I'm sorry to hear about Sadie's condition. I will be helping you with your question.
I understand Sadie was on Lysodren util very recently. Most common adverse effects seen with Lysodren therapy in dogs include lethargy, lack of muscle coordination, weakness, apetite loss, vomiting, and/or diarrhea. Neurologic signs can be seen, but are not common. If these adverse effects are noted, it is recommended to temporarily halt Lysodren therapy and supplement with glucocorticoids like the prednisone you were given. So until now everything that was done is on right tract. Normally if these side effects persist 3 hours after steroids are supplemented, we usually get suspicous of other underlying medical problems.
You mentioned that her left side of the face looks like she had a stroke. It sounds like it may be Horner's Syndrome. Horner's syndrome is a common neurological disorder of the eye and facial muscles. There are many reasons for Horner's Syndrome. The dysfunction may be caused by damage to the nerves. This may be due to an injury such as a bite wound or blunt trauma, a tumor or herniated vertebral disc. Middle or inner ear disease can also cause Horner's Syndrome.
Most cases of Horner's Syndrome will resolve spontaneously. It is important to treat any underlying disease. There are several diagnostic tests that can be performed by a neurologist to determine if there is an underlying cause in your pet.
If you have any other questions please ask me. I'll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and I wish Sadie speedy recovery.