Intervertebral disc disease (IVDD) is a premature degeneration of the intervertebral disc, the cushion located between the bones of the spine in the back (vertebrae). This degeneration can lead to disc rupture or herniation, often known as a “slipped disc” which is very painful and can have serious implications on quality of life.
Discovery of a genetic variant that results in short limb length due to a change in how cartilage is converted to bone during development is also responsible for changes in the intervertebral discs which can lead to risk for Type I disc herniation.
Pet parents can take special precautions to care for dogs with increased risk for IVDD and know signs to look for in order to seek out prompt treatment if disc herniation should occur.
Caring for dogs at risk
- Maintain a healthy weight
- Avoid situations that would encourage your dog to jump up or down. A comfy place for your dog to rest at the same level of the floor, or ramp to a bed or couch can help prevent jumping off furniture.
- Consider low-impact, solo exercise instead of rough social play with other dogs.
- Use a harness, rather than a collar for walks on leash
What is disc herniation?
Bones of the spine (vertebrae) are separated by cushions called intervertebral discs. The discs are made up of 2 components:
- Nucleus pulposus: This soft, inner core of the disc allows the spine to withstand forces of compression and torsion.
- Annulus fibrosis: The tough, outer layer of the disc protects the nucleus pulposus and is connected to the vertebrae above and below the disc.
Chronic degeneration of the annulus fibrosis can result in disc rupture or herniation into the spinal canal. This results in inflammation and puts pressure on the spine as well as nearby nerves which can lead to signs such as pain, incoordination and in severe cases, paralysis.
Symptoms:
Disc herniation can occur slowly over days or weeks or can occur acutely after an event such as a fall, or jumping off furniture. Disc herniation often occurs in the neck or mid-to-lower back region. Clinical signs may include Back Pain and reluctance to move as well as lameness (difficulty walking) in the hindlimbs or all 4 limbs.
Diagnosis and Treatment
Symptoms of disc herniation can also be caused by other medical conditions. Examination by a veterinarian as well as possible imaging (X-ray, CT-Scan, MRI) may be indicated to diagnose and localize the site of disc herniation. Treatment may include strict rest and medications such as anti-inflammatories and muscle relaxants. In severe cases, surgery may be necessary.
Breeds Affected
The genetic mutation associated with IVDD risk is also correlated to chondrodystrophy, a defect ossification of cartilage which results in short limbs. This genetic variant has been observed in the breeds below and may also be present in additional breeds not listed.
- Basset Hound
- Beagle
- Bichon Frise
- Cardigan Welsh Corgi
- Cavalier King Charles Spaniel
- Chesapeake Bay Retriever
- Chihuahua
- Chinese Crested
- American Cocker Spaniel
- Coton de Tulear
- Dachshund
- Dandie Dinmont Terrier
- English Springer Spaniel
- French Bulldog
- Havanese
- Jack Russell Terrier
- Nova Scotia Duck Tolling Retriever
- Pekingese
- Pembroke Welsh Corgi
- Poodle (Miniature and Toy)
- Portuguese Water Dog
- Scottish Terrier
- Shih Tzu
Science and Genetics
A mutation in the Fibroblast growth factor 4 (FGF4) gene on chromosome 12 was found to lead to an increase in expression of FGF4 in the neonatal intervertebral disc increasing risk for IVDD and also impacts endochondral ossification, resulting in short limbs. An additional mutation in chromosome 18 which affects expression of FGF4 appears to affect limb length, but has not shown to be associated with increased risk for IVDD.
Mode of inheritance:
Risk for IVDD is inherited as a dominant trait. Dogs with one or two copies of the risk variant are at increased risk for IVDD.
Possible Test Outcomes
| Genotype | Phenotype |
|---|---|
| No variant detected | No increased risk based on the variant tested |
| CARRIER: 1 copy of the risk allele in the FGF4 gene | Increased risk for IVDD |
| AFFECTED: 2 copies of the risk allele in the FGF4 gene | Increased risk for IVDD |