Objective: To determine whether the finding of hyperintense hippocampal signal intensity on double inversion recovery (DIR) magnetic resonance imaging is correlated with hippocampal volume loss and metabolic abnormalities in patients with mesial temporal lobe epilepsy (MTLE).
Methods: This retrospective study had institutional review board approval, and informed consent was obtained. Thirteen patients with unilateral hippocampal sclerosis and 13 age-matched healthy control subjects were included. Quantitative assessment for hippocampus of the patients and the control subjects was determined, including DIR, 3-dimensional T1-weighted imaging and proton magnetic resonance spectroscopy. Hippocampal relative signal intensity on DIR images (RSIDIR), volumes, and N-acetylaspartate-to-choline and creatine/phosphocreatine ratios were measured during one magnetic resonance imaging session, and asymmetry indexes (AI) of bilateral hippocampi were calculated. Hippocampal RSIDIR and AIDIR were compared between the patients and the control subjects. The RSIDIR and AIDIR were further correlated with the quantitative MR measures and with the age at onset and duration of MTLE. Statistical analyses were performed with Student t test, 1-way analysis of variance, and Pearson correlation.
Results: On DIR images, the hippocampi ipsilateral to the seizure focus demonstrated relatively extreme hyperintensity. The ipsilateral hippocampi showed significantly increased RSIDIR compared with contralateral hippocampi and the healthy subjects (F = 197.956, P < 0.001). The hippocampal AIDIR in the patients was also significantly higher than that in the control group (t = 24.896, P < 0.001). Significant Pearson correlations (2-tailed) were obtained between the RSIDIR and the volume of the ipsilateral hippocampi (r = −0.762, P < 0.01) and between the RSIDIR and duration of epilepsy (r = 0.557, P < 0.05). Moreover, there were significant correlations between the AIDIR and the AIvolume (r = 0.609, P < 0.05) and between the AIDIR and the duration of epilepsy (r = 0.610, P < 0.05). However, no significant correlations of hippocampal DIR measures with proton magnetic resonance spectroscopy were obtained.
Conclusions: Double inversion recovery imaging of the brain can yield complementary information about hippocampal pathology and efficiently lateralize the hippocampal sclerosis in patients with MTLE.