Resting and Acetazolamide-Challenged Technetium 99m-ECD SPECT in Transient Global Amnesia

ABSTRACT

BACKGROUND AND OBJECTIVE: Transient global amnesia(TGA) is a neurological syndrome affecting preferentially middle-aged or elderly people and characterized by sudden onset of transient impairment of antegrade amnesia with variably retrograde amnesia. TGA was defined over 30 years ago, but the etiology remain unclear. Several mechanisms have been proposed, including arterial thromboembolic ischemic attacks in both posterior cerebral artery territories, epilepsy, and migraine. Although many studies have reported TGA, only a few reported cerebral perfusion studies using SPECT because of the brief duration of the episode. Technetium-99m-ethyl cysteinate dimmer(ECD) is superior to sensitivity of lesion detection and lesion to normal contrast, probably due to lower back diffusion from the brain to the blood and its excellent radiochemical stability. So we evaluate pathophysiologic mechanism of TGA by using 99mTC-ECD SPECT with or without acetazolamide(ACZ) stress. METHODS: We evaluated six patients with transient global amnesia, four women and two men, age ranges 56 to 78 years, mean 62.2 years. Measurements of CBF and vascular reserve using 99mTC-ECD with or without ACD stress were performed during or after TGA episode. RESULTS: One patient, who was evaluated in TGA episode showed that regional cerebral blood flow was decreased in both anteroinferior frontal, both temporal, right thalamus, both inferior parietal and left parietal region with impaired vascular reserve in left inferior temporal and right thalamus. Others, who were evaluated more than 6days in TGA episode showed that regional cerebral blood flow was decreased in left temporal (4), both temporal region (1), left thalamus (2) and both basal ganglia (1) with preserved vascular reserve except one, showed impaired vascular reserve in left thalamus. CONCLUSION: This result show that severe hypoperfusion of bilateral temporal region and impaired vascular reserve in left temporal region in TGA episode. Other patients who were recovered from TGA showed hypoperfusion of left temporal region and preserved vascular reserve. 99mTc-ECD with acetazolamide SEPCT that sensitively detects localized impaired cerebraovascular reserve should help elucidate these processes. But further study with more cases is necessary for evaluation of pathophysiology of TGA.