Intervertebral Disc Disease (IVDD) in dogs

What is Intervertebral Disc Disease? 

There are two types of Intervertebral Disc Disease (IVDD).  

The most common type of IVDD and is characterised by the rupture of the inner portion of the disc through the outer layer into the spinal canal where the spinal cord is located. This causes two types of damage, compression (pressure) and contusion (bruising) of the spinal cord. This is referred to as type 1 intervertebral disc extrusion. 

This type of IVDD is most common in Chondrodystrophoid breed dogs (dogs have short legs relative to their body) such as Dachshund, Terriers, Basset Hounds, Lhasa Apso and Beagles but can occur in any dog. In these dogs, an underlying abnormality causes premature degeneration (early decline) causing the disc to become hard and inflexible. As a result it may rupture or herniate from something as simple as jumping up or down from furniture. These dogs often show quite significant neurological signs which can range from spinal pain, a wobbly gait (ataxia), muscle weakness in their legs making it difficult to stand or walk (paresis), to complete paralysis. In severe cases, some dogs may also lose sensation and the ability to feel their legs. 

A second type of IVDD is where the disc protrudes into the spinal canal without rupturing (Bulging disc). Type 2 disc protrusions usually occur over a longer period of time (chronic) and many dogs present with only mild symptoms which progress slowly over many months. This type of disc disease usually occurs in older, large breed dogs such as German Shepherds, Dobermans and Labradors but again can occur in any breed. The chronic spinal cord compression with this type of disc disease often causes atrophy (degeneration) of the spinal cord. Disc degeneration results in diminished shock-absorbing capacity and can ultimately lead to disc protrusion and spinal cord compression. 

With either type of IVDD, compression of the spinal cord disrupts the signals from the brain to the rest of the body and the severity of clinical signs will depend upon the degree of cord compression and bruising. These compressive diseases are surgical diseases of the spinal cord. 

Clinical Signs  

The clinical signs will vary dependant on the location of disc that is causing the injury and the type of IVDD – Type 1 or Type 2.  

The initial signs are usually associated with pain these include abnormal posture such as a hunched back, shivering, panting, unwillingness to move or settle and difficulty jumping or using stairs. This can progress to difficulty walking, poor control of the limbs, weakness, ataxia (wobbly walking) or complete paralysis and being unable to urinate. 

The most commonly affected region of the dog is the in the middle of the spine where the chest meets the abdomen (thoracolumbar region). Spinal cord compression in this region affects the nerves which connect the back legs to the brain and so dogs often appear weak or unable to stand on their hindlimbs. Unfortunately, the nerves which connect the urinary bladder to the brain also lie in this region of the spinal cord so in more severe cases, when the hindlimbs are paralysed, the dog may be unable to urinate properly. 

If a dog ruptures a disc in the neck, this may cause forelimb lameness, severe pain or all four legs can be affected depending on the type and amount of force endured by the spinal cord. 

Diagnosis 

IVDD is diagnosed through a combination of the dog’s history, a neurological examination, and advanced imaging. 

The neurological exam determines the segment/region of the spinal cord affected and diagnostic imaging such as MRI or CT scans are used to localise the exact location of the damaged disc. Imaging also allows us to also rule out any other conditions like fractures, masses or tumour, blood clots, cartilage embolism and inflammatory diseases. 

Any spinal injury is considered an emergency, and your pet needs to be referred and assessed by a Specialist Surgeon as soon as possible following the onset of clinical signs. Prognosis varies significantly with degree of function remaining when the pet is evaluated and surgically treated. Delay in treatment can worsen the prognosis. The ultimate factor determining the prognosis is the initial impact of the disease that cannot be assessed by examination or advanced imaging. 

Are all disc ruptures treated with surgery? 

The recommended treatment is based on the stage and grade of the disease.  

Animals that are still able to walk may be managed with medication and cage confinement. Complying with strict confinement is extremely important to allow for healing of a ruptured disc. Physical therapy under the guidance of a veterinarian (including controlled supervised swimming, massage and passive range of motion exercises) is also essential to prevent muscle wastage and preserve joint function. If the animal does not improve or continues to worsen surgery is the recommended treatment.  

More severely affected animals (those who are unable to stand and walk) or animals where there is no improvement or deterioration with rest are considered for surgery.  

What does surgery involve? 

The most common type of surgery is a decompressive procedure which involves removal of the extruded/protruded disc material compressing the spinal cord. The procedure involves burring away part of the vertebrae (bone) allowing access to the spinal canal to remove the damaged disc material relieving the pressure placed on the spinal cord. We may also cut a hole (fenestration) into the disc to remove any residual disc material that may herniate into the spinal canal in the future. 

When will we know if the surgery is successful? 

Unfortunately, success cannot be determined immediately. The return of neurological function, walking ability, and relief from pain may not occur for several days to weeks after surgery. Many animals will feel much better immediately after surgery, but others take longer to improve.  

Sadly, some patients will have irreversible spinal cord damage that cannot be detected until 3-14 days post the onset of clinical signs. Progressive myelomalacia starts to occur at the time of the injury and is not always seen at the time of surgery. This condition is progressive and irreversible damage to the spinal cord that results in death.   

Complications can occur at surgery, including haemorrhage (bleeding) around the spinal cord. This may worsen the chance of a successful surgery.  

Postoperative care 

In most cases, your dog will stay in hospital until they have regained bladder function. It may take days, weeks or months for them to regain the ability to walk and this depends on how severe their signs were before surgery. The prognosis following surgery is directly related to the neurological status and duration of clinical signs before surgery but unless they are very severely affected (loss of deep pain sensation), about 85-90% of dogs will achieve a functional outcome after spinal surgery for IVDD. Due to the nature of spinal cord injuries, the outcome is determined by the initial impact or trauma which cannot be assessed before and during surgery. Only time will tell if the individual animal can recover.  

During the initial 6-12 weeks following surgery restricted activity is essential. We recommend that your pet is confined to a crate/cage or small room with non-slip flooring. In many cases they will require assistance walking and will need to be carried or sling/tail walked outside for toileting. If there are other pets in your household, you will need to keep them separated. Large breed dogs can be challenging to safely manage at home and you will require the help of other people. This is important to note and ensures that you provide adequate care and prevent injury to yourself and pet.  

Physical therapy is an important part of your pets post surgical care. During the healing process it is important to maintain muscle tone and avoid muscle wastage and joint stiffness. The specific type of rehabilitation therapy, as well as the protocol for performing the rehabilitation therapy, will be outlined on an individual basis. 

Other types of spinal cord injuries 

Other types of non-surgical, spinal cord injuries may result from non-compressive disease processes where there is direct injury or compromise to the blood supply of the spinal cord. Fibro-cartilaginous embolism (FCE) is similar to a “stroke” in the brain and involves the interruption of the blood supply to an area of the spinal cord by a small embolism. This disease requires MRI for diagnosis and is not surgical.  

Acute non-compressive or high velocity low volume extrusion may also occur where the volume of herniated disc is so small that it does not compress the cord when it enters the spinal canal but the impact of extrusion causes contusion (bruising) and concussion to the spinal cord – these are also known as “explosive or missile” discs. These cases do not benefit from surgery and require months of rest and rehabilitation if the condition improves or recovers. The prognosis depends on the initial impact to the spinal cord, and only time will tell whether a patient recover or not. 

Other conditions that can present and show similar signs to IVDD include: 

  • Vertebral Fractures 
  • Spinal masses or tumours 
  • Blood clots 
  • Infection  
  • Inflammatory diseases 
  • Acute bilateral cranial cruciate ligament rupture 
  • Acute abdominal pain (e.g., acute pancreatitis) 
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