Metabolic ataxias.

The nervous system is vulnerable to intrinsic and extrinsic metabolic perturbations. In particular, the cerebellum, with its large Purkinje cells and its high density of neurons and glial cells, has high metabolic demand and is highly vulnerable to metabolic derangements. As a result, many disorders of intermediary metabolism will preferentially and sometimes selectively target the cerebellum. However, many of these disorders present in a multisystem fashion with ataxia being a part of the neurologic symptom complex. The presentation of these disorders depends on the time of onset and type of metabolic derangement. Early infantile or intrauterine-onset diseases will present in a young child typically with global hypotonia and both nystagmus and ataxia become more apparent later in life, while later-onset diseases usually present primarily with ataxia. It is important to note that the majority of these disorders are progressive if they are untreated. This chapter provides a review of acquired and genetic metabolic disorders that target the cerebellum, and discusses their diagnostic evaluation and therapy.