The progressive cerebral degenerations of childhood are a heterogeneous group of disorders characterized by the loss of previously acquired skills during development. They stand in contrast to the static encephalopathies, mental retardation, cerebral palsy, and autism. The causes of both progressive and static disorders are varied and include infectious, inflammatory, neoplastic, and vascular etiologies, this chapter will, however, deal only with those that result from genetic mechanisms. The importance of these disorders even with this restriction is emphasized by the series of Dyken and Krawiecki which found that genetic neurodegenerative conditions made up approximately 15% of admissions to pediatric neurology services in two institutions over a 10-year period (Dyken & Krawiecki, 1983).

General comments on evaluation

The evaluation of degeneration results in special difficulties when presenting in childhood. For the young child, the early findings may be subtle and may be mistaken for normal variation or static difficulties such as mental retardation or cerebral palsy. It is only when evaluated over time, or with a clear presentation, will the diagnosis be uncovered. It is not difficult to suspect a particular disorder when all the characteristic symptoms and signs are present – the challenge comes in doing this early in the course (Clarke, 1997).

Once the suspicion has arisen that one is dealing with a progressive condition, the evaluator must cope with a seemingly endless list of disorders (Dyken & Krawiecki, 1983). Compounding this difficulty, disease classification by biochemical abnormality, typical for these disorders, usually does not serve the purpose of clinicians. This type of designation allows one to determine the appropriate biochemical test, but does not easily direct the clinical diagnosis. Algorithms and computerized database programs have been developed to assist the clinician. When appropriately used they may be of significant benefit, however, one must recognize that the symptom complex does not appear all at once, but evolves. A knowledge of the course of disease and timing of the evolution of signs is therefore useful (Clarke, 1997).

These challenges aside, it is to be emphasized that presently there is the ability to make a diagnosis in many of the conditions which previously either were simply clinical descriptions or required invasive pathologic investigation.