Cervical spondylomyelopathy (CSM) is a multifactorial disease characterized by cervical spinal cord compression secondary to vertebral canal stenosis. The stenosis results from vertebral malformation, which may be associated with secondary degenerative changes of structures surrounding the spinal cord.
Two basics groups of dogs are recognized. The first one includes immature or young adult large-breed dogs such as Great Danes or Dobermans which present with osseous compression (bony stenosis). These developmental abnormalities (which can affect the articular facets, pedicle or vertebral arches) are directly responsible for the spinal cord compression, and multiple sites of compression are not uncommon. The second category includes middle-aged or older dogs which have soft tissue compression (articular facet synovial hypertrophy or cyst formation, dorsal longitudinal and ligamentum flavum hypertrophy, osteophyte production, dorsal or lateral disc extrusion or protrusion) with subsequent acquired stenosis of the vertebral canal.
The most common presentation of cervical spondylomyelopathy is a hind limb ataxia (or wobbliness) and progressive weakness. Initially the forelimbs may appear less severely affected than the hind limbs. Neurological examination most often is consistent with a neck problem. Cervical pain is usually mild or undetectable without deep palpation. In the case of nerve root compression, pain is usually more evident, especially on forelimb extension. Survey radiographs of the cervical spine are useful in order to rule out other differentials and may show vertebral malformation and/or degenerative changes typical of this syndrome. The diagnosis of cervical spondylomyelopathy is based on the demonstration of extradural cord compression by diagnostic imaging studies (computed tomography (CT) or magnetic resonance imaging (MRI)). These imaging modalities help to localize accurately the site and the type of compression (static or positional and traction-responsive or not). Each case should be assigned a definite subtype because therapy should be aimed at correcting the abnormality in that individual case, rather than treating every case the same way. MRI offers the advantage of giving better resolution of soft tissue (ligament structures, compression or parenchyma malformation, spinal cord atrophy) as well as three-dimensional views. An MRI requires general anesthesia and carries a very low risk (<1%) of complication including death.
Treatment consists of either medical management or surgery. Medical management consists of anti-inflammatory medications and exercise restrictions. Surgery should be considered in dogs that have progressing symptoms despite medications. Various surgical techniques are used to treat cervical spondylomyelopathy depending on the precise nature of the problem. Two basic types of surgical interventions are direct decompression techniques, such as ventral slot, dorsal laminectomy or facetectomy, and indirect decompression techniques via distraction/fusion.
The prognosis for cervical spondylomyelopathy syndrome is overall fair. Generally dogs will have a favorable response initially to medications, but symptoms can progress with time. Surgery tends to offer a better long solution, however many variables are to be considered. Generally speaking, about 75-80% of dogs will have a positive outcome with surgery.