Embryological background of truncular venous malformation in the extracranial venous pathways as the cause of chronic cerebro spinal venous insufficiency.

The truncular venous malformation (VM) represents an embryologically defective vein where developmental arrest has occurred during the vascular trunk formation period in the 'later stage' of the embryonic development. A relatively simple truncular VM lesion such as a venous web at the hepatic venous outlet causes portal hypertension giving a profound damage/impact to the liver. A similar condition involving the head and neck venous system may cause chronic cerebro-spinal venous insufficiency (CCSVI) and may be involved in the development or exacerbation of multiple sclerosis.