Background: The mechanism of transient global amnesia (TGA) is not clear. Attempting to support the hypothesis that retrograde venous hypertension causing cerebral venous ischemia plays a role in the pathogenesis of TGA, the authors used cranial three-dimensional time-of-flight (TOF) MR angiography (MRA) to detect a possible intracranial retrograde venous flow in TGA patients.
Methods: The frequency of abnormal venous signals on cranial three-dimensional TOF MRA was compared in 10 TGA patients with the signals in 50 age- and gender-matched normal individuals. In TGA patients with abnormal venous signals, other examinations (cerebral digital subtraction angiography, upper extremity digital subtraction venography [DSV], and thoracic inlet MRI) were performed to elucidate the etiology of these abnormal intracranial venous flow patterns.
Results: Abnormal venous signals on three-dimensional TOF MRA were found in five (50%) of the TGA patients and none of the control subjects (p < 0.001). Compression leading to occlusion of the left brachiocephalic vein by the sternum and aorta during regular breathing, as depicted by upper extremity DSV and thoracic inlet MRI, occurred consistently among these five TGA patients with abnormal venous signals.
Conclusions: Retrograde intracranial venous flow caused by left brachiocephalic vein occlusion was found only in patients with transient global amnesia (TGA). This result suggests that TGA patients may have an underlying impairment of cerebral venous outflow that increases their vulnerability to TGA attack.