3 Tesla Magnetic Resonance Imaging of Hippocampal Asymmetry: Results from the Dallas Heart Study
Lucarelli, Richard T.
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BACKGROUND: Asymmetry of the hippocampus is regarded as an important clinical finding but limited data on hippocampal asymmetry is available for the general population. Here we present hippocampal asymmetry data from the Dallas Heart Study determined by automated methods and its relationship to age, sex, and ethnicity. METHODS: 3D-MPRAGE MRI were obtained in 2082 DHS-2 participants. The MR images were analyzed using two standard automated brain segmentation programs, FSL-FIRST and Freesurfer. Individuals with imaging error, self-reported stroke, or major structural abnormalities were excluded. Statistical analyses were performed to determine significance of the findings across age, sex, and ethnicity. RESULTS: At the 90th percentile FSL-FIRST demonstrated hippocampal asymmetry of 9.8% (95% CI 9.3 to 10.5%). The 90th percentile of hippocampal asymmetry measured by the difference between hippocampii over the larger hippocampus was 17.9% (95% CI 17.0 to 19.1%). Hippocampal asymmetry increases with age (P=0.0216) and men have greater asymmetry than women as shown by FSL-FIRST (P=0.0036), but ethnicity is not significantly correlated with asymmetry. To confirm these findings Freesurfer was used. Freesurfer showed asymmetry of 4.4% (95% CI 4.3 to 4.7%) normalized to total volume, and 8.5% (95% CI 8.3 to 9.0%) when normalized by difference/larger hippocampus. Freesurfer also showed that hippocampal asymmetry increases with age (P=0.0024), and that men had greater asymmetry than women (P=0.03). CONCLUSION: There is a significant degree of hippocampal asymmetry in the population. The data provided will aid in the research, diagnosis, and treatment of temporal lobe epilepsy and other neurological disease.