Intervertebral Disc Disease (IVDD)
IVDD is generally classified as either Type I or Type II. Before explaining the difference between the two, let me start by explaining the anatomy.
The canine spine is made up of various vertebrae: 7 cervical (neck), 13 thoracic (mid back, what the ribs attach to in the back), 7 lumbar (lower back), 3 sacral (pelvic) and caudal (tail-this number varies by breed). In between these vertebrae are the discs. The only exceptions are between the first two cervical vertebrae, there is no disc and the three sacral vertebrae are fused, so have no discs in between. The outside of disc (annulus fibrosus) is fibrous and surrounds a gelatinous center (nucleus pulposus). Intervertebral disc herniation refers to the displacement of a part of the disc. Herniations can arise from trauma, but most often are due to degeneration of the disc.
HANSEN TYPE I:
Typically occurs in chondrodystrophic breeds (short legs/long body) such as dachshunds, bulldogs, corgis, pugs, Basset hounds, and beagles
Acute rupture of the disc material beyond the annulus and into the spinal canal
Clinical signs are acute and painful
HANSEN TYPE II:
Occurs in any breed but is more common in non chondrodystrophic dogs 7 years of age and older
Age-related, gradual, degenerative process
Disc material is displaced from the disc space, but contained within an intact annulus, may be compressive or non-compressive
Clinical signs are slow and progressive
In order to picture the difference between Type I and Type II, think of a Boston Creme donut (my favorite). The donut itself is the outside of the disc (annulus fibrosus) and the creme is the inside of the disc (nucleus pulposus). In Type I IVDD, the creme squirts outside of the donut and into the surrounding area. In Type II IVDD, the creme stays inside the donut, but the donut is no longer round, either the whole donut is flattened/widened or a portion of it is. Did that help you visualize? I hope so, but now I want a donut!
Clinical signs may progress in the following order and they return in the reverse order:
Ataxia (trouble walking)
Conscious Proprioception (CP) deficits, the dog does not place limbs correctly, may “knuckle” the foot or scrape toes when walking because they have lost the position sense of the foot.
Motor deficits/weakness
Sensation deficits
Loss of deep pain sensation
In Type I IVDD there is an acute rupture, so this an urgent situation and the dog should be assessed by a veterinarian immediately to determine if surgical intervention is necessary. If the dog still has deep pain intact, there is generally a good outcome with surgery. However, a longer delay in surgery could lead to progression of symptoms. The longer the spinal cord is compressed by either disc material, swelling, or both, the greater risk of long term damage.
There are two areas that are most commonly affected, the cervical and the thoracolumbar regions.
Cervical (neck) disc disease:
Commonly affects chondrodystrophic breeds (dachshunds and beagles at highest risk).
C2-C3 is most commonly affected.
Neck pain is common and often the only sign. This presents as the dog carrying the head low, stiffness or decreased range of motion in the neck, vocalizing, and spasms in the neck muscles.
There may be a front limb lameness if the nerves are affected.
Severe cases may demonstrate ataxia, CP deficits, and/or weakness of the limb(s).
Thoracolumbar (lower back) disc disease:
The most common site is T12-T13 to L1-L2, but other areas may be affected.
10% of dogs have back pain with no neurologic deficits.
Signs: reluctance to jump, run, or climb stairs, lower back may be rounded
Neurologic signs may range from mild ataxia of the hind limbs to having no motor control to even stand. They may have urinary or fecal incontinence.
Neurologic signs may be on both sides, or only one side, depending on how the disc material is extruded.
In severe cases, myelomalacia may result. This is a syndrome where the spinal cord is damaged above and below the initial site and could lead to respiratory arrest.
DIAGNOSIS
Differential diagnosis can be made from the examination, however definitive diagnosis requires imaging; usually MRI is recommended. From the MRI the veterinarian is able to see the exact location and extent of the extrusion which helps plan for the potential surgery.
TREATMENT
Surgery is indicated when there is severe and/or progressing neurological deficits. Hemilaminectomy is the most common surgery performed, which involves removing part of the vertebra (the lamina) on one side so that there is access to remove the herniated material that is impinging the spinal cord. Even though this material is removed, there has been trauma to the spinal cord and nerves so it takes time for the tissues to heal and recover. Surgery performed within the first 24 hours following injury has a better recovery prognosis, as well as dogs that have deep pain sensation intact prior to surgery. (In thoracolumbar IVDD, recovery rate for non-ambulatory dogs with deep pain sensation is 85-95%, with most regaining the ability to walk in 1-4 weeks. For dogs with the loss of deep pain sensation, the recovery rate drops to 50% IF the surgery is performed within 24 hours of the loss of deep pain.)
Rehabilitation is crucial to recovery whether surgery was performed or not. In the acute phase, treatment focuses on pain control, promoting healing, and normalizing tone. In the subacute phase, treatment focus is on promoting healing, preventing re-injury, normalizing tone and working on stability. In the chronic phase, treatment focuses on preventing re-injury, stability, controlled mobility, and independent mobility. Mobility training focus is on the neurodevelopmental sequence. Neurodevelopmental sequence applies to all beings, human and canine. As we develop, movement progresses through a series of movement patterns, and each pattern provides the foundation for subsequent patterns. For example, human babies learn to pick up their head, roll over, sit, crawl, kneel, stand, and then walk. Canines have a similar pattern: head and neck control, lateral (side) lying, sternal (sphinx position), sitting, standing, and walking. With the rehab evaluation, it is determined where the dog is lacking proper movement and why, then the treatment plan stems from that point outward, building on each step until maximum independence is achieved.
An important thing to remember is it takes time for the body to heal. Even when surgery is successful, it may take many weeks for the neurological symptoms to start reversing back towards normal. It also takes a lot of time to “re-learn” motor patterns. Home exercise program follow through is crucial to success as the repetition helps the body not only become stronger, but to achieve these crucial re-learning steps.
Another key thing to recovery is activity restriction. It’s HARD, especially with an active dog, or if you have another dog that wants to play, but is imperative to follow through with this. Running, jumping, using stairs, uncontrolled activity, playing with other dogs are all on the “absolute no” list. Whether surgery was performed or not, these activities risk further injury to the current site, or injury to another disc. As hard as it is, it’s not worth the risk! Depending on the cause of the initial injury, some or all of these activities may be restricted for life. A chondrodystrophic dog with one IVDD incident is at risk of future disc extrusions so often you have to adapt their activity and how they play, access the couch or the bed, etc. Your rehab professional can help you with ways to make adaptations and let your dog have an enjoyable life.
Next week’s blog: Osteoarthritis/decreased mobility in elderly dogs
References:
Millis, Darryl L. & Levine, David. (2014). Canine Rehabilitation and Physical Therapy (2nd edition), Elsevier
Zink, Chris & Van Dyke, Janet B. (2018). Canine Sports Medicine and Rehabilitation (2nd edition), WILEY Blackwell