Unlike humans and even IVDD in the cervical (neck) region in dogs, T-L IVDD can be a true veterinary emergency. Because of the anatomy of the spinal cord in dogs, unlike people, as a disc herniates (ruptures), it actually impacts the spinal cord creating compression within the spinal canal and potentially life-threatening paralysis. All dogs are susceptible to disc disease and rupture, but the Beagle, Dachshund, Cocker Spaniel, Corgi and Bassett Hound are most frequent. These particular breeds, known as Chondrodystrophic, have intervertebral discs that tend to dehydrate and become more cartilaginous with time making them more prone to cracking and rupturing. Along with the cervical region (see Cervical Disc Disease), the mid-back and lumbar spinal areas are most at risk. Where the cervical discs cause mainly sharp pain and discomfort, the T-L discs, when ruptured can cause varying degrees of partial to irreversible paralysis. Early surgical intervention is the key to success and most cases, if operated early, have a very good prognosis.
Most dogs will initially have pain due to nerve root irritation, but this may only be the early warning sign, as compression from ongoing herniation results in cord dysfunction and loss of placement perception and motor function. Initially, a dog may avoid jumping and going upstairs and show tenseness and pain on being picked-up. This is the first indication, especially in a chondrodystrophic breed, that medical attention is needed.
Pain control and strict confinement are necessary if a patient is to recover from early disc disease. It is important to know that proper management and compliance is critical, but still may not prevent continued herniation and an owner should not wait if paralysis begins to set in. For a patient to recover medically without further progression, 3 weeks of no running, jumping or stairs and being carried outside is usually required. Pain medication as prescribed by your veterinarian should be administered for at least the first week of the restricted period.
Progression of Signs
It is important for the owner to be very observant of any progression, particularly the knuckling or dragging of the toes, indicating there is now a loss of proprioceptive reflexes. The tail is also a great indicator of progression. Loss of a good tail wag usually correlates with increased cord compression and paralysis can follow. The neurological progression scale is as follows: PAIN, KNUCKLING, TAIL WAG, DRAGGING THE REAR (MOTOR PARALYSIS), DEEP PAIN PERCEPTION FOLLOWED BY LOSS OF DEEP PAIN PERCEPTION. These are the factors evaluated to deem a patient as a surgical candidate. The last indication of severe progression is the LOSS of DEEP PAIN perception, and intervention before this point is critical.
The goal of T-L IVDD surgery is to relieve the pressure on the spinal cord caused by the herniated disc. It is vitally important, in order for surgery to be successful, that we be able to identify the specific disc that is herniated. Fortunately only one disc will herniate at a time and the odds of a second disc occurring in the future is about 10%. Localization of the specific disc is based on neurological exam, a very detailed radiographic imaging and an MRI if available. The MRI unit at the VRC was acquired with these patients in mind. Once the site of herniation has been found, then a decompressive surgical procedure known as a hemilamenectomy is performed to relieve pressure and allow the spinal cord to heal. The spinal cord is a very recoverable tissue as long as compression has not resulted in permanent cord injury.
Patients are hospitalized for 3 – 5 days postoperatively or until it is confirmed that they can urinate voluntarily on their own. At home they need time to continue the healing process and this requires close confinement to a small area. Reevaluation with the surgeon at 2 and 6 weeks postop is advocated to assess the progress.