MRI, 1H-MRS, and functional MRI during and after prolonged nonconvulsive seizure activity

Background: Various structural and functional changes, such as focal edema, blood flow, and metabolism, occur in the cerebral cortex after focal status epilepticus. These changes can be assessed noninvasively by means of MRI techniques, such as fluid-attenuated inversion recovery (FLAIR), LEG-triggered functional MRI (EEG-fMRI), and proton MR spectroscopy (MRS). Methods: The authors report on a 40-year-old patient with nonlesional partial epilepsy in the left posterior quadrant in whom these MRI techniques were applied in an active seizure focus and repeated during a follow-up of 1 year. Results: FLAIR imaging taken at the time of status epilepticus showed a signal hyperintensity in the occipital region. H-1-MRS of this cortical region showed elevated lactate, decreased N-acetylaspartate (NAA), and elevated choline (Cho), In the same region, EEG-fMRI revealed an area of signal enhancement. After seizure control, recovery of lactate and Cho was observed, whereas the NAA level remained reduced. The structural abnormality demonstrated on FLAIR disappeared within 3 months. Conclusions: Repetitive MRI with sensitive sequences during clinically critical periods may disclose the structural correlate in a previously nonlesional epilepsy case. Corresponding to the clinical evolution, reversible and irreversible focally abnormal metabolism can be determined with 1H-MRS, reflecting both increased neuronal activity and neuronal damage.