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Images in Neurology
September 2005

Hippocampal Magnetic Resonance Imaging Abnormalities in Transient Global Amnesia

Arch Neurol. 2005;62(9):1468-1469. doi:10.1001/archneur.62.9.1468

Transient global amnesia (TGA) is an episodic dysfunction of declarative memory that usually resolves within less than 12 hours. Its cause is still poorly understood.

Studies on neuroimaging findings in TGA are heterogeneous and conflicting and most of them report the lack of obvious abnormalities.1 A recent study demonstrates a punctuate lesion on diffusion-weighted images (DWIs) in the hippocampus in more than 80% of patients with TGA.2 Can this hippocampal lesion be considered the structural correlate of TGA? Here we confirm the presence of this abnormality in 3 patients with TGA. The diagnosis of TGA was based on the current criteria.3 Within 5 months, 4 consecutive patients (aged 67, 65, 60, and 62 years) with TGA underwent brain magnetic resonance imaging (MRI). The MRI was performed within 4 days of the onset of symptoms: on day 3 in patient 1, on day 2 in patient 2, on day 4 in patient 3, and on day 2 in patient 4. In 3 of these patients, MRI (Figure 1) showed a small punctuate focus of high signal in the right hippocampus, clearly evident on DWI. The lesions matched with small areas of low signal on apparent diffusion coefficient maps. These signal abnormalities suggest ischemic lesions. The MRI showed no abnormalities in the remaining patient. Diffusion-weighted imaging allowed prompt recognition of small abnormalities in the hippocampus with high sensitivity; comparison and matching with correspondent apparent diffusion coefficient maps increased specificity.

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