Neuro Corner Answers
Dr. Andrew Isaacs
DVM Diplomate ACVIM (Neurology)
Dogwood Veterinary Referral Center
Primary interests include intervertebral disc disease, seizure management, luxations/fractures of the spine, and surgery for brain tumors
Question
LINDA WANTS TO KNOW MORE:
How many do you see with the rear legs affected by nerve root signature pain vs. the front legs?
ANSWER
“Root signature” is a term used to describe outward signs an owner or veterinarian would see secondary to irritation of the nerve roots. “Nerve roots” is a term referring to the anatomical origin of the nerves as they arise off of the spinal cord. Basically, you can think of the nerve roots as the beginning of the nerve that comes off of the spinal cord and travels down the leg. There are nerve roots in both the neck and the lower back that go to the thoracic and pelvic limbs respectively. If the nerve roots are irritated it will cause the dog to hold up the leg as if painful and can mimic a lameness.
We do see root signature in both the pelvic and thoracic limbs, but it is more common in the thoracic limbs (front legs). The reason is due to the fact that it is more likely to have a disk rupture in the cervical spine versus the lower lumbar spine.
The majority of the time lameness is due to an orthopedic disease and not a neurological disease. However, if an orthopedic cause cannot be identified, “root signature” should be considered.
There are several things that can irritate the nerve roots and cause “root signature,” but the top two are herniated/protruded intervertebral disks and tumors. If “root signature” is suspected in your dog, the two ways to proceed are either conservatively with rest and medications or to have advanced imaging performed to identify the exact cause. This decision depends on multiple variables including history and exam findings (severity of pain and concurrent neurological deficits) and is best discussed with your veterinarian.