Understanding Intervertebral Disc Disease
Intervertebral disc disease (IVDD) is one of the most common neurological conditions affecting dogs. The intervertebral discs act as shock-absorbing cushions between the vertebrae of the spine. When these discs degenerate, rupture, or bulge, they can press on the spinal cord or nerve roots, causing pain, weakness, and in severe cases, complete paralysis.
Types of IVDD
There are two primary types of disc herniation in dogs:
- Hansen Type I (Extrusion): The disc's inner material (nucleus pulposus) ruptures and is explosively extruded into the spinal canal. This type tends to cause sudden, severe signs and is most common in chondrodystrophic breeds — those with disproportionately short legs.
- Hansen Type II (Protrusion): The outer ring of the disc (annulus fibrosus) bulges into the spinal canal without fully rupturing. This type is more common in larger, older dogs and typically causes a slower, more gradual progression of signs.
Breeds at Higher Risk
Chondrodystrophic breeds carry a significantly higher risk of Type I IVDD due to early disc degeneration starting in young adulthood:
- Dachshunds (by far the most commonly affected)
- French Bulldogs
- Beagles
- Corgis
- Shih Tzus
- Bassett Hounds
Larger breeds such as German Shepherds, Labrador Retrievers, and Dobermans are more susceptible to Type II IVDD.
The Spinal Cord and Where IVDD Strikes
IVDD most commonly affects two regions of the spine:
- Thoracolumbar region (mid-back): Accounts for the majority of cases and affects the hind limbs, bladder, and bowel.
- Cervical region (neck): Causes neck pain, and in severe cases, weakness in all four limbs.
Recognising the Signs
Symptoms depend on the location and severity of disc herniation. They are graded on a scale from I to V:
| Grade | Signs |
|---|---|
| I | Pain only — no neurological deficits |
| II | Weakness (paresis), ataxia (wobbly gait), but still walking |
| III | Severe weakness — able to move limbs but unable to walk |
| IV | Paralysis with intact deep pain sensation |
| V | Paralysis with absent deep pain sensation — most severe |
Diagnosis
After a thorough neurological examination to localise the lesion, imaging is essential. MRI (Magnetic Resonance Imaging) is the gold standard for visualising disc herniations and their impact on the spinal cord. CT scanning is also widely used and highly effective. Plain X-rays can suggest disc disease but cannot definitively confirm or grade spinal cord compression.
Treatment Options
Conservative Management
Appropriate for Grade I and some Grade II cases. This involves:
- Strict rest (cage/crate confinement) for 4–6 weeks
- Anti-inflammatory and pain-relieving medications
- Controlled, gradual return to activity
- Physiotherapy once the acute phase resolves
Surgical Decompression
Recommended for Grade II–V cases, particularly where there is no improvement with medical management or where neurological signs are worsening. The most common procedures include:
- Hemilaminectomy: Removal of part of the vertebral arch to access and remove herniated disc material — standard for thoracolumbar IVDD.
- Ventral Slot: An approach used for cervical disc herniations.
The speed of surgical intervention is critical. Dogs that retain deep pain sensation generally have a very good prognosis with surgery. Those without deep pain sensation (Grade V) require urgent surgery, and outcomes are more variable.
Prevention and Reducing Risk
While IVDD cannot always be prevented, the following measures can reduce risk and severity:
- Maintaining a healthy body weight to reduce spinal load
- Using ramps or steps to avoid jumping on/off furniture
- Using a harness instead of a neck collar
- Avoiding repetitive high-impact activities in high-risk breeds