Transient partial amnesia following coronary and peripheral arteriography

Sir, I read with interest the recent article by Yildiz et al. [1] regarding transient partial amnesia following coronary and peripheral arteriography. In 1993, my colleagues and I reported two cases of transient global amnesia following selective cerebral angiography with iohexol, a non-ionic monomer [2–4]. In both of our cases, the patients experienced short-lived amnesia following the angiographic studies, with complete resolution of symptoms and restoration of normal memory within a matter of hours. Yildiz and colleagues report a case in which they assume that the amnesia experienced by their patient, which was associated with headache and right upper limb numbness, was as a result of disruption of the blood brain barrier by the large volume of contrast medium used. As was pointed out in our paper in 1993, the cause of transient amnesia remains unclear, and possible causes that have been suggested include epilepsy (with the discharge in the temporal lobe), transient ischaemic attacks and migraine. The most commonly accepted theory is that the phenomenon is due to transient vascular insufficiency involving the medial temporal lobe, with the memory loss resulting from direct involvement of the hippocampus. The vascular supply to this area is predominantly through the posterior cerebral artery. Possible mechanisms for this vascular insufficiency include vasospasm, dislodged atherosclerotic plaques, catheter-induced emboli or particulate matter in the contrast matter causing ischemia. Another possibility is direct neurotoxicity caused by blood brain barrier disruption, but the fact that the patient reported in Yildiz’s paper experienced right upper limb sensory symptoms and headache certainly raises the distinct possibility that a direct ischaemic event took place. While the theory that transient amnesia results directly from blood brain barrier disruption is plausible, and is supported by the likelihood that these events are more common after injection of highly ionic or hyperosmolar contrast, the possibility of ischaemic events arising from catheter manipulation cannot be discounted. Radiologists engaging in vascular studies involving the aortic arch or its branches must constantly maintain vigilance to minimize the risk of precipitating ischaemic cerebral events as a result of plaque or embolic dislodgement.