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Investigations on Alterations of Hippocampal Circuit Function Following Mild Traumatic Brain Injury
Published on: November 19, 2012
Serial changes in delayed focal hippocampal lesions in patients with transient global amnesia
Hiroki Ueno1, Hiromitsu Naka, Tomohiko Ohshita
1Department of Clinical Neuroscience and Therapeutics, Hiroshima University, Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan. hirokiueno@hiroshima-u.ac.jp
Abstract:
The etiology of transient global amnesia (TGA) is not well understood. MR studies, including studies using diffusion-weighted imaging (DWI), have been used to investigate the pathophysiology of TGA, and focal hippocampal lesions have been detected in some studies. The aim of this study was to investigate serial changes in MR images from the patients with TGA. In seven TGA patients, serial MRI scans (from the same day of the onset to several days after the onset of symptoms) using a 1.5-T MR unit were prospectively evaluated. In four patients, the duration of TGA was over 12 hr. Three of those patients showed small punctate hippocampal hypersensitivity with decreased ADC values on DW images. These lesions were detected in the postacute phase (a time window of 24 - 48 hr after the onset of symptoms). In follow-up studies performed several days after the onset of symptoms, DWI lesions had disappeared in the subacute phase (7-10 days after the TGA episode). The delayed hippocampal lesion on DW images with 1.5-T MRI in patients with TGA appears to be associated with longer duration of symptoms, to persist for several days and to disappear in the chronic phase.
Insights
Transient global amnesia (TGA) findings on MRI show temporary hippocampal lesions. These diffusion-weighted imaging (DWI) lesions appear delayed, lasting several days before resolving.
Area of Science:
- Neurology
- Radiology
- Neuroimaging
Background:
- The causes of transient global amnesia (TGA) remain unclear.
- Magnetic Resonance (MR) imaging, particularly diffusion-weighted imaging (DWI), is used to study TGA pathophysiology.
- Previous studies have identified focal hippocampal lesions in some TGA patients.
Purpose of the Study:
- To examine serial changes in MR images of patients experiencing TGA.
- To correlate imaging findings with TGA duration and symptom onset.
Main Methods:
- Prospective evaluation of serial MRI scans from seven TGA patients.
- Scans were performed from symptom onset up to several days post-onset using a 1.5-T MR unit.
- Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values were analyzed.
Main Results:
- In four patients with TGA duration exceeding 12 hours, three exhibited punctate hippocampal hypersensitivity with reduced ADC values on DWI.
- These lesions were observed in the postacute phase (24-48 hours after symptom onset).
- DWI lesions resolved by the subacute phase (7-10 days post-episode).
Conclusions:
- Delayed hippocampal lesions on DWI, detected by 1.5-T MRI, are associated with longer TGA symptom duration.
- These lesions persist for several days and resolve in the chronic phase.
- Serial MRI, especially DWI, can reveal transient pathophysiological changes in TGA.
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