Use and meaning of the anatomical terms "Plexus choroideus" and "Tela choroidea" in veterinary and human medicine.

The anatomical terms Plexus chor(i)oideus (CP) and Tela chor(i)oidea (TC) are listed without explanations in the official nomenclature handbooks Terminologia Neuroanatomica and Nomina Anatomica Veterinaria. Definitions of CP and TC exhibit discrepancies in medical dictionaries and anatomy handbooks. The aim of our study was to analyse this problem in detail and to discuss a possible unified use of the terms in science and teaching. The authors conducted a systematic literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, identifying and analysing relevant scholarly articles. Additionally, comprehensive original handbooks on human and veterinary anatomy in English and other European languages were examined. The definitions of the terms CP and TC differed considerably between articles and did not match the most frequently given explanations in handbooks. In general use, it seems to have become accepted that TC represents the smooth, thin part of the roof of the third and fourth ventricles, and CP the frond- or fringe-like vascularised structures invaginated into the lateral, third and fourth ventricles. However, it is controversial which tissue layers should be included in their description. Etymologically, only the vascular network should be termed (choroid) plexus, but embryologically and functionally, epithelium, pial connective tissue, and vascular network form an inseparable entity. Similarly, the smooth part of the ventricle roof consists of a (less) vascularised pia-derived stroma and lining epithelium. Including all these layers in the definition of CP as well as TC might be advisable and also corresponds to the use of the terms in clinical context.