Many of you have been with me for a while on these TidBit Tuesdays. So, today’s case is a toughie. Do you know how to localize this toughie?

Neurologic Examination:
Mentation: BAR
Cranial nerves: all normal
Gait: Paraplegia (no voluntary movement)
Reflexes: reduced withdrawal in both pelvic limbs, poor anal tone, and reduced cutaneous trunci reflex to T13 bilaterally. All remaining reflexes normal.
Postural reactions: Absent both pelvic limbs, normal both thoracic limbs
Palpation: Painful at T12-T13, remainder non painful.
Other: Absent nociception in both medial and lateral toes of both pelvic limbs.

Neuroanatomic lesion localization: What do you think? If you’re not sure how to work through this case, follow the steps below.

1) Does this dog have neurologic disease? Yes! (This may sound like a silly question, but I think it is a good place to start because it make you examine the situation more carefully and not become tunnel visioned.)

2) Are forelimbs and intracranial structures normal? If you said “yes”, then I agree Therefore the lesion is likely caudal to T2.

3) Our choices for lesion localization are T3-L3, L4-S3 or neuromuscular at this point.

4) Are reflexes NORMAL? No! Therefore, the lesion must be where the reflex arc is stationed (L4-S3) or neuromuscular.

5) Sensory neuropathies are extremely rare so an animal with loss of nociception is much more likely to have a spinal lesion than a neuromuscular lesion. Based on that, we can consider this most likely L4-S3 and NOT neuromuscular.

6) But wait! What about that back pain and reduced c. trunci reflex? The cutaneous trunci reflex reflects a T3-L3 myelopathy, and the back pain certainly supports that. Don’t forget that back and neck pain can have neural and non-neural causes so while it supports a T3-L3 myelopathy it shouldn’t be the only sign.

Neuroanatomic Lesion localization: Folks, this is an example of multifocal neuroanatomic lesion localization affecting T3-L3 and L4-S3 spinal cord.

Primary differentials would include acute diseases affecting the spinal cord (such as FCE, disc herniation, trauma) plus spinal shock, or a true multifocal spinal cord disease (such as meningomyelitis or neoplasia).

What is Spinal Shock?

Spinal shock occurs when there a change of the local spinal environment that results in temporary cessation of reflexes caudal from the injury. In most models, the injury is at the TL junction, so the pelvic limb spinal reflexes are temporarily lost. This is transient! For most animals, the reflexes return in 1-3 days if not shorter. It is important to note that there is NO pathology in the pelvic plexus. So, while this looks like a L4-S3 myelopathy, the loss of cutaneous trunci and focal spinal pain is the hint that this might be a T3-L3 myelopathy with a secondary L4-S3 spinal shock. The neuroanatomic lesion localization is correct (multifocal), but the differential diagnoses should include spinal shock.

Predictive Models

How do you know when you have a pet with spinal shock or a pet with a multifocal disease when you have multifocal spinal cord lesion localization? The honest truth is you don't know until you do an MRI and show that only one lesion is present. However, there was a predictive model published several years ago (2022: https://onlinelibrary.wiley.com /doi/10.1111/jvim.16352) that showed smaller breeds, with a history of less than 24 https: As with all predictive models, this isn't fool proof, but it is a start. For the case above, I would strongly consider spinal shock with a T3-L3 myelopathy. Indeed, this is what we had; we had an FCE at T12-L1 on MRI and no additional lesions in the L4-S3 segment.

Hope this TidBit was helpful to your practice! Please reach out if you have a case I can help with, or if you have an idea for a TidBit Tuesday mailer. Happy March Madness!