[Mechanical problems in cerebral venous circulation].

Generally speaking, the cerebral circulation is not well known. This lack of knowledge causes problems for the physicians nad here are two examples: 1) resistance of the cerebral circulation. It is an accepted fact that the blood flow in the brain is particularly rapid. Classical anatomical data and recent mechanical notions invalidate this statement. With an average speed in the veins, the blood cannot, in a given time, complete such a long and complex course. What hypothesis could be expressed to find a solution? 2) The physiological role of the spinal fluid. It is an accepted fact that the spinal fluid is only a protecting device of the nerve centers. Recent studies let to believe that it could also have a role in the regulation of the venous flow. There are other mechanical problems: what are the characteristics of the flow in the venous sinus? in the venous junctions? in the venous dilations? Although lesions of the venous cerebral circulation present clinical manifestations to which the vein specialists are not accustomed to, they cannot deny the fact that this is a familiar pathology.