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

Abstract

Background:The 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. Objectives:The 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 design:Retrospective case series of horses undergoing CT examination of the head as part of the investigation of headshaking at the Equine Centre, University of Bristol.Methods: Case 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.Results: A 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 headshaking and non-head-shaking groups.Main limitations: Retrospective 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.Conclusions: Whilst 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.

Impact of Different Diagnostic Procedures on Diagnosis, Therapy, and Outcome in Horses with Headshaking: Recommendations for Fast-Track Advanced Diagnostic and Therapeutic Protocols

“…When examining the equine head, CT as a three-dimensional imaging technique proved to be superior to radiographs in the diagnosis of multiple clinical conditions [ 29 , 30 ]. Additionally, the CT of the head was evaluated as important for diagnostic investigation in horses with HS, even though only in 4/101 horses, possible causative underlying diseases were diagnosed [ 31 ]. This was confirmed within this study, as CT was more beneficial than other imaging techniques such as radiographs, endoscopy, and MRI, which did not reveal any clinically relevant additional impact.…”

Surgical treatment of headshaking by removal of a paracondylar process fragment via modified hyovertebrotomy approach: A detailed anatomical and surgical description in an adult horse

“…2 The temporal bone (pars petrosa) releases the facial nerve (cranial nerve VII) via the foramen stylomastoideum in close proximity and rostral to the PCP. 1 Fracture of the PCP has previously been reported [3][4][5] and was associated with facial nerve paralysis, 3,4 headshaking, 4,5 and poor performance. 4 Resolution of clinical signs was achieved with conservative management in three out of five horses.…”

“…4 Resolution of clinical signs was achieved with conservative management in three out of five horses. 4,5 However, two cases required surgical intervention. The objective of this study was to describe in detail the relevant anatomy and a surgical approach tailored to the purpose of accessing the PCP and report its application in a clinical case.…”

Trigeminal‐mediated headshaking: A diagnostic challenge

“…Careful anamnesis, physical examination and often diagnostic imaging are therefore required for correct diagnosis (Pickles et al, 2014). Previously, ‘idiopathic headshaking’ was diagnosed in 97% of headshakers presenting to equine hospitals; however, with the advent of advanced imaging modalities such as computed tomography (CT), causative pathology is identified in up to 10% (Fairburn et al, 2023). This emphasises the merits of these ancillary diagnostic techniques and suggests that, perhaps, we may even still be overdiagnosing true, functional, trigeminal‐mediated headshaking.…”

“…Previously, 'idiopathic headshaking' was diagnosed in 97% of headshakers presenting to equine hospitals; however, with the advent of advanced imaging modalities such as computed tomography (CT), causative pathology is identified in up to 10% (Fairburn et al, 2023).…”