Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs

摘要

Caudal occipital malformation syndrome (COMS) is a recently described disorder in dogs that is believed to be analogous to Chiari type I malformation of human beings. The disorder has been recognized in a number of small-dog breeds, with Cavalier KingCharles Spaniels being most commonly reported, and there is strong evidence to suggest that COMS is a heritable condition in Cavalier King Charles Spaniels. The underlying abnormality in dogs with COMS is a malformation of the caudal portion of the occiput, resulting in overcrowding of the caudal fossa. The diagnosis of COMS in dogs and Chiari type I malformation in people is most often made by means of magnetic resonance imaging (MRI). Affected individuals typically have some degree of cerebellar compression as a result of the occipital malformation, as well as constriction of the cervicomedullary junction in the vicinity of the foramen magnum. It is thought that the bony compression at the cervicomedullary junction, in conjunction with turbulent CSFflow and pressure changes in the region, results in hypertrophy of the underlying meninges over time, and dural fibrosis has been documented histologically in humans and dogs with this malformation. Focal meningeal hypertrophy at the level of the foramen magnum is believed to be responsible for progressive constriction at the cervicomedullary junction, which in turn leads to increased CSF pressure in the intracranial and spinal compartments over time.