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.

Summary Background Early results from the use of neuromodulation by percutaneous electrical nerve stimulation for the management of trigeminal‐mediated headshaking in horses were promising but lacked sufficient case numbers and long‐term follow‐up. The neuromodulatory procedure has since been established as EquiPENS™. Objectives The aim of this study was to report long‐term results from a larger number of cases and to investigate for predictors of outcome. Study design Prospective case series using international, multi‐centre data. Methods Eligible cases were horses with a veterinary diagnosis of trigeminal‐mediated headshaking, which received EquiPENS™ neuromodulation at trained centres between August 2013 and November 2017. The standard protocol was an initial three‐procedure course, with additional procedures should a horse go into remission but then relapse. Data collected included signalment, history, diagnostic tests performed, details of any complications, whether horses had gone into remission and the length of remission. Results Results were obtained from 168 horses, with 530 procedures. The complication rate was 8.8% of procedures. In all but one case, complications were mild and transient, without self‐trauma. Remission of headshaking following the initial course occurred in 53% (72/136) of horses. Median length of time recorded in remission was 9.5 weeks (range 2 days to 156 weeks ongoing). Where signs recurred, most horses went back into remission following additional procedures, usually for longer than from the previous procedure. No predictors for outcome were determined. Main limitations No placebo or control group, owner‐assessed results. Conclusions EquiPENS™ neuromodulation can be an effective and safe treatment for the management of trigeminal‐mediated headshaking in some horses. An increased understanding of neuromodulation could help optimise the technique. Advances in treatment for trigeminal‐mediated headshaking will remain limited until there is a greater understanding of the aetiopathogenesis of the condition.

La presente investigación analiza las diferencias entre empresas con presencia de capital extranjero de acuerdo con su tamaño, en términos de las actividades de innovación, vinculación externa y los modos de innovación. A partir de un abordaje econométrico sobre datos de la Encuesta Nacional de Empleo e Innovación, demostramos que las empresas con presencia de capital extranjero presentan un comportamiento diferenciado una vez que se estratifican por tamaño. Las empresas extranjeras vis-à-vis las nacionales tienden a realizar mayores esfuerzos de innovación y se caracterizan por implementar modos de innovación más complejos, que combinan los modos DUI y STI. Sin embargo, del análisis por estrato de tamaño surge que las empresas extranjeras de mayor tamaño relativo realizan relativamente menos esfuerzos de innovación promedio e implementan modalidades menos complejas. Estos resultados revalorizan los análisis que consideran la heterogeneidad de empresas extranjeras y demuestran que las de mayor tamaño relativo no son las de mejor performance innovadora, al contrario de lo que ocurre con las empresas de capital nacional.