Intervertebral Disc Disease (IVDD) in Dogs

To the team at Westville Veterinary Hospital, I cannot thank you enough. My heart is overflowing with joy. Your team is skilled & takes the utmost care of all animals. 

From the bottom of my heart, and my baby girls'

we are very happy to DEFINITELY recommend your hospital as number 1!

Aaliah and Hachiko Hassan

What is the Intervertebral Disc?

The spine is the name given to the collection of bones (vertebrae) inside which the spinal cord is contained. The spinal cord is made of cables of nerves (like the wires running in an electrical cable), linking the brain to the local nerves that control the movement of the limbs and other functions (the peripheral nervous system).

The intervertebral disc is a spongy, doughnut shaped pad in the main joint between the vertebrae. The disc lies just underneath the spinal cord in dogs and cats. Each disc has a semi-liquid centre (nucleus pulposus) and a tough outer fibrous layer (annulus fibrosus). The discs form a bridge between two neighbouring vertebrae and act as a cushion, giving strength and flexibility to the spine.

There are seven cervical (neck) vertebrae, 13 thoracic (chest) vertebrae, seven lumbar (lower back) vertebrae, three sacral vertebrae (which are fused), and a variable number of tail vertebrae

Intervertebral disk disease (IVDD) is one of the most common diseases causing paresis in dogs. It may result in a variety of clinical signs, ranging from spinal hyperesthesia to paraplegia. Many dogs recover if given the proper treatment and nursing care. Losing the ability to walk is an emergency. Do not wait to see if it gets better; consult with your vet without delay!

The area of the back or neck just over the disk involved is generally painful (whereas many degenerative spinal processes are not painful). In milder cases, pain at the site of the disk may be the only symptom. As inflammation increases in the spinal cord, neurologic deficits can occur. Disk herniation in the neck tend to have more pain and less dysfunction.

One of the first dysfunctions (or deficits) is the loss of what is called conscious proprioception. Conscious proprioception is the ability to perceive where one’s feet are and orient them properly. The examiner will turn the foot over so that the top of the foot is on the ground and will see if the patient replaces the foot in the proper position. Dogs with poor proprioception will scuff their toes or even occasionally fail to flip their feet while walking and will walk on the tops of their feet. Nerves responsible for conscious proprioception are located on the outside of the spinal cord so when the disk herniates, these nerves feel the pressure first.

After the nerves that affect conscious proprioception go, next are the nerves for voluntary motion (including voluntary control of urination/defecation), followed by the nerves for superficial pain perception, and ultimately the nerves for deep pain perception (usually tested by applying a strong pinch to the toe).

Hansen Type I Disk Herniation

In Hanson Type I disk herniation, the nucleus pulposus becomes dehydrated and mineralized. It loses its gelatinous cushioning properties and suddenly extrudes, slapping right into the spinal cord and its tender surrounding ligaments. The classic victim is a young dog of a breed that involves a long back and short legs, though any dog can be affected. The damage to the spinal cord can range from mild inflammation to total destruction.

Hansen Type II Disk Herniation

Here the degeneration is slower and the fibres of the annulus fibrosus become soft. As the disk is compressed by the normal forces between the vertebrae, the annulus fibrosus bulges upwards and puts pressure on the spinal cord more slowly. The classic victim here is an older large breed dog.  German Shepherd dogs seem predisposed.

With a patient with spinal weakness, the veterinarian must determine whether the problem involves actual compression of the spinal cord. This determination is important because compression can benefit from surgery/anti-inflammatories while other spinal diseases cannot. Compression in the spinal cord does not have to be from a disk herniation; it could be a vertebral fracture or dislocation, a tumour, or a disk infection. Any of these things could be putting pressure on the spinal cord or nerves and if there is a physical compression, it could – at least in theory - be relieved with surgery.

A non-compressive disease will not benefit from surgery. Such non-compressive diseases include: spinal degeneration, spinal infection or inflammation, demyelination injuries, or fibrocartilaginous embolism.

The Neurologic Examination

By testing different reflexes, the doctor can localize the area of the spinal cord that is affected. This might be the cervical area (neck), the thoracolumbar area (where the chest and abdomen come together), the lumbar (lower back), or the sacral area (where the tail starts). The thoracic (chest) area of the spinal cord is usually spared in disk disease because the ligaments connecting the ribs to the back provide extra protection for the spinal cord.

Advanced Imaging

If surgery is being considered, then it becomes necessary to identify the exact disk space involved so that the surgeon will know where to cut. As a general rule, there is not much point in performing a procedure to specifically localize a compressive lesion unless surgery is being considered.

A CT scan is performed in addition to or instead of a myelogram. This gives an even more accurate image of the disk herniation and its location, as well as whether there is more than one disk involved. 

Surgical treatment consists of drilling a hole in the vertebrae to remove the part of the IVD that is putting pressure on the spinal cord. Recovery time varies from 1 to 4 weeks. Despite carrying a small risk of causing further trauma, surgery should prevent further deterioration and relapse in the future.

Success of surgery depends mainly on how much spinal cord function has been lost and especially whether or not, and for how long, the animal has lost the ability to feel pain in its toes. The prognosis is very good for most animals that retain pain sensation. Paralysed dogs with no pain sensation in their rear legs have a slightly better than 50:50 chance of recovering the ability to walk, unless this sensation has been lost for more than 48 hours when, unfortunately, the prognosis then becomes very poor.