The Expert's Guide to Intervertebral Disc Disease: Guest Post with Dr. Gainsburg

At Sage Veterinary Imaging (SVI), we have a team of experienced veterinarian radiologists and neurosurgeons by your side. This week, we’re welcoming our resident neurologist and neurosurgeon, Dr. Larry Gainsburg. He helps us explain what Intervertebral Disc Disease (IVDD) is and how it can affect your dog. 

Fair warning: Dr. Gainburg gets pretty technical here, but this is super useful information for anyone who really wants to dive into the specifics of IVDD. He covers which breeds IVDD affects most, how degeneration occurs, and provides several in-depth case studies with successful outcomes. Don’t worry - there are answers for your pet in pain!

If you have a dog of any breed with an acute onset of paralysis on the pelvic limbs or severe weakness of all four limbs, please contact Sage Veterinary Imaging in Round Rock, Texas to reach Dr. Gainsburg.

About the Author

Dr. Gainsburg started the first veterinary neurology and neurosurgery practice in the Baltimore area in 1987. He has been practicing veterinary neurology and neurosurgery for over 32 years. 

He graduated from the University of Florida College of Veterinary Medicine in 1980. He then spent 3 years in general and emergency practice before completing a residency in Neurology at the University of Pennsylvania School of Veterinary Medicine, followed by a clinical fellowship in Neurology and Neurosurgery at the North Carolina State University College of Veterinary Medicine. 

For the past 20 years, Dr. Gainsburg has been performing MRIs for pets at Johns Hopkins University while also contributing to numerous clinical research studies that improve the lives of animals with neurological conditions.

 Since 2001 and prior to joining Sage Veterinary Imaging, Dr. Gainsburg worked with Dr. Jaime Sage (Founder and Head Radiologist at SVI) and her mentor Dr. Patrick Gavin making diagnoses and treating pets with neurological disorders in Round Rock, Texas.

Inverterabal Disc Disease (IVDD) in Dogs 

Figure 1 - A medical illustration of the parts that make up a normal canine spine. 

Intervertebral disc disease (IVDD) is an unfortunately common problem in many dogs and refers to the degenerative process which occurs in the intervertebral discs. These are structures located between adjacent vertebral bodies, and they are situated immediately beneath the spinal canal through which the spinal cord travels. The intervertebral discs consist of an outer, fibrous part called the annulus fibrosus and a normally soft inner part called the nucleus pulposus. (See Figure 1) 

It is easy to think of the disc in comparison to a jelly doughnut, with the dough portion likened to the outer fibrous part and the jelly likened to the soft inner part. In a normal, healthy disc these two parts function to provide movement and stabilize the various forces that are placed on the spine associated with normal activities. Discs are often compared to shock absorbers, as they function in this manner. 

Most disc herniations are the result of degeneration of the discs, and this is what is referred to as intervertebral disc disease. There are different types of degeneration, but the end result is a less compliant shock absorber and a more brittle and weaker fibrous structure.  

This ultimately results in bulging (protrusion) and eventually tearing of the annulus, which allows the inner nucleus to extrude through it. This is referred to as a disc herniation, rupture, extrusion, or “slipped disc.” Structurally, the top side of the disc, which is situated immediately beneath the spinal cord is 2-3 times thinner than the bottom side, such that disc herniations typically occur on the top, resulting in disc content extruding upward and compressing the spinal cord.  Therefore, think of the jelly doughnut situated with the hole facing upward so the “jelly” is pushed into the spinal canal. The resulting disc compression then causes the typical progression of clinical signs of pain, weakness, and ultimately paralysis as the volume of extruded disc content increases. (See Figure 2) 

Figure 2

Certain breeds of dogs are very overrepresented with regard to IVDD-related disc herniations. At Sage Veterinary Imaging, we commonly diagnose and treat intervertebral disc disease in Dachshunds, French bulldogs, Beagles, Shih-Tzus, Pekingese, Corgis, and Bassett Hounds. These are termed chondrodystrophic dogs, characterized by long bodies and short legs. 

Although the overall majority of dogs that have a disc herniation occur tend to be older dogs, the Dachshunds and French Bulldogs in particular often have early disc degeneration, and members of these breeds can develop weakness or paralysis as early as 3 years of age.

The severity of the clinical signs in a given patient with a disc herniation can be quite variable, as they are dependent upon the rapidity of onset of the compression, the amount of spinal cord compression, the duration of the compression, and the exact location of the involved disc. 

Dogs with acute (sudden) compressive disc herniations which result from activities such as jumping off furniture will often become severely weak or even paralyzed immediately. (See Figures 3 & 4) 

Figure 3

Figure 4

Those with more chronic and often progressive disc protrusions or extrusions may develop much more severe compression. (See Figures 5 & 6) However, the spinal cord is able to compensate for this pressure much more effectively when it occurs over a more prolonged period of time such that a dog with this type of disc herniation may be still walking, yet another dog with the same or less compression may become paralyzed when it occurs abruptly. 

Figure 5 - The above images are from a 4-year-old spayed female Labrador retriever that presented with an acute onset of right hindlimb paralysis with left hindlimb weakness. She was not painful when examined and began improving within 48 hours. The MRI demonstrates the presence of a non-compressive disc extrusion at L2-3. These types of disc extrusions cause spinal cord contusion without compression and are not surgically treatable, but often have a very favorable prognosis.

Figure 6 - The above images are from a 13-year-old Dachshund who presented with severe pelvic limb weakness which began after another dog jumped on him. The dog did not improve with medical management. The disc extrusion was found to be quite chronic at the time of surgery, which explains why the spinal cord is so severely compressed yet the dog is not fully paralyzed. The dog began improving on the second day following surgery.

Disc extrusions which occur in the cervical (neck) spine will typically be extremely painful, whereas they may or may not have weakness or paralysis. When such patients do become weak, the weakness will affect the front and rear limbs. By contrast, those with disc extrusions in the back will often not be as painful but will usually have some degree of weakness that affects only the rear limbs. 

Although the majority of disc extrusions occur in patients that have degenerative disc disease, sometimes non-degenerative discs will herniate. This happens when excessive forces are applied to a normal disc, resulting in a very forceful extrusion of disc content with normal, soft consistency. These types of disc herniations occur suddenly and result in more of a bruised, contused spinal cord without compression. (See Figures 7 & 8) 

Figure 7 - The above images are from an 11-year-old Dachshund that presented with significant hindlimb weakness two days after she became painful. The disc content signal intensity is less hypointense (lighter) than the previous patient and was found at the time of surgery to be acute and much more easily removed. The dog made a full recovery.

Figure 8 - The above images are from a 5-year-old Pug that presented for yelping in pain and limping on the left front limb. He was found to also have some rear limb weakness as a result of the very left-sided disc extrusion at C6-7. The limping on a front limb is common in dogs with disc extrusions in the lower cervical spine and can be mistaken for a front leg injury. It is due to disc compression on a nerve root supplying the limb on the affected side and is referred to as a root signature. The dog made a full recovery following surgery.

Non-compressive disc extrusions typically occur in larger breeds of dogs, and can be seen in cats. These patients are painful when the extrusion occurs, but tend not to be painful subsequently. Because some dogs with compressive disc extrusions can have very similar histories and present with identical signs, it is of utmost importance to do spinal imaging as soon as possible to distinguish between a compressive and a non-compressive spinal cord injury.

Early signs of disc herniation may be subtle and related only to pain. It is common for dogs with thoracolumbar extrusions to be reluctant to go upstairs, jump onto things, or move around freely. They may groan or yelp out when picked up. Sometimes this is thought to be due to abdominal pain, but upon close examination, these dogs will be found to have a focal area of pain along the back. 

As the problem worsens, the pain may intensify and you may see the dog walking as though drunk. This is referred to as ataxia. Once this occurs, it is usually due to significant spinal cord compression, and your veterinarian should be contacted immediately, as this can progress to complete paralysis quickly. 

Dogs with cervical disc extrusions are often exquisitely painful, and may try to bite if approached or handled when they are in such pain. When they occur in the low cervical spine, they may be associated with lameness on one or the other front limb and may be confused with some type of injury to the affected limb. (See Figure 9)

Although much less common, disc extrusions do sometimes occur in cats, and these occur almost exclusively in the lumbar (lower back) region. (See Figure 10) They can also be compressive or non-compressive. When they are associated with significant spinal cord compression, they too are treated surgically. 

Figure 9 - The above images are from a 3-year-old French Bulldog which became acutely paralyzed and could not move his rear legs when he presented. The study demonstrates a severe disc extrusion extending over the length of two vertebra, with disc content in the ventral (bottom), lateral (side), and dorsal (top) spinal canal. This breed is known for rapidly progressive disc extrusions once the clinical signs begin. The patient has recovered partial function of the rear limbs.

Figure 10 - The above images are from a 10-year-old domestic shorthair cat that became severely painful and subsequently lost the use of his tail. When examined, he had low lumbar pain, a limp tail, and mild rear limb weakness. The MRI demonstrates the presence of a massive disc extrusion of the L6-7 disc. Note the markedly distended bladder which is a common feature of disc herniations in the low lumbar spine. Although disc herniations are far more common in dogs, they should be considered in cats with weak pelvic limbs and/or spinal pain.

Lastly, once dogs with thoracolumbar disc extrusions become paralyzed, they will also lose the ability to control their bowel and bladder function. Loss of fecal continence will not prevent the dog from passing stool. It will just happen without their control. Urinary incontinence is a much greater concern since the bladder will become overfilled, and unless the urine is manually expressed, the bladder wall will become weakened and lose its normal tone. Urinary tract infections are often a sequela to urinary incontinence and can potentially become a serious medical concern.  

Dogs with mild signs of disc herniation may be able to be treated medically and recover. The most important aspect of medical management is strict rest and confinement, as even simple walking may put enough pressure on the disc to cause additional disc content to extrude into the spinal canal and produce greater spinal cord compression. 

Think of pushing and pulling on the jelly doughnut. As long as there is more jelly inside, it doesn’t take much movement to squeeze more through the hole. Ideally, unless it is not tolerated by the dog, he or she should be kept crated other than when taken outside for elimination purposes. 

Smaller dogs should be carried to a location that is commonly used for elimination, then carried back inside when finished. Large breeds should be walked as limited a distance as possible for such purposes.

Medications such as steroids or non-steroidal anti-inflammatory drugs, pain relievers, and muscle relaxants are frequently administered to these patients. Medical management should be continued for 4 weeks if the dog responds well, but it is strongly recommended that they are further worked up if there is no response within 3-4 days, or if they worsen at any time during which they are being medically managed.

Dogs with moderate to severe weakness or paralysis should have diagnostic imaging to determine the exact location, severity, and type of spinal cord injury. It is important to establish whether a compressive or non-compressive injury is present, as they are treated quite differently. 

Dogs with significant spinal cord compression will do better and recover more quickly following surgical decompression, as the underlying cause is being addressed, vs. medical management, which is equivalent to putting a band-aid on the problem. For dogs with thoracolumbar disc extrusions that have lost all motor function but retain good sensation in the pelvic limbs, immediate surgical decompression will provide the best chance for the return of function. 

Dogs with significant loss of motor function due to a compressive cervical disc extrusion are also in need of immediate surgery. The cervical spinal canal is larger in relation to the size of the spinal cord, and therefore it requires a larger quantity of disc content, and therefore marked spinal cord compression to lose most or all functionality of all four limbs. 

What about deep pain?

Why is this so important? Deep pain pathways, unlike motor pathways, tend to project to several levels on both sides of the spinal cord. Therefore, loss of this function indicates a more thorough spinal cord injury, and in the continuum of spinal cord functional loss, deep pain is the last function to be lost. 

Furthermore, nerve fibers which carry this information are the least susceptible to the effects of pressure. The loss of this function is therefore associated with the most severe of spinal cord injuries. It usually is not apparent when a given patient loses this function, which makes it more difficult to assess the prognosis accurately. 

In general, once this deep pain is lost, there is a notably reduced chance of recovery even with surgical intervention. Therefore, dogs with complete loss of voluntary motor function and normal pelvic limb sensation are considered surgical emergencies. Although dogs that retain voluntary motor function are not necessarily surgical emergencies, they will often make faster and more complete recoveries if their spinal cords are decompressed prior to complete paraplegia. 

On that same note, dogs with chronic disc extrusions and significant pelvic limb weakness are usually much more difficult to fully decompress. Disc material often adheres to the spinal cord, as well as the vertebral venous sinuses (very thin vein-like structures which run the length of the spine and are attached to the inside of the spinal canal) after it has extruded. 

Removal of the disc content, therefore, requires some degree of manipulation of the spinal cord and is frequently associated with moderate hemorrhage from the vertebral sinuses, which can significantly prolong the surgical time. Furthermore, these chronically compressed spinal cords are much less tolerant of any surgical manipulation and these patients are often neurologically more compromised postoperatively before they begin to show improvement.

If you have a dog with cervical or thoracolumbar pain and/or weakness in either the pelvic limbs or all four limbs, you should see your primary care veterinarian as soon as possible. Referral for a complete neurological examination and imaging should be done early in the course of the problem for the most favorable prognosis. 

If you are an owner of a French Bulldog, please note that this breed is particularly known to have rapidly progressive signs once they begin, and often have severe spinal cord compression resulting from disc extrusions. It is therefore recommended to have these dogs referred once they begin to demonstrate back or neck pain and/or limb weakness. 

Sage Veterinary Imaging in Texas

Sage Veterinary Imaging in Round Rock, Texas is the only outpatient veterinary imaging center in Central Texas. We are a one-stop shop for imaging and diagnosis. MRIs with us are faster and easier than with other providers. Because no referral is needed and there’s very little paperwork, you save time and get a treatment plan right away. 

You want state-of-the-art, high-tech imaging equipment so you get the best images available, with the most information. Knowledge is, indeed, power! Our MRI produces research-grade images that allow our radiologists to find and assess the problem with exceptional detail. Results go to you and your veterinarian so a treatment plan can be made.