Nuclear magnetic resonance relaxometry in a penicillin model of focal epilepsy

Magnetic resonance imaging (MRI) is effective in demonstrating pathologic lesions in patients with epilepsy. It has been suggested that MRI might also reveal functional abnormalities at an interictal epileptic focus when no gross structural change such as gliosis or tumor is present. Experimental epileptic foci were produced by topical application of penicillin to the cortex of rats. In vitro proton nuclear magnetic resonance (NMR) relaxometry of tissue excised from the experimental foci revealed an increase in spin-echo relaxation time as compared to that in control tissue. The elevated relaxation times occurred in tissue samples from areas of active electroencephalographic (EEG) spiking. This is the first direct demonstration of an alteration in proton magnetic resonance parameters by functional abnormalities (focal interictal spike activity) in the brain, supporting the concept that MRI might be similarly affected.