Continuum, Sleep Disorders, June 2007, Volume 13, Issue 3

The classification of sleep disorders is necessary to discriminate among disorders in order to facilitate an understanding of the symptoms, etiology, pathophysiology, and treatment. The earliest sleep classification system was organized largely according to the major symptoms-insomnia, excessive sleepiness, and abnormal events that occur during sleep-because the pathophysiologic basis for many of the sleep disorders was unknown. The latest edition of the International Classification of Sleep Disorders, Second Edition (ICSD-2), published in 2005, combines a symptomatic presentation (insomnia) with one organized in part on the basis of pathophysiology (circadian rhythms) and in part on body systems (breathing disorders). This organization is necessary because of the varied nature of the sleep disorders and because the pathophysiology for many of the disorders is unknown. The ICSD-2 is not only a listing of the sleep disorders but also a text manual that lists relevant information about the diagnostic features and epidemiology to help the reader more easily differentiate among the disorders.(C) 2007 American Academy of Neurology

Insomnia is one of the most frequent sleep complaints and accompanies many neurologic conditions. Chronic insomnia is classified into primary and secondary (comorbid) categories; idiopathic, psychophysiologic, and paradoxical insomnia are subdivisions of primary insomnia in adults. The most accepted pathophysiologic model of insomnia considers it to result from a state of physiologic hyperarousal. Cognitive-behavioral therapies (CBTs) are effective and should be considered the first line of management for chronic primary insomnia. Modern hypnotics are safer than older drugs and can be used for chronic insomnia if CBT is ineffective or not easily available. Rare neurologic disorders with prominent insomnia include fatal familial insomnia and Morvan syndrome.(C) 2007 American Academy of Neurology

The restless legs syndrome (RLS) consists of four obligatory features: (1) an urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations in the legs; (2) the urge to move, or unpleasant sensations begin or worsen during periods of rest or inactivity such as lying or sitting; (3) the urge to move, or unpleasant sensations are partially or totally relieved by movement such as walking or stretching, at least as long as the activity continues; and (4) the urge to move, or unpleasant sensations are worse in the evening or night than during the day or only occur in the evening or night. The cause of idiopathic and familial RLS is unknown, although the most important pathophysiologic clues come from autopsy material showing that iron is decreased in the substantia nigra of patients with RLS. There is also some evidence that underactivity of the endogenous dopaminergic and the endogenous opioid system with its enkephalins and endorphins may be pathogenetic as well. Secondary forms of RLS may be associated with peripheral neuropathy and radiculopathy, low ferritin levels, renal failure, rheumatoid arthritis, fibromyalgia, and multiple sclerosis. Pregnancy can be an exacerbating factor for RLS. Dopaminergic agonists are the first line of treatment, but opioids, gabapentin (Neurontin), and benzodiazepines are effective as well. Periodic limb movements in sleep (PLMS) are present in many but not all adult patients with RLS (80%), and PLMS also occurs with high prevalence in normal older adults even if RLS is not present. PLMS is therefore neither a sensitive nor specific-enough index of RLS to be diagnostic of RLS. PLMS without RLS rarely results in symptomatic sleep disruption, but in cases where symptomatic sleep disruption in the absence of RLS can definitely be attributed to the PLMS, the diagnosis of periodic limb movement disorder is made. However, it is not uncommon for a patient's PLMS to disrupt the sleep of the bed partner.(C) 2007 American Academy of Neurology

As a percentage of daily life, sleep is most abundant during infancy, childhood, and adolescence. Distinct disorders of sleep, wake, and circadian rhythm emerge during these critical periods and manifest fundamental behavioral and biological change. Understanding the normal development of sleep and wake throughout childhood is essential to proper clinical identification of these disorders. Appropriate testing and therapy can dramatically impact the course of a disease and improve the future of a child. Since adult sleep and wake conditions may begin in the first 2 decades of life, early intervention is important. Neurologists who appreciate the developmental aspects of sleep, wake, and circadian rhythm are uniquely positioned to intercede in cases that may seem perplexing to other medical professionals.(C) 2007 American Academy of Neurology

Evaluation and treatment of nocturnal events can be challenging for several reasons. These events may be related to sleep state, be associated with medical or neurologic disorders, or occur coincidentally during sleep. Disorders such as sleepwalking, REM sleep behavior disorder, and sleep-related eating disorder provide unique insights into neurophysiology and neurochemistry.In this chapter, the major nocturnal events are reviewed using the International Classification of Sleep Disorders, Second Edition. We outline key clinical and laboratory features that aid in the diagnosis of these events. The relationship of events to underlying pathology and specific treatments are discussed.(C) 2007 American Academy of Neurology