Microdysgenesis in resected temporal neocortex: incidence and clinical significance in focal epilepsy

Fifty patients underwent superficial temporal lobectomy for intractable temporal lobe epilepsy. Total cure rate was 52%, and significant improvement was achieved in 88%. Cytoarchitectural changes in gray and white tissue were analyzed under light microscopy. Neuronal dysgenesis was correlated with the duration of seizure disorder, age of onset, and other etiologic factors, and with clinical outcome. Temporal lobes from 33 neurologically normal autopsy brains which were age- and sex-matched with patients were examined as controls. Severe neuronal ectopia (greater than 8 neurons/2 mm2 white matter) was present in 42% of patients with epilepsy and in none of controls. There was neuronal clustering in 28% of those with epilepsy, and Chaslin's (subpial) gliosis in 38%. Controls did not have these changes. The presence of severe neuronal ectopia and clustering was predictive of a favorable clinical outcome following surgery (p less than 0.05). No correlation was found between microdysgenesis and other factors. These findings suggest that the presence of neuronal dysgenesis may be of significance in the clinical outcome following surgery, and that the abnormal tissue may be important as a morphologic substrate for seizures in some patients.