Decreased blood perfusion in temporal lobe in transient global amnesia

Transient global amnesia (TGA) is an episodic dysfunction of declarative memory, which is assumed to be a benign disorder. The previous publications showed that brain perfusion single photon emission computed tomography (SPECT) was shown to be abnormal during the acute stage and to become normal with normalization of memory function. The aim of this study was to determine the areas involved in episodes of TGA and the rate of normalization by evaluation of cerebral blood flow (CBF) using SPECT. Between March 2003 and June 2009, 185 patients admitted to Seoul National University Bundang Hospital, who fulfilled standard clinical criteria for the diagnosis of TGA (Hodges &Warlow, 1990) participated in the present study. Technetium-99m L,L-ethylcysteinate dimer (99mTc-ECD) SPECT was performed during early period after TGA attacks on 144 patients (42 men and 107 women). On the patients with an abnormal brain imaging during early period, follow-up imagings were performed after 6 and 12 months. Abnormal perfusion was demonstrated in 68% of 144 subjects within 7 days after the acute stage. Significant unilateral or bilateral hypoperfusion of the temporal region was observed in 88 out of 98 patients (89.9%, P < 0.01). Ten(10.2%) patients had decreased perfusion in other lesions including thalamus, basal ganglia, frontal and parietal lobe. These changes normalized in the follow-up studies in 10 of 60 patients after 6months. In 50 patients with persistent hypoperfusion, repeat SPECT performed one year later demonstrated a normalization. The present study was preliminary, but at least suggested that temporal region are closely involved in the symptoms of TGA. Although the phenomenon is expected to have a very good prognostic outcome, perfusion imaging using the SPECT is not always normal. Although, in most cases, the perfusion abnormalities returned to normal, eventually, hypoperfusion was demonstrated long after the clinical symptoms disappeared in some cases. This study suggests that SPECT technique is useful in revealing the pathophysiological mechanism of TGA and that TGA attacks are associated with cerebral blood flow change of temporal lobe region.