A Radiographic Technique for Assessment of Morphologic Variations of the Equine Caudal Cervical Spine

SIMPLE SUMMARY: Equine Caudal Cervical Morphological Variation (ECCMV) has been acknowledged as a common finding in horses. The equine sixth cervical vertebrae (C6) with two caudal ventral laminae appears to be prone to the most congenital variation. The direct clinical relevance of this condition is currently unknown. A standardized method of assessment and diagnosis in live horses would allow for scientifically robust, quantitative studies into the relevance of this syndrome. Equine radiographic imaging is standard within veterinary practice and offers an accessible screening and diagnostic tool for veterinarians and provides a starting point for assessment. Here, we present a systematic method for locating cervical landmarks and radiographing with specific views as a reliable, repeatable imaging procedure for identifying ECCMV. If ECCMV is linked to poor performance, pain-based behaviors, lameness, and horse and rider safety and welfare, then a protocol for testing and diagnosis could be vital to improving horse rehabilitation, management, and wellness. ABSTRACT: Equine Caudal Cervical Morphologic Variation (ECCMV) is a congenital malformation of the caudal cervical spine distinct from the more commonly recognized Cervical Vertebral Stenotic Myelopathy (CVSM). The most common presentation of ECCMV is recognized on the sixth cervical vertebra (C6). In “normal” presentations, the transverse processes on the left and right sides have a caudal lamina projecting ventrally below the caudal vertebral body in a heel shape. With ECCMV, variations occur to the structure of the caudal ventral lamina on one or both sides of C6 and may include the seventh cervical (C7) and first thoracic (T1) vertebrae and ribs, in varying configurations. Whereas the prevalence of ECCMV is not known, it has been recognized for many years and has been reported to occur with relatively high frequency within multiple populations of domesticated horses. To date, there is no documented link between the occurrence of ECCMV and clinical signs. However, based on retrospective studies, multiple authors have recognized the potential impact on performance that this condition may have. Establishing a reliable radiographic protocol for the consistent diagnosis of ECCMV would allow quantitative, scientific evaluation of the problem and support clinicians working in this field. We present a radiographic technique, which has been illustrated by diagnosis of ECCMV in three horses and confirmation of the diagnoses in two cases via postmortem examination.