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C h e c k o u t A B M P 's l a t e s t n e w s a n d b l o g p o s t s . Av a i l a b l e a t w w w. a b m p . c o m . 49 concept of Swedenborg, who said: "CSF is secreted by the blood vessels in the brain." Part of that evidence came in 1969, when T. H. Milhorat removed the choroid plexi from both lateral ventricles (choroid plexectomy) in a human subject and in monkeys, and found no changes in the volume of CSF secretion, or in its composition, contradicting conventional knowledge. 13 Even after a total choroid plexectomy, the CSF still secreted at the rate of approximately 1 liter per day. 14 • Circulation. In the classical model, we should obviously see CSF flowing through the different cavities of the ventricular system. However, when M. Klarica and a team of researchers inserted a cannula inside the aqueduct of Sylvius in numerous cats, they did not see any net flow of CSF via the cannula for more than three hours. This data added to their suspicion of a faulty classical model, and made these scientists wonder whether CSF really "circulated." 15 The old model described CSF flowing unidirectionally within the brain ventricles and surrounding the brain tissue. Large molecules have been used in the past to study CSF physiology, and this may have caused numerous misconceptions about CSF circulation. In these older experiments, the injection of macromolecules into the ventricular spaces to define the circulation of CSF gave the wrong impression that the walls of the ventricles were impermeable, and that CSF is transported in a linear manner from the lateral ventricles to the third and fourth ventricles, then into the subarachnoid spaces and all the brain cisterns. 16 Recently, the injection of marked tritium ( 3 H water) into the CSF system demonstrated water distribution in the ventricles in almost all possible directions, including a retrograde path LYMPH IN THE BRAIN The lymphatic system from the classical perspective (left). Recent research shows a new model integrating the central nervous system (right). © UVA Health. 1 inside the ventricles, which is opposite to the direction given by the classical model. 17 J. D. Fenstermacher led a study that also showed that marked tritium passes through the ventricular wall of the brain (ependymal), confirming that the ventricular wall is not impermeable. 18 • Reabsorption. Under normal CSF pressure, marked tritium ( 3 H water) is reabsorbed into the brain capillaries around the ventricles (periventricular capillaries), suggesting that CSF bulk water is produced, as well as absorbed, into the brain tissue. 19 If the CSF is not mainly produced by the choroid plexi, but locally in every aspect of the brain tissue (parenchyma), it is also reabsorbed in the same places, everywhere within the brain. In fact, CSF components can be found in spaces around major cranial and extra-cranial nerves (perineural lymphatic pathways), such as the olfactory nerves, the optic nerves, and the auditory nerves, as well as other cranial and/or spinal nerves. Once recognized, these areas can be stimulated by a trained manual therapist to facilitate reabsorption into the lymph pathways. Today we know that in the case of hemorrhage or infection, large proteins can accumulate in the central nervous system (CNS), and the brain needs to be cleaned and drained. Previously, what system was truly responsible for this important function was a mystery. Additionally, the CNS requires fast communication pathways for circulation of immune-competent cells and stimulation of the immune system. This, too, remained misunderstood without our latest findings of a lymph system presence in the brain. LYMPH & GLYMPH: THE GLIOVASCULAR CLEARANCE SYSTEM Now, let's look within the brain itself—not just the pathways of the cerebrospinal fluid. In 2012, researchers demonstrated that tracers injected into the ventricular CSF of mice entered the parenchyma of the brain, and were transported into a small space between the brain capillaries and the astrocytes surrounding them. 20 Astrocytes cover approximately 99 percent of all cerebral capillaries (see Image 2, page 50). This is a very slow clearance pathway in the CNS, present in most mammals, that facilitates the removal of CNS interstitial fluid, as well as waste products, including amyloid beta proteins that accumulate in pathologies such as Alzheimer's disease. The function of the glymphatic system is lymphatic-like in the brain, but the fluid within the system is not lymph fluid, as it is not located inside the CNS lymph