Computed tomographic findings in 101 horses presented for the investigation of headshaking

Abstract

SummaryBackgroundThe majority of horses presenting to a hospital with signs of headshaking receive a diagnosis of trigeminal‐mediated headshaking. This diagnosis is one of exclusion, so ruling out other possible causes of headshaking is essential.ObjectivesThe aims of this study were to describe the computed tomographic (CT) findings in horses that were presented for investigation of headshaking and underwent CT examination of the head under standing sedation. A secondary aim was to establish whether the proximity of the apices of the caudal maxillary cheek teeth to the infra‐orbital canal varied between age‐matched groups of horses presented for CT examination for investigation of headshaking and those presented for investigation of other conditions.Study designRetrospective case series of horses undergoing CT examination of the head as part of the investigation of headshaking at the Equine Centre, University of Bristol.MethodsCase records of horses that had standing CT images of the head obtained, reviewed and reported at the Equine Centre, University of Bristol over a 5‐year period (February 2012–March 2017) were reviewed. Cases that had presented for investigation of headshaking were included. The proximity of the apices of the maxillary cheek teeth to the infra‐orbital canal was assessed in age‐matched horses presenting for CT for investigation of headshaking and other reasons.ResultsA total of 101 horses presented for investigation of headshaking were included. There were four horses in which CT detected likely causative pathology for the headshaking which had not been identified by other diagnostic tests; however, radiographs had not been obtained in two of these horses. Three horses had periapical infection of the maxillary cheek teeth, and one horse had a fracture of the paracondylar process of the occipital bone. Clinical signs resolved following treatment in three horses; two with periapical infection and one with a paracondylar process fracture. One horse with periapical infection was lost to follow‐up. There was no significant difference in the proximity of the apices of the maxillary cheek teeth to the infra‐orbital canal between the head‐shaking and non‐head‐shaking groups.Main limitationsRetrospective study; pre‐selection of cases through discussion of the case and, in some instances assessment of videos of the behaviour, by the last author, prior to referral; lack of radiographs.ConclusionsWhilst trigeminal‐mediated headshaking is the most common cause of headshaking in horses, it is a diagnosis of exclusion so thorough investigation to rule out other possible causes is essential. We consider CT examination of the head to be a valuable tool in this investigation, although the diagnostic yield is likely to be low.