Movement disorders in the pediatric age group appear phenomenologically the same as those in adults. Therefore, when considering the topic of pediatric movement disorders, a classification scheme based on the specific kinds of abnormality, whether they are tics, chorea, myoclonus, and so on, has great utility in this patient population. However, when evaluating a child with a movement disorder, it is important to consider the inherent dynamism related to growth and development, and the contribution of this state to the presentation and evolution of various diseases. While children may manifest the gamut of dyskinetic conditions, whether bradykinetic or hyperkinetic, it must not be presumed that children are miniature adults, nor should it be expected that the course of a disorder will exactly parallel that seen in adults. Having introduced this element of uncertainty, which is familiar to all child neurologists, it is still worthwhile to try to formulate a cogent overview of childhood movement disorders. Indeed, several other chapters in this book deal with conditions that are primarily diseases of childhood (Tourette's syndrome [see Chapter 39], idiopathic torsion dystonia [see Chapter 28]), and the reader is directed to these for comprehensive reviews. This chapter, however, considers the various movement disorders that may present in childhood, with special emphasis on the more common presentations.
Although centers specializing in movement disorders are not uncommon, clinics with a special emphasis on childhood conditions relating to movement are relatively rare. Thus, there are few reports in the literature that address the question of what the most common disorders might be in childhood. An exception has been the review of Fernandez-Alvarez and Aicardi, who in a large series of children with movement disorders, reported an occurrence of tics (39%), dystonia (24%), tremor (19%), chorea (5%), myoclonus (3%), akinetic-rigid syndromes (2%), and mixed disorders (8%) of a total of 684 patients, excluding those with cerebral palsy (Figure 45–1).1 These figures may not be representative of the general population, given that the source is a tertiary referral center, but no other broadly based data are currently available. It is striking, however, how these percentages differ from an adult movement disorder population, in which essential tremor and akinetic-rigid syndromes such as Parkinson's disease (PD) would certainly be more predominant.
Distribution of movement disorders in 673 children seen in a tertiary referral center. (Adapted from Fernandez-Alvarez E and Aicardi J. Movement Disorders in Children. London: MacKeith Press, 2001. Used with permission.)
Probably the most well-studied movement disorder to date in terms of epidemiology in childhood is that of tics. Large-scale studies of school-age children have estimated the prevalence at between 10% and 20%.2,3 Studies of Tourette's syndrome (TS) have varied over the years in their estimations of prevalence, but recent reports indicate it to be as high as 3–4% in school-age children, with a ...