title: Imaging features of atlanto-occipital overlapping in dogs.
abstract: The imaging features of four dogs with atlanto-occipital overlapping are described. This malformation appeared to play a role in the development of neck pain, ataxia, variable cerebellar involvement, medullary kinking, and possibly syringomyelia. Using cervical radiographs, three of the four dogs were initially diagnosed with an atlanto-axial malformation. Because this disorder could not account for all clinical signs, magnetic resonance and computed tomography images were also acquired. These provided a more complete evaluation of the craniocervical junction, allowing detection of atlanto-occipital overlapping, medullary kinking, occipital dysplasia, abnormalities of the dens, and syringomyelia in these dogs. Head position during imaging affected the degree of atlanto-occipital overlap. These findings emphasize the need to modify the currently accepted imaging recommendations for dogs with head and neck pain and/or cranial cervical myelopathy. We suggest that the entire craniocervical junction be evaluated, even if atlanto-axial subluxation has already been detected. Moreover, we propose that atlanto-occipital overlapping is a perhaps underrecognized disorder that can influence the clinical signs and therapeutic outcome of dogs with anomalies of the craniocervical junction.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, T6 002B Vet Res Tower, Ithaca, NY 14850, USA. sc224@cornell.edu
authors.forename: Sofia
authors.initials: S
authors.lastname: Cerda-Gonzalez
authors.forename: Curtis W
authors.initials: CW
authors.lastname: Dewey
authors.forename: Peter V
authors.initials: PV
authors.lastname: Scrivani
authors.forename: Karen L
authors.initials: KL
authors.lastname: Kline
mesh_terms: D000818:Animals; D001270:Cervical Atlas / Q000002:abnormalities / Q000000981:diagnostic imaging*; D004283:Dog Diseases / Q000000981:diagnostic imaging*; D004285:Dogs / Q000002:abnormalities*; D005260:Female; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000662:veterinary; D008297:Male; D009777:Occipital Bone / Q000002:abnormalities / Q000000981:diagnostic imaging*; D011859:Radiography