Transient global amnesia: Linked to a systemic disorder of amino acid catabolism? Giuseppe SancesarioZaira EspositoAlessia F. MozziGiulia M. Sancesario • Alessandro MartoranaAngela GiordanoRoberto SorgeBarbara Mari • Gianfranco SpallettaMaria Grazia MarcianiSergio Bernardini

Dear Sirs,We aimed to verify whether transient global amnesia(TGA) could be sustained by acute changes of amino acidsin the blood, analogous to the transient memory lossinduced by experimental tryptophan depletion [1, 2].Plasma amino acids were studied in control healthysubjects (aged 48–65) and in patients (aged 49–70) duringthe amnesic attack (n = 9) and longitudinally at 3 days(n = 12) and 16–24 months (n = 9) after the amnesicepisode, or retrospectively in patients (n = 9) who had anamnesic episode 2–3 years before. Routine blood tests formetabolic disorders were also studied. Patients who ful-filled the operational criteria for TGA showed massiveimpairment of both retrograde and anterograde episodicmemory during the acute phase [3–5], but 3–4 days laterthe memory tests were within the normal range in everycase [6]. Brain RMN and EEG examinations showed norelevant abnormalities, even though minimal theta dis-charges and/or chronic vascular encephalopathy wereobserved in about half of the patients [5]. Emotional stressand intense physical exertion were reported by 9/21patients [7]. The study has been approved by theappropriate ethics committee and has therefore been per-formed in accordance with the ethical standards laid downin the 1964 Declaration of Helsinki and its later amend-ments. All persons gave their informed consent prior totheir inclusion in the study.Blood tests were free from abnormalities, but lactatedehydrogenase (LDH) and aspartate aminotransferase(AST), respectively involved in anaerobic glycolysis and inamino acid metabolism, came out to be constantly overex-pressed during, as well as shortly and long after, theamnesic attack (Fig. 1). The levels of plasma amino acidswere similar in controls and in patients with a current TGAattack (Table 1). However, the values of glutamine and