Ultrasound Measurements of the Dorsal Subarachnoid Space Depth in Healthy Trotter Foals during the First Week of Life

The aim of this study was to determine ultrasonographic measurements of the depth of the dorsal subarachnoid space in healthy foals so as to obtain reference values. The depth of the dorsal subarachnoid space was recorded in 50 trotter foals at day 1 (D1), 4 (D4), and 7 (D7) after birth, measuring the distance between the dura mater and the dorsal portion of the pia mater at the level of the cisterna magna, both in cross-sectional and longitudinal scans. Average, standard deviation, minimum and maximum values were calculated. Wilcoxon signed rank test was applied to verify data distribution. Analysis of variance (ANOVA) for repeated measurements and Bonferroni test as post hoc were applied to verify differences among D1, D4, and D7, both for cross-sectional and longitudinal scans. Student’s t-test for unpaired data was performed between fillies and colts to verify differences related to gender. Significance level was set at P < .05. Cross-sectional measurements were 7.2 ± 0.7 mm at D1, 7.4 ± 0.7 mm at D4, and 7.5 ± 0.6 mm at D7, whereas longitudinal measurements were 7.3 ± 0.6 mm at D1, 7.6 ± 0.6 mm at D4, and 7.6 ± 0.5 mm at D7. Differences in dorsal subarachnoid space depth were observed at D1 versus D7, both for cross-sectional and longitudinal scans, whereas no differences were found between fillies and colts. In this study, a reference range for the depth of the dorsal subarachnoid space has been reported in foals.