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DEFINITIONS AND EPIDEMIOLOGY

Pediatric movement disorders encompass a large spectrum of signs and symptoms that occur in a wide range of conditions, some of which may herald the development or sequelae of infectious disease. Accurate diagnosis of these disorders is essential for treatment, prognostication, and counseling. Interest in infectious etiologies of pediatric movement disorders has increased because of recent attention to pathophysiology involving immunologic mechanisms. This chapter provides an overview of pediatric movement disorders, emphasizing their association with infectious diseases.

Movement disorders are traditionally defined as neurological syndromes in which there is either an excess or paucity of movements unrelated to weakness or spasticity. However, in children spasticity is included in the discussion of movement disorders because it often coexists with other movement disorders, especially in cerebral palsy.1 There are two broad categories of movement disorders: hyperkinetic (excess of movement or tone) and hypokinetic (paucity of movement or tone) (Table 22-1). As we classify movement disorders by phenomenology; specific disorders will be defined in the section on clinical presentation below. The diagnosis and treatment sections will then address each movement disorder separately in the context of infectious disease.

TABLE 22-1Categorization of Common Movement Disorders in Children by Phenomenology

PATHOGENESIS

Movement disorders can be the result of dysfunction at any level of the central (brain or spinal cord) or peripheral (anterior horn cell, nerve roots, plexus, peripheral nerve, neuromuscular junction, or muscle) nervous system. Many movement disorders are associated with pathologic alterations in the basal ganglia or their connections. The basal ganglia include the caudate, putamen, globus pallidus, subthalamic nuclei, and substantia nigra. Table 22-2 summarizes areas of dysfunction associated with specific movement disorders.

TABLE 22-2Areas of Dysfunction Associated with Specific Movement Disorders

Although the precise pathophysiology of many movement disorders is unknown, infectious and immune-mediated pathophysiology in children has garnered considerable attention. Examples include congenital infections, Sydenham chorea, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS), and acute cerebellar dysfunction.

Congenital infections such as toxoplasma and rubella cross the placenta in utero and can cause fetal infection, resulting in significant neurologic sequelae. Approximately half of infants with congenital CMV or toxoplasmosis go on to develop cerebral palsy with the associated movement disorders (Table 22-3), and two-thirds ...

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