The controversy on choroid plexus function in cerebrospinal fluid production in humans: how long could different views be neglected?

The aim of this article is to provide a different perspective to choroid plexus (CP) physiology and pathophysiology from that presented in the recently published review by Spector et al (1). This review with an extensive insight into the relevant literature data had an intention to interpret CP functions focusing on adult humans. The CP is claimed to be the key “organelle” for interpretation and understanding of the classic cerebrospinal fluid (CSF) physiology hypothesis. Namely, it is believed that CSF is actively formed mainly by the CP inside brain ventricles, after which it circulates from the ventricles through the entire CSF system to be passively absorbed into the venous sinuses and/or via paraneural sheaths of nerves into the lymph (2-5). Since CSF secretion by the CP is an active process, it seems logical that CSF secretion is the main generator of CSF circulation if (physiological) volume of CSF is to be maintained within the CSF system. In other words, CSF secretion and absorption inside the CSF space should be balanced, because the amount of secreted CSF must be the same as the amount of passively absorbed CSF. Any other relationship would result in an imbalance of CSF volume, and in time, a pathological process (4). The CP is, in fact, presented as a biological pump by which CSF is produced in an active process, since the CSF formation rate (secretion) should not be significantly altered by moderate changes in the ventricular pressure (3,5).