Epiglottic Retroversion

Epiglottic retroversion is a rare cause of upper airway dyspnoea that occurs when the epiglottis does not maintain its position and flexes dorsally and caudally obstructing the rima glottidis. The condition was first reported in two dogs in 2009 (Flanders and Thomspon, 2009) with a more recent series of 24 dogs reported (Skerrett et al, 2015). The condition has also been reported in humans (Zalzal et al, 1987; Woo, 1992) and horses (Parente et al, 1998; Terron-Canedo and Franklin, 2013). In all species, the signs are similar and range from abnormal respiratory noise with exercise intolerance to severe dyspnoea.

In humans, the condition is also known as epiglottic prolapse or collapse and occurs as part of an upper respiratory tract obstructive syndrome called laryngomalacia, which has two distinct forms of either congenital or adult-onset. Congenital laryngomalacia generally spontaneously resolves by the second year of life, whereas adult-onset laryngomalacia may be either idiopathic or secondary to head and neck surgery or central nervous system trauma. The treatment for severe adult-acquired epiglottis prolapse is usually with either epiglottopexy or epiglottectomy.

Of the 27 dogs reported in the literature, 10 dogs were Yorkshire terriers with a variety of other breeds reported. Sixteen of the reported 27 dogs were over 8 years of age at initial diagnosis. No definitive cause for epiglottic retroversion in dogs has been determined. The majority of cases (19/24 dogs) in the case series reported by Skerrett et al (2015), were classified as secondary epiglottic retroversion as there was concurrent or historical upper airway disease such as elongated soft palate, tracheal collapse, laryngeal collapse, bronchial collapse and laryngeal paralysis. These conditions are likely to cause increased negative inspiratory pressures which could then affect epiglottis position. Primary epiglottic retroversion where there are no significant concurrent airway problems has been reported in a minority of dogs in the literature. These dogs typically present with intermittent clinical signs precipitated by stress or exercise (Skerrett et al, 2015). In these dogs, it would seem more likely that there is a primary problem with the structure or function of the epiglottis that prevents it from maintaining a normal position when there is an increase in physiological negative inspiratory pressure.  [...]