Time Is on Our Side: Age as a Diagnostic and Pathologic Clue in Pediatric Movement Disorders

Abstract

Pediatric movement disorders encompass a heterogeneous array of neurologic symptoms and syndromes and may be acquired or inherited. Movement phenomenology and age at symptom onset provide important clues in identifying the underlying etiology and establishing a diagnosis. Movement disorders are classified as hyperkinetic (increased movement) or hypokinetic (reduced amplitude and/or rate of movement). In children, hyperkinetic movement disorders are substantially more common than hypokinetic disorders; in adults, a mix of hyper- and hypokinetic disorders is the norm. We present a framework for evaluating a child with abnormal movements and describe a broad range of pediatric movement disorders: chorea, neurotransmitter-associated syndromes, tic disorders, stereotypies, primary dystonias, and dystonic cerebral palsy. Recently described genes associated with pediatric movement disorders, such as ADCY5-related dyskinesia, NKX2.1-associated chorea and dystonia, and the primary dystonias (DYT2 and DYT26), are highlighted. The developmental regulation of neurotransmitter metabolism, a dynamic process that leads to dramatic shifts in neurotransmitter availability in childhood and adolescence, is also reviewed. The myelination and maturation of long-range neuronal networks are described, and the timing of these changes is related to the timing of childhood movement disorders. Incorporating age and timing into a framework for assessing abnormal movements in children has the potential to improve both clinical and research approaches to these disorders. Understanding the genetic and pathophysiologic bases of abnormal movements may aid clinicians in rapidly recognizing and distinguishing these disorders. Recognizing the clinical specificity and age dependency of abnormal movements in children may guide researchers in identifying the molecular underpinnings of these disorders. Key words: Movement disorders, gene expression, childhood development, childhood hyperkinetic disorders