Abnormal of the CNS

—  Central nervous system (CNS) malformations are grouped into neural tube defects and associated spinal cord malformations; encephaloceles; disorders of structure specification (gray matter structures, neuronal migration disorders, disorders of connectivity, and commissure and tract formation); disorders of the posterior fossa, brainstem, and cerebellum; disorders of brain growth and size; and disorders of skull growth and shape.Classification of these conditions into syndromic, nonsyndromic, and single-gene etiologies is also important. These disorders can also be seen as isolated findings or as being a consequence of environmental exposures. Elucidation of single-gene causes has outpaced our understanding of epigenetic and environmental mechanisms.These disorders are heterogeneous in their presentation. Common presentations and clinical problems include disorders of head size and/or shape; hydrocephalus; fetal ultrasonographic brain abnormalities; neonatal encephalopathy; developmental delay, cognitive impairment, and mental retardation; hypotonia, motor impairment, and cerebral palsy; seizures, epilepsy, and drug-resistant epilepsy; cranial nerve dysfunction; and spinal cord dysfunction.