Clinical trials in restless legs syndrome--recommendations of the European RLS Study Group (EURLSSG)

The European Restless Legs Syndrome (RLS) Study Group (EURLSSG) is an association of European RLS experts who are actively involved in RLS research. A major aim of the Study Group is the development and continuous improvement of standards for diagnosis and treatment of RLS. Several members developed study designs and evaluation methods in investigator-initiated trials early in the 1990s, and all members have since contributed to many pivotal and nonpivotal drug trials for the treatment of RLS. The recommendations on clinical investigations of pharmacological treatment of RLS patients summarize the group's expertise and knowledge acquired through clinical trials. The recommendations primarily address how to plan and conduct confirmatory, randomized clinical studies in patients with idiopathic RLS. Advice is presented for the diagnosis of RLS and clinical and polysomnographic inclusion and exclusion criteria. Primary and secondary endpoints for an evaluation of efficacy are based on a critical description of validated methods for both short- and long-term trials, also in special populations (children, pregnant women, elderly patients). The recommendations include the assessment of augmentation. Finally, general issues including the evaluation of safety and tolerability, as well as specific neurological and cardiovascular risks and sleep attacks/daytime somnolence, are discussed. The aim of these recommendations is to support research groups or pharmaceutical companies in the design of optimized study protocols.

The influence of different definition criteria on the PLM index

BACKGROUND

Different criteria for the scoring of periodic leg movements (PLM) have been recently proposed. We investigated to what extent changes in PLM criteria for leg movement duration, intermovement interval and combination of bilateral leg movements (LM) influence the PLM index.

METHODS

The nocturnal polysomnographies of 40 consecutive patients (20 males, 20 females, mean age 52+/-16 years) with sleep-wake complaints but without severe sleep-related breathing disorders (AHI<20) were evaluated. All patients showed a minimum of 100 LMs during the night. For each night eight PLM indices during sleep (PLMS) and eight PLM indices during wakefulness (PLMW) were computed by systematically varying the following criteria: LM duration (0.5-5s vs. 0.5-10s), intermovement interval (5-90s vs. 10-90s), and separation criteria for LMs occurring in both legs (<5s onset to onset vs. <0.5s offset to onset). Data were analyzed using linear mixed models.

RESULTS

The two different intermovement intervals and the leg movement durations both had a statistically significant influence on the PLMS and PLMN indices. These variations were highly systematic but numerically small for the PLMS index while they were substantially larger for the PLMW index. The separation criteria or possible two-way interactions between the criteria had no influence on the PLM indices.

CONCLUSIONS

Different criteria had a negligible influence on the PLM index during sleep. Across-study or sleep-laboratory comparability can be assumed within our parameter set. This does not apply to the PLM index during wakefulness.

Functional microstates within human REM sleep: first evidence from fMRI of a thalamocortical network specific for phasic REM periods

High thalamocortical neuronal activity characterizes both, wakefulness and rapid eye movement (REM) sleep, but apparently this network fulfills other roles than processing external information during REM sleep. To investigate thalamic and cortical reactivity during human REM sleep, we used functional magnetic resonance imaging with simultaneous polysomnographic recordings while applying acoustic stimulation. Our observations indicate two distinct functional substates within general REM sleep. Acoustic stimulation elicited a residual activation of the auditory cortex during tonic REM sleep background without rapid eye movements. By contrast, periods containing bursts of phasic activity such as rapid eye movements appear characterized by a lack of reactivity to sensory stimuli. We report a thalamocortical network including limbic and parahippocampal areas specifically active during phasic REM periods. Thus, REM sleep has to be subdivided into tonic REM sleep with residual alertness, and phasic REM sleep with the brain acting as a functionally isolated and closed intrinsic loop.

Is daytime sleepiness a neglected problem in patients with restless legs syndrome?

The restless legs syndrome (RLS) is a common neurological disorder of sleep/wake motor regulation that is associated with sleep disturbances. Here, we review the evidence that RLS is also associated with increased daytime sleepiness. Summarizing 26 studies that assessed sleepiness by means of the Epworth Sleepiness Scale (ESS) in untreated subjects with idiopathic RLS, we found that 20 to 25% of subjects are at an increased risk for daytime sleepiness.

Plasma Levels of Tumor Necrosis Factor α and Soluble Tumor Necrosis Factor Receptors in Patients With Narcolepsy

BACKGROUND

Narcolepsy is a disabling sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. Recent studies suggest that the immune system might play a pathogenic role pointing to a possible involvement of inflammatory cytokines.

METHODS

We investigated a sample of 30 patients with narcolepsy in comparison with 120 sex- and age-matched and 101 sex-, body mass index (BMI)-, and age-matched randomly selected normal controls. In these groups, plasma concentrations of tumor necrosis factor alpha (TNF-alpha) and its soluble receptors p55 and p75 (soluble TNF receptor [sTNF-R] p55 and sTNF-R p75) were measured using commercial enzyme-linked immunosorbent assays.

RESULTS

The narcoleptic patients showed a significantly higher BMI compared with controls of the same age. Soluble TNF-R p75 levels were consistently elevated in the narcoleptic patients compared with their sex- and age-matched (P = .001) as well as sex-, BMI-, and age-matched counterparts (P = .003). Female narcoleptic patients exhibited higher sTNF-R p55 levels compared with their sex- and age-matched controls (P = .01), but this difference disappeared when comparing patients with sex-, BMI-, and age-matched normal controls. Tumor necrosis factor alpha levels did not differ significantly between groups.

CONCLUSION

Narcoleptic patients show increased plasma levels of sTNF-R p75, suggesting a functional alteration of the TNF-alpha cytokine system, further corroborating a possible pathogenic role of the immune system in this sleep disorder.

Association of auditory hallucinations and anticonvulsant hypersensitivity syndrome with carbamazepine treatment. A case report

Carbamazepine is effective in the treatment of acute mania and in the prevention of episodes in bipolar disorder, and it may also be useful in depression, impulse-control disorder and withdrawal from alcohol and benzodiazepine dependence. A potentially life-threatening side effect is the anticonvulsant hypersensitivity syndrome. Here, we describe a patient who developed severe auditory hallucinations followed by a distinct hypersensitivity syndrome most likely induced by carbamazepine treatment.

Emerging drugs for restless legs syndrome

Restless legs syndrome (RLS) is a common, but often underdiagnosed, neurological disorder, which is characterised by an imperative urge to move the extremities associated with paraesthesias, worsening of symptoms at rest and in the evening or at night, and, as a consequence, sleep disturbances. RLS affects 1-10% of the population. The aetiology of RLS is unknown, but besides genetic factors the dopaminergic and opioidergic system may play a crucial role and new developments also point to an exciting iron-dopamine connection in the pathophysiology of this burdening disorder. Due to the limited disease-specific knowledge, current treatment strategies are not curative, but nevertheless may produce an effective and lasting relief of symptoms. Although clinically based treatment has focused on levodopa, opioids and benzodiazepines for a long time, evidence-based and clinical guidelines identify dopamine agonists as a first-line treatment for daily restless legs symptoms. These substances are now in the process of registration for this indication. Ropinirole is the first dopamine agonist that has been approved by the FDA in May 2005. In addition, several promising new therapies with nondopamine profiles are under development for RLS.

Brain activation and hypothalamic functional connectivity during human non-rapid eye movement sleep: an EEG/fMRI study

Regional differences in sleep EEG dynamics indicate that sleep-related brain activity involves local brain processes with sleep stage specific activity patterns of neuronal populations. Macroscopically, it is not fully understood which cerebral brain regions are involved in the successive discontinuation of wakefulness. We simultaneously used EEG and functional MRI on 9 subjects (6 female: mean = 24.1 years, 3 male: mean = 26.0 years) and analyzed local blood oxygenation level dependent signal changes linked to the transition from wakefulness to different non-rapid eye movement (NREM) sleep stages (according to Rechtschaffen and Kales) of the first sleep cycles after 36 h of total sleep deprivation. Several brain regions throughout the cortex, the limbic lobe, the thalamus, the caudate nucleus, as well as midbrain structures, such as the mammillary body/hypothalamus, showed reduced activity during NREM sleep across all sleep stages. Additionally, we found deactivation patterns specific to NREM sleep stages compared with wakefulness suggesting that a synchronized sleeping state can be established only if these regions interact in a well-balanced way. Sleep stage 2, which is usually linked to the loss of self-conscious awareness, is associated with signal decreases comprising thalamic and hypothalamic regions, the cingulate cortex, the right insula and adjacent regions of the temporal lobe, the inferior parietal lobule and the inferior/middle frontal gyri. The hypothalamic region known to be of particular importance in the regulation of the sleep-wake cycle shows specific temporally correlated network activity with the cortex while the system is in the sleeping state, but not during wakefulness. We describe a specific pattern of decreased brain activity during sleep and suggest that this pattern must be synchronized for establishing and maintaining sleep.

Dopamine agonists for the treatment of restless legs syndrome

The restless legs syndrome is a neurological disorder characterised by the urge to move the extremities associated with paraesthesias, which are partially or totally relieved by movement, a worsening of symptoms at rest and in the evening or at night and, as a consequence, sleep disturbances. Restless legs syndrome is common and affects 1-10% of the population. The aetiology of restless legs syndrome is unknown, but, beside genetic factors, the dopaminergic system may play a crucial role. Current treatment strategies are not curative, but may nevertheless produce an effective and lasting relief of symptoms. Evidence-based and clinical guidelines identify dopamine agonists as a first-line treatment for daily restless legs symptoms, and such substances are in the process of registration for this indication. In May 2005, the first dopamine agonist, ropinirole, was approved by the FDA. This review discusses treatment studies of dopamine agonists in patients with restless legs syndrome and focuses on long-term treatment with dopamine agonists.

Functional neuroimaging studies in restless legs syndrome

Functional neuroimaging studies may contribute to elucidate pathophysiological mechanisms of the restless legs syndrome (RLS) which still remain unclear. Studies in patients with RLS have been performed using functional magnetic resonance imaging (fMRI), single photon emission computed tomography (SPECT) and, more recently, positron emission tomography (PET). SPECT and PET studies revealed some controversial results of the pre- and postsynaptic dopaminergic neurotransmission system and cerebral metabolism in RLS probably reflecting a dysfunction of the central dopaminergic system. However, it still has to be determined whether these alterations affect the nigrostriatal and/or other central dopaminergic systems like the diencephalospinal or mesolimbic pathway and whether they are the primary mechanisms or only secondary phenomena within the manifestation of RLS symptoms. A subtle receptor dysfunction or a synaptic dopaminergic deficit may play a major role. fMRI investigations of RLS patients revealed an activation in the red nuclei and brainstem close to the reticular formation during the symptomatic period, suggesting that subcortical cerebral generators are involved in the pathogenesis of RLS. However, both techniques are not yet clinically relevant methods to differentiate RLS from other movement disorders during sleep. Further investigations, especially at night when RLS symptoms are most pronounced, will lead to a better understanding of the mechanisms underlying RLS.

Rapid eye movement-related brain activation in human sleep: a functional magnetic resonance imaging study

In animal models, ponto-geniculo-occipital waves appear as an early sign of rapid eye movement sleep and may be functionally significant for brain plasticity processes. In this pilot study, we use a combined polysomnographic and functional magnetic resonance imaging approach, and show distinct magnetic resonance imaging signal increases in the posterior thalamus and occipital cortex in close temporal relationship to rapid eye movements during human rapid eye movement sleep. These findings are consistent with cell recordings in animal experiments and demonstrate that functional magnetic resonance imaging can be utilized to detect ponto-geniculo-occipital-like activity in humans. Studying intact neuronal networks underlying sleep regulation is no longer confined to animal models, but has been shown to be feasible in humans by a combined functional magnetic resonance imaging and electroencephalograph approach.

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.

Functional MRI during sleep: BOLD signal decreases and their electrophysiological correlates

Prominent local decreases in blood oxygenation level (BOLD) can be observed by functional magnetic resonance imaging (fMRI) upon acoustic stimulation during sleep. The goal of this study was to further characterize this BOLD signal decrease with respect to corresponding neurophysiological phenomena using a simultaneous electroencephalography (EEG)/fMRI approach in sleeping human subjects. Healthy volunteers were subjected to acoustic stimulation during non-rapid eye movement (NREM) sleep. On the basis of statistical parametric maps, the correlations between the fMRI response (both amplitude and extent of the BOLD response) and the concomittant changes in the EEG (delta power and K-complexes) were calculated. Amplitude and extent of the stimulus-induced negative BOLD effect correlated positively with measures of EEG synchronization, namely an increase in the number of K-complexes and EEG delta power. Stimulus-induced BOLD decreases were most prominent during light (stage 2) NREM sleep and disappeared during slow wave sleep, indicating an influence of the baseline degree of hyperpolarization. Our observations provide first evidence that 'negative' BOLD signal changes during human sleep are associated with electrophysiological indicators of altered neuronal activity. Increased number of K-complexes and delta power reflecting hyperpolarization suggests true cortical deactivation upon stimulus presentation. This sleep stage-dependent deactivation might serve to protect the brain from arousing stimuli, particularly during the light phases of sleep shortly after sleep onset.