ABSTRACT
There are a plethora of human diseases that involve dysfunction of the central and/or peripheral nervous systems (see Table 10.1). These diseases may be char acterized as those primarily involving nervous system failure and those in which neurological symptoms manifest secondary to other underlying disease entities. Examples of the latter category are metabolic, mitochondrial, and cancer-related diseases that eventually impact normal neurological function. These diseases are covered in other chapters and hence this chapter will focus on inherited genetic polymorphisms predominately affecting nervous system function. In general, neuro genetics presents a challenge to the field of clinical and molecular neuroscience due to the heterogeneity of the many nervous system diseases. Heterogeneity can be manifested at both the genotypic and phenotypic levels (Wolf, 1997). Genotypic heterogeneity reflects the presentation of similar phenotypes even though varying mutations exist within the same gene or in different genes. The opposing scenario also occurs in which different mutations within the same gene may produce remark ably different phenotypes. Phenotypic and genotypic heterogeneity have contributed to the complexity and variability of nervous system disease classification. Therefore, the organization of neurogenetic diseases based solely on genotypic mutations versus phenotype is a superficial approach.
