This chapter initially reviews the new advances in molecular genetics of idiopathic epilepsies in infants, children, adolescents and adults and provides a progress report on the search for chromosomal loci of epilepsy syndromes. After presenting an overview on the molecular genetics of idiopathic epilepsies, this chapter focuses on phenotypes and genotypes of genetic epilepsies that are commonly mistaken for movement disorders.
Understanding the genotypes and phenotypes of movement disorders and epilepsies in infants, children and adolescents is important because some motor signs of idiopathic epilepsies of infants, children and adolescents are mistaken for movement disorders and some movement disorders of children and adolescents are mistaken for the epilepsies. Moreover, understanding the new advances in the molecular genetics of movement disorders and epilepsies is important because they provide us with more than a glimpse of the new practice of molecular neurology. The epilepsies have traditionally been classified and subtyped on the basis of clinical and neurophysiologic concepts. The complexity and variability of phenotype and overlapping clinical features limit the resolution of phenotype-based classification and confounds epilepsy nosology. Identification of tightly linked epilepsy DNA markers and discovery of epilepsy causing mutations provide a basis for refining the classification of epilepsies.
Table 27.1 lists some of the epilepsies commonly mistaken for movement disorders and Table 27.2 gives some descriptions used by the referring physicians that made them mistakenly suspect a movement disorder in patients with juvenile myoclonic epilepsy (JME). Patients initially diagnosed to have movement disorders were verified to have myoclonias and rapid spike-wave complexes on CCTV-EEG telemetry.