Magnetic resonance spectroscopy in temporal lobe epilepsy

Abstract

We used proton magnetic resonance spectroscopy (1H MRS) to investigate the temporal lobes of 25 patients with temporal lobe epilepsy. Spectra were obtained from 2 x 2 x 2 cm cubes in the medial region of the temporal lobe, and were analyzed on the basis of signals from N-acetylaspartate (NAA), creatine + phosphocreatine (Cr), and choline-containing compounds (Cho). In comparison with control subjects, the temporal lobes ipsilateral to the seizure focus showed a mean reduction of 22% in the NAA signal, with a 15% increase in the Cr signal and a 25% increase in the Cho signal. There were smaller effects in the contralateral temporal lobes. These spectral abnormalities may reflect neuronal loss or damage, together with reactive astrocytosis. The NAA/Cho+Cr ratio was abnormally low in 88% of the patients, 40% showing bilateral effects. On the basis of the NAA/Cho+Cr ratio, we correctly achieved lateralization in 15 cases, with three incorrect. Two of the incorrect lateralizations also had imaging abnormalities on the contralateral side, and the other had severe bilateral abnormalities on MRS. We conclude that 1H MRS provides useful information in the preoperative investigation of patients with temporal lobe epilepsy, contributing to lateralization and detecting bilateral abnormalities.

Presurgical multimodality neuroimaging in electroencephalographic lateralized temporal lobe epilepsy

“…Some studies included patients suspected or proved to have bilateral independent TLE, a finding used to explain discordant or nonlateralized MRSI results [8,14]. The 1 H-MRSI sensitivity (55-65%) reported in the series by Connelly and associates [11] and Cross and colleagues [12], including some discordant lateralization, is nearly identical to our results.…”

“…Some studies included patients suspected or proved to have bilateral independent TLE, a finding used to explain discordant or nonlateralized MRSI results [8,14]. The 1 H-MRSI sensitivity (55-65%) reported in the series by Connelly and associates [11] and Cross and colleagues [12], including some discordant lateralization, is nearly identical to our results.Because of persistent findings of discordant lateralization, we emphasize the need for conservative 1 H-MRSI lateralization criteria, even at the expense of sensitivity. This may be less of an issue with [NAA], which we found to be highly reliable in predicting lateralization in patients who became completely seizure free.…”

“…The question remains whether this is a compromise in lateralization sensitivity for MRSI or if long-term outcome will demonstrate that bilaterally abnormal MRSI is ultimately correlated with non-seizure free outcome. Other early surgical outcome results [11,27] agree with ours that relatively symmetric but bilaterally abnormal HV or MRSI does not preclude seizure-free outcome.Despite some limitations, our results do provide data for recommendations regarding the selective use of FDG-PET in presurgical evaluation of patients with EEG-defined TLE. For patients with hippocampal atrophy, PET provides essentially no new lateralization or outcome information.…”

“…Several groups have reported the ability of 1 H-MRSI to detect unilateral and bilateral metabolite abnormalities in TLE [7][8][9][10][11][12][13][14][15][16][17]. No studies have compared 1 H-MRSI lateralization results directly with FDG-PET and quantitative MRI techniques in patients with and without hippocampal atrophy.…”

Reproducibility of Proton Magnetic Resonance Spectroscopic Imaging in Patients with Schizophrenia

“…Localized 1 H-MRS has been used to study a variety of brain disorders, including multiple sclerosis (Roser et al 1995), neoplasm (Alger et al 1990), epilepsy (Connelly et al 1994), Down's syndrome (Murata et al 1993), Huntington's disease (Jenkins et al 1993), and schizophrenia (Yurgelun-Todd et al 1996;Renshaw et al 1995;Nasrallah et al 1994;Maier et al 1995;Buckley et al 1994;Fukuzako et al 1995). 1 H-MRS has recently evolved to multislice 1 H-MRS imaging ( 1 H-MRSI) that permits imaging of signals arising from a large number of small single-volume elements (nominal volume resolution of 0.84 mL) within multiple whole brain slices, thus enabling mapping of the spatial extent of chemical abnormalities with improved resolution (Duyn et al 1993).…”