Localisation of epileptic focus using SPECT and proton magnetic resonance spectrometric imaging

The goal of this study was to investigate the alterations of brain anatomy, function and metabolism associated with temporal lobe epilepsy. Three imaging techniques were used: single photon emission tomography (SPECT), magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopic imaging (1 H MRSI). Fifteen patients with medically refractory complex temporal lobe epilepsy were studied by SPECT, MRI and MRSI and ten controls by MRI and MRSI. Five patients showed MR images with T 2 hyper signal. SPECT images demonstrated significant (> 15%) regional hypoperfusion at compared with the contralateral lobe in nine patients. Spectroscopic images of the N-acetyl aspartate (NAA) showed hypo intensities in the epileptic region in eleven patients. Quantitative results using metabolites ratios showed: 1) significant decrease of the NAA over creatine (Cr) ratio ipsilaterally to the focus determined by electro-clinical analysis (2.76 ± 0.17) in comparison with contralateral region (3.26 ± 0.20; p < 0.05); 2) the value of the NAA/Cr ratio was significantly lower in the ipsilateral and the contralateral lobes to the focus in patients compared to controls (3.97 ± 0.13; p < 0.01). Finally, when compared to electro clinical data, MRI was able to lateralize the focus in 33% of the cases, SPECT in 60% and MRSI was positive in 74%. These results open the perspective to use these three non-invasive imaging techniques as a clinical tool for lateralization and localization of focal refractory epilepsy. (authors). 39 refs., 2 tabs., 4 figs