, conversely, it is very rare in ponies. Terminology of this condition is confusing, but recurrent laryngeal neuropathy (RLN) is correct as it refers to both partial and total unilateral laryngeal dysfunction. 

Unilateral idiopathic degenerative neuropathy of the left recurrent laryngeal nerve which innervates the intrinsic laryngeal muscles. Loss of adductor dysfunction occurs first but causes no clinical signs, but adductor muscle dysfunction i.e. of the cricoarytenoideus dorsalis (CAD) causes an inability to fully open the larynx during exercise. Occasionally unilateral laryngeal paralysis, (left or right sided) is caused by guttural pouch mycosis or damage to the recurrent laryngeal nerves at some other site, e.g. in the cervical area, due to a perivascular irritant injection, cervical or intra-thoracic tumour, post oesophageal or thyroid surgery.

•   History - the type of noise and its onset in relation to fast work. RLN may be progressive in some cases.

•   Affected horses make an abnormal inspiratory noise (‘whistle’ or ‘roar’) at exercise plus possibly poor exercise performance.

•   Palpate the dorsal laryngeal area for evidence of laryngeal muscle atrophy.

•   Endoscopy at rest, including during nasal occlusion and after inducing swallowing (see maximal abduction after swallow). Evaluate for asymmetry and asynchrony. Laryngeal function graded

  from 1= normal to 4 = total hemiparesis.

o DO NOT EVALUATE LARYNGEAL FUNCTION IN SEDATED HORSE o Always check for evidence of prior laryngeal surgery endoscopically

•   Listen to respiratory sounds during fast exercise.

•   Treadmill or Overground endoscopy is optimal – can see what actually happens to the larynx

  during exercise or those where history and resting endoscopy do not correlate.

•   Ultrasonography of the ipsilateral cricoarytenoideus muscle can show characteristic changes 

RLN Treatment 

• Mild cases/ horses doing light work; Perform a vocalcordectomy or ventriculectomy ("Hobday's operation"), or ventriculocordectomy to prevent vocal fold obstruction at work surgically or using a transendoscopic laser

•   Severe cases need Laryngoplasty (tieback) – a prosthesis mimics action of CAD muscle to permanently abduct the left arytenoid. Complications include loss of surgical abduction, coughing due to aspiration tracheitis (rarely pneumonia) due to lack of adduction during swallowing, postoperative wound infections.

•   Other options (rarely used in UK) include arytenoidectomy, laryngeal re-innervation using nerve- muscle pedicle graft from omohyoideus and branches of C1, tracheostomy (tube or surgical) or retire to a less athletic pursuit! 

0. Bilateral laryngeal paralysis
   

0. Uncommon. Causes: hepatic encephalopathy, organophosphate or lead poisoning, after general anaesthesia. Can cause life threatening airway obstruction therefore temporary tracheostomy should be performed and the underlying cause treated if possible. 

0. Arytenoid chondritis 

0. Common in USA, rare in UK – does racing on dirt predispose to it? Endoscopically see swollen, reddened arytenoids unilaterally or bilaterally, possibly mucosal ulceration, granulomas or draining sinus tracts and reduced motility. This disorder can resemble RLN due to laryngeal asymmetry present. Treatments include long term antibiotics and if unsuccessful a partial or total arytenoidectomy. 

0. Laryngeal Dysplasia (Cricopharyngeal - laryngeal dysplasia" or "rostral displacement of the palatopharyngeal arch, 4th branchial arch defects)
   

0. Rare congenital abnormality with variable abnormal/missing cricopharyngeus (upper oesophageal sphincter mm), thyroid and cricoid cartilage unilaterally or bilaterally. Some affected horses have abnormal respiratory noises, possibly poor performance even belching/colic due to aerophagia. Laryngeal palpation reveals a space between cricoid and thyroid. Endoscopically may see collapse of palato- pharyngeal arch over the dorsal arytenoids, reduced movement of arytenoid on affected side – often (the right side). Radiography (unsedated) shows air in proximal oesophagus. Ultrasonography can confirm the cartilaginous defects. 

0. Abnormal respiratory secretions in trachea and bronchi and assessment of mucosal changes: 

0. These provide an accurate assessment of presence of pulmonary disease - see medicine notes 

0. Tracheal cartilage nodules: 

0. Small, white nodular cartilaginous protrusions sometimes visible endoscopically on the luminal aspects of tracheal cartilages. Not clinically significant. 

0. Tracheal collapse: 

0. Occurs in small pony breeds and donkeys. Affected ponies show stridor, dyspnoea, exercise intolerance or may be undiagnosed due to the low workload of these animals. Caused by a cartilage deformity and/or degeneration of dorsal trachealis ligament that may cause separation of the tracheal mucosa from dorsal ligament. If problem, is in the cervical trachea this causes an expiratory obstruction (and noise) whilst intra-thoracic obstructions cause and expiratory obstruction. The tracheal collapse can be diagnosed endoscopically or radiographically. Treatment includes external tracheal stenting if the defects are all cervical (rare) or intra-luminal stents. Surgery is difficult and expensive and not always successful and usually best to try conservative treatment by keeping affected ponies quiet and rested during clinical episodes. 

0. Post tracheostomy airway obstruction:  

0. Airflow obstruction may occur due to the development of excessive granulation tissue at the surgical site, or from inward collapse of completely transected tracheal rings once the tracheostomy tube is removed. Tracheal fistulas also occur rarely. 

0. Tracheostomy
   

0. There are three basic types of equine tracheostomy including temporary tracheostomy which is usually an emergency procedure where a smaller diameter tracheostomy tube is inserted, usually for a matter of days, to bypass an acute upper airflow obstruction. Permanent tracheostomy or permanent tracheal fistula are elective procedure where a larger metal tracheostomy tube or a stoma is used to bypass a permanent upper airway obstruction.