[Two cases of transient global amnesia (TGA) immediately after coronary angiography: pathogenesis of the primary TGA].

Two cases of transient global amnesia (TGA) following coronary angiography are reported. Nonionic contrast media was used and injected at room temperature. Both cases showed sudden amnesia about 15 minutes after the left ventriculography. A clinical feature was typical to TGA, showing repeated questions with retrograde and antegrade memory disturbance without any other neurological abnormality. Diffusion-weighted images (DWI) of magnetic resonance imaging revealed no fresh lesion in both cases. The patients recovered from TGA attack within 24 hours. Some cases have been reported which display a manifested TGA following cerebral or coronary angiography. In these situations, embolism, the effect by the contrast media was suspected as the cause of TGA. Since most TGA cases in a classical meaning (primary TGA) showed no abnormality in both DWI and T2-weighted image (T2WI), the cerebral ischemia was not really considered to be the cause of the condition. Therefore, the pathogenesis of the TGA is suggested to be much more functional rather than anatomically abnormal. The pathogenesis of the primary TGA was thought to be some kind of hypersensitivity to the external stress or the stress reaction of the hippocampal cell. This stress may lead to cellular depolarization and the following repolarization (spreading depression), which showed transient abnormality in DWI and not a permanent abnormality in T2WI.