Idiopathic trigeminal neuritis is the most common neurologic cause of acute, flaccid mandibular paralysis, or “dropped jaw.” The pathology affects primarily the mandibular branch (i.e., motor efferent to the muscles of mastication) of the trigeminal nerve; however, the sensory afferents can also be affected. Microscopically, idiopathic trigeminal neuritis is described as a bilateral nonsuppurative neuritis mainly associated with demyelination and, less commonly, axonal loss. It occurs most often in middle-aged or older dogs and occasionally in cats. (Because the condition is rare in cats, this article discusses dogs only.) The condition is self-limiting and completely resolves in 2 to 6 weeks with supportive care alone.
We ran blood tests and urine tests and no other issues came up, the vet felt an x-ray wouldn't show us anything helpful, so we didn't proceed. We were told, among other things, to take her home and feed her pre-moistened food and watch for signs of dehydration etc. And to expect it to just disappear in 1-9 weeks (which, yes, is different from the description above - I guess she wanted to prepare me just in case).
But I have to say that I think Eco's pretty much better already after 8 days. Today she crunched her kibble again, and she played with her toys and even tried a little bit of tug - which he hadn't done for the past week. Although at times she still has her mouth open, it's not as severe as it was last week and I'm so grateful that she's well on her way to healing. She doesn't look so silly slack jawed with her teeth showing like she's about to say something silly.
I asked the vet if dogs continue to have this affliction and she said that everything she's seen indicates it only happens once in their lifetime. Good. Now that we have that over with we can carry on with normally healthy Labrador life! Why it happened to a 3 year old dog I'm not sure, but I'm just glad she's on the mend. Thank you for your support and well wishes, much appreciated!