Neuronal migration disorders part II: magnetic resonance imaging

With the widespread use of magnetic resonance imaging (MRI), neuronal migration disorders (NMD), including lissencephaly, pachygyria, polymicrogyria, schizencephaly, unilateral hemimegalencephaly and gray matter heterotopia, are more frequently and easily diagnosed. When NMD is a diagnostic consideration, MRI should be the imaging method of choice with the high contrast between gray and white matter it provides and its high resolution multiplanar display of anatomy. Magnetic resonance imaging displays the size, configuration and distribution of cortical gyri and cortical thickness for the evaluation of possible lissencephaly, pachygyri and polymicrogyri. It will successfully demonstrate deposits of gray matter in abnormal locations when gray matter heterotopias are present. With its multiplanar imaging capability, MRI will demonstrate the cleft extending from the pial surface to the ventricular ependyma whether the lips of the cleft are fused or separate, thus providing the diagnosis of schizencephaly.