Objective: To prospectively assess the frequency of mesiotemporal abnormalities seen on brain MRI in healthy subjects in comparison with patients with temporal lobe epilepsy (TLE).
Methods: Ninety-nine consecutive patients (48 women, mean age 36.1 +/- 16.1 years; range 10 to 75) with TLE and 51 healthy volunteers (26 women, mean age 39.3 +/- 10.8 years) prospectively underwent the same MRI protocol, specific for TLE. Images were reviewed independently by 2 neuroradiologists blinded to clinical information. Cortical atrophy and signal intensities in the amygdala, hippocampus, cingulate gyrus, subcallosal area, insula, temporal parietal, and occipital lobe were graded relative to cortical signal intensity in the frontal lobe. Intrarater and interrater reliability were also assessed.
Results: Interrater and intrarater measurements demonstrated consistent and repeatable results. Forty-seven of 99 (47.5%) patients showed either unilateral or bilateral major T2/fluid-attenuated inversion recovery hyperintensities of the hippocampus, and 19 patients (19.2%) showed hippocampal atrophy seen at T1/inversion recovery sequences. In the controls, 15/51 (29.4%) individuals had unilateral or bilateral hyperintensities, which did not differ from the rate of occurrence in patients (p = 0.08). Conversely, unilateral hippocampal atrophy was found in 1 control, which was significantly different (p = 0.005) from the rate of occurrence in patients. Hyperintensity plus structural hippocampal atrophy were only seen in patients.
Conclusions: On brain MRI, either unilateral or bilateral hippocampal hyperintensities are frequently encountered in healthy volunteers. Conversely, hippocampal atrophy, especially when associated with concomitant hyperintensity, was seen exclusively in the epilepsy group, indicating that the combination of these 2 variables represents the strongest and most reliable indicator of epilepsy.