Transient global amnesia: cerebral venous outflow impairment-insight from the abnormal flow patterns of the internal jugular vein.

Cerebral venous reflux is found frequently in transient global amnesia (TGA) patients. The cerebral venous reflux mostly results from left brachiocephalic venous obstruction, and the level of reflux depends on different respiratory status. For further understanding of the role of venous outflow impairment in the pathogenesis of TGA, we used color duplex sonography to reveal the flow patterns in the internal jugular vein (IJV) and its branches (JB) under different respiratory conditions. We compared the frequency of abnormal venous flow of IJV and/or JB on color duplex sonography between 17 TGA patients and 17 age- and gender-matched normal individuals both at rest (regular breathing) and at deep inspiration. Further, these venous-flow abnormalities in IJV and JB were well described. Cranial 3-D time-of-flight magnetic resonance arteriography (MRA) were performed in all patients three to seven days after their TGA attacks and in all normal individuals to analyze the abnormal flow signals in the intracranial venous structures. In the result, abnormal flow-patterns in the left IJV and/or left JB during regular breathing were found more frequently in TGA patients than normal individuals (65% vs. 6%; p < 0.001). These abnormalities in TGA patients were (1) isolated reversed flow in the left JB, (2) segmental reversed flow in the left distal IJV and (3) continuous reversed flow in the left IJV and JB. The MRA study revealed that only the most severe reflux in the IJV causes intracranial venous reflux; six were in the group of continuous reversed flow in left IJV and one was in the group of segmental reversed flow in left distal IJV. These findings suggest that TGA might be one of the clinical manifestations of the "cerebral-type intermittent venous claudication," which stems from cerebral venous outflow impairment, insufficient venous collaterals and specific precipitating factors.