"Retinopathy and optic nerve pathology are frequent
early clinical signs of MS but also occur with acute
raised intrathoracic pressure as blood is forced back
into the head producing surges of intracranial venous pressure (‘Valsalva retinopathy’)[4–13]. Apart
from such acute events, chronic venous hypertension may result from arteriovenous anastomoses
(AVA), in particular dural arteriovenous ?stulas
(DAVFs), within the head [14,15] or spine [16]. Borden et al. [17]" David Talbert, London

Note this paper preceded Zamboni's CCSVI paper! http://www.direct-ms.org/sites/default/files/Talbert%20Venous%20pressure%20MS%2008.pdf