A journey through formation and malformations of the neo-cortex

Malformations of cortical development (MCD) are a heterogeneous group of disorders characterized by abnormal structure of the cerebral cortex. MCDs are an important cause of development delay and intractable epilepsy in children. In this review, we explore the embryological stages of development of neo-cortex, the imageology of various malformations which may occur during the journey of this development, the recent advances in imaging techniques used for diagnosing these malformations, and finally a simplified radiological approach to malformations of cortical development.

We discuss the classification of MCD according to the embryologic stage of cerebral cortex at which the abnormality occurred and the unique imaging features of various malformations, including microcephaly, hemimegalencephaly, lissencephaly, focal cortical dysplasia, heterotopias, polymicrogyria, schizencephaly, and neonatal CMV infection. Also, a rare variant of hemimegalencephaly, namely posterior quadrantic dysplasia, is illustrated; the diagnosis of which is crucial for neurosurgeons to decide management. The technological advancement in the imaging of MCD has taken a leap in the recent years. Imaging now also plays an enormous role in mapping of the abnormalities, delineation of proper surgical boundaries, and quantifying risks of visual, language, and sensorimotor dysfunction. With the introduction of various motor-sparing surgeries and disconnection procedures, proper identification and delineation of these malformations have gained utmost significance.

Knowledge of the wide imaging spectrum of MCD, familiarity with recent advances in imaging and an optimal radiological approach is essential for the general radiologist to accurately diagnose and prognosticate MCD as well as provide the best surgical approach to the operating surgeon.