Molecular basis of diseases of the Nervous System

The central nervous system (CNS) is composed of cellular components organized in a complex structure that is unlike other organ systems. At the macroscopic level, the parenchyma of the CNS can be categorized into two structurally and functionally unique components: gray and white matter. The CNS can be divided into a number of anatomic regions, each with specific neurologic or cognitive functions. Disease or damage to these regions produces neurologic or cognitive deficits that correlate with the anatomic location and extent of disease. There are several ways to divide these structures. The main divisions are the cerebrum, cerebellum, brainstem, and spinal cord. Developmental neuropathology encompasses a broad variety of cerebral malformations and functional impairments caused by disturbances of brain development, manifesting during ages from the embryonic period through adolescence and young adulthood. The neurologic and psychiatric manifestations of neurodevelopmental disorders range widely depending on the affected neural systems and include such diverse manifestations as epilepsy, mental retardation, cerebral palsy, breathing disorders, ataxia, autism, and schizophrenia. In terms of morbidity and mortality, the spectrum is extremely broad: the mildest neurodevelopmental disorders can be asymptomatic, whereas the worst malformations often lead to intrauterine or neonatal demise. This chapter focuses on the genetic disorders of brain development, caused by mutations of gene loci or chromosomal regions with important neurodevelopmental functions.