Computed Tomography Assessment of the Conus Medullaris and the Dural Sac Termination in Adult Sheep: Anatomical Implications for Lumbosacral and Sacrococcygeal Injections

Abstract

This study aimed to provide information about the conus medullaris (CM) and dural sac (DS) termination points in sheep. Thirteen adult Merino-mixed sheep were anaesthetised and underwent lumbosacral computed tomography (CT) myelography. A spinal injection was administered using a Tuohy needle while the sheep were in sternal recumbency. After confirming the presence of cerebrospinal fluid, 0.4 ml kg-1 iodinated contrast media was injected, and a CT scan was conducted. The analysis focused on determining the vertebrae at which the CM and DS ended. The results showed that in eight cases, the conus ended at the first sacral vertebra, while in five sheep, the termination point was identified at the level of the second sacral vertebra. DS termination occurred in the 3rd sacral vertebra in one animal, the 4th sacral vertebra in another sheep, the 1st caudal vertebra in six cases, and the 2nd caudal vertebra in five cases. The findings highlight the need for caution during lumbosacral injections in sheep, as the CM concludes caudally to this space. It is also essential to be aware that the DS persists caudal to the sacrococcygeal space for safe epidural injections in this region.