Laryngeal hemiplegia (LHP, also known as ‘Roarers’), Laryngopalatal dislocation (DDSP or Displaced Soft Palate), epiglottic entrapment (EE), abnormal alar folds (false nostril noise) and persistent lymphoid hyperplasia (PLH) are the most common conditions causing dynamic upper respiratory tract obstruction resulting in poor performance in horses.
Examination of the horse
Careful examination of the horse’s upper respiratory tract by endoscopy, assessment of respiratory noise made by the horse, either by observation on the racetrack or treadmill, thorough questioning of the rider as to the sequence of either loss of performance or commencement of any respiratory noise, are all important for a full clinical assessment.
Almost all yearlings scoped for yearling sales exhibit some lymphoid hyperplasia. Its persistence beyond the breaking in period, early training and early 2-year-old racing, affects the young horse and may lead to the further development of soft palate problems.
False nostril noise is common and not considered significant unless associated with poor performance. Surgery is indicated if positive improvement occurs with false nostril tie back. Recently, the use of stick-on nose bands appears to alleviate this problem.
Inspiratory noises are associated with mechanical or functional interference to the upper airway, for example chondritis (inflammatory changes to the throat cartilages), and narrowing of the larynx (LHP). ‘Whistling’ or ‘roaring’ noises are heard on inspiration only, during fast exercise. Surgery can improve these conditions.
Expiratory noises, or gurgling sounds, can be very inconsistent but are most frequently associated with entrapped epiglottis (EE) and laryngo-palatal dislocation (dorsal displacement of the soft palate or DDSP). These are difficult problems with subtle subclinical variations and evaluations should include the use of figure 8 head stall (drop over nose bands), tongue tie and careful assessment of noise character, and any changes of noise associated with changes in head carriage. Treadmill evaluation improves diagnostic assessment.
Surgery is at best 50% successful. Most recent scientific research indicates that DDSP (soft palate problems) are related to inflammatory (infectious) changes within the inside walls of the guttural pouches.
Surgical correction of LHP, DDSP and EE must initially be evaluated on the degree of noise, level of fatigue and poor performance, previous racing performance, the economic status of both horse and owner, and the presence of other factors, such as leg lameness.
Other upper airway conditions
Other less common conditions occur. Deviation of nasal septum is diagnosed on endoscopic examination; surgical correction often leaves high residual noise levels. Sub-epiglottic cysts, cleft palate, guttural pouch infection, hypoplastic epiglottis and arytenoid chondritis all reduce the horse’s ability to accommodate high rate airflow and therefore lower performance.
Diagnosis of upper airway conditions
The use of standard exercise testing by means of high-speed treadmills, simultaneous examination of dynamic airway function by endoscopic examination, as well as radiographic evaluation of the epiglottis, nasal passage and assessment of septal deviation are all becoming essential for the diagnosis of upper airway dysfunction.