Clean Run - June 2011 - 52

of this type of disc disease occurs between three and six years of age. As the disc degenerates, it dehydrates and the inner gelatinous portion becomes less like jelly. These processes interfere with the ability of the discs to absorb shock and place additional mechanical stress on the outer portion of the disc. Normal wear and tear often causes further weakening until the nucleus pulposus is allowed to leak into the vertebral canal causing a concussive trauma (bruising) to the cord and secondary displacement or compression of the spinal cord due to the presence of disc material within the canal. Fibroid Metaplasia (Hansen Type II IVDD) This typically occurs in non-chondrodystrophoid breeds later in life. The discs dehydrate more slowly and dogs are usually minimally affected while they are young and active. Clinical problems generally arise between ages six and eight and may or may not cause clinical signs. With this type of disc disease, the outer shell bulges into the vertebral canal, causing chronic spinal cord compression (but does not cause the acute spinal cord bruising like the more explosive Type I disc rupture).

from a human, and this is largely related to how forces are distributed through the body of a biped as compared to a quadruped, and differences in spinal cord anatomy. In the human, the spinal cord ends and splits into nerve roots much higher than the spinal cord of the dog. A disc bulge of the lower back in a person may present with severe pain or sciatica in one leg, but a dog with a herniation in the same location may be unable to walk. Clinical signs vary depending on the affected segment of the spinal cord and with the type of disc rupture. Neck or back pain is often the earliest or only clinical sign, which is often mistaken for abdominal pain or constipation. It is typical for agility patients to perform subpar, knock bars, or appear “roached” in the back. More severely affected dogs may have decreased awareness of where their paws are placed when walking, or even lose the ability to move their legs. Urinary retention, fecal incontinence, complete paralysis, and loss of feeling in the feet can also develop. This progressive spinal cord dysfunction can take minutes to months to occur. Typically, dogs with a disc rupture in their neck remain ambulatory but experience a great deal of discomfort. If the herniated disc occurs in the mid to lower back, clinical signs are typically more severe (due to the smaller size of the vertebral canal) and only affect the hind limbs. Examination Patients that present with spinal pain should be thoroughly evaluated to rule out underlying orthopedic conditions (bilateral cranial cruciate ruptures are commonly mistaken for disc ruptures) and metabolic abnormalities. A proper neurological

History and Clinical Signs
Disc herniation can present as a sudden or chronic injury. The way a dog exhibits signs of disc herniation can vary significantly

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Clean Run - June 2011

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