Departments of Clinical Sciences (Whitty, Carney, Scrivani) and Biomedical Sciences (Miller, Miller), Cornell University, Ithaca, New York, 14853, USA.
Vet Radiol Ultrasound. 2022 Jul;63(4):436-449. doi: 10.1111/vru.13074. Epub 2022 Feb 21.
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.
茎突骨鞘（SPS）是鼓室颞骨的一部分，是围绕茎突、锤舌骨和茎舌骨背侧部分的不完整骨套。在接受头部 CT 的马中，我们观察到 SPS 大小的一系列变化，并质疑这些差异是否是颞颌骨骨关节炎（THO）的早期特征，或者是与年龄、体重、性别或品种相关的正常解剖变异。我们假设 SPS 大小与年龄和体重呈正相关，但与性别或品种无关。我们使用了我院进行头部 CT 的马的便利人群（2008-2017 年），无论 THO 状态如何，进行了回顾性横断面研究，来调查这些假设。样本包括 102 匹马。SPS 高度的中位数在中部（4.3 毫米）大于外侧（2.4 毫米），宽度中位数为 11.1 毫米：两侧无差异。公马的 SPS 宽度中位数（11.6 毫米）显著大于种马（8.7 毫米；P<0.05）和母马（10.0 毫米；P<0.05）。SPS 大小与体重和品种之间没有相关性。单变量和多变量分析最初发现 SPS 高度与年龄之间存在显著关联。在去除异常值和 2 岁以下的马后进行的二次分析发现了类似但不太明显的结果（SPS 高度的年增长率从 3.2-3.8%降至 0.9-2.6%）。大多数关联在按年龄组进行调查时并不显著，但在老年马中，尺寸增大的年增长率可能更快。过度的 SPS 增大被认为是 THO 的一个重要组成部分。
