Cortical dysplasias comprise a variable spectrum of clinical, neuroradiological and
histopathological findings. We report about a cohort of 25 pediatric patients (mean
age 8.1±4.8) with severe drug resistant early onset focal epilepsies (mean age 2.1±0.4),
mental/psychomotor retardation, and multilobar epileptogenesis. Compared to aged matched
biopsy controls, microscopical inspection of neurosurgically resected specimens revealed
dysplastic neurons with/without balloon cells in only seven patients. According to
Palmini's classification system, these lesions were categorized as focal cortical
dysplasia (FCD) type II. All other patients presented with rather subtle but statistically
significant neuroanatomical abnormalities. We identified increased numbers of ectopic
neurons in white matter and cortical gliosis. However, most intriguing was our finding
of a microcolumnar arrangement of cortical neurons in layer III. These microcolumns
can be statistically defined as vertical lining of more than 8 neurons (two times
standard deviation of cell countings obtained from controls). In addition, neuronal
perikarya were significantly smaller in epilepsy patients. Although histological abnormalities
during postnatal maturation of the brain challenge any neuropathological classification
in this group of young patients, we propose to classify these findings according to
FCD type I. Our observations support a concept compatible with regional loss of high
order brain organization.
