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Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association2022; 63(4); 436-449; doi: 10.1111/vru.13074

Associations between styloid process sheath CT sizes and age, body weight, and breed in horses.

Abstract: The styloid process sheath (SPS) is a part of the tympanic temporal bone and an incomplete bony sleeve surrounding the styloid process, tympanohyoid cartilage, and dorsal part of the stylohyoid bone. In horses undergoing head CT, we observed a range of SPS sizes and questioned whether differences were early features of temporohyoid osteoarthropathy (THO) or normal anatomic variations associated with age, body weight, sex, or breed. We hypothesized that SPS sizes were positively correlated with age and body weight, but not with sex or breed. Using a convenience population of horses that underwent head CT at our institution (2008-2017), regardless of THO status, we investigated these hypotheses in a retrospective cross-sectional study. The sample comprised 102 horses. The median SPS height was larger medially (4.3 mm) than laterally (2.4 mm) and the median width was 11.1 mm: no difference was detected between sides. Geldings had a significantly larger median SPS width (11.6 mm) than stallions (8.7 mm; P < 0.05) and mares (10.0 mm; P < 0.05). No association was detected between SPS sizes and body weight and breed. Univariate and multivariate analyses initially found significant associations between SPS heights and age. Secondary analyses performed following removal of outliers and horses <2-years old found similar but less pronounced results (annual increase in SPS heights decreased from 3.2-3.8% to 0.9-2.6%). Most associations were insignificant when investigated by age group, but the annual rate of increased size might be faster in older horses. Excessive SPS enlargement was theorized as an essential component of THO.
© 2022 American College of Veterinary Radiology.
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Publication Date: 2022-02-21 PubMed ID: 35188312DOI: 10.1111/vru.13074Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigates the relationship between the size of the styloid process sheath (SPS) in horses and factors such as age, body weight, sex, and breed. The results suggest a correlation between SPS dimensions and age, but no significant connection with body weight, sex, or breed. The study also postulates that excessive growth of the SPS could be a factor in temporohyoid osteoarthropathy, a particular horse bone disease.

Research Methodology and Sample

  • The researchers used a retrospective cross-sectional study approach to investigate their hypotheses. This type of study is suitable for identifying and analyzing variations within a population at a specific point in time.
  • The study relied on a convenience sample of horses who had head CT scans at the research institution between 2008 and 2017.
  • This sample included 102 horses with a variety of ages, sexes, breeds, and body weights.

Findings: Styloid Process Sheath Dimensions

  • The study found variations in the dimensions of the styloid process sheath (SPS), a bony structure located in the horses’ heads.
  • The median SPS height was found to be larger medially (4.3 mm) than laterally (2.4 mm), and the median width was measured at 11.1 mm. There was no discernible difference between the sides.

Correlation with Sex

  • The researchers found that geldings, or castrated male horses, had a significantly larger median SPS width (11.6 mm) than either stallions (8.7 mm) or mares (10.0 mm).

Correlation with Age

  • Both univariate and multivariate analyses initially found significant associations between SPS heights and the horses’ ages.
  • After removing outliers and horses under 2 years old, secondary analyses found similar but less pronounced results. It suggests that as horses age, the height of their SPS also increases, but the rate of increase might be faster in older horses.

No Correlation with Weight and Breed

  • The researchers did not find any association between SPS sizes and the horses’ body weight or breed. Thus, they concluded that these factors do not significantly affect the SPS sizes in horses.

Link to Temporohyoid Osteoarthropathy

  • The study theorized that excessive enlargement of the SPS might be an essential component in the development of temporohyoid osteoarthropathy (THO), a degenerative disease affecting the bones in a horse’s skull.

Cite This Article

APA
Whitty JA, Miller AV, Miller AD, Carney PC, Scrivani PV. (2022). Associations between styloid process sheath CT sizes and age, body weight, and breed in horses. Vet Radiol Ultrasound, 63(4), 436-449. https://doi.org/10.1111/vru.13074

Publication

Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association
ISSN: 1740-8261
NlmUniqueID: 9209635
Country: England
Language: English
Volume: 63
Issue: 4
Pages: 436-449

Researcher Affiliations

Whitty, Justin A
  • Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.
Miller, Allison V
  • Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.
Miller, Andrew D
  • Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.
Carney, Patrick C
  • Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.
Scrivani, Peter V
  • Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.

MeSH Terms

  • Animals
  • Body Weight
  • Cross-Sectional Studies
  • Female
  • Horse Diseases / diagnostic imaging
  • Horses
  • Male
  • Retrospective Studies
  • Tomography, X-Ray Computed / veterinary

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Citations

This article has been cited 3 times.
  1. Hartl B, Strohmayer C, Vali Y, Lyrakis M, Kneissl SM. Computed tomographic signs of hyoid apparatus disease in 165 horses. Front Vet Sci 2025;12:1631185.
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  2. Lloyd-Edwards RA, Mulders E, Sloet van Oldruitenborgh-Oosterbaan MM, Veraa S. Computed Tomography of the Hyoid Apparatus in Equine Headshaking Syndrome. Vet Sci 2025 May 23;12(6).
    doi: 10.3390/vetsci12060511pubmed: 40559747google scholar: lookup
  3. Dash RF, Perkins JD, Chang YM, Morgan RE. Computed tomography of the equine temporohyoid joint: Association between imaging changes and potential risk factors. Equine Vet J 2026 Jan;58(1):125-133.
    doi: 10.1111/evj.14495pubmed: 40322953google scholar: lookup
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