Recirculation of cerebrospinal fluid through the tela choroidae is why high levels of melatonin can be found in the lateral ventricles.

Evidence is presented to support the hypothesis that cerebrospinal fluid (CSF) is transported through the tela choroidae and recirculated in the ventricular system. The concept that the CSF is resorbed by the arachnoid villus-superior sagittal sinus system is accepted as fact. The experimental studies on which the currently accepted theory is based were published in 1914 by Dr Lewis Weed. Weed used a low pressure (near physiologic) method and a high pressure (non-physiologic) method. His observations with the high pressure method are a basis for the theory of arachnoid villus absorption. On the other hand, his low pressure method provides evidence that CSF is absorbed in the area of the basilar cisternae. Studies of communicating hydrocephalus and chemical analysis of ventricular melatonin give evidence that CSF recirculates through the tela choroidae back into the ventricles.