Magnetic resonance imaging of disturbances in neuronal migration: illustration of an embryologic process.

Twenty-three cases of suspected congenital anomalies involving disorders of cortical proliferation, migration or cortication were retrospectively collected over an 18 month period. Pathologic confirmation was present in five cases. The theoretical sequential stages of cortical development are discussed as keys to the interpretation of MR images of anomalies resulting from arrest of the developmental process. MRI is the imaging modality of choice for suspected defects of cortex formation since it distinguishes gray from white matter, delineates the corticomedullary junction, records details of cortical surfaces, detects abnormal white matter, identifies heterotopias and records unrelated congenital abnormalities. Histopathologic confirmation of two cases of isolated heterotopia and three cases of polymicrogyria were available. Comparative images of MR, CT and pathologic specimens are presented.