title: Caudal anaesthesia of the infraorbital nerve for diagnosis of idiopathic headshaking and caudal compression of the infraorbital nerve for its treatment, in 58 horses.
abstract: BACKGROUND
  Idiopathic headshaking is often a facial pain syndrome, but a diagnostic protocol has not been described. In a previous study, caudal compression of the infraorbital nerve for treatment offered a fair success rate, but low case numbers and short follow-up time were limitations.
  
  
  OBJECTIVE
  To describe a diagnostic protocol for headshaking, examining the role of bilateral local analgesia of the posterior ethmoidal nerve (PET block). To report longer-term follow-up after surgery of the original cases and further cases and to determine whether changes to the technique influence success rates and complications.
  
  
  METHODS
  Records of horses that had undergone PET block and caudal compression surgery at 3 hospitals were reviewed. Modifications to the surgical technique included placing additional coils into the infraorbital canal and/or performing concurrent laser cautery of the nerve. Follow-up information was obtained by telephone contact with owners.
  
  
  RESULTS
  The PET block was performed in 27 horses, with a positive result in 23 of 27 (85%). Surgery was performed in 58 horses. A successful outcome was initially achieved in 35 of 57 (63%) horses, but recurrence occurred between 9 and 30 months later in 9 (26%). Surgery was repeated in 10 of 31 (32%) horses. Final success rate, considering only response to the last performed surgery, was 28 of 57 (49%) horses with median follow-up time of 18 months (range 2-66 months). Nose-rubbing was reported post operatively in 30 of 48 (63%) horses. This resolved in all but 4 horses, which were subjected to euthanasia. Response to PET block or change in surgical technique did not appear to influence outcome or complications.
  
  
  CONCLUSIONS
  The diagnostic protocol described is recommended for the investigation of headshakers. Caudal compression offers the best prognosis for a successful outcome compared with other treatments, for horses in which the only alternative is euthanasia. Surgical treatment of the disorder requires refinement, and the pathogenesis of the disorder requires investigation.
authors.affiliation: Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, North Somerset, UK. veronica.roberts@bristol.ac.uk
authors.forename: V L H
authors.initials: VL
authors.lastname: Roberts
authors.forename: J D
authors.initials: JD
authors.lastname: Perkins
authors.forename: E
authors.initials: E
authors.lastname: Skärlina
authors.forename: D A
authors.initials: DA
authors.lastname: Gorvy
authors.forename: W H
authors.initials: WH
authors.lastname: Tremaine
authors.forename: A
authors.initials: A
authors.lastname: Williams
authors.forename: S A
authors.initials: SA
authors.lastname: McKane
authors.forename: I
authors.initials: I
authors.lastname: White
authors.forename: D C
authors.initials: DC
authors.lastname: Knottenbelt
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D006257:Head / Q000503:physiopathology; D019416:Head Movements; D006734:Horse Diseases / Q000503:physiopathology / Q000601:surgery*; D006736:Horses; D009915:Orbit / Q000294:innervation*; D012189:Retrospective Studies; D013997:Time Factors