“THE MANY SONOGRAPHIC FACES OF THE CHRONIC CEREBROSPINAL VENOUS INSUFFICIENCY: HOW TO PERFORM DOPPLER EXAMINATION IN A MULTIPLE SCLEROSIS PATIENT” by Dr. M. Simka)
VENOUS INSUFFICIENCY: HOW TO PERFORM DOPPLER EXAMINATION IN A MULTIPLE SCLEROSIS PATIENT.
Multiple sclerosis patients nearly always are found abnormal venous outflow obstacles in extracranial veins draining the central nervous system. These venous outflow blockages are described as chronic cerebrospinal venous insufficiency (CCSVI) and finding of CCSVI parameters in the sonographic examination is highly pathognomonic for multiple sclerosis.Venous obstacles compromising blood outflow from the brain and spinal cord can be very diverse. A whole constellation of venous pathologies can be found, including: occlusion, stenosis, narrowing, septum and inverted valves.
Nowadays it is thought that these venous obstacles are primarily congenital, although a presence of post-traumatic or post-thrombotic lesions is also possible. However, irrespective of the actual origin of these venous occlusions and stenoses, to look properly for these venous pathologies by means of Doppler ultrasound it is necessary to understand hemodynamic principles ruling the venous outflow from the brain and spinal cord. Both the brain and spinal cord are enclosed in osseous chambers (skull in case of the brain and spinal canal in case of the spinal cord. Therefore, vessels directly draining the brain and spinal cord are: first, non-collapsible that means that they contain approximately the same volume of the blood, irrespective of velocity and direction of the flow; second, they cannot shrink or dilate consequently to pressure or outflow resistance changes, as varicose veins do. Moreover, cerebral veins and sinuses as well as spinal veins and venous plexuses lack valves, and flow characteristics in these vessels depends nearly exclusively on the level of flow resistance in the extracranial and extraspinal veins. However, despite valveless nature of these veins, because of their localization inside the rigid osseous chambers, a reflux similar to that that accompanying varicose veins cannot occur. Of course, refluxes in the veins draining the central nervous system can be found, but they are rather manifestations of vicarious shunts (flow bypassing an obstacle) and they differ significantly from those found in varicose veins. At the moment, details of venous hemodynamics in the territory of brain and spinal cord are not completely elucidated. Yet, basic principles of the physiologic venous return from the brain are as follows: