The equine cervical spine: comparing MRI and contrast-enhanced CT images with anatomic slices in the sagittal, dorsal, and transverse plane

Background: The impact of cervical pathology on performance is of great importance to the horse industry. Accurate diagnosis of cervical disease with imaging modalities, including computed tomography (CT) and magnetic resonance imaging (MRI), requires thorough appreciation of normal cervical anatomy. Objectives: (1) To describe in detail the anatomy of the equine cervical spine by comparing anatomical sections with corresponding MR and contrast-enhanced CT images in the sagittal, dorsal, and transverse plane. (2) To discuss the ability of MR and contrast-enhanced CT imaging to visualize anatomical structures in the cervical spine. Animals and methods: Three cervical spines of young adults (3-8 years), collected immediately after humane euthanasia, were used. The spine was stabilized on a frame in a natural flexed position with an angle of 20°. MR and contrast-enhanced CT imaging was performed within six hours after euthanasia. Anatomical sections of 1 cm were made in the sagittal, dorsal, and transverse plane and compared with corresponding CT and MR images. The intervertebral disk thickness, facet joint angle, sagittal dural space diameter and ventromedial facet joint projection were quantified. Results: The anatomic location of clinically important structures including the facet joints, spinal cord, cervical nerve roots and intervertebral disks were reliably identified in the anatomical sections and their corresponding MR images. Contrast-enhanced CT images depicted all osseous borders, whereas MR images were superior for soft tissue structures. Conclusion and clinical importance: This study enhances our understanding of normal cervical spine anatomy and the diagnostic usefulness of cervical MRI and contrast-enhanced CT in the horse.