MORPHOMETRY IN TEMPORAL-LOBE EPILEPSY

We demonstrate a method for quantitating changes in volume and morphol ogy of the temporal lobe in epilepsy. The temporal lobes of 10 neurolo gically normal subjects and six subjects with web defined left-sided m esial temporal epilepsy were studied, From high resolution T-1-weighte d magnetic resonance images, the grey and white matter were manually s egmented over a predetermined extent. The volumes of the grey and whit e matter were determined. Using the segmented images, the grey matter/ CSF surface and the white matter/grey matter surface were reconstructe d, allowing estimates of the surface area and calculation of indices o f curvature for the two surfaces. The index of curvature was calculate d for each vertex of a polygonal mesh that was fitted to the surfaces. An index of grey matter thickness (grey matter volume/white matter su rface area) was also calculated. There was a significant bilateral dec rease in the total volume (p < .01), grey matter volume (p < .001) and grey matter thickness index (p < .05) in epileptic subjects. In addit ion, there was a bilateral decrease in white matter surface area (p < .05) and a small left-sided decrease in white matter volume (p < .05) in epileptic subjects. The average distributions of indices of curvatu re for both surfaces differed significantly (p < .05) between normal a nd epileptic subjects. In the grey matter/CSF surface of normal subjec ts, a large peak corresponding to surface concavity was present. The a mplitude of this peak was significantly lower in epileptic subjects (p < .05 for the right hemisphere; p < .001 for the left hemisphere).