NPY and epilepsy: Due to this normal anatomical variation, counts in epilepsy cases in CA1 and CA4, as quantified on CV, CB, CR and NPY at each level were compared to mean control values for that level and then expressed as four grades: 0–25% neuronal loss (Grade 1), 25–50% neuronal loss (Grade 2), 50–75% neuronal loss (Grade 3) and 75% or greater neuronal loss (Grade 4).