It's Monday morning, and your first case is presenting for "not walking well". Let's review some neuroanatomic lesion localization so you can be awesome on a Monday morning!

Signalment: 4 year old FS Labrador X
History: The dog was outside playing in the backyard last night when suddenly she yelped and fell over. The owners use this dog for sport as well as for a pet, so she is known to be a very stoic dog. Right away they worried about pain because she vocalized. It was apparent that she couldn't walk back into the house, so they put her on a blanket and carried her inside. She was able to stand up but couldn't use her right front or right rear leg normally. They gave her dinner (which she ate) and allowed her to rest until the visit today. (Why didn't they take her to ER? I don't know...I'm just the neurologist!)

Physical examination on presentation was unremarkable. (Yes, you examined her stifles, and they appear stable).
Neurologic examination:
Mentation: BAR, very excited to see you (she's very excited to see EVERYONE)
Cranial nerves: all normal (high five for doing a full cranial nerve exam!)
Gait: She has an ambulatory right hemiparesis, with frequent falling to the right. She is able to walk 5-6 steps, unassisted, before falling or having her right limbs slide out. Note, the definition of ambulatory is the ability to walk a minimum of 5 unassisted steps IN ALL LIMBS.
Reflexes: No withdrawal reflex in the right front leg, absent bicep and triceps reflexes right front leg. The reflexes are normal in all other limbs
Postural reactions: Absent paw replacement right front leg a right rear leg. Normal paw replacement in both left front and left pelvic limb.
Palpation: No signs of pain on palpation or cervical ROM.
Nociception: She has motor in all four limbs, so you do NOT need to test nociception (deep pain)

Neuroanatomic lesion localization: Right C6-T2 myelopathy (spinal cord)

Why? We know the dog is mentally normal and has normal cranial nerves. She does not have a seizure history therefore there is no evidence of intracranial disease. You can cross that body part off. Therefore, the lesion must be caudal to the foramen magnum. A forelimb AND pelvic limb are affected which means this lesion must be cranial to T3. If the lesion was caudal to T3, only a pelvic limb, or limbs, should be affected. That narrows our window of concern to C1-T2, correct? From there, you need to evaluate the reflexes. If they are normal, the lesion is likely C1-C5 but in rare situations it is C6-T2. Normal reflexes aren't super useful to narrow this window further. However, she has reduced to absent reflexes in the right front leg. Reduced to absent reflexes suggest a lesion in the reflex arc itself, which is located C6-T2 in most dogs. Why did I say this was a spinal cord, not a peripheral nerve injury? If you guessed it was because the pelvic limb on the same side was affected you'd be correct! The long tracts (paw replacement testing, upper motor control) going to or from the pelvic limb must travel through the C6-T2 part of the spinal cord. If the dog has sustained damage to the spinal cord, the tracts to the pelvic limb should be affected. If the nerves to the front leg are damaged peripherally (i.e. with brachial plexus injury) the pelvic limb should be normal. You did it!

Differential diagnoses: This dog has an acute onset, non-painful spinal cord disease. I would include an FCE, AHNPE (acute hydrated nucleus pulposus extrusion) and possibly at Type I disc herniation on the top of my list. As we learned last week, we cannot ever take meningomyelitis off the list so that goes on the list, but lower. Lastly, although trauma wasn't witnessed, this was an acute onset disease, so trauma goes on the bottom of my list until proven absent.

We performed an MRI and diagnosed her with a suspected FCE. She entered rehab and supportive care and is doing well! With mobility and deep pain present, she is likely to make a good recovery but may not have completely normal mobility in the front right limb because the plexus was involved.

Did you enjoy this case? Did you find it difficult? Please let me know if have any topics or a lesion localization case that you wish I'd cover on a TidBit Tuesday. Have a great week!