Prognostic value of proton magnetic resonance spectroscopic imaging for surgical outcome in patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy

Abstract

The objective of this study was to assess which features of temporal lobe proton magnetic resonance spectroscopic imaging (1H-MRSI) are associated with satisfactory surgical outcome in patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy. We studied 21 patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy defined by magnetic resonance imaging volumetric measurements who underwent surgical treatment. 1H-MRSI was used to determine the relative resonance intensity ratio of the neuronal marker N-acetylaspartate to creatine + phosphocreatine (NAA/Cr) for mid and posterior temporal lobe regions of the left and right hemisphere, as well as an asymmetry index. Values lower than 2 SDs below the normal mean were considered abnormal. We used Engel's classification to assess surgical outcome with respect to seizure control. Eleven patients (52%) were in class I-II and 10 (48%) were in class III-IV. All 21 were operated on the side of maximal electroencephalographic (EEG) lateralization. Concordant lateralization of decreases in NAA/Cr to the side of surgery and normal NAA/Cr values in the contralateral posterior-temporal region were significantly associated with good surgical outcome: 11 (69%) of 16 patients with 1H-MRSI abnormalities concordant with EEG lateralization and none of the 5 patients with nonconcordant 1H-MRSI had a good outcome (class I-II); 10 (77%) of 13 patients with normal NAA/Cr contralateral to the EEG lateralization versus 1 (12.5%) of 8 of those with NAA/Cr reduction contralateral to EEG lateralization were in class I-II. Regression correlation analysis showed significant linear correlation between the midtemporal NAA/Cr relative asymmetry ratio and surgical outcome; the greater the asymmetry, the better the outcome. We conclude that discriminant 1H-MRSI features associated with favorable surgical outcome in patients with temporal lobe epilepsy and bilateral hippocampal atrophy were (1) concordant 1H-MRSI lateralization, (2) a greater side-to-side asymmetry of NAA/Cr, and (3) an absence of contralateral posterior NAA/Cr reduction.

Mesial temporal lobe epilepsy: How do we improve surgical outcome?

“…Bilateral abnormalities, however, have also been reported using MRSI techniques in 45% of MTLE patients. It is unclear whether spectroscopy aids in the prediction of seizure freedom following surgery 33,34…”

Magnetoencephalography-directed surgery in patients with neocortical epilepsy

“…A mean follow-up duration of 21 months (range [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] A. N. Mamelak, et al I 0 4 4 1 0 1 few -II 0 1 1 3 0 3 many diffuse IIIA 0 1 1 2 0 2 dense IIIB 3 8 11 0 0 0 total --3 14 17 6 0 6 * None, 0; few, five or fewer spikes; many, six or more spikes per 4-hour recording session.…”

Value of Proton-MR-Spectroscopy in the Diagnosis of Temporal Lobe Epilepsy; Correlation of Metabolite Alterations With Electroencephalography

“…MRI and at the same time H-MRS, which are non-invasive techniques, play an extremely important role in the diagnosis of hippocampal sclerosis and MTLE; MRI shows an atrophic-small or firm hippocampus and also hyperintense, diffuse edematous areas at the hippocampi on T2W images [1][4][6][8][13]. H-MRS predicted the metabolite peaks, measured in different parts of both hippocampi and NAA decrease in the spectrum usually provides the lateralization and localization of the epileptic focus [1][5][6][7][8][10][12][13][14].…”

“…Neuropsychological evaluation, brain magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging are the other diagnostic approaches in the assessment of epileptic foci [3][4][5][6][7]. Cerebral MRI usually shows atrophy or high signal intensity in the affected hippocampus or amygdala; however, in some patients with MTLE, it may reveal no abnormalities [1][3][7][8][9]. Proton-MR-Spectroscopy (H-MRS), a non-invasive technique, has been suggested for its usefulness in the evaluation of MTLE and epileptogenic areas.…”

“…Proton-MR-Spectroscopy (H-MRS), a non-invasive technique, has been suggested for its usefulness in the evaluation of MTLE and epileptogenic areas. By detection of metabolites in the mesial temporal structures (hippocampus and the amygdala), H-MRS can give sensitive and reliable results, may aid in the lateralization of epileptic foci and the diagnosis of MTLE [1][3][4][6][7][8][9][10][11]. Lateralization is a procedure that is used to determine the hemisphere which is responsible for the genesis of seizures [1][4][6][7][11].…”