title: Extramedullary spinal cysts in dogs.
abstract: OBJECTIVE
  To (1) synthesize the terminology used to classify extramedullary spinal cysts in dogs to clarify some of the commonly reported misconceptions, and (2) propose a classification scheme to limit confusion with terminology.
  
  
  METHODS
  Literature review.
  
  
  METHODS
  An online bibliographic search was performed in January 2013 for articles relating to extramedullary spinal cysts in dogs using PubMed (http://www.pubmed.gov/) and Google Scholar (http://scholar.google.com/) databases. Only peer-reviewed clinical literature describing cystic lesions pertaining to the spinal cord and associated structures was included.
  
  
  RESULTS
  From 1962 to 2013, 42 articles were identified; 25 (95 dogs) reported meningeal cysts, 10 (24 dogs) described 60 extradural cysts, 3 reports (18 dogs) described discal cysts or acute compressive hydrated nucleus pulposus extrusions (HNPE). Spinal cysts were categorized by location based on cross-sectional imaging as meningeal or extradural non-meningeal. Sub-classification was then performed based on surgical findings and pathology. Meningeal cysts included arachnoid diverticulae and Tarlov (perineural) cysts. Extradural non-meningeal cysts included intraspinal cysts of the vertebral joints, ligaments and discs. Discal cysts also fit this category and have been reported extensively in humans but appear rare in dogs.
  
  
  CONCLUSIONS
  Extramedullary spinal cysts should be first classified according to location with a sub-classification according to pathologic and surgical findings. Previous canine cases of discal cysts appear to represent a different disease entity and the term acute compressive HNPE is therefore preferred.
authors.affiliation: Davies Veterinary Specialists, Higham Gobion, Hertfordshire, England.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Lowrie
authors.forename: Simon R
authors.initials: SR
authors.lastname: Platt
authors.forename: Laurent S
authors.initials: LS
authors.lastname: Garosi
mesh_terms: D000818:Animals; D016080:Arachnoid Cysts / Q000473:pathology / Q000662:veterinary*; D004283:Dog Diseases / Q000145:classification / Q000473:pathology*; D004285:Dogs; D008279:Magnetic Resonance Imaging / Q000662:veterinary*; D013118:Spinal Cord Diseases / Q000473:pathology / Q000662:veterinary*; D009626:Terminology as Topic