What are migrational anomalies of the central nervous system (CNS)?
Normal neuronal migration occurs during fetal brain development as neurons migrate from the germinal matrix to the cortex along radial glial fibers. Partial or total arrest of this process leads to a migrational anomaly. These anomalies include the following:
- • Focal cortical dysplasia (subtle subcortical high T2-weighted signal intensity and blurring of the gray-white matter junction).
- • Heterotopias (abnormal gray matter found anywhere along glial migration pathways to the cortex).
- • Schizencephaly (a cleft lined by gray matter extending from the outer cortex to the [lateral] ventricles).
- • Polymicrogyria (too many small nodular gyri).
- • Pachygyria (abnormally thickened gyri).
- • Lissencephaly (complete absence of gyri).
Children with CNS migrational anomalies typically present with developmental delay or seizures