Computed tomography findings in horses presented with signs of head-shaking.

Background: Trigeminal nerve-mediated head-shaking (TNMH) in horses is a diagnosis made by exclusion. Computed tomography (CT) is frequently used to identify any disease process that could cause the clinical signs of head-shaking. Although abnormalities are frequently identified, it is unknown whether treatment of these conditions improves clinical signs.

Objectives: To ascertain the clinical significance of CT findings in horses presented with a complaint of head-shaking.

Study Design: Retrospective case series.

Methods: CT and patient records were reviewed and all abnormal findings and any treatments subsequently carried out was recorded. A questionnaire was sent to referring veterinarians and owners were contacted by telephone to establish whether treatment of the identified condition improved clinical signs.

Results: This study included 103 horses presented for head CT with the complaint of head-shaking with follow-up information obtained for 84 horses (81.6%). The diagnosis of TNMH was based on a combination of positive maxillary nerve block and/or response to treatment for TNMH. Although TNMH was the most common diagnosis with 62 horses (60.2%) affected, in 22 horses (21.4%), a primary disease process was identified and treatment of the condition eliminated signs of head-shaking. Clinically relevant primary diseases included dental fracture, primary sinusitis, temporo-mandibular joint arthritis, nuchal bursitis, musculoskeletal pathologies, basisphenoid fracture, otitis externa and a mass affecting the infra-orbital nerve.

Main Limitations: Some clinical information was missing and follow-up information was not obtained in all cases.

Conclusions: CT was perceived as a useful diagnostic tool by most veterinarians, ruling out significant abnormalities. In over 20% of the cases, a treatable primary condition was identified leading to complete resolution of clinical signs.