Diagnosis and Surgery of Alar Fold Collapse in Horses

From 1998 to 2013, 478 harness racehorses, 12 Thoroughbred racehorses and 2 Icelandic horses were referred to the Norwegian School of Veterinary Medicine and underwent a comprehensive, standardized dynamic evaluation of nasopharyngeal, laryngeal, and nostril regions on a high-speed treadmill (1). Twenty-five horses from this population were diagnosed with bilateral AFC and received alar fold (AF) resection surgery. AFC was diagnosed when a continuous abnormal expiratory vibrating flutter noise coincided with visible inspiratory filling of the nasal diverticulum throughout the exercise test, and when temporarily suturing the AFs in a dorsal position alleviated these signs. Surgery involved complete resection of both AFs, including three to five cm. of the ventral conchae to avoid any pocket formation at the bottom of the diverticulum nasi (2). The owners and/or trainers of all of the included horses were contacted by telephone, and racing records were obtained from the national official race statistics.

Presenting complaints according to the owners/trainers were poor performance (#7), abnormal respiratory noise (#10), or both (#8). Three of the 25 horses had previously undergone partial AF surgery, but the owners/trainers were not satisfied as the horses still had abnormal respiratory noise and perceived poor performance. The 25 AFC affected horses were from two to eight years of age at the time of surgery (mean 4.3 years). Seventeen horses (68 %) were male, nine stallions and eight geldings, and eight (32%) horses were female. Twenty-one horses (84 %) were Standardbred horses, two were Coldblooded trotters, one was a Thoroughbred racehorse and one an Icelandic stallion used in high-speed gaited competitions. Ten of the Standardbreds, or 40 % of all horses in the study, were also diagnosed with intermittent dorsal displacement of the soft palate (iDDSP). Eighteen of the 25 owners/trainers stated that the abnormal respiratory noise from the nostrils improved after resecting the AFs and that twenty of 25 horses had excellent cosmetic results. Twenty of 25 horses continued racing or competing after surgery. Fifteen horses (75 %) of these 20 horses improved their mean kilometre racing time performance demonstrating a beneficial effect of AF resection. Five horses did not return to racing after AF surgery for reasons not related to AFC. Nasopharyngeal pressure was measured preoperatively (baseline and after tying open the alar folds) in five of the horses, and when racing again post-operatively in three of these horses. Our data demonstrates that AFC creates a dynamic expiratory obstruction (mean +33.5 cm H2O). Tying open the AFs returns expiratory pharyngeal pressures to the normal range (mean +19.6 cm H2O) and complete surgical resection seemingly improves the expiratory nasopharyngeal pressures further (mean +15.0 cm H2O). Since iDDSP also creates a dynamic expiratory obstruction, and was diagnosed in 40% of the horses in this study, it is interesting to speculate whether there is a physiologic association between these disorders due to the restriction of airflow in the region of the nares. Nasopharyngeal pressure measurement shows promise as an objective test to screen horses for AFC.