Hydration status substantially affects chronic cerebrospinal venous insufficiency assessments.

We sought to determine the effect of hydration on the criteria for chronic cerebrospinal venous insufficiency (CCSVI), a proposed hypothesis for the etiology of multiple sclerosis (MS). Sixteen subjects (11 MS and 5 controls) were asked to fast overnight. The following morning, 2 CCSVI ultrasound examinations were performed: 1 in the mildly dehydrated state, and another 30-45 minutes after rehydrating with 1.5 L of Gatorade. Seven subjects fulfilled CCSVI criteria in the dehydrated state. Of these, 5 (71%) no longer fulfilled CCSVI criteria after rehydration. One additional subject met CCSVI criteria only after rehydration. Hydration status has a substantial effect on CCSVI criteria, suggesting that the sonographic findings of CCSVI may represent a physiologic rather than pathologic state.