Transient global amnesia: seven years of experience with diffusion-weighted imaging in an emergency department

Background/aims: Hippocampal lesions on diffusion-weighted imaging (DWI) are commonly described in transient global amnesia (TGA). We evaluated the utility of DWI and the presence of hippocampal lesions in the diagnosis of TGA.

Methods: A total of 203 TGA episodes were diagnosed at our emergency department from January 2003 to May 2010. DWI (5-mm slice thickness) was performed using a 1.5 T scanner. Patients were divided into 2 groups based on the presence of hippocampal lesions on DWI: DWI- and DWI+. The clinical characteristics and the time interval from development of amnesia to magnetic resonance imaging (MRI) were compared.

Results: 16 patients had hippocampal lesions on DWI. The DWI- and DWI+ groups had similar clinical characteristics. The overall median time interval from amnesia to MRI was 6 h, and this interval was significantly longer for the DWI+ group than the DWI- group [9 h (IQR 6.5-25) vs. 5 h (IQR 4-9), p = 0.002].

Conclusion: DWI has a low diagnostic yield when performed early in the course of TGA. Positive findings can confirm the diagnosis, but in negative results, careful interpretation is required, including the time interval from amnesia to MRI.