In summary for this case so far, we have a sudden onset and a dog with poorly ambulatory paraparesis, normal spinal reflexes suggesting a T3-L3 lesion, a right sided panniculus cut-off near L3 suggesting a T13-L1 lesion.
You can use the VITAMIM D acronym to think about the possible differential diagnosis and I have done this for you in the attached slide. When you do this, remember that it is crucial to take into account the speed of onset and the progression. For example, a stroke will have a very acute onset. So if your dog has a slow onset (say over 3 days) a stroke is out! Etc etc for all the various categories of diseases.
Perhaps have a look at this list and see which disease you would go for! I have circled in green those that may / may not be more or less likely but every thing is possible! You can also consider what tests you would recommend.
I will finish the case tomorrow.
Thanks for joining. Best wishes. Nicolas