Measurement of sub-arachnoid space depth in healthy foals of different breeds

Aim: The purpose of this study was to determine ultrasonographic measures of the depth of the dorsal subarachnoid space in healthy foals of different breeds in order to: 1) obtain a range of values to be used as reference; 2) verify sub-arachnoid space (SA) depth increase during the first week of life; 3) verify the presence of differences related to gender. Material and methods: The depth of the dorsal sub-arachnoid space was recorded in 64 foals of different breeds at 1 day (T1), 4 (T4) days and 7 (T7) days of life, measuring the distance between the dura mater and the dorsal portion of the pia mater in a cross-sectional view just cranial to the wings of atlas. The probe was then rotated and the longitudinal scan was visualized, then measurements were taken just caudal to the occipital bone at the level of the cisterna magna. Mean and standard deviation were calculated. Skewness-Kurtosis test was applied to verify data distribution. Time-dependent changes were recorded using the analysis of variance and gender-related differences were recorded using the t-test for unpaired data. Results: Differences related to time were recorded in Thoroughbred foals, while no differences were obtained in show jumping and Quarter Horse foals. Differences related to gender were observed in all the breeds examined. Discussion and conclusions: A correlation between cerebro-spinal fluid (CSF) pressure and ultrasound measurements at the SA has been recently reported in the foal. In the present study, measures of dorsal SA during the first week of life were reported for foals of different breeds. The present findings show that the dorsal SA measurements might be a safe, reliable and a not invasive method to evaluate foals with neurologic signs in the perinatal period and to assess indirectly the increase of CSF pressure.