Brain - Dysplasia

With the increasing use of generational toxicity studies, recognizing neural dysplasia is becoming increasingly important. Dysplasias include developmental abnormalities in size, organization, and location of various elements of the neural structures. Figure 1 shows, at low magnification, the appearance of uncommonly recognized incidental rodent hippocampal dysplasia. In this dramatic example, note the abnormal undulating CA1 region (arrows) and malformed dentate gyrus (arrowhead). CA3 appears relatively normal. Figure 2, labeled for comparison, shows normal rat hippocampal structure. Dysplastic neuronal lesions are usually encountered in the cortex, hippocampus, and cerebellum, but any part of the brain can be affected. In most cases, effects, if any, are not detected clinically but could account for abnormal clinical neurologic signs such as seizures in individual animals. Models of neural dysplasia in rats include treatment with methylazoxymethanol acetate followed by induction of epileptiform seizures by pilocarpine.