An Introduction into Intervertebral Disc Disease

Back pain is a condition that I see extensively in people and in dogs alike and in both patient groups, it can be debilitating.

In people, it is one of the most common causes of sick leave on an annual basis. There is a plethora of terms to describe back pain including ‘slipped disc’, ‘disc herniation’, ‘disc disease’ and ‘intervertebral disc disease (IVDD)’. All of these terms can evoke fear in patients and owners alike, resulting in the condition being mismanaged by many.

Firstly, let me put one or two of these fears and misconceptions to bed. DISCS DON’T SLIP! A disc cannot slip as it is very firmly fixed to each end plate of the vertebral bodies it sits between. The use of this term is a massive bug-bear of mine as it conjures up images of discs slipping out on the spinal column, resulting in fear and avoidance of activities for the risk of making the condition worse. IT DOESN’T HAPPEN!!!

Secondly, discs heal. Discs are like any other tissue in the body and they have the marvellous ability to fix themselves over time. Interestingly, research shows that the more severe a disc issue, the more the body responds and works overtime to heal itself in a conservative manner. There are a couple of exceptions and I will address these shortly. Due to the body’s ability to repair injured discs, patients are not left with a ‘weakness for life’ in this area. Just like straining a muscle or having a simple fracture in a bone, once healed, we move on unhindered. Many people focus on back injuries once they have occurred, resulting in unnecessary avoidance of activities or movements.

Intervertebral Disc Disease in Dogs

(A = Normal Disc; B = Disc Bulge; C = Disc Protrusion; D = Disc Extrusion; E = Disc Sequestration)

Jam Donuts
The simplest way to think about a disc is to imagine a jam donut. In the centre of the donut there is gooey jam and surrounding it there is dough. The disc is very similar in design – in the centre there is the gelatinous nucleus pulposus (pink blob above in diagram A) and around it is a fibrocartilaginous outer ring called the annulus fibrosus. A normal healthy disc is flexible and a great shock absorber due to its high-water content. As we age, the water content reduces from the disc. This causes a decrease in flexibility and can lead to bony changes (osteophytes) at the edges of the vertebral bodies. Most of the time these changes do not cause us any problems and unless we have a scan, we have no idea they are there. Interestingly, recent studies in people have found the evidence of disc bulges and prolapses in 20-29 year-old people who were totally symptom free. The same study found evidence of disc pathology in older people who were also symptom free, concluding that disc changes are normal and frequently cause no problems at all. Sometimes though, we do experience pain.

Intervertebral Disc Disease (IVDD) is commonly seen in dogs. In many breeds it is caused due to age related changes. Dogs tend to develop IVDD from 8 years upwards. Dehydration and mineralisation of the disc occurs slowly over time, leading to rigidity and small cracks occurring in the annulus. As a result, the nucleus pulposus can bulge within the annulus (diagram B), compressing and sensitising the nerve structures in the area. In some cases, the annulus can rupture, resulting in disc extrusion or sequestration (D and E above) (urgent medical attention required). In both of these cases, the disc material can cause concussion and compression of the spinal cord. This can cause severe pain and loss of movement. The extent of nerve cell loss and damage is determined by the type of force (i.e. is it a gradual compression or fast, blunt trauma), the degree of force applied to the spinal cord and the length of time the force is applied to the spinal cord.

Symptoms
Chronic degeneration is a slow process and the most common clinical signs are intermittent pain and a reluctance to move. This reluctance can last for a few days and then resolves. Acute traumatic events can occur suddenly, and clinical symptoms can be evident in less than one hour. Minor damage can cause a loss of co-ordination when walking, giving the appearance of a ‘drunken-like’ gait. Acute trauma, especially if a violent concussive force has occurred, can lead to an inability to walk or move the legs voluntarily. Severe damage can result in the loss of peripheral and deep pain sensation. The loss of deep pain is a medical emergency and needs urgent veterinary attention.

65% of disc problems occur in the thoracolumbar spine of dogs, 18% in the neck. Problems in the thoracolumbar spine may result in your dog having a roached back, firm abdomen due to guarding, possibly an altered hind limb gait, neurological changes when tested and a reluctance to move. Dogs with neck pain can have issues moving all four limbs. Pain and muscle spasm are commonly seen in all cases of IVDD.

Some breeds develop IVDD at a much younger age. These breeds are known as chondrodystrophic breeds and are genetically predisposed to developing disc related problems. Such breeds include dachshunds, corgis, basset hounds, Shih tzus, and French Bull Dogs. These breeds typically show signs of IVDD from 3 years, but some as young as 2 months old have shown evidence of it. Greyhounds are NOT in this group and typically develop IVDD as a result of ageing and also previous trauma.

Treatment
If your dog is showing signs of back pain, please take it to the vet immediately for an assessment. In most cases, pain relief, heat packs, gentle massage, rest and gentle movement can help. A visit to a Physiotherapist is advisable to guide you and your pet through the acute stage and they can assist with long term management of the condition. Incidentally, the same goes for you. If you are experiencing back or neck pain, see a Physiotherapist!!!

Lynne Harrison BSc (Hons) (Phty), MSc (Vet. Phty)
Physiotherapist
APAM MCSP ACPAT Cat. A