Introduction. The limbic system primarily responsible for our emotional life and memories is known to undergo degradation with aging and diffusion tensor imaging (DTI) is capable of revealing the white matter integrity. The aim of this study is to investigate age-related changes of quantitative diffusivity parameters and fiber characteristics on limbic system in healthy volunteers. Methods. 31 healthy subjects aged 25–70 years were examined at 1,5 TMR. Quantitative fiber tracking was performed of fornix, cingulum, and the parahippocampal gyrus. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) measurements of bilateral hippocampus, amygdala, fornix, cingulum, and parahippocampal gyrus were obtained as related components. Results. The FA values of left hippocampus, bilateral parahippocampal gyrus, and fornix showed negative correlations with aging. The ADC values of right amygdala and left cingulum interestingly showed negative relation and the left hippocampus represented positive relation with age. The cingulum showed no correlation. The significant relative changes per decade of age were found in the cingulum and parahippocampal gyrus FA measurements. Conclusion. Our approach shows that aging affects hippocampus, parahippocampus, and fornix significantly but not cingulum. These findings reveal age-related changes of limbic system in normal population that may contribute to future DTI studies.

Epilepsy is more than a grey-matter disorder affecting large white matter connections of the brain with seizure generation and propagation. The mechanism for such changes remains unclear. The purpose of this study was to investigate the microstructural changes in the corpus callosum in temporal lobe epilepsy (TLE) patients and whether these abnormalities are related to antiepileptic drug (AED) therapy. Ten TLE patients receiving AED therapy, ten TLE patients with no therapy and ten controls were included in the study. The regions of interest in the corpus callosum were outlined to each Witelson region (WR). Fractional anisotrophy (FA), apparent diffusion coefficient (ADC), three main diffusivity values (λ1, λ2, λ3) and tractography were acquired from each WR. DTI indices of these tracts and each WR were compared between the three subject groups and correlates examined with clinical variables that included duration of epilepsy, gender, AED type and AED therapy exposure. In TLE subjects with receiving AED therapy significantly (p<0.05) decreased FA and increased ADC values of corpus callosum were obtained when compared to the other groups. There was no significant relationship between AED type and DTI indices. Analysis of eigen values in the splenium of corpus callosum (WR7) showed λ1 values were significantly decreased in relation to AED medication duration (p<0.05). FA values of rostrum and corpus showed a reduction with duration of epilepsy. TLE is associated with abnormal integrity of corpus callosum white matter tracts. AED therapy may cause additional damage on secondary degeneration and medication time effects especially on the splenium of corpus callosum.

This study investigated diffusion abnormalities in the parts of corpus callosum (CC) of patients with Alzheimer's disease (AD) using diffusion tensor magnetic resonance imaging (DT-MRI). Twenty-one patients with AD and 20 healthy volunteers participated in the study. MRI was performed with a 1.5 T system. Conventional MR images and diffusion tensor images were obtained for all participants. We divided the CC into three parts as rostrum, body and splenium. The apparent diffusion coefficiency (ADC) and fractional anisotropy (FA) were measured in all parts. FA values for the CC were lower in AD patients than the values of controls. In AD patients the lowest values were found in the rostrum of the CC and CC body FA values were also lower than the splenium, but the difference did not reach statistical significance. DT-MRI is a promising technique to investigate microstructural changes in white matter regions in AD. Early detection of the disease has been increasingly studied in AD. Further studies with larger populations are needed to confirm the role of diffusion tensor imaging in the evaluation of memory impairment.