Internal carotid artery dolichoarteriopathies in the horse: An endoscopic and anatomic study

Endoscopy of the guttural pouches in neonatal foals occasionally reveals atypical aspects in the course of the extracranial internal carotid arteries (ICAs) that are hardly seen in adult horses. While in veterinary medicine the data available on the presence of these anomalies in domestic mammals are limited and incomplete, in human medicine the morphological aspects of the ICAs have been the subject of extensive studies. Anomalies in the course and geometry of ICAs are commonly defined as dolichoarteriopathies, and should be classified as tortuous, kinked or coiled. To document whether the anomaly ICAs in foals can be attributed to dolichoarteriopathies, and to assess the incidence of carotid anomalies, two studies were conducted. An endoscopic study of the guttural pouch was carried out on 50 foals (24 M and 26 F) < 4w of age to examine the course of those ICAs in close contact with the pouch and an anatomical study was performed on the heads of 20 fresh horse carcasses (13 one-month-old foals, 1 seven-month-old and 6 adults) using vascular casts of the extracranial tracts of the ICAs to examine their morphology. The results showed the presence of ICA anomalies, including tortuosity, kinking, or coiling, only in foals < 4w olds and their absence in adults. The presence of a specific geometry in the foal was confirmed by both endoscopic and anatomical studies with 66 % and 71 % of the animals having dolichoarteriopathies, respectively, with a predominance of bilateral cases. Tortuosity was more common, and there appeared to be no gender difference in susceptibility. These anomalies could arise from the excessive length of the ICA in the extracranial course in relation to the distance between the origin of the vessel and its entry into the cranial cavity and based on this hypothesis, tortuosity, kinking and coiling in foals should be considered a simple transient anatomical variability and not a pathological event.