When things go bump in the spine...
So many interesting cases happened this past week! Please join me today as we evaluate a 4 year old FS Mixed breed 10 kg dog, together. Her presenting complaint was acute onset difficulty walking in the last 24 hours.
Neurologic Examination:
Mentation: BAR
Cranial nerves: all normall
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: Hmmmm....let's take a moment and think this through.
1) Does this dog have neurologic disease? Yes!
2) Are forelimbs and intracranial structures normal? I'd say, yes. Okay, the lesion is caudal to T2.
3) Our choices for lesion localization are, T3-L3, L4-S3 or neuromuscular at this point.
4) Are reflexes affected? Yes. Therefore the lesion must be L4-S3 or neuromuscular. 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 but could be from non-neural causes. Is this multifocal spinal cord?
5) Hold the phone, Barnes. Tell me why this isn't neuromuscular? Okay, I'll tell you. Sensory neuropathies are extremely rare and are usually congenital. Therefore, to have a loss of deep pain this animal needs to have a spinal cord lesion. Moving on then....
Neuroanatomic Lesion localization: Folks, this is an example of multifocal neuroanatomic lesion localization of 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).
What is Spinal Shock?
Spinal shock occurs when there is "reverberation" and a change of the local environment that results in temporary cessation of reflexes downstream 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.
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 recently published (https://onlinelibrary.wiley.com/doi/10.1111/jvim.16352) that showed smaller breeds, with a history of less than 24 hours, are more likely to have spinal shock. 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 February!