While it is recommended to take a Chihuahua to his veterinarian first, a dog with back problems may then be referred to a veterinary neurologist.
The following should be done to diagnose this:
A full and complete physical -
The vet will look for signs of shaking, increased heart and respiratory rates, tenderness to the abdominal region, weakness to the back end, and lameness to any of the legs
(complete blood count and serum biochemistry panel)
Panniculus test -
This is a somewhat non-invasive test in which a small needle is poke into the dog's skin. This is to test the amount of feeling that the Chihuahua has in that area. If he can feel the needle, the skin will react. By moving the needle along the area, a veterinarian can determine which vertebrae are affected.
Proprioceptive deficits testing -
This checks how well a dog is able to recognize the placement of his limbs without seeing how they are manipulated.
Myostatic exam -
more commonly known as the Knee jerk reflex
Deep pain / withdrawal reflex -
Normally if a dog's toe is pinched, he will withdraw his leg. When a dog has a back injury such as IDD, this automatic reflex may be absent.
Radiographs will be able to help a veterinarian determine not only possible slipped discs in the back, but other problems as well including other trauma, cysts, tumors or infection in the spine. When IDD is suspected, the vet will be looking for discs that have calcified (normally they are invisible under x-ray). This normally noninvasive test can be very painful for a Chihuahua with a severe back problem; for this reason having the dog sedated while his body is positioned will be considered.
Many people think of this as the 'dye test'. A safe dye is injected into the dog's body that will allow the neurologist to see the outline of the spinal cord. This is always done before any surgery.
(Magnetic Resonance Imaging) - This is another option that may be used to gain a good view of the dog's spine.