Mielopatía Estenótica Cervical
Cervical stenotic myelopathy (CSM) is one of the most common causes of spinal ataxia in young horses. The layman’s term for CSM is wobbler syndrome. Alternative scientific terms to describe the condition include cervical vertebral malformation/instability and cervical compressive myelopathy. In this condition, neurologic gait deficits result from compression of the spinal cord by malformed cervical vertebrae. Developmental orthopedic diseases of the appendicular skeleton, such as physitis, joint effusion, osteochondrosis, and flexural limb deformities, occur more frequently in horses with CSM. A direct cause-and-effect relationship between osteochondrosis and CSM has not been identified; however, the associative relationship indicates that the pathophysiology of these two conditions is similar.The cause of CSM is likely multifactorial, consisting of genetic and environmental influences. It is unlikely that CSMis heritable by simple Mendelian dominant/recessive patterns. The mode of inheritance more likely involves multiple alleles and variable penetrance, which determine genetic predisposition to CSM. A high plane of nutrition, micronutrient imbalance, rapid growth, trauma, and abnormal biomechanical forces likely contribute to the development of CSM in genetically predisposed individuals.
Spinal cord compression can be dynamic or static in horses with CSM. Dynamic compression results from vertebral instability and produces intermittent spinal cord compression during ventroflexion of the neck; compression is relieved when the neck is in the neutral position. Static compression is defined as continuous spinal cord impingement regardless of cervical position. Both static and dynamic compression are associated with narrowing of the vertebral canal from C3 to C6, regardless of the site of spinal cord compression, indicating that generalized vertebral canal stenosis is an important factor in the pathophysiology of CSM.
CSM has been increasingly recognized as a cause of spinal ataxia and cervical pain in horses older than 10 years. Spinal cord compression in this age group primarily results f rom osteoarthritic enlargement of the caudal cervical articular facets, with or without some degree of vertebral instability. Affected horses appear neurologically normal until osteoarthritic enlargement of the articular facets impinges on the cervical spinal cord. Not every horse with osteoarthritis of the caudal cervical vertebrae develops spinal cord compression. Similar to humans who develop spinal cord compression secondary to articular facet osteoarthritis in middle age, horses that develop neurologic gait deficits are predisposed due to an existing narrowed vertebral canal.