provides a shock absorber function so that during flexion, extension, compression, traction, we’re not putting bone against bone resulting in new bone formation
Intervertebral disc.
the tough circular exterior of the intervertebral disc that surrounds the soft inner core, the nucleus pulposus
annulus fibrosus
This is a process that affects both the nucleus, pulposus, and the annulus fibrosis
Intervertebral disc degeneration
In the nucleus we see a _____________ where we convert that collagenous matrix to cartilaginous tissue
chondroid metaplasia
In ______________ breeds it occurs at a very accelerated rate
Chondrodystrophic
In ____________ breeds, you have less altered nucleus that is creating a bulge in a weakened annulus and so the degree of compression is less
non-chondrodystrophic
Why do degenerate discs herniate and where does this occur?
- see it in the cervical and particularly the lumbosacral spinal cord (greatest potential for flexion/extension)
- we lack the conjugal ligaments that provide reinforcement to the annulus in the thoracic spinal column
- chondrodystrophic breed
- the nucleus underwent a massive herniation event and actually ruptured meningeal vessels
- the animal was euthanized because of a poor prognosis for recovery
- the problem was ascending-descending myelination
leptomeningeal hemorrhage
- chondrodystrophic breed of dog
- not leptomeningeal hemorrhage
- there was a degree of compression that was sufficient to block venous drainage of the gray matter
- loss of blood flow in the GM in the presence of blood
- poor prognosis for recovery
Hemorrhagic infarction
What is the early stage of demyelination?
sheath swelling
If you are caudal to the compression, you are only going to see the change in the amputated portion of the axon and this would be in _______________ pathways, Therefore, you would see this in ventral and ventrolateral funiculi
descending
Cranial to the insult, again, it is only the amputated segments and so this would be an _____________ pathway and the change would be localized to dorsal and dorsolateral funiculi
ascending
The change would be irreversible, but in some instances, with time you can see functional recovery, and this reflects the functional plasticity of neural networks
mild degrees of axonal degeneration
In the non-chondrodystrophic breeds, I am most likely to see simply the ___________ if anything at all.
Wallerian degeneration
an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (i.e. farther from the neuron’s cell body) degenerates
Wallerian degeneration
Cervical Vertebral Instability: You see overgrowth of cartilage during development, and this is in both the appendicular and axial skeleton, the overgrowth can drive degenerative changes because the metabolic support of that cartilage is challenged
osteochondrosis
Ischemic damage to the spinal cord and very prominent white matter changes
Cervical Vertebral Instability -> Overriding vertebral body
- a situation seen in quarter horses
- there is an instability problem, becoming a physiologic response to the instability
- the proliferation of bone and connective tissue that stabilizes the joint
- extensive new bone formation in the dorsal aspect of the vertebral arch, and the effect is to reduce the diameter of the spinal canal, causing a very slowly progressive, compressive insult.
cervical static stenosis
Most likely to be associated with ascending-descending myelomalacia
Herniation of a degenerate intervertebral disc in a chondrodystrophic dog breed
Histological examination of the spinal cord at the level of L3-L4 reveals no significant microscopic lesions. How do you interpret these findings?
the disc herniation reduced blood flow to the spinal cord, resulting in loss of function but not axon degeneration. The loss of function would likely have been reversible with removal of the herniated disc.
