Response from the Fenway Friesian Foundation that is working on the genetics of Friesian Megaesophagus:
Laurie- that’s interesting. I believe this would make only the 3rd or 4th case of megaesophagus I’ve personally seen where the dilation is only in the cervical esophagus (not affecting only the thoracic portion or esophagus).
We see poor motility of the pylorus (the muscle that controls the exit of the stomach) in horses with gastroparesis and we see a fair number of horses that have both megaesophagus and gastroparesis.
The foam in the esophagus we see often too. I believe it is latherin, which is a protein in sweat and it’s also present on saliva in order to help lubricate the saliva during chewing.
Was the larynx paralyzed on only the left side? That is what you’d commonly see with roaring. We are growing curious about the larynx after seeing horses with megaesophagus have bilateral laryngeal paralysis, which is apparently quite rare vs. just having one side paralyzed. We can’t attribute the bilateral paralysis to anything else you’d typically be able to tie it to such as guttural pouch mycosis, EPM, or toxicity from exposure to chemicals like herbicides, pesticides or fertilizers.