Hippocampal Region Asymmetry Assessed by 1H-MRS in Rolandic Epilepsy


Address correspondence and reprint requests to Dr. S. Lundberg at University Children's Hospital, S-751 85 Uppsala, Sweden. E-mail: staffan.lundberg@kbh.uu.se


Summary:  Purpose: In a previous study, we reported hippocampal abnormalities on magnetic resonance imaging (MRI) in six of 18 children with rolandic epilepsy (RE). In this study, metabolic changes were analyzed in the hippocampal region with proton magnetic resonance spectroscopy (1H-MRS).

Methods: In 13 children with electroclinically typical RE and 15 healthy controls, 1H-MRS results of both hippocampal regions were analyzed. The voxels, 2 × 2 × 4-cm each, were placed to include the head and body of the hippocampus. A PRESS sequence with TR 2,000 ms and TE 32 ms was used. Total N-acetylaspartate (tNAA), glutamine and glutamate (Glx), and choline compounds (tCho) were related to total creatine (tCr), and asymmetry indices (AIs) were calculated. MRI was performed in all 13 patients and in 13 controls.

Results: The tNAA/tCr AI of the hippocampal region was significantly higher in children with RE than in control children (z = 4.49; p < 0.001). The AIs of Glx/tCr and tCho/tCr did not show a significant difference between the groups. Lateralization of the interictal epileptiform activity corresponded with the lower tNAA/tCr ratio in 10 of 13 patients. MRI revealed a hippocampal asymmetry in four of 13 in the RE group, three of them showed concordance between the lateralization of the lower tNAA/tCr ratio and the smaller hippocampus. In the control group, a subtle asymmetry in four of 13 children was found.

Conclusions: A significant asymmetry of the hippocampal regions, measured by tNAA/tCr ratios, indicates an abnormal neuronal function in children with RE.