Canine intervertebral disk disease (IVDD) and chronic spinal cord compression were first described in the late 1800s. Today, IVDD is the most common clinical spinal disorder in dogs. Manifestations can include pain, a partial loss of limb function, paralysis, and sometimes a loss of hind limb nociception. Chondrodystrophic dogs and dogs over 2 years of age are more commonly affected, but IVDD can occur in any breed. Cervical IVDD is more common at the C2-C3 site, and thoracolumbar IVDD is more common in the lower thoracic or upper lumbar regions.<\/p>\n
Although surgical and medical therapeutic options are available, acute, progressive, severe, and compressive injuries are best managed with surgery. Prognosis is very good when dogs maintain intact nociception. Prognosis is less favorable with loss of nociception but is not always hopeless. This article discusses the many manifestations of this disorder and current therapeutic recommendations.<\/p>\n
Take-Home Points<\/strong><\/p>\n Intervertebral disk disease (IVDD) and chronic spinal cord compression myelopathy associated with IVDD in the dog were first described in the late 1800s.1-3<\/sup> From the early to middle l900s, significant works describing the clinical and radiographic manifestations of IVDD were published. In the 1950s, numerous reports described the predisposition for IVDD in chondrodystrophic dogs.1<\/sup> Hoerlein, Olsson, Hansen, Funkquist, and many others contributed significantly to the literature in the 1950s and 1960s, forming the foundations of our current medical and surgical therapies for IVDD.1,4-9<\/sup> Numerous publications concerning modification of surgical technique, radiologic diagnosis, pathology, pathophysiology, and incidence of IVDD have appeared since the 1970s.10-13<\/sup> Most of the current literature describes modifications of previous techniques, ancillary therapies, genetic studies,14,15<\/sup> and a concentration on physical therapy techniques.16<\/sup><\/span><\/p>\n Today, IVDD is the most common clinical spinal disorder in dogs. IVDD is manifested by pain, a partial loss of limb function, paralysis, and sometimes a loss of feeling in the hind limbs. It occurs most frequently in chondrodystrophic dogs such as the dachshund, French bulldog, Pekingese, Shih Tzu, basset hound, and American cocker spaniel. IVDD can also occur in many other, nonchondrodystrophic breeds, such as the German shepherd and Labrador retriever. In addition, over the past several years, noncompressive forms of the disease have been more detailed in the literature. <\/span><\/p>\n The intervertebral disk is located between each vertebra except for the C1-C2 junction. The normal intervertebral disk consists of a fibrous outside ring (anulus fibrosus) and a soft gel-like center (nucleus pulposus). The function of the intervertebral disk is to connect the vertebrae, act as a shock absorber, and provide rotational stability to the vertebral column. Degeneration of the intervertebral disk occurs when the nucleus pulposus begins to dehydrate or lose water. A dehydrated disk no longer functions as a good shock absorber. <\/span><\/p>\n In the chondrodystrophic dog, degeneration of the intervertebral disk begins between 2 months and 2\u00a0years of age. By 1\u00a0year of age, 75% to 100% of all intervertebral disks have undergone degeneration in some chondrodystrophic dogs.1<\/sup> This type of degeneration occurs rapidly and is frequently followed by mineralization of the intervertebral disk. Recent evidence suggests that this rapid degenerative process is associated with expression of a fibroblast growth factor 4 retrogene on chromosome\u00a012.14,15<\/sup> A different type of intervertebral disk degeneration occurs in nonchondrodystrophic dogs; it is a slow aging process most evident between 6 and 10\u00a0years of age and is rarely accompanied by mineralization. Some contend it is a similar process, just at a slower pace.17<\/sup><\/span><\/p>\n One often pictures the middle-aged chondrodystrophic patient that presents with back pain and paraparesis or paraplegia resulting from an intervertebral disk extrusion (IVDE); however, other forms exist. Compressive forms consist of extrusion of the nucleus pulposus into the vertebral canal (Hansen type 1; <\/span>FIGURE 1<\/b><\/span>) and protrusion of the intervertebral disk into the canal (Hansen type 2; <\/span>FIGURE 2<\/b><\/span>). Noncompressive forms of the disease are fibrocartilaginous emboli (FCE; <\/span>FIGURE 3<\/b><\/span>), acute noncompressive nucleus pulposus extrusion (ANNPE; <\/span>FIGURE 4<\/b><\/span>), and hydrated nucleus pulposus extrusion (HNPE; <\/span>FIGURE 5<\/b><\/span>). These forms can only be definitively distinguished with advanced imaging.<\/span><\/p>\n\n
IVDD Anatomy, Function, and Pathogenesis<\/h2>\n
Types and Signs of IVDD<\/h2>\n
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Figure 1. Transverse computed tomography (CT) image of a massive Hansen type 1 cervical intervertebral disk extrusion in a chondrodystrophic dog (arrow). The compressive nuclear material in the vertebral canal and that still remains within the anulus is heavily mineralized and is readily seen on a CT scan. In chondrodystrophic dogs, the mineral content of the nucleus pulposus often allows diagnosis with the CT scan.<\/span><\/a><\/div><\/div>Figure 2A. Sagittal magnetic resonance image of a Hansen type 2 intervertebral disk protrusion in the cervical spine of a nonchondrodystrophic dog.<\/span><\/a><\/div><\/div>FIGURE 2B. Transverse magnetic resonance image of a Hansen type 2 intervertebral disk protrusion in the cervical spine of a nonchondrodystrophic dog. Note the distortion of the spinal cord caused by the type 2 compression on the transverse image (arrow).<\/span><\/a><\/div><\/div>Figure 3A. Sagittal T2-weighted magnetic resonance image of a fibrocartilaginous emboli in the cervical vertebral column of a nonchondrodystrophic dog.<\/span><\/a><\/div><\/div>FIGURE 3B. Transverse T2-FatSat (fat suppression) magnetic resonance image of a fibrocartilaginous emboli in the cervical vertebral column of a nonchondrodystrophic dog. Note the increased signal over a large area in the cervical intumescence (arrow).<\/span><\/a><\/div><\/div>FIGURE 4A. T2-weighted sagittal image of a dog with an acute onset of a thoracolumbar syndrome. An acute noncompressive nucleus pulposus extrusion is evident at the L1\u2013L2 junction (arrow).<\/span><\/a><\/div><\/div>FIGURE 4B. Transverse image of a dog with an acute onset of a thoracolumbar syndrome. Note that the hydrated L1\u2013L2 intervertebral disk has a reduced volume as compared to the adjacent intervertebral disk and the hyperintensity in the cord on the transverse image (arrow).<\/span><\/a><\/div><\/div>