Developmental malformation of the corpus callosum: a review of typical callosal development and examples of developmental disorders with callosal involvement

This review provides an overview of the involvement of the corpus callosum (CC) in a variety of developmental disorders that are currently defined exclusively by genetics, developmental insult, and/or behavior. I begin with a general review of CC development, connectivity, and function, followed by discussion of the research methods typically utilized to study the callosum. The bulk of the review concentrates on specific developmental disorders, beginning with agenesis of the corpus callosum (AgCC)—the only condition diagnosed exclusively by callosal anatomy. This is followed by a review of several genetic disorders that commonly result in social impairments and/or psychopathology similar to AgCC (neurofibromatosis-1, Turner syndrome, 22q11.2 deletion syndrome, Williams yndrome, and fragile X) and two forms of prenatal injury (premature birth, fetal alcohol syndrome) known to impact callosal development. Finally, I examine callosal involvement in several common developmental disorders defined exclusively by behavioral patterns (developmental language delay, dyslexia, attention-deficit hyperactive disorder, autism spectrum disorders, and Tourette syndrome)

Neurobiology of Sleep-Related Movements

Sleep-related movements comprise a broad spectrum of simple and usually stereotyped movements that are sometimes associated with sleep disturbance (insomnia, sleep fragmentation, and non-restorative sleep). They may represent a physiological variant or a sleep disorder, depending on their intensity, frequency, and associated sleep disruption degree. Sleep-related movements involve usually the lower limbs; they can be idiopathic or associated with other sleep disorders, neurological disease, and medical condition or occur as a consequence of drug use. Several pathophysiological hypotheses have been proposed, but for the majority of these disorders, the neurobiological mechanism is far from being completely understood. Further studies are needed to elucidate the pathophysiology of sleep-related movements in order to better appreciate their clinical significance. This chapter describes the neurobiology of sleep-related movements, namely, periodic limb movements, alternating leg muscle activation, hypnagogic foot tremor, high-frequency myoclonus, excessive fragmentary myoclonus, propriospinal myoclonus at sleep onset, neck myoclonus during sleep, sleep bruxism, sleep-related rhythmic movement disorder, sleep-related leg cramps, and sleep starts. We also present a mechanistic model of the potential role of the spinal central pattern generator for locomotion in generating the leg movements