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Understanding Chiari-like malformation: where are we now?
  1. Rita Gonçalves, DVM, DipECVN, MRCVS
  1. Department of Veterinary Sciences, School of Veterinary Science, University of Liverpool, Chester High Road, Neston, Cheshire CH64 7TE
  1. e-mail: r.goncalves{at}

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CHIARI-LIKE malformation (CM) has been recognised in the Cavalier King Charles spaniel (CKCS) for many years and it is now thought to affect as many as 95 per cent of dogs within this breed (Dewey and Rusbridge 2008). CM has been defined as decreased caudal fossa volume with caudal descent of the cerebellum, and often the brainstem, into or through the foramen magnum (Cappello and Rusbridge 2007). This malformation is often associated with the development of syringomyelia, a condition in which fluid-filled cavities develop within the spinal cord as a consequence of abnormal cerebrospinal fluid movement (Rusbridge and others 2006). Currently, the most accepted theory for syringomyelia formation is that it most likely develops secondary to changes in cerebrospinal fluid (CSF) flow dynamics in the subarachnoid space at the cervicomedullary junction. This includes changes in velocity, pressure differentials and turbulence, caused by a relative obstruction of CSF flow by herniated cerebellar components, which results in repetitive distension of the spinal cord and accumulation of tissue fluid – the syringomyelia (Nishikawa and others 1997, Rusbridge and others 2006).

In humans, type I Chiari malformations are characterised as a developmental failure of the occipital bone resulting …

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