Migration disorders (MD) are increasingly recognized as an important cause of epilepsy and developmental delay. Up to 25 % of children with refractory epilepsy have a cortical malformation. MD encompass a wide spectrum with underlying genetic etiologies and clinical manifestations. Research regarding the delineation of the genetic and molecular basis of these disorders has provided greater insight into the pathogenesis of not only the malformation but also the process involved in normal cortical development. Diagnosis of MD is important since patients who fail three antiepileptic medications are less likely to have their seizures controlled with additional trials of medications and therefore epilepsy surgery should be considered. Recent improvements in neuroimaging have resulted in a significant increase in the recognition of MD. Findings can be subdivided in disorders due to abnormal neurogenesis, neuronal migration, neuronal migration arrest and neuronal organization resulting in different malformations like microcephaly, lissencephaly, schizencephaly and heterotopia. The examination protocol should include T 1-w and T 2-w sequences in adequate slice orientation. T 1-w turbo-inversion recovery sequences (TIR) can be helpful to diagnose heterotopia. Contrast agent is needed only to exclude other differential diagnoses.
Georg Thieme Verlag KG Stuttgart New York.