The bones of the back (vertebrae) possess a canal in which the spinal cord travels.  Between the vertebrae are spongy cushions (disks) which act as shock absorbers.  The disks lie just beneath the spinal canal.  When the disk becomes weak, the rubbery outer material or the jelly-like inner material of the disk can bulge into the spinal canal, pressing on and injuring the spinal cord and roots of nerves that exit the cord.  This causes pain in the neck or back and weakness or paralysis in the hind legs.

Incidence
Most disk problems occur in the neck (cervical disks) or in the lower back (lumbar disks).  Chondrodystrophic breeds of dogs are those with backs disproportionately long for their legs, such as beagles, dachshunds, bassets, Shih Tzus, Lhaso Apso, and Pekingese.  Beagles frequently have cervical disk problems which tend to occur at 1 to 3 years of age.  Dachshunds often have lumbar intervertebral disk problems between 3 and 6 years of age.

Signs
Protrusion or extrusion of intervertebral disks in the neck cause severe pain in the neck and at times, a front leg.  The pain can be severe preventing the dog from moving its head without moving its body at the same time.  Disk problems in the neck can also prevent the dog from being able to lower its head to eat or drink.

Lumbar disks cause lower back pain which may cause the dog to stand and walk with its back arched.  It may be unable to feel where its feet are placed and will stand with the toes on hind foot knuckled under.  More severely affected cases may stagger when walking or be unable to walk or stand, depending on the degree of compression of the spinal cord.

Diagnosis
Your veterinarian can make a diagnosis of intervertebral disk disease based on your pet’s history and physical exam findings.  Radiographs (x-rays) of the back may provide further evidence.  In cases with severe pain or paralysis, a myelogram may be necessary.  A myelogram is performed by injecting a dye into the spinal canal that makes the spinal cord visible on radiographs.  The dye lining the spinal cord can demonstrate where the spinal cord is compressed and the degree of compression.  Computerized tomography (CT) scans or magnetic resonance imaging (MRI) may be used in special cases.

Treatment
Mild cases of disk disease will spontaneously improve with forced rest (cage or baby crib confinement).  The disk material forms scar tissue and contracts withdrawing pressure from the spinal cord and nerve roots.  About 1/3 of dogs that recover will have similar problems in the future with other disks.

Severe disk problems require surgery to remove the disease disk material and decompress the spinal cord.  If all feeling has been lost in the hind legs, emergency surgical decompression is needed to prevent permanent paralysis.

Prevention Measures
Disk disease may not be preventable in susceptible breeds.  However, the severity of compression or risk of recurrence can be reduced by preventing obesity, encouraging mild daily exercise, and preventing sudden compression of disks.  Jerking on leashes connected to collars or allowing the dog to jump off furniture or climb down stairs can cause sudden compression of disks and should be avoided in dogs at risk for disk disease.

For more information, contact your local veterinarian or the MU Veterinary Medical Teaching Hospital 573-882-7821 or visit their web site.