DENDRITIC MORPHOLOGY IN EPILEPTOGENIC CORTEX FROM TRPE PATIENTS, REVEALED BY INTRACELLULAR LUCIFER-YELLOW MICROINJECTION AND CONFOCAL LASER-SCANNING MICROSCOPY

Biopsy material was obtained from cortical epileptogenic zones (eight temporal, one occipital, one parietal and one frontal) of eleven patie nts aged 1.5-47 years with therapy-resistant partial epilepsy (TRPE) u ndergoing epilepsy surgery. Control autopsy material (two temporal, tw o occipital, one parietal and one frontal) was removed from six neurol ogically healthy cases within 6-10 hours postmortem delay. In each spe cimen, 100-300 pyramidal and nonpyramidal neurons were visualized by i ntracellular Lucifer Yellow microinjection. Single neurons were imaged using CLSM generated serial optical sections; 2-D reconstruction of e ach neuron was made using z-projection of serial optical images, and 3 -D reconstructions and rotations were computerized. Neuronal maps from TRPE biopsies, compared to control autopsies, show markedly increased numbers of dendritic abnormalities of single pyramidal and non-pyrami dal neurons in layers I, II-III, V-VII, and in the subcortical white m atter. The abnormalities include: (1) increased number of non-pyramida l cells in layer I; (2) many pyramidal cells with two or three dendrit es originating apically, rather than one single apical dendrite, in la yers II-III; (3) atypical orientation of oblique apical and basal dend rites in pyramidal neurons of layers II-VII; (4) increased number of a typical 'dinosaur-like' and fusiform cells in layers V-VII; (5) numero us neurons in the white matter. These abnormalities may be etiological in cases with early onset, and predisposing in cases with late onset.