CT measurements of mesial temporal lobe herniation in epileptics.

The purpose of this study was to develop a quantitative method for describing preoperatively herniation of the mesial temporal lobe structures in epileptic patients. This was done by opacifying the CSF of the basal cisterns with metrizamide and measuring the position and contour of the mesial temporal lobe. The measurements were fitted to complex polynomial curves, which were then analyzed. The shapes of the curves, the surface area between the curves and the x axis, and the angles at which the curves intersected the x axis were all found to be reliable indicators of the presence or absence of herniation of the mesial temporal structures. In the 18 patients studied, chronic herniation of the mesial temporal lobe was found at the time of surgery in 13 cases and had been assessed correctly preoperatively with the aid of the polynomial curves in each instance.