Pachygyria, lissencephaly (smooth brain), and polymicrogyria (multiple small gyri) are all the results of abnormal cell migration. The abnormal migration is typically associated with a disorganized cellular architecture, failure to form six layers of cortical neurons (a four-layer cortex is common), and functional problems. The abnormal formation of the brain may be associated with seizures, developmental delay, and mental dysfunctions.
Normally, the brain cells begin to develop in the periventricular region (germinal matrix) and then migrate from medial to lateral, to form the cerebral cortex.
The term 'pachygyria' does not directly relate to a specific malformation but rather is used to generally describe physical characteristics of the brain in association with several neuronal migration disorders; most commonly disorders relating to varied degrees of lissencephaly. Lissencephaly is present in 1 of 85,470 births and the life span of those affected is short as only a few survive past the age of 20. [1] Pachygyria is a condition identified by a type of cortical genetic malformation. Clinicians will subjectively determine the malformation based on the degree of malposition and the extent of thickened abnormal grey differentiation present. [2]
Different imaging modalities are commonly used for diagnosis. While computed tomography (CT) provides higher spatial resolution imaging of the brain, cerebral cortex malformations are more easily visualized in vivo and classified using magnetic resonance imaging (MRI) which provides higher contrast imaging and better delineation of white and gray matter. [3] Diffuse pachygyria (a mild form of lissencephaly) can be seen on an MRI as thickened cerebral cortices with few and large gyri and incomplete development of the Sylvian fissures [4]
