many research studies into compression of the spinal cord and its’ effect in dogs and the amount of compression and the length of time of compression to cause nerve death is well known. Figs 1-3. We know that removal of the compression by decompressive surgery such as a hemi-laminectomy in the lower back or a ventral slot procedure in the neck must be done within the peracute time frame to be most effective. The purpose is to restore the neurons so that they do not die. So, a pet which “Goes Down” peracutely has compression on the spine that if alleviated within the first 24 to 48 hours can expect with a 95% chance of returning to a state of near normalcy. With this early surgical decompression, the average number of days until the pet is walking again is 14 days. If the pet has lost Deep Pain Perception (DPP) the prognosis drops to 50% of the pets returning to functional status. What was not known until recently is that Stem cell therapy with decompressive surgery greatly increases the chances of recovery.
A 95% chance of recovery with surgery in the peracute stage is a much better outcome than the “functional recovery” that happens when surgical decompression is not done. Decompressive surgery has been the mainstay of veterinary therapy and many veterinarians recommend euthanasia for “down” pets that cannot have this surgery. Decompressive surgery can be performed with benefit however in any of the stages of spinal cord injury even in chronic cases. Spinal cord injury occurs in two stages that span the peracute and acute time frames. The first stage is the direct injury from the force of the compression that causes immediate cell death, swelling, hemorrhage, restricted blood flow, inflammation and pain. The second stage results from damage due to reduced cellular life support functions, poor blood flow, inflammation, production of free radicals, hyper-excitability and exhaustion of the neurons ability to “fire”. In addition, there is a production of chemical mediators that eventually will impair healing and regeneration of the neurons. See Figure 5. Counteracting these effects in the peracute and acute phases of damage is crucial in determining the future of the restoration to function.
Before the advent of stem cell therapy the outcome for pets receiving traditional medicinal care for cervical disc disease was 50% to 70% returning to functional walking while 30% of these cases relapse and 18% are considered medical failures with no return to functional walking. When the IVDD occurs in the lower back with loss of function to the rear legs, 55% return to function with medical therapy alone yet 31% relapse with 14% considered medical failures. Stem cell therapy is an opportunity to dramatically change these statistics by increasing the number of neurons that survive the IVDD compressive event and fostering regeneration, re-myelination, and restoration of function of the spinal nerves.
Refer to Figure 5. Notice the area in the center of the spinal cord that is surrounded by a ring of connected astrocytes. This central area contains inflammatory cells and chemical mediators that kill the neurons and eventually form the glial scar that prevents migration of healing axons and neurons through this area. There is poor blood flow and swelling of the entire spinal cord. Neurons are dying, axons are severed, axons have lost their myelin sheath. The glial cells are dying (astrocytes and oligodendrocytes) and chemicals are being released that inhibit myelin from reforming and prevent healing of the axons. Note that some neurons and axons do however survive.