WHAT IS IVDD?
Understanding the disease
Your questions answered
IVDD is Intervertebral Disc Degeneration. It is commonly referred to as intervertebral disc disease, but to be clear, it is a genetic disorder that causes a disease process in the intervertebral discs of the spinal cord. 1:4 dachshunds are now affected by IVDD. What happens over time is that the consistency, which is normally very watery, begins to dry out and is more or less replaced with cartilage which sometimes leads to calcification. It’s actually the genetics of the short legs, not the long backs of dachshunds, that pre-disposes them to IVDD.
It’s difficult to ascertain if your dog will be effected by this genetic disease; typically signs appear when the dog is between 3 and 8 years old. However, they are not ever immune no matter what age.
When it comes to IVDD, education is key!
Remember prevention is better than cure
A diagram showing a dachshund’s spine and all the vertebrae in each section of the spine.
T4-13, L1-8, S1-3, and Ca1 vertebrae.
Image credit: The Dachshund Spine by Lisa J Emerson
Getting down to the nitty gritty of IVDD
The intervertebral discs sit between the vertebrae (bones) and act as shock absorbers. The vertebral spine is made up of 7 vertebrae in the cervical neck region, 13 in the middle thoracic section and another 7 in the lower lumbar back region. In between all those are the intervertebral discs. IVDD can occur in all areas of the vertebral column and whilst we most commonly see it occurring in the thoracic and lower lumbar region many dachshunds also suffer in the cervical (neck) region.
Discs have a soft centre, like a jelly cushion. It is a viscous gel, a bit like jam in the middle of a doughnut, which is called the nucleus pulposus (nucleus). Surrounding this, is a fibrous ring which is a bit like a hard tough outer shell, and it is called the annulus fibrosus. The nucleus (the soft gel like centre) is made up of about 80% water, which acts as a cushion when natural forces through movement occurs. It stretches and compresses and acts like a shock absorber between all the vertebrae in the spine with normal movement. The annulus (outer shell) restricts the expansion of the nucleus and provides stability to the spine during any movement or bending of the spine. However, the spinal cord is anatomically poorly located, and sits directly above the discs, which is why problems can occur when the disc goes wrong and begins to degenerate.
How is IVDD categorised?
Disc Disease IVDD was first categorised by Hansen in 1952. It was categorised into Type 1 and Type 2. There are two ways a disc can degenerate and Hansen Type 1 is the most commonly type seen in dachshunds. It is also seen in other breeds, but is seen most commonly in the chondrotropic breed of dogs. It is more correctly known as hypochondroplastic.
What does hypochondroplastic mean?
It is a gene mutation which causes abnormal cartilage production. But this is what also contributes to the characteristic body shape of these breeds, like dachshunds (i.e. short legged bendy legged dogs). As well as dachshunds, other breeds can also be affected; to name a few Pekinese, Bassets, Beagles, Corgis and some Spaniel breeds. As a result, these are the types of dogs we see having problems. The cartilage in the dachshund breed isn’t made properly; hence there is not the long bone growth seen in long legged bred dogs.
So, what happens?
Due to this gene mutation, (hypochondroplasia), the nucleus (gel like soft centre) becomes hard and rigid, which becomes cartilaginous. Hansen Type 1, or (Chondroid Metaplasia), which is the fancy name given to Hansen Type 1 disease, results in changes to the nucleus pulposus. This is where the nucleus (jelly like soft centre pulp) degenerates. The matrix of the nucleus loses the ability to hold water, and therefore the loss of fluid results in replacement of cartilage and becomes calcified. When calcification occurs, the nucleus can no longer act as a cushion and the compressive forces are transferred to the annulus (the outer shell). With increased forces, the annulus becomes thicker, in an attempt to stabilise the spine. Through its loss of biomechanical integrity, the nucleus then explodes through the annulus. This applies direct pressure to the spinal cord, which in turn, causes concussive damage as well as persistent compression. When this happens, we see the signs and symptoms that our dachshunds display so suddenly.