Parasomnias and Movement Disorders of Sleep

Neurologists are often enlisted to help diagnose, evaluate, and manage a spectrum of abnormal spells during the night ranging from parasomnias to motor disturbance that span the sleep-wake cycle. Parasomnias are undesirable emotional or physical events that accompany sleep. These events typically occur during entry into sleep from wakefulness, or during arousals from sleep, and are often augmented by the sleep state. Some parasomnias, such as the rapid eye movement (REM) sleep behavior disorder may be extremely undesirable, while others such as somniloquy are often of little concern. The parasomnias include a spectrum of abnormal emotions, movements, behaviors, sensory perceptions, dream mentation, and autonomic activity. Basic physiologic drives, such as sex, hunger, and aggression, may manifest as sleep-related eating, sleep-related sexual behaviors, and sleep-related violence. Parasomnias have a very bizarre nature, but are readily explainable, diagnosable, and treatable. They are hypothesized to be due to changes in brain organization across multiple states of being, and are particularly apt to occur during the incomplete transition or oscillation from one sleep state to another. Parasomnias are often explained on the basis that wakefulness and sleep are not mutually exclusive states, and abnormal intrusion of wakefulness into non-REM (NREM) sleep produces arousal disorders, and intrusion of wakefulness into REM sleep produces REM sleep parasomnias and REM sleep behavior disorder (RBD). Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD), two closely related conditions that often result in disturbed sleep onset and sleep maintenance, are also reviewed in this article. Although the mechanisms that underlie idiopathic RLS or PLMD are not fully understood, there is currently substantial evidence that dopaminergic dysfunction is likely involved in both conditions. The discussion will conclude with the "other parasomnias" and sleep-related movement disorders of clinical interest to the neurologist.