Malformations of Cortical Development

Categories

• group I: abnormal cell proliferation or apoptosis
• group II: abnormal neuronal migration
• group III: abnormal cortical organization

Group	Characteristics	Conditions
Group I	abnormal proliferation of neuronal and glial cells	Microcephaly macrocephaly FCDs without and with balloon cells (Taylor dysplasia types IIa and IIb), hemimegalencephaly, tuberous sclerosis, dysembryoplastic neuroepithelial tumors (DNETs), gangliogliomas, gangliocytomas
Group II	abnormal neuronal migration	Lissencephaly Band Heterotopia
Group III	abnormal cortical organization	Polymicrogyria, schizencephaly, type I FCDs, mild MCDs

Group	Affected step of development	MCDs resulting from the disturbance	Short definition of the MCD
Group I	Progenitor cell proliferation and apoptosis	Microcephaly	Abnormally small head and brain
		Macrocephaly	Abnormally big head and brain
		Hemimegalencephaly	Overgrowth of (part of) a cerebral hemisphere
		Focal cortical dysplasia	Disturbed lamination and dysmorphic neurons
Group II	Neuronal migration	Lissencephaly type I	Absence of normal convolutions/folds
		Periventricular heterotopia (PH)	Neurons accumulating at the ventricles underneath a normal cortex
		Subcortical band heterotopia/double cortex	Band of grey matter located between the lateral ventricular wall and the cortex
Group III	Neuronal organisation	Cobblestone lissencephaly/lissencephaly type II	Overmigration of neurons to localize on the surface of a brain with reduced gyri
		Polymicrogyria	Too many (usually small) folds/convolutions
		Schizencephaly	Fluid-filled cleft from ventricle(s) to pia lined by heterotopic grey matter