Identification of a major susceptibility locus for restless legs syndrome on chromosome 12q

[Neurophysiological and neuroimaging studies for restless legs syndrome and periodic leg movement disorder]

The restless legs syndrome (RLS) is a clinical diagnosis based on the four essential criteria defined by the International Restless Legs Syndrome Study Group (IRLSSG). An idiopathic form can be separated from a symptomatic form. Neurophysiological studies have investigated the pathophysiology of the idiopathic RLS or have been used to exclude a symptomatic cause, in particular polyneuropathy. So far cortical excitability changes, corticomotor, somatosensory and auditory pathways, spinal cord excitability, B-wave rhythm and cycling alternating pattern, as well as reflex mechanisms have been investigated by electroencephalography, evoked potentials, Bereitschaftspotentials, nerve conduction and thermal threshold measurements, electromyography, transcranial Doppler sonography, measurements of the spinal flexor reflex as well as neuroimaging techniques. The etiology of the RLS cannot be revealed by these methods, neurophysiological studies in RLS are, however, useful for a better understanding of the pathophysiology and for exclusion of a polyneuropathy or other symptomatic causes. In addition to neurophysiological investigations, small fiber neuropathy, which seems to be a more common finding in RLS patients than expected to date, may need biopsy for confirmation. This review will focus on investigations of the different systems involved with diverse neurophysiological methods.

The reliability, validity and responsiveness of the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) in a trial population

Background

The aim of this study was to determine the reliability, validity and responsiveness of the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) in a clinical trial setting.

Methods

Two matching, placebo-controlled, multinational studies assessing the effectiveness and safety of ropinirole for treating moderate-to-severe Restless Legs Syndrome (RLS) formed the basis of this psychometric assessment. Validity and reliability were assessed using baseline data. Responsiveness was determined using longitudinal data collected at baseline and 12 weeks.

Results

A total of 547 subjects formed the baseline validation population; 519 were used for assessing responsiveness (n = 284/263 and 271/248 for both studies, respectively). Construct validity assessment confirmed that an overall life impact score could be calculated. All item-scale correlations were = 0.4, except items 1 (r = 0.36) and 5 (r = 0.35) in one study. Floor and ceiling effects were minimal. Cronbach's alpha values were 0.82 and 0.87, respectively, confirming internal consistency reliability. Correlations with the International Restless Legs Syndrome Study Group's severity rating scale (International Restless Legs Scale; IRLS) were moderate (r = -0.68 and -0.67, respectively; p < 0.0001). The RLSQoL was able to discriminate between levels of sleep problems (p < 0.0001) and between levels of global health status determined by a Clinical Global Impression of severity (CGI-S) (p < 0.0001). Responsiveness was demonstrated by significant differences in overall life impact change scores between CGI improvement levels after 12 weeks (p < 0.0001).

Conclusion

The RLSQoL is a valid, reliable and responsive measure of quality of life for patients with RLS, in a clinical trial setting where group comparisons are anticipated.

Restless Legs Syndrome

Restless legs syndrome (RLS) is clinically defined as an urge to move the legs with or without paresthesia, worsening of symptoms with rest and transient improvement with activity, and worsening of symptoms in the evening and night. This is often genetic but may also occur in the setting of iron deficiency, uremia, pregnancy, neuropathy, and possibly other conditions. The pathology is probably related to central nervous system iron dysregulation. Effective treatments include dopaminergics and narcotics. Recent advances in our understanding of RLS clinical presentation, epidemiology, etiology, and treatment will be discussed.

Prevalence and clinical characteristics of restless legs syndrome in Japanese patients with Parkinson's disease

To explore the clinical significance of restless legs syndrome (RLS) in Parkinson's disease (PD) and the causal relationship between these two disorders, we made a comparison of both the prevalence of RLS and the severity of sleep disturbance manifested on the Pittsburg Sleep Quality Index (PSQI) between patients with PD (n=165) and age- and sex-matched control subjects (n=131). The prevalence of RLS diagnosed by clinical interview was significantly higher in PD patients than in control subjects (12% vs. 2.3%). PSQI score was significantly higher in PD patients with RLS than in both patients without RLS and controls. However, PSQI score was not statistically different between the latter two groups. Among the PD patients with RLS, only 2 had a positive family history of RLS. Only 3 PD patients had requested treatment for the disorder. Our results emphasize the etiological link between RLS and PD in a Japanese cohort, and the existence of RLS is thought to be one of the most important factors aggravating sleep disturbance in PD, despite the low RLS severity.

The restless legs syndrome

The restless legs syndrome (RLS) is one of the commonest neurological sensorimotor disorders at least in the Western countries and is often associated with periodic limb movements (PLM) during sleep leading to severe insomnia. However, it remains largely underdiagnosed and its underlying pathogenesis is presently unknown. Women are more affected than men and early-onset disease is associated with familial cases. A genetic origin has been suggested but the mode of inheritance is unknown. Secondary causes of RLS may share a common underlying pathophysiology implicating iron deficiency or misuse. The excellent response to dopaminegic drugs points to a central role of dopamine in the pathophysiology of RLS. Iron may also represent a primary factor in the development of RLS, as suggested by recent pathological and brain imaging studies. However, the way dopamine and iron, and probably other compounds, interact to generate the circadian pattern in the occurrence of RLS and PLM symptoms remains unknown. The same is also the case for the level of interaction of the two compounds within the central nervous system (CNS). Recent electrophysiological and animals studies suggest that complex spinal mechanisms are involved in the generation of RLS and PLM symptomatology. Dopamine modulation of spinal reflexes through dopamine D3 receptors was recently highlighted in animal models. The present review suggests that RLS is a complex disorder that may result from a complex dysfunction of interacting neuronal networks at one or several levels of the CNS and involving numerous neurotransmitter systems.

Population history and its impact on medical genetics in Quebec

Knowledge of the genetic demography of Quebec is useful for gene mapping, diagnosis, treatment, community genetics and public health. The French-Canadian population of Quebec, currently about 6 million people, descends from about 8500 French settlers who arrived in Nouvelle-France between 1608 and 1759. The migrations of those settlers and their descendants led to a series of regional founder effects, reflected in the geographical distribution of genetic diseases in Quebec. This review describes elements of population history and clinical genetics pertinent to the treatment of French Canadians and other population groups from Quebec and summarizes the cardinal features of over 30 conditions reported in French Canadians. Some were discovered in French Canadians, such as autosomal recessive ataxia of the Charlevoix-Saguenay (MIM 270550), agenesis of corpus callosum and peripheral neuropathy (MIM 218000) and French-Canadian-type Leigh syndrome (MIM 220111). Other conditions are particularly frequent or have special genetic characteristics in French Canadians, including oculopharyngeal muscular dystrophy, hepatorenal tyrosinaemia, cystic fibrosis, Leber hereditary optic neuropathy and familial hypercholesterolaemia. Three genetic diseases of Quebec First Nations children are also discussed: Cree encephalitis (MIM 608505), Cree leukoencephalopathy (MIM 603896) and North American Indian childhood cirrhosis (MIM 604901).

Restless legs syndrome

Restless legs syndrome is a very common and still under-diagnosed neurologic condition that can cause severe morbidity. The pathology centers around central nervous system iron homeostatic dysregulation with subsequent alterations in dopaminergic functioning. Genetic studies will hopefully soon identify specific abnormalities. Treatment of restless legs syndrome with dopaminergic medications is highly effective, although augmentation may occur eventually and require dosing flexibility.

The restless legs syndrome

The restless legs syndrome is a common disorder that encompasses an idiopathic form of genetic or unknown origin and symptomatic forms associated with many causes. Symptomatic forms occur during pregnancy and are coincident with uraemia, iron depletion, polyneuropathy, spinal disorders, and rheumatoid arthritis. For the hereditary forms, at least three gene loci, located on chromosomes 12, 14, and 9, have been traced so far. Prevalence in the general population is between 3% and 9%, increases with age, and is higher in women than in men. Treatment is needed only in the moderate to severe forms of the disorder and mostly in elderly people. Pathophysiology and treatment may be closely linked to the dopaminergic system and iron metabolism. Dopaminergic treatment with levodopa and dopamine agonists is the first choice in idiopathic restless legs syndrome, but augmentation and rebound should be monitored in long-term treatment. Various other drugs, such as opioids, gabapentin, and benzodiazepines, provide alternative treatment possibilities.

Genetics of normal and pathological sleep in humans

The complexity of sleep-wake regulation, in addition to the many environmental influences, includes genetic predisposing factors, which begin to be discovered. Most of the current progress in the study of sleep genetics comes from animal models (dogs, mice, and drosophila). Multiple approaches using both animal models and different genetic techniques are needed to follow the segregation and ultimately to identify 'sleep genes' and molecular bases of sleep disorders. Recent progress in molecular genetics and the development of detailed human genome map have already led to the identification of genetic factors in several complex disorders. Only a few genes are known for which a mutation causes a sleep disorder. However, single gene disorders are rare and most common disorders are complex in terms of their genetic susceptibility, environmental factors, gene-gene, and gene-environment interactions. We review here the current progress in the genetics of normal and pathological sleep and suggest a few future perspectives.

Restless Legs Syndrome

RLS is a common condition that is likely to be encountered by primary care physicians in their practice. The currently available medications are highly effective in treating RLS. The knowledge of clinical presentation and diagnostic features of RLS will empower the primary care practitioners to effectively treat their patients who have RLS.

Analysis of familial and sporadic restless legs syndrome in age of onset, gender, and severity features

Restless Legs Syndrome is characterized by the irresistible, often indescribable unpleasant urge to move the limbs while resting. It has an estimated prevalence of approximately 29.3 % in US private practice. Restless Legs Syndrome often has a familial component; whether the familial and non-familial forms differ in terms of clinical features has previously been investigated, with the only significant factor emerging as younger age at onset in familial cases. Our study further explores a possible underlying difference between familial and sporadic forms of RLS by comparing familial RLS with sporadic RLS in terms of demographic and clinical features including subject gender, age of onset, and severity measures based an the IRLSSG severity scale. Both gender and family history are significant predictors of onset age in an overall model and also significant when analyzed independently. Participants who reported more severe RLS symptoms were significantly younger in age and progressed more rapidly. Two variables from the IRLSSG severity scale were significantly associated with age of onset when tested independently: discomfort and the urge to move the limb for relief. Our analysis supports the prevailing hypothesis that RLS is divided into earlier onset disease with a clear genetic component and later onset disease with unclear etiology, and that one or more endophenotypes might exist within the disorder which could further characterize these subjects for future genetic studies.

Current treatment options for restless legs syndrome

Restless legs syndrome (RLS) is a common but often underdiagnosed neurological disorder characterised by an imperative desire to move the extremities associated with paraesthesias, motor restlessness, worsening of symptoms at rest in the evening or at night and, as a consequence, sleep disturbances particulary. Additionally, most patients with RLS have periodic limb movements during sleep and relaxed wakefulness. The aetiology of RLS remains unknown. Treatment of RLS is generally symptomatic, a causal therapy is possible only in the secondary forms. Dopaminergic agents including levodopa and dopamine agonists such as pergolide, pramipexole, cabergoline and ropinirole are regarded as the treatment of choice for idiopathic RLS, however, the development of augmentation of symptoms, especially under levodopa therapy, may be a major problem. Except in special circumstances, opioids and anticonvulsants such as gabapentin or benzodiazepines, are regarded as second-line treatment. In secondary RLS, the underlying illness should first be treated, although dopaminergic drugs may also be helpful.

Family studies in insomnia

OBJECTIVE

Several predisposing factors to insomnia have been hypothesized, including a familial component; however, few studies have focused on this topic. The aim of this study is to evaluate the prevalence of insomnia among first-degree relatives of chronic insomniacs and to compare the symptoms between sporadic and familial insomnia.

METHODS

Two hundred fifty-six consecutive chronic insomniacs completed a clinical interview, psychometric questionnaires, a questionnaire on the family history of insomnia and, when indicated, a polysomnography. A control group was performed to estimate a base-rate incidence of insomnia in their families.

RESULTS

Patients with primary (n=77) and psychiatric (n=104) insomnia were definitely included. Of those with primary insomnia, 72.7% reported familial insomnia compared with 24.1% in the noninsomnia control group. Among the psychiatric insomniacs, 43.3% reported familial insomnia. The mother was the relative most frequently affected. Comparisons between the family prevalence rates of insomnia assessed by the probands and by first-degree relatives show high concordance. A tendency to a younger age at onset was observed in familial and primary insomnia.

CONCLUSION

This study reports a significant increase of familial aggregation of insomnia, warranting further genetic studies in primary insomnia with early age at onset.

Bilateral thalamic gray matter changes in patients with restless legs syndrome

Restless legs syndrome (RLS) is a common neurological disorder of a primary unpleasant sensation with an urge to move the legs occurring at rest. The etiology of idiopathic RLS is unknown and structural cerebral abnormalities have so far not been detected. We studied 51 right-handed patients with an idiopathic restless legs syndrome in two independent samples (Regensburg RLS-group: n = 28, Munich RLS-group: n = 23) and compared them to 51 sex- and age-matched healthy volunteers. High-resolution T1-weighted magnetic resonance imaging (MRI) of each subject was obtained and analyzed using voxel-based morphometry (VBM) to detect regionally specific differences in gray matter between patients and controls. Conjunction analysis was used to combine results from both centers. In patients with idiopathic RLS, both study centers observed independently a bilateral gray matter increase in the pulvinar. In the conjunction analysis including all patients and controls from both study centers, a significant gray matter increase in the pulvinar bilaterally (right: x = 16, y = -21, z = 12, Z = 4.57; left: x = -16, y = -24, z = 12, Z = 4.10) was present. This is the first demonstration of structural changes in the brain of patients with idiopathic RLS. These changes in thalamic structures are either involved in the pathogenesis of RLS or may reflect a consequence of chronic increase in afferent input of behaviorally relevant information.

History of the development of sleep medicine in the United States

Sleep Medicine has only recently been recognized as a specialty of medicine. Its development is based on an increasing amount of knowledge concerning the physiology of sleep, circadian biology and the pathophysiology of sleep disorders. This review chronicles the major advances in sleep science over the past 70 years and the development of the primary organizations responsible for the emergence of Sleep Medicine as a specialty, sleep disorders as a public health concern and sleep science as an important area of research.

Genes for normal sleep and sleep disorders

Sleep and wakefulness are complex behaviors that are influenced by many genetic and environmental factors, which are beginning to be discovered. The contribution of genetic components to sleep disorders is also increasingly recognized as important. Point mutations in the prion protein, period 2, and the prepro-hypocretin/orexin gene have been found as the cause of a few sleep disorders but the possibility that other gene defects may contribute to the pathophysiology of major sleep disorders is worth in-depth investigations. However, single gene disorders are rare and most common disorders are complex in terms of their genetic susceptibility, environmental effects, gene-gene, and gene-environment interactions. We review here the current progress in the genetics of normal and pathological sleep.

Restless legs syndrome and pregnancy

OBJECTIVE

To perform a large and detailed epidemiologic study on restless legs syndrome (RLS) during pregnancy and the puerperium.

METHODS

A structured clinical interview, assessing symptoms since the beginning of pregnancy, was performed to a population of 642 pregnant women at the time of delivery and at follow-up evaluation (1, 3, and 6 months after delivery). Main hematologic tests were also evaluated. A woman was considered affected if she met the International RLS Study Group criteria for RLS diagnosis.

RESULTS

Twenty-six percent of women were affected by RLS during their pregnancy. The disease was strongly related to the third trimester of pregnancy and tended to disappear reaching the time of delivery. Affected women presented lower values of hemoglobin and mean corpuscular volume compared with healthy subjects (both groups received the same supplemental iron and folate therapy).

CONCLUSIONS

Pregnancy is associated with transient restless legs syndrome.

The clinical neurophysiology of the restless legs syndrome and periodic limb movements. Part I: diagnosis, assessment, and characterization

OBJECTIVE

The restless legs syndrome is a common sensorimotor disorder impacting on sleep which has been known for centuries, but only recently become recognized as a significant clinical and pathophysiological problem. The definition of RLS has evolved until certain key clinical features have been defined as diagnostic, while others are strongly associated: the urge to move is seen as primary. Epidemiology suggests ethnic variation with highest frequency in populations of European origin; family and genetic studies support a genetic basis to many idiopathic cases while links to secondary disorders usually involving low iron stores are also known. Abnormalities of brain iron transport and consequent dysfunction of the dopamine system are suspected sources of the disorder.

METHODS

The literature was searched for all references relating clinical neurophysiologic investigations to the diagnosis, assessment, and characterization of RLS.

RESULTS

RLS is defined clinically and diagnosed by medical history while its frequent concomitant, periodic limb movements (PLM), must be diagnosed by polysomnography or movement recording. Severity of RLS is generally assessed by subjective measures, but sleep recording and measurement of PLM frequency and association with sleep disruption are also used to measure severity. A provocative test, the suggested immobilization test, can also be used with both subjective and movement recording. RLS and PLM in RLS are both associated with the circadian cycle and are maximal early in the sleep period. PLM appear to be associated both with unstable EEG phases involving the cyclic alternating pattern and cyclical autonomic changes whose initiation may precede the muscle activity.

CONCLUSIONS

While RLS remains a subjective disorder, neurophysiologic measures have been important, especially for assessment. Ambulatory methodologies may offer the most accurate and economical means of assessing motor activity as a key marker of RLS and of accurately measuring PLM from night to night. As the pathophysiology of RLS is better understood, more focused techniques may be developed to measure its presence and severity in individual patients.

Restless legs syndrome: association with streptococcal or mycoplasma infection

Group A beta-hemolytic streptococcal infections have been reported to cause neuropsychiatric symptoms, such as chorea, tics, and obsessive-compulsive disorder, presumably through autoimmune damage to basal ganglia. Mycoplasma pneumoniae infections have also been reported to cause damage to the basal ganglia. Restless legs syndrome is a movement disorder with focal restlessness, an irresistible desire to move, and exacerbation by long periods of sitting or lying. We present three children with transient restless legs syndrome-like symptoms possibly associated with group A beta-hemolytic streptococcal infection or Mycoplasma pneumoniae infection. One of three patients had persistently elevated enzyme-linked immunosorbent optical density values against human caudate and putamen.

Restless legs syndrome

In the past 10 years, restless legs syndrome (RLS) has gained recognition as a common sleep disorder. There are several therapeutic options in treating patients with RLS. RLS causes significant sleep disturbance and negatively impacts on patient quality of life. Pharmacologic treatment can result in improved sleep and quality of life issues. RLS patients should be evaluated for iron deficiency anemia; iron replacement in deficient patients may lead to a resolution of symptoms or may reduce the severity of their symptoms. For patients with daily symptoms, the initial therapy is dopamine agonists. Low doses given in the evening or 2 hours before bed provide adequate relief of symptoms for many RLS patients. Augmentation can be seen with all dopamine agents, but is most prevalent with levodopa. Levodopa therapy is best used for milder intermittent symptoms or in aggravating situations, such as long car rides. Opiates and antiepileptics remain a beneficial therapy for RLS and are useful in patients who experience pain as part of their RLS. Newer anticonvulsants may provide additional treatment options, but they have yet to undergo clinical trials. Intravenous iron also may provide relief of RLS symptoms; however, dosing and safety issues have not been fully evaluated in a RLS population.

The 14q restless legs syndrome locus in the French Canadian population

A new restless legs syndrome locus on chromosome 14 recently has been reported in one family of Italian origin. Our study aimed to replicate this finding and determine the importance of this locus in the French Canadian population. Markers spanning the region were genotyped in 14 large families and linkage assessed using two-point and multipoint logarithm of odds scores. Possible linkage to this locus was found in one of our kindreds providing support for the existence of this locus and indicating that this locus may be responsible for a small fraction of French Canadian restless legs syndrome.

Restless legs syndrome: an update on treatment options

Restless legs syndrome (RLS) was first described in 1672 but it is only recently that this disorder has attracted attention in defining its phenotype, and identifying its aetiology, pathogenesis and pharmacological treatment. RLS can be divided into primary (idiopathic) and secondary forms. RLS is common, affecting 5-15% of the total population and manifesting at any age from childhood to late adulthood. Prevalence tends to increase with patient age and there may be geographic variation. There is a clear genetic contribution to primary RLS and evidence for dopaminergic dysfunction. Although not all patients with RLS require medication, there can be a substantial reduction in the patient's quality of life related to pain, poor sleep and excessive daytime sleepiness. A variety of medications are now available for the symptomatic treatment of RLS. Dopaminergic therapy is currently the treatment of choice, usually initiated with a long-acting dopamine agonist, thereby avoiding some of the complications associated with levodopa. Anticonvulsants may be used as second-line treatment. Levodopa should be reserved for those patients who fail to respond to alternative medications because of the high risk of inducing augmentation. Hypnosedatives also have a role in RLS management. Patients with intractable RLS may require combination treatment. Several systemic disorders can cause RLS, and these should be identified and treated appropriately.

Restless legs syndrome: an overview of the current understanding and management

Over the last few years, major progress in research has improved our understanding of the restless legs syndrome (RLS). Although frequently under-diagnosed, several epidemiological studies have estimated its prevalence in western countries at 4-10% of the general population. Its diagnosis is usually made on a clinical basis, according to the criteria established by the International RLS Study Group (Mov Disord 1995; 10:634). Furthermore, major advances have also been achieved regarding our understanding of the pathophysiology of the disorder. Thus, several brain imaging studies, as well as pharmacological challenges, suggest the presence of a dopaminergic dysfunction playing a major role in its causation. In addition, a strong association has been discovered between brain iron deficiency and RLS. Eventually, dopaminergic drugs have shown therapeutic efficacy in various large-scale therapeutic trials, and, today, dopaminergic agonists represent the first line of treatment. In conclusion, these and other recent findings shed light on our understanding and management of one of the most common movement disorders.

Restless legs syndrome in patients on dialysis

The past decade has seen an explosion of interest in both idiopathic and secondary restless legs syndrome (RLS). Secondary RLS occurs in patients with uremia, pregnancy, and iron deficiency. Patients experience an irresistible urge to move the legs that is worse during inactivity and at night. RLS affects 6.6% to 62% of patients on long-term dialysis therapy and is associated with a greater mortality risk. The wide range of reported prevalence is explained in part by variations in methods of diagnosis. The International Restless Legs Syndrome Study Group defined diagnostic criteria that have improved the quality of RLS research. Advanced neurological imaging techniques suggest the pathophysiological state of idiopathic RLS involves dysfunction of subcortical areas of the brain. Dopaminergic pathways and neuronal iron handling have been implicated. Limited studies of patients with uremic RLS suggested similar mechanisms, but anemia, hyperphosphatemia, and psychological factors also may have a role. The few clinical trials in uremic RLS suggest that treatment should involve the reduction of potential exacerbating agents (tricyclic antidepressants, selective serotonin uptake inhibitors, lithium, and dopamine antagonists), correction of anemia (with erythropoietin and iron), and use of levodopa or dopamine agonists. Other agents shown to be of benefit in idiopathic RLS can be tried, but may be limited by side effects in patients with uremia (benzodiazepines, opioids, gabapentin, carbamazepine, and clonidine). Symptoms of uremic RLS will disappear within a few weeks of successful renal transplantation. The progress made to date in unraveling the pathophysiological state of uremic RLS should stimulate additional research toward targeted therapy.

Genomewide linkage scan identifies a novel susceptibility locus for restless legs syndrome on chromosome 9p

Restless legs syndrome (RLS) is a common neurological disorder that affects 5%-12% of all whites. To genetically dissect this complex disease, we characterized 15 large and extended multiplex pedigrees, consisting of 453 subjects (134 affected with RLS). A familial aggregation analysis was performed, and SAGE FCOR was used to quantify the total genetic contribution in these families. A weighted average correlation of 0.17 between first-degree relatives was obtained, and heritability was estimated to be 0.60 for all types of relative pairs, indicating that RLS is a highly heritable trait in this ascertained cohort. A genomewide linkage scan, which involved >400 10-cM-spaced markers and spanned the entire human genome, was then performed for 144 individuals in the cohort. Model-free linkage analysis identified one novel significant RLS-susceptibility locus on chromosome 9p24-22 with a multipoint nonparametric linkage (NPL) score of 3.22. Suggestive evidence of linkage was found on chromosome 3q26.31 (NPL score 2.03), chromosome 4q31.21 (NPL score 2.28), chromosome 5p13.3 (NPL score 2.68), and chromosome 6p22.3 (NPL score 2.06). Model-based linkage analysis, with the assumption of an autosomal-dominant mode of inheritance, validated the 9p24-22 linkage to RLS in two families (two-point LOD score of 3.77; multipoint LOD score of 3.91). Further fine mapping confirmed the linkage result and defined this novel RLS disease locus to a critical interval. This study establishes RLS as a highly heritable trait, identifies a novel genetic locus for RLS, and will facilitate further cloning and identification of the genes for RLS.

Restless legs syndrome: diagnostic criteria, special considerations, and epidemiology. A report from the restless legs syndrome diagnosis and epidemiology workshop at the National Institutes of Health

BACKGROUND

Restless legs syndrome is a common yet frequently undiagnosed sensorimotor disorder. In 1995, the International Restless Legs Syndrome Study Group developed standardized criteria for the diagnosis of restless legs syndrome. Since that time, additional scientific scrutiny and clinical experience have led to a better understanding of the condition. Modification of the criteria is now necessary to better reflect that increased body of knowledge, as well as to clarify slight confusion with the wording of the original criteria.

SETTING

The restless legs syndrome diagnostic criteria and epidemiology workshop at the National Institutes of Health.

PARTICIPANTS

Members of the International Restless Legs Syndrome Study Group and authorities on epidemiology and the design of questionnaires and scales.

OBJECTIVE

To modify the current criteria for the diagnosis of restless legs syndrome, to develop new criteria for the diagnosis of restless legs syndrome in the cognitively impaired elderly and in children, to create standardized criteria for the identification of augmentation, and to establish consistent questions for use in epidemiology studies.

RESULTS

The essential diagnostic criteria for restless legs syndrome were developed and approved by workshop participants and the executive committee of the International Restless Legs Syndrome Study Group. Criteria were also developed and approved for the additional aforementioned groups.

Mutational analysis of neurotensin in familial restless legs syndrome

A susceptibility locus for restless legs syndrome (RLS) has been identified recently on chromosome 12q. This region contains several transcribed genes including neurotensin (NTS), which, as an important modulator of the dopaminergic transmission, represents a strong functional and positional candidate in the context of RLS. In this study, NTS was evaluated for mutational analysis. A panel of 19 individuals from 4 families supporting linkage to 12q was investigated using a combined denaturing high-performance liquid chromatography (dHPLC) and direct sequencing method. Analysis of the NTS genomic sequence revealed 2 intronic polymorphisms and 1 variant located in the 5' untranslated region (UTR). None of the observed variants co-segregated with RLS and no disease-associated polymorphisms were detected in any of the analyzed families. Based on these results, it is unlikely that NTS is the gene responsible for RLS in chromosome 12-linked families.

Autosomal dominant restless legs syndrome maps on chromosome 14q

Restless legs syndrome (RLS) is a common neurological disorder characterized by an irresistible desire to move the extremities associated with paraesthesia/dysaesthesia. These symptoms occur predominantly at rest and worsen at night, resulting in nocturnal insomnia and chronic sleep deprivation. In this paper, we show significant evidence of linkage to a new locus for RLS on chromosome 14q13-21 region in a 30-member, three-generation Italian family affected by RLS and periodic leg movements in sleep (PLMS). This is the second RLS locus identified so far and the first consistent with an autosomal dominant inheritance pattern. The new RLS critical region spans 9.1 cM, between markers D14S70 and D14S1068. The maximum two-point log of odds ratio score value, of 3.23 at theta = 0.0, was obtained for marker D14S288. The accurate clinical evaluation of RLS-affected, as well as unaffected, family members allowed for the configuring of RLS as a phenotypic spectrum ranging from PLMS to RLS. Motor component, both while awake and during sleep, was an important aspect of the phenotype in the family analysed. The complementary clinical and genetic studies on multiplex families are likely to be of the utmost importance in unfolding the complete expressivity of RLS phenotype spectrum.

Perchance to dream: solving the mystery of sleep through genetic analysis

Sleep has been identified in all mammals and nonmammalian vertebrates that have been critically evaluated. In addition, sleep-like states have also been identified and described in several invertebrates. Despite this prevalence throughout the animal kingdom, the function of sleep remains a mystery. The completion of several genome sequencing projects has led to the expectation that fundamental aspects of sleep can be elucidated through genetic dissection. Indeed, studies in both the mouse and fly have begun to reveal tantalizing suggestions about the underlying principles that regulate sleep homeostasis. In this article we will review recent studies that have used genetic techniques to evaluate sleep in the fruit fly and the mouse.

Restless legs syndrome and periodic limb movement disorder

Restless leg syndrome and PLMD are nocturnal movement disorders associated with significant adverse effects on the health and well-being of patients and their families [66]. Although the pathophysiological basis remains to be fully described, current research points to abnormalities in CNS function and neurotransmitter systems. The accurate diagnosis of RLS and PMD requires a thorough history, physical examination, diagnostic tests, and often, a referral to a sleep disorders specialist. Considering the prevalence of these conditions and their negative impact, nurses should be well-versed in the assessment and management of these problems as well as in the appropriate education of patients and their families. Nursing research is greatly needed, particularly with regard to the development and testing of biobehavioral interventions designed to decrease associated symptoms and improve clinical outcomes. Finally, because of the complexity of the clinical presentation of RLS and PLMD, this population of patients presents nurse clinicians and researchers alike with an extraordinary opportunity for interdisciplinary collaboration.

Restless legs syndrome

Restless legs syndrome (RLS), first described in 1672 and given its name in 1945, is one of the most common sleep and movement disorders. Modern population-based studies demonstrate a prevalence between 5% and 15% in adult white populations. According to the diagnostic criteria, RLS is defined as an irresistable desire to move limbs, usually associated with paresthesias/dysesthesias and motor restlessness. The symptoms start or worsen at rest and improve with activity. Additionally, the symptoms worsen in the evenings and/or nights, which often results in disturbance of sleep with daytime tiredness. There is often a family history of RLS. Initially, the disease course is usually fluctuating and later may become continuous or chronic-progressive. The diagnosis is based on the patient history and is supported by a normal neurological examination. RLS is confirmed by the finding of periodic limb movements (PLM) in polysomnographic investigations and by a response to dopaminergic medication. A large number of studies have confirmed the effect of levodopa (L-dopa) in the treatment of RLS. A majority of the patients treated over a longer period of time with L-dopa, however, develop problems with an effect called augmentation, where the RLS symptoms begin appearing earlier during the day and involve new parts of the body with increasing severity. A large number of studies have now confirmed that dopamine agonists can also be effective in RLS therapy, and that this treatment seems to involve less risk for augmentation. This paper provides a general review of RLS with a focus on current treatment options.

Restless legs syndrome and periodic limb movements of sleep: fact, fad, and fiction

Restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) are common disorders seen in sleep disorder centers. Although RLS in universally thought to cause daytime sleepiness, the role of PLMS in causing sleepiness (or any symptom!) has been more controversial. Recent publications have show that PLMS do not cause either subjective or objective sleepiness, but may be a marker for respiratory effort related arousals. In regards to patients with end-stage renal disease, PLMS may mark mortality. In this same group of patients, gabapentin and normalization of hematocrit may be effective therapies for RLS/PLMS. Melatonin may prove to be an alternative therapy for PLMS.

Family history study of the restless legs syndrome

BACKGROUND

Although there is a relatively high rate of occurrence of sporadic cases of restless legs syndrome (RLS), the systematic study of family history of RLS in populations of RLS patients has been very limited. The objective of the present study was to determine the risk of RLS for first- and second-degree relatives of a population of primary RLS patients not selected for the number of affected relatives in their families and to obtain an estimate of the degree of genetic involvement in RLS.

METHODS

Consecutively consenting patients from two different sites who met the criteria for RLS completed a worksheet that asked them to indicate their current age, the date of their earliest RLS symptoms, and the names and RLS status of all of their first- and second-degree relatives. Controls with no clinical history of RLS also completed the worksheet.

RESULTS

First- and second-degree relatives of patients with RLS had a significantly greater risk of RLS than the first- (P<0.001) and second-degree relatives (P<0.003) of controls. The risk of RLS was found to be greater for first-degree relatives of early-onset, rather than late-onset, RLS probands (P<0.001).

CONCLUSIONS

This study provides a complete systematic examination of the risk of RLS among relatives of RLS probands and controls using the same assessment methodology. Although the results are consistent with a genetic etiology for RLS, they do not support the presence of one simple, Mendelian-inherited major gene in most RLS families.

Complex segregation analysis of restless legs syndrome provides evidence for an autosomal dominant mode of inheritance in early age at onset families

A strong familial component of restless legs syndrome (RLS) is known. The objective of this study therefore was to investigate the likely mode of inheritance of RLS. RLS patients and their first-degree relatives were investigated and classified in RLS affected and RLS nonaffected subjects. Assessments were based on direct, personal standardized diagnostic interviews. Complex segregation analysis was performed with the families stratified according to the mean age at onset of the disease within the families. Two hundred thirty-eight RLS patients, 537 first-degree relatives, and 133 spouses were interviewed. Two groups of families were stratified: mean age at onset up to 30 years of age (Group A) and older than 30 years (Group B; p < 0.005). In Group A, segregation analysis strongly favored a single major gene acting autosomal dominant with a multifactorial component. Parameter estimates were 0.003 for the allele frequency, 1.0 for the penetrance, and 0.005 for the phenocopy rate. In Group B, no evidence for a major gene could be elucidated. The segregation pattern found in our families argues for an autosomal allele acting dominantly in RLS families with an early age at onset of symptoms and suggests that RLS is a causative heterogeneous disease.

The genetics of sleep disorders

The contribution of genetic components to the pathology of sleep disorders is increasingly recognised as important. Genetic studies have identified genes that may be important in the regulation of circadian rhythms, which in turn determine the time of sleep onset and waking. Recent studies have shown that mutations in hPER2 are associated with autosomal-dominant familial advanced-sleep-phase syndrome. Genetic studies in a canine model of narcolepsy and in knock-out mice have led to the identification of the hypothalamic hypocretin (orexin) neurotransmitter system as a key target for human narcolepsy. The contribution of genetic factors to obstructive sleep apnoea syndrome (OSAS) has led to a better understanding of this complex disorder that may be part of a larger syndrome associated with respiratory, cardiovascular, and metabolic dysfunction. The aim of this review is to discuss the current knowledge on the role of genetic factors in sleep disorders, in particular circadian disorders, narcolepsy, restless-legs syndrome, and OSAS.

Evidence for a genetic association between monoamine oxidase A and restless legs syndrome

BACKGROUND

Impairment in the central dopaminergic system has been consistently suggested as an etiologic factor in restless legs syndrome (RLS).

OBJECTIVE

To investigate a possible role for the MAOA and MAOB genes in RLS using a population-based association study.

METHODS

In addition to a dinucleotide repeat located within the second intron of the MAOB gene, a functional variable number of tandem repeat (VNTR) polymorphism recently identified in the MAOA gene promoter region was examined, using 96 extensively characterized patients and 200 control subjects matched for ethnic background. The relationship between variation at these loci and several clinical features was also considered.

RESULTS

Pertaining to the MAOA gene, females with the high activity allele had a greater risk (OR: 2.0; 95% CI: 1.06 to 3.77) of being affected with RLS than females carrying the low activity alleles. The authors did not observe this association among the male subjects (OR: 0.98; 95% CI: 0.31 to 3.14). Interestingly, females carrying the high transcription alleles showed a longer sleep onset latency (U = 163.5; p = 0.015) and exhibited a higher movement index during the Suggested Immobilization Test (Student's t-test = -2.02; p = 0.048). No differences were observed regarding the MAOB gene in our sample.

CONCLUSIONS

The high activity allele of the MAOA gene may represent a modifying factor involved in the severity of RLS manifestations in females.

Treating restless legs syndrome: current pathophysiological concepts and clinical trials

Restless legs syndrome is a distinctive clinical syndrome with a prevalence of about 5% in the general population. One of the outstanding characteristics of restless legs syndrome is its extreme responsiveness to dopaminergic agents. Together with the latest pathophysiological and genetic findings, recent epidemiological and clinical data give a new insight into the classification of restless legs syndrome, thus building the theoretical foundation for the development of new pharmacological methods in its treatment. Current efforts within this area focus on establishing dopaminergic substances for therapy. The hypothesis of a disturbed iron metabolism in restless legs syndrome has been revived by recent theoretical considerations. The present review attempts to explain current strategies of treatment for restless legs syndrome in relation to aetiological, genetic and pathophysiological findings.

Restless legs syndrome: a sensorimotor disorder of sleep/wake motor regulation

Restless legs syndrome (RLS) remains an underappreciated sensorimotor disorder of sleep/wake regulation. It is one of the few sensorimotor disorders that is provoked by rest and that also follows a clear circadian pattern. Recent epidemiologic studies have verified that the condition is common in populations derived from the north and west of Europe, and have begun to uncover some of the genetic substrate of the disorder. New instruments have been developed to facilitate diagnosis and assessment of severity. The pathogenesis of the condition remains uncertain, but recent discoveries implicate areas of the nervous system from the spinal cord up to the basal ganglia. A current hypothesis undergoing vigorous exploration is that the condition results from a deficiency of dopaminergic function based on abnormalities of iron transport and storage. Therapeutically, studies have shown the dopamine agonists to be the most reliable treatment for severe cases, whereas other recent studies have successfully utilized a number of other medications, including levodopa, opioids, and anticonvulsants. New standards provide guidelines for management of RLS and make specific pharmacotherapeutic recommendations.