Choroid plexus portals and a deficiency of melatonin can explain the neuropathology of Alzheimer's disease.

Presently, the textbook description of cerebrospinal fluid absorption is through the arachnoid granules into the superior sagittal sinus. The theory is based on non-physiologic experiments and fails to explain multiple observations. Photographs and microphotographs of choroid plexus portals are included. Evidence is presented that cerebrospinal fluid is moved from the choroid fissure into the ventricular system. The deposition pattern of corpora amylacea demonstrates the bulk flow of cerebrospinal fluid. Melatonin is found in higher concentration in the cerebrospinal fluid than in simultaneously sampled blood. Melatonin is a potent antioxidant and the loss of its protection in the cerebrospinal fluid in Alzheimer's disease can explain the pattern of cell destruction. Challenges of the embedded dogma of the arachnoid granule absorption of cerebrospinal fluid have been ignored; however this old faulty theory must be abandoned in order to understand the pathophysiology of Alzheimer's disease.