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Trigeminal Nerve Asymmetry in Horses With Idiopathic Trigeminal-Mediated Headshaking: A Retrospective Case-Control Magnetic Resonance Imaging Study.
Abstract: Nerve atrophy results in trigeminal nerve (TN) asymmetry detectable by magnetic resonance imaging (MRI) in humans, but similar studies have not been performed in horses with idiopathic trigeminal-mediated headshaking (ITMHS). Objective: Horses with ITMHS show greater MRI-detected trigeminal-nerve asymmetry than controls. Methods: A total of 20 adult horses with ITMHS and six unaffected control horses. Methods: Retrospective case-control study of the TN cross-sectional area (TNCSA) based on 3-Tesla MRI scans of the equine brain. TNCSA and its side-to-side differences at four defined measurement points were compared within the two study groups using a linear mixed model. Intraclass correlation coefficient analysis was used to evaluate intra-rater repeatability. The primary outcome was side-to-side TNCSA asymmetry, minimizing confounding effects such as body size. Results: Significantly greater TNCSA side-to-side differences (asymmetry of TN) were detected in horses with ITMHS (F = 11.271, p < 0.001). Horses with ITMHS exhibited a 4.1 to 7.6-fold greater TN asymmetry compared to control horses. Absolute TNCSA did not differ significantly between groups but was influenced by body weight. Measurements demonstrated excellent repeatability, and tentative cut-off values could be calculated to discriminate between ITMHS and control horses based on TNCSA asymmetry. Conclusions: The asymmetry of the TNCSA in horses with ITMHS indicates unilateral or asymmetric disease of the TN. The present study highlights the value of MRI examinations in ITMHS and could pave the way for targeted therapeutic approaches.
© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
Publication Date: 2025-07-31 PubMed ID: 40739903PubMed Central: PMC12311309DOI: 10.1111/jvim.70196Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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This research study investigates the asymmetry of the trigeminal nerve (TN) in horses suffering from idiopathic trigeminal-mediated headshaking (ITMHS), using magnetic resonance imaging (MRI). The study found that horses with the health issue showed more pronounced nerve asymmetry compared to healthy horses, suggesting a potential explanation and avenue for treatment.
Research Objective
The primary objective of this research was to detect differences in the cross-sectional area of the trigeminal nerve (TNCSA) in horses with ITMHS and unaffected horses, using MRI technology. The main focus was on differences in TNCSA from one side to the other (nerve asymmetry), as similar patterns have been observed in humans with nerve atrophy.
Methodology
- A total of 20 adult horses diagnosed with ITMHS and six healthy horses were chosen for the study.
- The investigators performed a retrospective case-control study comparing the TNCSA in both groups of horses based on 3-Tesla MRI scans of each horse’s brain.
- The research team measured TNCSA and its side-to-side differences at four defined points, using a linear mixed model for comparison.
- Moreover, to assess the repeatability of the measurements, the researchers utilized the intraclass correlation coefficient analysis.
Findings
- Horses with ITMHS displayed significantly greater side-to-side TNCSA differences (F = 11.271, p < 0.001).
- These affected horses showed a 4.1 to 7.6-fold greater TN asymmetry compared to the unaffected horses, indicating a condition influencing the nerve on one side more than the other.
- The study found no significant difference in absolute TNCSA between groups but witnessed an influence by body weight.
- Measurements showed excellent repeatability which led to the creation of tentative cut-off values to differentiate between ITMHS and control horses based on TNCSA asymmetry.
Conclusions
The paper concludes that TNCSA asymmetry in horses with ITMHS suggests a unilateral or asymmetric disease of the trigeminal nerve. This discovery underscores the importance of MRI examinations in diagnosing and understanding ITMHS. The results could potentially inform targeted therapeutic approaches for the treatment of this condition.
Cite This Article
APA
Heun F, Delarocque J, Feige K, Hellige M.
(2025).
Trigeminal Nerve Asymmetry in Horses With Idiopathic Trigeminal-Mediated Headshaking: A Retrospective Case-Control Magnetic Resonance Imaging Study.
J Vet Intern Med, 39(5), e70196.
https://doi.org/10.1111/jvim.70196 Publication
Researcher Affiliations
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
- Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
MeSH Terms
- Animals
- Horses
- Retrospective Studies
- Case-Control Studies
- Magnetic Resonance Imaging / veterinary
- Horse Diseases / diagnostic imaging
- Horse Diseases / pathology
- Male
- Female
- Trigeminal Nerve / diagnostic imaging
- Trigeminal Nerve / pathology
- Trigeminal Nerve Diseases / veterinary
- Trigeminal Nerve Diseases / diagnostic imaging
- Trigeminal Nerve Diseases / pathology
Conflict of Interest Statement
Authors declare no off‐label use of antimicrobials. The authors declare no conflicts of interest.
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