Intervertebral Disk Disease 

When the intervertebral disks become damaged, this is referred to as intervertebral disk disease ("Disk disease", "Slipped disk"). As disks age, they lose water content, and become less able to withstand compression. They become less able to withstand forces placed upon them. If too much force is placed on them, they can be squeezed and expand or rupture. This rupture usually occurs in an upward direction, and the disk extrudes into the spinal canal where the spinal cord is. Signs develop either because of the force of the disk material hitting the cord, or due to the disk material compressing the spinal cord.

    Intervertebral disk disease can occur in any area of the spinal cord. Dachshunds appear predisposed, as their disks age or degenerate quicker than most dogs.  In addition, the elongated trunk of the Dachshund makes the breed a prime target for the disease.  It is most prevalent between the ages of three and six years. Dogs less than 1 year of age rarely have intervertebral disk disease. Geriatric dogs are occasionally affected. Clinical signs of disk disease are rare in cats.

Canine Intervertebral Disk Disease - Article from the Dachshund Club of America.

Disk Disease - Information on Disk Disease from Michael Wolf, DVM; Diplomate  Oakland County, MI.