Alterations in equine guttural pouch morphology with head position: observations using a new technique for producing accurate casts.

ABSTRACT

BACKGROUND: An improved technique for preparing casts of the equine guttural pouch is described. The new technique is simplified and inexpensive in comparison to previous techniques and produces highly accurate anatomic models which are both durable and flexible. METHODS: Silicone rubber bathtub caulk was injected into the guttural pouches of horse cadavers. The silicone was allowed to cure overnight, and casts were removed by dissection. The new technique was then used to evaluate changes in the shape of the guttural pouch with changes in head position. RESULTS: With flexion of the atlanto-occipital joint, the lateral compartment of the guttural pouch in particular was found to change considerably in size in shape. The angle of inclination of the ventral border of this pouch increased with flexion, as did the depth of the impression made by the rostral portion of the stylohyoid bone. In addition, the lateral compartment diminished in thickness rostrally in casts from flexed animals. CONCLUSIONS: The viscous silicone caulk resulted in superior casts of the equine guttural pouch. Observations of changed pouch shape with head position agree well with previous reports of increased difficulty in draining the lateral compartment of the horse's guttural pouch when the head is held in the flexed position.