On your schedule today is a 9 year old German Shepherd Dog with a history of struggling to sit and stand. The owners have been noticing signs for about 3 months and think things have been getting worse. This dog is one of your favorite patients and is wonderfully cooperative when in the clinic!

Physical Examination: A little bit of resistance to full hip extension, remainder normal.

Neurologic Examination:
Mentation: normal
Cranial nerves: No worries here!
Gait: mild pelvic limb weakness (paraparesis), no significant ataxia or lameness
Reflexes: reduced withdrawal in the right pelvic limb, all other reflexes and all other limbs are normal.
Postural reactions: normal paw replacement testing in both TL, reduced to normal paw replacement left pelvic limb, reduced paw replacement testing right pelvic limb
Palpation: marked discomfort with tail jack, and direct digital pressure to the lumbosacral region

What do you do next?
I am working on a neurologic examination lab for an IVECCs conference and in this lab the participants will be asked to seek out next steps. So, what do you do? If it was me, I would localize the lesion.

Neuroanatomic lesion localization
If you draw a little stick figure of a dog, you can safely cross off the head and thoracic limbs. We don’t see evidence of cranial nerve deficits, mentation changes or thoracic limb changes. That focuses our gaze on T3-L3, L4-S3 and neuromuscular causes. Working backwards, we can eliminate neuromuscular because we don’t typically see focal spinal pain (only) with painful neuromuscular disease. How do we differentiate between T3-L3 and L4-S3 myelopathies?

Reflexes, you’re right! How were those pesky things? The withdrawal reflex was reduced in one limb, wasn’t it? The withdrawal reflex tests the sciatic nerve (L6-S3). If we have a reflex deficit, we have a problem in the nerve or the associated spinal cord segment. Why the paw replacement deficits? The right leg is easy to explain – the sciatic nerve carries the proprioceptive information to the spinal cord. If there is trouble in the peripheral nerve or the spinal cord segment of that nerve (L6-S3 in this case), we can see delayed proprioception. The left limb doesn’t have evidence of decreased withdrawal, so you’ll have to believe me when I tell you that this is still likely due to sciatic nerve involvement. The sciatic nerve is HUGE so damaging one small part could result in a minor delay of paw replacement without a clinically observable reflex deficit. So, in conclusion, our lesion localization is L4-S3, with a focus at L6-S3, more on the right.

What are your top differential diagnoses?
One of my top concerns for this dog is a lumbosacral degeneration. This typically involves intervertebral disc degeneration, ligament hypertrophy and bone changes including articular facet osteoarthritis and coning of the vertebra. The best way to diagnose this is to do an MRI. That allows us to look at the soft tissues (nerves, disc) and the hard tissues (bones).

A recent study by Medina-Serra et al (2025) showed that over 30% of patients undergoing a spinal MRI had 3 or more painful etiology identified! That means they diagnosed an intervertebral disc herniation, nerve root entrapment and facet disease in 1 patient – each of these can cause pain on their own. They also found a normal MRI in 20% of patients with detectable pain on evaluation. We need to pair the neurologic examination findings, with the physical examination findings (osteoarthritis of the hips? Stifle disease?) AND the MRI findings when trying to sort out what is the root cause of a patient’s pain and how best to treat it. Without the MRI we could have assumed this was osteoarthritis of of the hips. Without a complete physical or neurologic examination, we might have assumed this was only lumbosacral disease based on the MRI.
I don’t have all the answers but hopefully a TidBit of knowledge will help you be proactive for your elderly, large breed dogs with pain BEFORE they progress too far.

If you’d like to read more about this study you can find it here: https://doi.org/10.3390/ani15050761
Thanks for reading! I hope you have a pain free day!