Congenital occipitoatlantoaxial malformation in a Warmblood mare

Computed tomography identified mineralisation of the longitudinal odontoid ligament of the horse is associated with age and sex but not with the clinical sign of head shaking

Mineralisation of the longitudinal odontoid ligament has recently been identified in three horses undergoing computed tomographic (CT) examination, but published studies describing the clinical relevance of this finding are currently lacking. The objective of this retrospective, analytical, cross-sectional study was to investigate the relationship of this image finding to primary presenting complaint, age, breed, use and sex of the patient, and determine any association to the clinical signs of head shaking, neck pain or restricted range of neck motion. Computed tomographic images of 96 horses undergoing examination of the head and cranial cervical spine, for a variety of clinical reasons, were assessed for the presence of mineralisation within the longitudinal odontoid ligament. Clinical records were reviewed; presenting problem, signalment, clinical signs and final diagnoses were recorded and potential associations of presenting primary problem, signalment and individual clinical signs with mineralisation in the longitudinal odontoid ligament investigated, using univariable and multivariable ordinal logistic regression analysis. Final multivariable analysis confirmed significant associations of increasing severity of mineralisation with increasing age (P = .002) and being female (P = .038). There was no association of mineralisation of the longitudinal odontoid ligament with the syndrome of idiopathic head shaking or other clinical signs investigated in this sample of horses. Authors therefore recommend that the clinical significance of mineralisation of the longitudinal odontoid ligament be interpreted cautiously for equine CT studies.