Malformations and Neurocutaneous Disorders

This chapter discusses malformations and neurocutaneous disorders. Malformations of the central nervous system (CNS) are irreversible structural defects caused by disturbances of normal prenatal or postnatal development. Normal maturation of the CNS involves a predictable sequence of stages, each precisely timed in its evolution. With an insult to one or more of those stages, it can result to brain malformation. The specific types of malformations seen are determined by the timing of the insult to the brain, the duration of that insult, and its severity. The neurological deficits caused by some cerebral malformations are rarely apparent immediately after birth, because subtle neurological abnormalities usually cannot be appreciated at that time, even by the most skilled examiner. The most definitive way to confirm the presence of a CNS malformation and to delineate its pathology is by direct histopathological examination. An understanding of the sequence of events in neuroembryology provides a framework for an appropriate classification scheme for the array of malformations seen clinically.