Limbic lobe of the human brain: evaluation with turbo fluid-attenuated inversion-recovery MR imaging.

PURPOSE To determine whether brain cortices have different signal intensities on turbo fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) images. MATERIALS AND METHODS Coronal 5-mm-thick turbo FLAIR MR images in 56 neurologically normal patients (27 male and 29 female patients; age range, 12-73 years; mean age, 47 years) were evaluated retrospectively. Cortical signal intensities in the amygdala, hippocampus, cingulate gyrus, subcallosal area, insula, temporal lobe, parietal lobe, and occipital lobe were graded relative to cortical signal intensity in the frontal lobe. Contrast-to-noise ratios were compared for each cortical area. RESULTS Increased signal intensity was frequently seen in the amygdala, hippocampus, cingulate gyrus, and subcallosal area, regardless of patient age. Signal intensities of temporal, parietal, and occipital cortices were similar to that of frontal cortex, and signal intensity of the insula was slightly higher than that of frontal cortex. There were no significant differences with respect to sex and laterality, whereas significant differences were found among cortical regions (P <.01). The contrast-to-noise ratios of the amygdala, hippocampus, cingulate gyrus, and subcallosal area were significantly greater than those of all other gray matter structures (P <.05). CONCLUSION On turbo FLAIR images, high signal intensities of cortices of the limbic lobe are frequently seen in neurologically normal brain. These findings should not be considered abnormal.