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Dog: Intervertebral Disk Disease

General information

Other common/scientific names: bulged disk, IVDD, herniated disk, ruptured disk, slipped disk

A dog’s spine is composed of a long series of bones called vertebrae. These bones maintain the structure of the body and protect the spinal cord which is housed within the vertebrae. The vertebrae are connected through a series of ligaments. The vertebrae are divided into sections based on their location, i.e. cervical (neck), thoracic (chest), lumbar (lower back) and sacrum (tailbone). Between each vertebra are structures called disks which act as shock absorbers. The spinal cord runs through the vertebrae on top of the disks. The disks are composed of two layers: the gel-like center and the outer fibrous ring.

Intervertebral disk disease refers to the condition where the disk(s) deteriorates. The inner gel portion may calcify (harden) losing its resiliency or cushioning ability. The fibrous ring becomes thin and the gel-like center can either bulge or rupture (herniate) upward into the spinal cord. This bulging or ruptured disk causes irritation, pressure and damage to the spinal cord.

Abb. GG4TNIB9
Abb. GG4TNIB9: This is a illustration of a longitudinal section through the spine.

Abb. GG4TOT04
Abb. GG4TOT04: This is an illustration of a cross section of the intervertebral space indicating the disk, spinal cord and vertebra.

Abb. GG4TQON6
Abb. GG4TQON6: This is an illustration of two cross sections of the intervertebral space.
Figure (a) illustrates a disk bulging off to the side causing pressure where nerves exit the spinal cord. Figure (b) illustrates a disk bulging upward compressing the spinal cord.

Causes

The most common cause of intervertebral disk disease is normal aging and degeneration of the disk. The long, low chondrodystrophic breeds are more prone to IVDD. These breeds include the Dachshund, Basset Hound, Corgi, Pekingese and Lhasa Apso where there is a genetic predisposition for disk degeneration. While most herniated disks are caused by degeneration, trauma such as being hit by a car or falling off of furniture can be a cause. Middle-aged dogs are more commonly affected.

Cardinal symptom

Pain

Symptoms

Disk disease can occur anywhere along the spine but is most commonly seen in the neck area, mid back area and lower back area. The clinical signs will depend on the location of the diseased disk and the amount of spinal cord damage. Bulging disks cause less severe symptoms; whereas, a ruptured disk can cause severe signs. The most common clinical sign of disk disease is pain. This may be acute (sudden) or chronic (long lasting). Cervical disk disease causes a stiff neck and neck pain - especially when the neck is moved. A bulging disk in this area can cause limping on a front limb. Cervical disk rupture can lead to weakness, wobbliness, knuckling of the paws and paralysis in all four limbs. Disk herniation in the mid to lower back area may cause back pain, hind limb weakness, wobbly gait, paralysis of the hind limbs and loss of bladder or bowel control.

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Abb. GG4TWP9Q: Herniated Disk.
This is a photograph of a dog with a herniated disk causing paralysis in both hind limbs.

Diagnosis

A complete physical and neurologic examination should be performed on all dogs showing signs of disk disease. A neurologic examination helps determine which spinal nerves are affected by testing the nerve reflexes. While radiographs of the spine may reveal a calcified, ruptured disk compressing the spinal cord, not all herniated disk are visible on radiographs. A definitive diagnosis can only be made with a myelogram (a radiograph taken after a special dye has been injected into the space surrounding the spinal cord), magnetic resonance imaging (MRI) or computed tomography (CT). These procedures require general anesthesia. A myelogram can pinpoint the exact area of spinal cord compression. An MRI evaluates the disk and spinal cord, while at CT scan shows malformation of the vertebrae. Myelograms, MRIs and CT scans are typically performed at universities or referral clinics specializing in neurology and orthopedics.

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Abb. GG4U4PAO: Herniated Disk.
This is a photograph of an anesthetized dog undergoing CT.

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Abb. GG4U68FR: Herniated Disk.
This is an MRI image of herniated disk. The red arrow points to the bulging disk (C). The spinal cord is indicated as (B) and the vertebrae are shown as (A).

Treatment

Conservative Treatment

Treatment can be conservative therapy if the signs are mild. This includes 4 to 6 weeks of strict rest and short leash walks - no running, jumping, playing or stairs. Medications including corticosteroids or NSAIDs (non-steroidal anti-inflammatory drugs) are used to relieve spinal cord swelling and pain. Massage, physical therapy and acupuncture can be used for pain control.

Surgical Treatment

Surgical treatment is indicated if the dog does not respond to conservative therapy, the pain is recurrent or the dog cannot walk. The surgical technique used will depend on the location of the herniated disk. Cervical herniations are surgically treated by removing the protruding disk material to take pressure off the spinal cord. Fenestration of other disks in the area may also be performed to prevent future disk ruptures. Fenestration involves making an incision into the bottom of the disk to allow the gel-like center to be removed.

Thoracic and lumbar herniations are surgically treated with a hemilaminectomy. This procedure removes one wall of the vertebrae to allow extraction of the protruding disk material. Disk fenestration is usually performed at the same time to prevent future disk rupture.

Postoperative care will include anti-inflammatory and pain medications. Strict cage confinement except for urination and bowel movements is needed for one month. Physical therapy in the form of slings, carts, exercises and swimming is used to regain strength and coordination. This is especially important with dogs which are very weak or paralyzed. If bladder control is lost, the bladder may need to be expressed to prevent it from becoming too distended. A soft padded bed is vital to prevent bed sores.

Prognosis

Prognosis will depend on the amount of disk material that has ruptured, the amount of spinal cord swelling and damage, the length of time the disk has been ruptured and the severity of clinical signs. Many dogs respond well to treatment, have immediate pain relief and regain full mobility. Dogs which are paralyzed prior to surgery may take 1 to 3 weeks to regain mobility. Severe damage to the spinal cord can result in permanent paralysis and urinary/fecal incontinence.

Prevention

Dogs which have suffered from disk disease are prone to recurring episodes. Preventing these dogs from jumping on furniture and building ramps to avoid stair stepping can reduce these recurrences. These preventative measures should also be taken for chondrodystrophic dogs. All dogs should also be maintained at a healthy weight to decrease the stress on the vertebral disks.

Tips

During rehabilitation, placing a towel or sheet under your dog’s abdomen can be used as a means of support. Allowing your dog to gradually bear weight on the affected limbs can aid with his recovery. Please administer all medications and follow all instructions as prescribed by your veterinarian.

CAUTION

If you notice neck or back pain, weakness, wobbliness or paralysis, call your veterinarian immediately. The quicker disk disease is diagnosed and treated, the better chance of recovery.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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