[Form, size and variations of the plexus chorioideus ventriculi IV]

The form, size and variations of the Plexus chorioideus ventr. IV were investigated on 55 brain stem specimens. Because up until now there has been no definitive standard nomenclature, the plexus has been divided into a medial part (Pars medialis)--with its Processus fastigii, Processus inferior and Processus paramedianus--and into a lateral part (Pars lateralis). The plexus parts which stickout of the apertures are accordingly termed Partes aperturae lateralis et mediana. The greatest transverse expansion (= span of the plexus) varies between 27 and 52 mm. The greatest longitudinal values measured along the arc are between 10 and 40 mm. The variability of the Processus fastigii--if present--varies between 3 and 9 mm in length and has been schematically presented along with the position of the Processus paramedianus and the length of the Processus inferior. The size of the plexus-free middle area, its form and form-varitions, likewise has been studied and has been presented in schematic drawings and evidenced with photographs, along with those of the Apertura lateralis and the diverse lengths of the Pars aperturae mediana.