What is an intervertebral disc?
Intervertebral discs are the shock absorbing pads that separate the individual bones (vertebrae) along the neck and back, with the exception of the first two vertebrae of the neck. They are made up of two layers, the fibrous outer layer of the annulus fibrosus and the gel-like inner layer of the nucleus pulposus. Because of this, you may have heard them described using the analogy of a jam donut. Although, this doesn’t quite fully describe the way in which they support the spine, as they’re a lot tougher than a donut! It might make more sense to think of them as something like a wine gum, they will squish and deform with force but can return to a shape that resembles what it started as.
Canine spinal anatomy. Source: Meadows Veterinary Clinic of East Peoria
What is IVDD?
IVDD is a term used to describe several conditions involving damaged intervertebral discs that go on to cause injury to the spinal cord. The most common types of IVDD (types I and II) occur with degenerated discs. This means the nucleus pulposus has become calcified rather than the normal gel-like consistency, meaning that it has a reduced ability to absorb shock. This happens naturally with age but certain breeds are predisposed to this degenerative process happening earlier in life. Additionally, there are some types of IVDD that can occur in healthy discs. The most recognised types of IVDD are:
Type I or intervertebral disc extrusion (IVDE):
This involves herniation of the nucleus pulposus (inner layer) into the spinal canal. The material that herniates in an IVDE is usually calcified and so it tends to sit within the canal causing compression on the spinal cord. This commonly affects chondrodystrophic dogs (dachshunds, shih tzus, bassett hounds, etc.) between ages 4 and 6 and is most common in the mid-back but can occur in the neck. This can cause weakness and wobbliness of all four limbs if it occurs in the neck or just the back legs if it occurs in the back, but it can also cause complete paralysis in severe cases. The area is often painful and you may begin to notice a reluctance to jump or do stairs before it really starts to affect movement.
Type II or intervertebral disc protrusion (IVDP):
This involves protrusion of the annulus fibrosis (outer layer) caused by shifting of the inner layer of the disc. This type of IVDD is most similar to what we think of in people as a “bulging disc”. They are more common in mobile areas of spinal column such as the mid-back (thoracolumbar junction) and where the lower back meets the pelvis (lumbosacral junction). They occur more in older non-chondrodystrophic dogs e.g. Labrador, Border Collie, German Shepherd, etc. They are generally chronic and degenerative in nature and will be more slowly progressive than an IVDE. IVDP usually causes pain in an area but can also involve weakness and a reluctance to jump or do stairs. Similar to conditions like osteoarthritis (OA), there can be flare ups when managing this type of IVDD. IVDP is also one of the causes of Wobbler’s syndrome when it occurs within the neck.
Diagram showing normal disc (A), IVDE (B), and IVDP (C). Source: Elwood Vet.
Acute non-compressive nucleus pulposus extrusion (ANNPE):
This type of IVDD can be traumatic in nature rather than degenerative. There is a tearing of the outer layer of the disc and subsequent rupture of the nucleus pulposus which causes bruising of the spinal cord. They are sometimes referred to as "type III" or "high velocity, low volume" disc extrusions but these are now considered outdated names. It most commonly happens around the mid-back and is more common in border collies, likely due to them being such a naturally active breed. ANNPE’s are often described as non-painful but the initial impact will likely cause some pain, however, they will likely not become more painful after 24 hours unlike with an IVDE. They are also very lateralised, meaning that they affect one side more than the other and can often look as though they are only affecting one leg. This is very similar to another spinal condition called fibrocartilaginous embolism (FCE), which is like a stroke to the spinal cord i.e. blood vessels are blocked causing a lack of blood supply to the cord and subsequently causing neurological symptoms. ANNPE and FCE can sometimes be differentiated on an MRI scan and this is an important differentiation to make as ANNPE’s require more gentle rehab in the early stages due to the rupture of the annulus fibrosus.
Hydrated nucleus pulposus extrusion (HNPE):
This type is similar to IVDE but involves hydrated nucleus pulposus material (instead of degenerated/calcified) causing the compression on the spinal cord, therefore some patient’s may not actually be painful. However, they can be very compressive and cause the patient to be unable to stand or even complete paralysis. It is most common in cervical spine (neck).
There are also reports of an intradural-intramedullary intervertebral disc extrusion (IIVDE) or intramedullary disc extrusion (IMDE) where part of the nucleus pulposus can penetrate and even become embedded in part of the spinal cord. This has been treated surgically in some case reports and has a similar presentation and prognosis to an ANNPE.
What should I do if I think my dog has suffered IVDD?
If you think your dog is showing signs of spinal pain, seems uncoordinated, or has lost the ability to walk it is important that you take them to see your vet as soon as you can. This is because certain types of IVDD can be very painful and progress to paralysis quite quickly. There are also several conditions that present in a similar way (as well as there being several different types of just IVDD!) so it’s important to get the right diagnosis in order to start the most effective and appropriate treatment. Some cases of IVDE and ANNPE’s happen suddenly but IVDE and IVDP can also be more gradual and with IVDE may continue to progress over the course of a few hours/days. There are some key things to look out for that could indicate spinal pain including reluctance to jump or do the stairs, a low head carriage (common for neck disc), and a rounded back (common for back disc). Other things to look out for include possible loss of bowel or bladder control and being sensitive to touch over their back/neck. Until you’re able to see your vet, you should make sure that your dog is cage rested, although if your dog is unable to walk, they will likely see them as an emergency.
How is IVDD diagnosed?
In very chronic cases (where the disc has been prolapsed/bulging for a long time), some evidence may be visible on x-ray or CT but the best way to diagnose IVDD is with a thorough neurological examination and MRI scan. This often requires referral to specialist hospital that has a neurology and neurosurgery department. An MRI is the only type of imaging that can really distinguish between the different types of disc disease and through this blog, you will hopefully see why getting a firm diagnosis if possible, is important to have effective treatment for each type. It also helps to rule out anything like FCE, cancer or cysts that can also compress the spinal cord and cause similar symptoms but require different treatments.
Testing the dog's patella reflex. Source: Clinician's Brief
How is it treated?
Currently, the standard practice for IVDE is surgery for most cases. Conservative management can be considered if there is spinal pain only or if there is pain and mild neurological deficits. However, there is some very interesting research being done by Cambridge Vet School on conservative management of IVDE, regardless of the severity, and the results so far are showing that conservative management can yield positive results for IVDE’s of varying severity! They have a facebook page where they share updates on their results under the name “Cambridge IVDD Research Group”.
Surgical options for IVDE depend on where the injury is and how severe the herniation is, these include**: ventral slot (for neck IVDE’s), hemilaminectomy (for IVDE’s in the back), dorsal laminectomy, pediculectomy/mini-hemilaminectomy, durotomy, and prophylactic fenestrations. Following surgery, rehabilitation in the form of physiotherapy and hydrotherapy is recommended to improve the speed and quality of your dogs recovery.
**In order to keep this blog from becoming a book, I will have to write a whole separate blog on the topic or leave it up to the reader to look up the individual surgeries for themselves, sorry!
Diagram of a hemilaminectomy surgery. Source: Veterian Key
The most likely course of treatment for IVDP is medical management consisting of medication and rehabilitation. Surgery can be done but is not always appropriate, however, it is better if done early on or if the symptoms are very severe. There may be some deterioration after surgery but this is usually temporary. Surgical options include (depending on area of spine, severity, and surgeon preference): hemilaminectomy, dorsal laminectomy, or lateral corpectomy.
By definition, there is no compression of the spinal cord with an ANNPE, therefore, the treatment is predominantly medication and intensive rehab. However, initially this rehab must be gentle due to the tearing of the annulus fibrosus, meaning there could be a chance of re-injury if the patient does too much too soon.
Surgery and medical management can have similar outcomes for HNPE. The surgery is similar to what is performed for IVDE but the decision over whether to go for surgery or not is generally based on if the patient is completely paralyzed due to severe compression on the spinal cord. This is especially important if the disc has occurred in the neck as this can also cause breathing difficulties. If the patient is able to be managed for 24-48 hours within a hospital and there is improvement, then the body will likely resorb the material due to high water content and avoid surgery but if not, then surgery may be necessary. Either way, rehabilitation is generally recommended following diagnosis or surgery to aid in recovery.
Is there anything I can do to prevent it?
If you have a breed that is predisposed to being affected by a certain type of IVDD, then you can try minimising the risk of a rupture by avoiding high impact activities like jumping in and out of the car, jumping on and off furniture, avoid throwing a ball for them to jump and catch, and providing non-slip matting if your floors are slippery. Unfortunately though, there is no guarantee that your dog will never have an episode of IVDD.
Can back supports help?
There’s currently no actual research on the use of back braces in dogs, solely anecdotal evidence. If you have one fitted to your dog but still allow them to perform lots of high impact activities, the brace is unlikely to prevent a disc from rupturing because the brace may prevent flexion and extension of the spine, but it won't prevent compression of the discs, which is the type of force/movement that will cause a disc to rupture. Additionally, they will not stop a disc from degenerating in a breed that is genetically predisposed to this happening e.g. dachshunds. They may be useful for acute (short lived) bouts of back pain and could even be helpful during recovery, if your dog is extremely ataxic (uncoordinated), as they could help reduce the risk of further injury from falling by providing stability to the trunk. However, some more research on their use would be great to have!
Dog back brace. Source: Walkin' Pets
Will my dog be disabled afterwards?
This will depend on how severely the spinal cord has been damaged at the time of injury. Dogs suffering from IVDD are often graded from 0-5:
1: Pain: not severe enough to result in any neurological dysfunction.
2: Paresis (reduced movement/weakness) with or without pain: as the lesion becomes more severe the degree of paresis and/or proprioceptive deficits becomes more severe.
3: Paralysis: total loss of voluntary movement in the affected limbs (and/or tail).
4: Paralysis with loss of voluntary urinary function.
5: Paralysis with loss of voluntary urinary function and loss of conscious perception of painful stimuli ('deep pain perception') in the affected limbs (and/or tail).
Some dogs will be up and walking straight away, although may be slightly wobbly on their legs, but unfortunately some are not so lucky and require assistance to move for several months or even the rest of their lives.
The best indicator of your dog being able to walk again is the presence of deep pain. If this is present, there’s a better chance your dog could walk again following intensive rehabilitation. If deep pain is absent and there’s no return of it within 2 months post-injury, then the chance of them consciously walking again is quite low. With intensive rehabilitation some patient’s are able to achieve a reflex-type gait known as spinal walking, but they will still likely require long term assistance to move. It is possible to manage a patient that has absent deep pain but it does require a lot of commitment to avoid pressure sores, UTI’s, joint and soft tissue contractures, and urine scalding among other things. One potential complication if there is no deep pain sensation is a condition called progressive myelomalacia, which is essentially the spinal cord dying off. This unfortunately has no cure and euthanasia is usually the only option, but it does tend to present fairly soon (2-4 weeks) after the initial injury.
Will my dog ever be able to run or play again?
Following several months of rehabilitation, your dog may be able to play again but you may have to change the way in which you play with them. This is especially true if they are not able to get up and move without your assistance. However, to reduce the risk of re-injury, even if they are able to get around independently, you should be cautious of certain activities. If your dog likes to chase after a ball or play tug of war, you need to be prepared to adapt the way you play as these activities cause a lot of stress on your dog’s neck and spine. Your rehabilitation therapist will be able to give you safer alternatives but some rules of thumb include never allowing your dog to run and catch a moving toy, if they like to retrieve toys, make sure the toy has always stopped moving before you allow them to chase after it, or you can try hiding the toy and allowing them to play hide and seek with it.
Source: Public Domain Pictures
Will my dog always be slightly wobbly?
There is a chance that your dog may have a slightly drunken appearance to the way they move but depending on how much they wobble when moving, it doesn’t have to stop them living a full life again.
What about assistive devices like slings or carts?
There are certain devices such as toe slings or booties that your rehabilitation therapist may recommend, depending on how your individual dog presents and the issues they are dealing with. If your dog is not walking independently, then you will likely be given or advised to use a sling for their back end, if it is a back disc, or a harness and sling system such as the "Help 'Em Up" system, if it is a neck disc and all four limbs are affected. Regardless of where the disc is, it is better to make the switch from collar and lead to harness and lead because leads can put extra pressure on the sensitive structures in the neck and increase the chance of further injury in this area.
If your dog is not up and walking without assistance by around 3-4 months after the injury or they have absent deep pain, it may be beneficial to look into a cart for them. We don't generally recommend it before then as carts can cost a few hundred pounds and a lot of dogs can get up and walking by this point. Additionally, some lazier dogs can get over reliant on them and so the early use of a cart could prevent them achieving their potential. However, if they get to 3-4 months and they still aren't walking, this may start to affect their mental health and you may notice them seeming more depressed. So the introduction of wheels at this point could improve their mental wellbeing and give them some independence back (as well as saving you from carrying them around!).
Help 'em up harness and sling. Source: K9 Carts
Will it ever happen again?
If your dogs has suffered from IVDD once, there is always the chance it could happen again, especially if their MRI scan showed other degenerated discs along the spine. However, you can minimise this risk by reducing high impact activities such as jumping off furniture, jumping out of the car, or jumping to catch a ball.
If you want any more information on IVDD or would like rehabilitation to assist in your dogs recovery, do get in touch!
All the best,