The Relationship between Proton MRS and Clinical, EEG, or Neuropsychological Features in Temporal Lobe Epilepsy
Authors: Kikuchi Scnichiro , Hattori Suguru , Shihata Nobuyoshi , Akata Takushiro , Kuhota Fumio , Takahashi Akio , Oya Nariyuki , Takeuchi Kazuo 
Published: August 2005

Purpose: There havc becii few reports on thc seimre rocus lateralimtion in temporal lobe epilcpsy (TLE) using proton magnetic resonance spectroscopy (‘H‐MRS) or studics that investigated the hippocampal function in TLE patients using ‘H‐MRS. We examincd hippoampal ‘H‐MRS studies, clinical symptoms, BEG investigations, and memory tests in TLE paticnts, to investigate whethcr ‘H‐MRS is useful to decide the sciz.urc focus and whethcr it reflects thc clinical rcdturcs or the hippocampal function.

Methods: ‘H‐MRS and EEG investigations wcre pcrformed on 21 unilateral TLE (left: n = 13, right: n = 8) patients. A Signa Horizon IST (GE‐YMS) was uscd for single‐voxel ‘H‐MRS. PRESS single spectra (repetition time = 2000 ins, echo time = 35 ms) were obtained from Sx I Sx2.0 ‐ cm rectangular regions centered oil thc bilateral hippocampi. From ‘H‐MRS spectra, the intensities of N‐acctylaspartatc (NAA) and creatinc were calculated nsing SAKE software. Thc NAA ratio (NAA/ creatine) i n the hippocampal area and the Laterality Index (LI) of the NAA ratio I [(contralatcral NAA ratio) ‐ (ipsilateral NAA ratio) / ((contralatcral NAA ratio) + (ipsilateral NAA ratio)) / 21 WCI'C used as indexes of ‘H‐MRS. As clinical symptoms, we examined thc onset age of illness, the frequency of seimre, and the duration of the illness. Scizure foci were determined by scalp EEG. Nincteen of the 2 I patients (left: n = I I, right: n = 8) consented to memory tcsts using the Rey Auditory Verbal Learning Tcst (AVLT) and the Benton Visual Rctention Test (BVRT). We used the sum of Trials 1–5 21s scores of AVLT, and used the Number Correct score and the Number of Errors score of BVRT (Form C, Administration A). The Pcarson correlation coetficicnt was used for statistical analysis.

Results: The mean NAA ratio in thc left sidc was 1.22 f 0.19 (left TLE: I, I 8 f 0. IS, right TLE: I .29 2 0.23). The mean NAA ratio in the right sidc was 1.37 ‘+ 0.18 (left TLE: 1.41 ’+ 0.13, right TLE: 1.30 ‐i. 0.24). In I 9 of thc 21 patients with TLE (left: 13/13, right: 6/8), the NAA mtio was less in the ipsilatccral seizure focus than in the contra‐ lateral seimre focus. Although thc NAA ratio did not correlate with the onsct age of illness or thc frequency of seizure, therc werc significant correlations with thc LI ofthe NAA ratio and the duration of the illnesh (r=0.445, p4.05). The mean AVLT score was 45.32 5 10.66. The mcan BVRT Numbcr Correct score was 6. I6 7times; 2.8 1 . Thc mean BVRT Number of Errors score was 5.84 i 4.81. Though there were no significant correlations in other tests or groups, therc was a significant correlation bctwceii the AVLT score and the left hippocampal NAA ratio in the patients with lelt seizure focus (r = 0.576, p41.05).

Conclusions: In TLE, the hippocampal NAA ratio scems to bc useful for thc lateralization of seizure focus because of a high ratc of agreement with laterality of seizure focus and the NAA ratio. Thc longer the duration of the illness, the lower the NAA ratio, due to the between the LI of the NAA ratio and the duration of thc il the NAA ratio correlated with the AVLT score, so the ‘H‐MRS might also reflect the hippocampal function to some degree.