Does your pet suffer from back pain? Could it be IVDD?
What is an intervertebral disc?
The spinal column contains the spinal cord which is protected by the the veterbra. A squishy shock absorber, called a vertebral disc sits between each vertebra.
What is intervertebral disc disease (IVDD)?
Intervertebral disc disease is a condition that occurs when the outer layer of the intervertebral disc ruptures and the inner material is displaced, putting pressure on the spinal cord that can cause serious damage.
When is surgery indicated for IVDD?
Clinical signs begin when a bulging or ruptured disc applies pressure on the spinal cord or nerve roots which exit the spinal cord. When this happens, the front legs are usually not involved. Sometimes a protruding disc can occur in the neck and all four limbs may have neurological deficits. Usually the lesion is below the neck, and the back legs can be affected in varying degrees. Owners typically notice their pet is reluctant to move, crying out in pain, appears to be uncoordinated, and/or their pet may have rear limb weakness. One of the most severe neurological signs of IVDD is the inability to move the rear legs (paralysis).
If your pet has mild neurological deficits (weakness, incoordination, pain, etc) and he or she is able to move his or her legs, medical treatment may be warranted. Medical management involves strict cage rest, anti-inflammatory drugs, and possibly muscle relaxants for at least 4-8 weeks.
The onset of paralysis is a surgical emergency!
What tests are needed preoperatively?
A neurological exam is performed to localize the general region of the spinal cord lesion. Radiographs are taken of the spine to rule out other causes for pain, weakness, or paralysis (e.g. vertebral fracture, tumor, infection, etc.). A CT scan can be performed under general anesthesia to localize the lesion to a specific disc and site of compression. Blood tests are usually performed to make sure there are no underlying issues with any other body systems.
A cerebrospinal fluid analysis may be taken prior to the myelogram. Cerebrospinal fluid bathes the spinal cord and brain. It functions to deliver nutrients and eliminate waste products. Diseases of the central nervous system (e.g. cancer, infectious disease, immune-mediated, etc.) frequently declare themselves within the fluid.
What are the risks of a Myelogram?
A needle is placed between two vertebrae and directed into the spinal canal. Therefore, needle can lacerate blood vessels and portions of the spinal cord. Secondary hemorrhage and swelling can exacerbate spinal cord compression and neurological signs. The Iodinated contrast material used for the procedure can precipitate seizures the first 24 hours post-surgery. However, the seizures are transient and generally resolve without additional complications. Overall these complications are extremely rare and occur in less than 5 % of the cases.
What is involved in IVDD surgery?
As in human patients, general anesthesia is used to make sure the animal is unconscious for muscle relaxation and pain control. This will involve using a pre-anesthetic analgesic (alleviates discomfort), a brief intravenous anesthetic in order to place an endotracheal tube and then gas anesthesia for the remainder of preoperative preparation and surgery.
Your pet is transferred to the operating room where a procedure called a hemilaminectomy is performed. In this procedure, a window is made in the vertebral bone in order to alleviate spinal cord compression and to allow access to the disc material to be removed. The adjacent discs may also be removed at the time of surgery which is called fenestration. This procedure reduces the risk of adjacent disc material causing compression at different site.
The operation takes can take several hours to perform. The animal will have an IV catheter placed and your pet will remain on IV fluids throughout the surgery and post operatively. The patient will receive post operative analgesics to alleviate discomfort. Your pet will also have a urinary catheter placed because they will not have the ability to urinate on their own in the immediate post operative period. It may take 3-5 days before your pet will be able to urinate independently and without a urinary catheter.
What are the risks of a hemilaminectomy surgery?
There are risks with any type of anesthesia. General anesthesia has expected side effects to brain, kidney, cardiac and respiratory function which typically do not cause a problem, and are managed by the nurse anesthetist. Patients are placed on a multi-parameter monitoring device, a respiratory ventilator and a blood pressure machine in order to closely monitor these body systems. Occasionally these side effects can be life-threatening in critical patients. Generally, the risk of anesthesia is less than 1 %.
Prognosis for this surgery is good depending on a couple factors. The main factor is the presence or absence of deep pain in the rear legs. In dogs that have maintained deep pain before surgery have a recovery rate of 80-95%. The recovery rate declines when deep pain is lost. Dogs that have lost deep pain but have surgery within 12 hours have a 50-60% recovery. Those that go to surgery 12-36 hours after loosing deep pain, have a recovery rate of 25%. After 36 hours the recovery rate is only 5%.
Some patients do not improve neurologically and may deteriorate. These patients may require a cart to become mobile again and lifelong bladder expressions.
Approximately 5% of cases develop myelomalacia post-operatively. Myelomalacia is a progressive condition where the spinal cord begins to die and become necrotic. This condition has a grave prognosis, and patients usually are euthanized.
What is included in post operative care?
Being patient, good nursing care and physical therapy are necessities during this period of convalescence. Strict cage rest is required to allow the spinal cord time to heal. Patients will usually not walk during the immediate post operative period. Voluntary motor control (e.g. ability to walk or stand) may take several weeks to return. The ability to urinate on its own, may take a couple days. You may be required to express the bladder a couple times a day until the dog is able to. The staff or doctor can show you how to express the bladder. Most of the time the patient remains hospitalized until he or she can urinate on their own.
The patient will be sent home with pain medications, most often times they will have a fentanyl patch applied to their skin. This will provide pain relief for a couple days and may be supplemented with oral medication once the patch has expired in 3-5 days.
Passive range of motion exercises may be started a few days post operative which involve gently flexing and extending the joints of the rear legs. There are a couple of rehabilitation centers in our area. If you are considering this course of action, we can provide information to you.
Consider reducing food intake during this period of convalescence, as it will trend towards weight gain. Additional weight gain will exacerbate discomfort and delay healing.