It's been ten days since we started Pasta on medicine for low levels of thyroxine in her blood, which is one possible cause for the slight drooping on the left side of her face that appeared suddenly about two weeks ago.
We were originally going to take her in for an MRI at the recommendation of one of the vets who examined her, but after I received a nice, informative email from Dr. Bart De Ridder in Belgium following my original post about Pasta's condition, I did more background research on possible causes for partial nerve paralysis in dogs, and I realised that a blood test we had done for Pasta about a month before the condition manifested indicated low levels of thyroxine, which is a hormone produced by the thryoid gland.
Upon reading more on the subject, I learned that low thyroxine level is a possible, and frequent, cause of facial nerve problems in many types of dogs as they grow older, including golden retrievers. We consulted the senior vet the next day, and showed him the test results. He concurred that it was better to try addressing the low thyroxine level first, and then move on to an MRI later if required.
So far, there's no apparent change in the facial droopiness, but it does seem like Pasta is more energetic than ever. She's taking long walks and bouncing around like a puppy, so she seems completely healthy but for the slight problem with her left eye.
Time will tell if the thyroid medication will eventually help resolve the facial nerve issue, but in the meantime, Pasta's having a great time.