Environmental risk factors for REM sleep behavior disorder: a multicenter case-control study

OBJECTIVE

Idiopathic REM sleep behavior disorder is a parasomnia characterized by dream enactment and is commonly a prediagnostic sign of parkinsonism and dementia. Since risk factors have not been defined, we initiated a multicenter case-control study to assess environmental and lifestyle risk factors for REM sleep behavior disorder.

METHODS

Cases were patients with idiopathic REM sleep behavior disorder who were free of dementia and parkinsonism, recruited from 13 International REM Sleep Behavior Disorder Study Group centers. Controls were matched according to age and sex. Potential environmental and lifestyle risk factors were assessed via standardized questionnaire. Unconditional logistic regression adjusting for age, sex, and center was conducted to investigate the environmental factors.

RESULTS

A total of 694 participants (347 patients, 347 controls) were recruited. Among cases, mean age was 67.7 ± 9.6 years and 81.0% were male. Cases were more likely to smoke (ever smokers = 64.0% vs 55.5%, adjusted odds ratio [OR] = 1.43, p = 0.028). Caffeine and alcohol use were not different between cases and controls. Cases were more likely to report previous head injury (19.3% vs 12.7%, OR = 1.59, p = 0.037). Cases had fewer years of formal schooling (11.1 ± 4.4 years vs 12.7 ± 4.3, p < 0.001), and were more likely to report having worked as farmers (19.7% vs 12.5% OR = 1.67, p = 0.022) with borderline increase in welding (17.8% vs 12.1%, OR = 1.53, p = 0.063). Previous occupational pesticide exposure was more prevalent in cases than controls (11.8% vs 6.1%, OR = 2.16, p = 0.008).

CONCLUSIONS

Smoking, head injury, pesticide exposure, and farming are potential risk factors for idiopathic REM sleep behavior disorder.

[Restless legs syndrome and nocturnal leg pain : Differential diagnosis and treatment]

Pain in the legs belongs to the five most frequent regional pain symptoms. Restless legs syndrome (RLS) presents a particular differential diagnosis for pain in the legs, which is characterized by a nocturnal urge to move the legs often associated with painful sensations in the legs. It is one of the most common neurological disorders and probably the leading cause of nocturnal pain in the legs. In this overview, the diagnosis and therapy of RLS as well as aspects of pain therapy of the disorder are presented. In addition, the differential diagnoses for exclusion of other specific causes of nocturnal pain in the legs are discussed.

Pain sensitivity and descending inhibition of pain in Parkinson's disease

BACKGROUND

Patients suffering from Parkinson's disease (PD) often complain about painful sensations. Recent studies detected increased subjective pain sensitivity and increased spinal nociception, which appeared to be reversible by dopaminergic treatment. Possibly, reduced descending pain inhibition contributes to this finding.

OBJECTIVE

Subjective pain thresholds as well as nociceptive reflex thresholds were investigated to isolate potential loci of the pathophysiological changes within the pain pathway. In addition, the diffuse noxious inhibitory control (DNIC) system as one form of descending control was assessed.

METHOD

15 patients with PD and 18 controls participated in the study. Electrical and heat pain thresholds as well as the nociceptive flexion reflex (NFR) thresholds were determined. Thereafter, the electrical pain thresholds were measured once during painful heat stimulation (conditioning stimulation) and twice during innocuous stimulation (control stimulation).

RESULTS

Patients with PD exhibited lower electrical and heat pain thresholds as well as lower NFR thresholds. Suppression of the electrical pain thresholds during painful heat stimulation (conditioning stimulation) compared with control stimulation did not differ significantly between the groups. No differences in the thresholds between patients with PD with and without clinical pain were seen.

CONCLUSIONS

Finding the NFR threshold to be decreased in addition to the decreased electrical and heat pain thresholds indicates that the pathophysiological changes either already reside at or reach down to the spinal level. Reduced activation of the DNIC system was apparently not associated with increased pain sensitivity, suggesting that DNIC-like mechanisms do not significantly contribute to clinical pain in PD.

Olfactory dysfunction in patients with narcolepsy with and without REM sleep behaviour disorder

Patients with idiopathic rapid eye movement sleep behaviour disorder (RBD) frequently develop Parkinson's disease and the majority present with hyposmia, which is a potential preclinical non-motor sign of Parkinson's disease. Accordingly, it has been proposed that the clinical symptoms of hyposmia and RBD in combination have to be considered as very early symptoms of Parkinson's disease. Since not only patients with idiopathic RBD but also patients in whom RBD is associated with narcolepsy present with an olfactory dysfunction we investigated if hyposmia in RBD patients with concomitant narcolepsy is RBD specific or if narcolepsy per se is associated with olfactory dysfunction. We studied olfactory function in 20 narcoleptic patients each with RBD (9 male and 11 female; mean age 45.4 +/- 14.0 years, range 20-75 years) and without associated RBD (8 male and 12 female; mean age 44.4 +/- 13.40 years, range 20-70 years) and 40 age- and gender-matched healthy control subjects using standardized 'Sniffin' Sticks'. Both, narcoleptics with (Narc/+RBD) and without RBD (Narc/-RBD) had a significantly higher olfactory threshold (Narc/+RBD, P = 0.0001; Narc/-RBD, P = 0.0001), lower discrimination scores (P = 0.001; P = 0.014) and lower identification scores (P = 0.057; P = 0.003) than controls. There were no symptoms or signs for early parkinsonism in both patient groups. Our results show for the first time that narcolepsy per se is associated with olfactory dysfunction. In contrast to patients with idiopathic RBD, hyposmia in patients with RBD associated with narcolepsy is unlikely to be a predictor for developing parkinsonism.

Efficacy of cabergoline in restless legs syndrome: A placebo-controlled study with polysomnography (CATOR)

OBJECTIVE

To assess the efficacy and safety of the dopamine agonist cabergoline in the treatment of patients with idiopathic restless legs syndrome (CATOR study).

METHODS

Patients with moderate to severe restless legs syndrome (RLS) were randomly assigned to cabergoline (single evening dose: 2 mg) or placebo and treated for 5 weeks in a double-blind, multicenter polysomnography (PSG) trial. The primary efficacy measures were the periodic leg movements during sleep arousal index (PLMS-AI) and sleep efficiency. These and further PSG variables were monitored by centrally evaluated PSG. Severity of RLS was assessed using the International RLS Study Group Severity Scale (IRLS), the RLS-6 scales, the Sleep Questionnaire Form A (SF-A; quality of sleep), and the Quality of Life for RLS questionnaire.

RESULTS

Forty-three patients were treated and 40 patients were evaluated with PSG (age 56 +/- 10 years, 73% women). Cabergoline was superior to placebo in terms of the PLMS-AI (-17.7 +/- 16.4 vs -4.5 +/- 20.0 placebo; p = 0.0024), sleep efficiency (+6.2 +/- 13.9% vs +3.3 +/- 11.7%; p = 0.0443), PLMS index (p = 0.0014), PLM index (p = 0.0012), and total sleep time (p = 0.0443). Improvements in IRLS total score (-23.7 +/- 11.2 vs -7.9 +/- 11.0 placebo; p = 0.0002), RLS-6 severity scales during the night (p = 0.0010) and during the day (p = 0.0018), Clinical Global Impressions severity item (p = 0.0003), sleep quality (p = 0.0180), SF-A sleep quality (p = 0.0371), and QoL-RLS (p = 0.0247) were larger in patients treated with cabergoline compared with the placebo group. Adverse events were only mild and well-known side effects of dopamine agonists.

CONCLUSION

Single-evening cabergoline is an efficacious and well-tolerated short-term therapy for sensorimotor symptoms of restless legs syndrome and associated sleep disturbances.

Pharmacotherapy of Parkinson’s disease in Germany

Treatment standards or guidelines have been developed for most features of Parkinson's disease (PD). However, data on the actual treatment that is put into practice are scarce. In 2000, a nationwide survey on the topic of sudden onset of sleep (SOS) in PD was initiated among the members of the German patient support group (deutsche Parkinson-Vereinigung, dPV). A part of this mailed questionnaire survey covering the antiparkinsonian and concomitant medication of the participants is presented here. This study analyses data sets from more than 6,500 PD patients. The mean dopaminergic dose was equivalent to 599 +/- 387 mg levodopa/die. The most frequently administered drugs were levodopa (94.2 %), dopamine agonists (DA) (71.7 %), amantadine (40.1 %), selegiline (27.6 %), entacapone (20.4 %), budipine (12.3 %), and anticholinergics (11.8 %). Costs of pharmacotherapy were estimated to be approximately <euro> 399 million/year in Germany. PD drug therapy in general strongly depended on age, disease duration, and the level of care. The treatment guidelines were apparently not consistently followed underlining the need for their continuous propagation throughout the medical community. In addition our data suggest that non-motor symptoms in PD are not adequately treated and that concomitant sedative medication contributes to the occurrence of SOS.

Effective cabergoline treatment in idiopathic restless legs syndrome

OBJECTIVE

To assess the efficacy and safety of the dopamine agonist cabergoline (CAB) in patients with restless legs syndrome (RLS).

METHODS

Patients with moderate to severe RLS were randomized into four groups receiving placebo, 0.5 mg, 1 mg, or 2 mg CAB once daily in a double-blind, placebo-controlled, multicenter dose-finding trial followed by an open long-term extension trial of 47 weeks. Efficacy was assessed with the RLS-6 scales and International RLS Study Group severity scale (IRLS).

RESULTS

A total of 85 patients (age 56 +/- 10 years, 71% females) were treated. Severity of RLS-6 scale symptoms during the night (the primary endpoint) was markedly improved by all CAB doses compared to placebo (placebo: -1.4 +/- 3.1, 0.5 mg CAB: -4.2 +/- 3.0 [p = 0.0082], 1.0 mg CAB: -4.0 +/- 2.9 [p = 0.0040], 2.0 mg CAB: -4.8 +/- 3.7 [p = 0.0026]). Similar results were found for the RLS severity at bedtime and during the day, IRLS, and satisfaction with sleep. A stable, clinically relevant improvement was achieved in all efficacy measures (severity during the night: change between last assessment and baseline: -5.6 +/- 2.5, rate of remission: 71.2%) throughout 1 year with a mean CAB dose of 2.2 mg per day. During long-term treatment, 6 of 66 treated patients were affected (n = 2) or possibly affected (n = 4) by mild augmentation. Under CAB therapy up to 1 year, 11 of 85 patients discontinued treatment due to a drug-related adverse event.

CONCLUSIONS

Cabergoline is an efficacious and well-tolerated option for the treatment of restless legs symptoms during the night and the day.

Combination of 'idiopathic' REM sleep behaviour disorder and olfactory dysfunction as possible indicator for -synucleinopathy demonstrated by dopamine transporter FP-CIT-SPECT

REM sleep behaviour disorder (RBD) and olfactory dysfunction are common and very early features of alpha-synucleinopathies, in particular Parkinson's disease. To investigate the hypothesis that these two clinical features in combination are an indicator of evolving alpha-synucleinopathy, olfactory function was assessed in RBD. We studied 30 patients (18 male, 12 female; mean age 48 +/- 14 years, range 19-78 years) with clinical (idiopathic, n = 6; symptomatic, n = 13, mostly associated with narcolepsy) or subclinical (n = 11, associated with narcolepsy) RBD according to standard criteria and 30 age- and gender-matched healthy control subjects using standardized 'Sniffin' Sticks'. RBD patients had a significantly higher olfactory threshold (P = 0.0001), lower discrimination score (P = 0.003), and lower identification score (P = 0.001). Compared with normative data, 97% of the RBD patients had a pathologically increased olfactory threshold, 63% an impaired odour discrimination score, and 63% a decreased identification score. On neurological examination, signs of parkinsonism were newly found in five patients with clinical RBD (not associated with narcolepsy), who usually had a long history of 'idiopathic' RBD. Four of the five patients fulfilled the UK Brain Bank criteria for the clinical diagnosis of Parkinson's disease. The underlying nigrostriatal degeneration of clinical Parkinson's disease was confirmed by I-123-FP-CIT SPECT in one patient and early nigrostriatal degeneration was identified by SPECT in a further two patients with 'idiopathic' clinical RBD out of 11 RBD patients who agreed to undergo SPECT studies. Our study shows that RBD patients have a profound impairment of olfactory function. Five patients with clinical RBD not associated with narcolepsy had clinical or imaging signs of nigrostriatal degeneration. This new clinical finding correlates with the neuropathological staging of Parkinson's disease (stages 1-3) as proposed by Braak. In stage 1, the anterior olfactory nucleus or the olfactory bulb is affected (along with the dorsal motor nucleus of the glossopharyngeal and vagal nerves). In stage 2, additional lesions consistently remain confined to the medulla oblongata and pontine tegmentum, which are critical areas for RBD. Midbrain lesions are found only in stage 3, in particular degeneration of dopaminergic neurons in the substantia nigra pars compacta. Thus, 'idiopathic' RBD patients with olfactory impairment might present with stage 2 preclinical alpha-synucleinopathy. Since narcoleptic patients are not known to have an increased risk of developing parkinsonism, the pathophysiology and clinical relevance of hyposmia in RBD/narcolepsy patients requires further research.

Restless legs syndrome?new insights into clinical characteristics, pathophysiology, and treatment options

We summarize recent advances in the clinical definition of restless legs syndrome (RLS), in understanding the basic mechanisms, and the successful treatments of RLS. New diagnostic instruments and severity scales have been developed for better phenotyping of the individual patient. Iron metabolism related components and the dopaminergic system have been extensively investigated in respect to the pathophysiology of RLS. The presence of mechanical hyperalgesia to pin-prick points towards an involvement of the nociceptive system. Genetic research has reported loci on chromosome 12q and 14q to play a role in the vulnerability to RLS. Placebo-controlled large-scale phase II and III treatment trials have shown that dopamine agonists are safe and efficacious agents for the treatment of this disorder.

Static mechanical hyperalgesia without dynamic tactile allodynia in patients with restless legs syndrome

Pain sensitivity was assessed in 11 patients (age 60 +/- 10 years) with 'primary' restless leg syndrome (RLS) (disease duration 18 +/- 15 years) and 11 age- and gender-matched healthy control subjects. Stimulus-response functions for pricking pain were obtained with seven calibrated punctate mechanical stimulators activating Adelta-high threshold mechano-nociceptors. Stimuli at the foot were significantly more painful than at the hand in both patients and healthy control subjects both in the morning and evening. Generally, pin-prick pain ratings in RLS patients were significantly elevated, by a factor of 5.3 in the upper limb and by a factor of 6.4 in the lower limb indicating a significant generalized static hyperalgesia more pronounced in the lower limb. In contrast, pain to light touch (allodynia = dynamic mechanical hyperalgesia) as tested by a battery of three gentle tactile stimuli was never reported. Acute single-dose dopaminergic treatment with 100 mg levodopa + 25 mg benserazide, 90 min prior to the evening measurements, largely resolved patients' RLS symptoms, but had no effect on pin-prick pain. Static hyperalgesia to pin-prick, however, was significantly reversed (median reduction -74%) by long-term individually tailored dopaminergic treatment. Our study shows that patients with RLS exhibit a profound static mechanical hyperalgesia to pin-prick stimuli, but no dynamic mechanical hyperalgesia (allodynia). This type of hyperalgesia is probably mediated by central sensitization to Adelta-fibre high-threshold mechanoreceptor input, a hallmark sign of the hyperalgesia type of neuropathic pain. The reduction of hyperalgesia in RLS patients by long-term dopaminergic treatment suggests that the pathophysiology of RLS includes disturbed supraspinal pain modulation involving the basal ganglia and/or descending dopaminergic pathways.

CSF hypocretin-1 levels in restless legs syndrome

CSF hypocretin-1 levels at 6 pm did not significantly differ between patients with restless legs syndrome (RLS) and control subjects as measured by direct radioimmunoassay and after acid extraction. The authors did not observe significant differences between early onset and late onset RLS. Hypocretin-1 levels did not correlate with RLS severity or polysomnographic measures. These results contrast with previous findings reporting significantly increased CSF hypocretin-1 in the late evening and mostly in early onset RLS.