Urinary 6-hydroxy-melatonin-sulfate excretion and circadian rhythm in patients with restless legs syndrome

Why the worsening at rest and worsening at night criteria for Restless Legs Syndrome are listed separately: review of the circadian literature on RLS and suggestions for future directions

The field of circadian research on Restless Legs Syndrome (RLS) and periodic limb movements (PLMs) is reviewed in general. RLS has five obligatory criteria for diagnosis: (1) an urge to move the legs often accompanied by uncomfortable leg sensations; (2) symptoms are worse at rest, i.e., lying or sitting; (3) there is a least partial and temporary relief of symptoms by activity, e.g., walking or stretching or bending the legs; (4) symptoms are worse later in the day or at night; and (5) mimics of RLS such as leg cramps and positional discomfort should be excluded by history and physical. In addition, RLS is frequently accompanied by PLMs, either periodic limb movements of sleep (PLMS) as determined by polysomnography or periodic limb movements while awake (PLMW) as determined by the suggested immobilization test (SIT). Since the criteria for RLS were based upon clinical experience only, an early question after the development of the criteria was whether criteria 2 and 4 were the same or different phenomena. In other words, were RLS patients worse at night only because they were lying down, and were RLS patients worse lying down only because it was night? Early circadian studies performed during recumbency at different times of the day suggest that the uncomfortable sensations, PLMS, and PLMW as well as voluntary movement in response to leg discomfort follow a similar circadian pattern with worsening at night independent of body position and independent of sleep timing or duration. Other studies demonstrated that RLS patients get worse when sitting or lying down independent of the time of day. These studies as a whole suggest that the worsening at rest and the worsening at night criteria for RLS are related but separate phenomena and that criteria 2 and 4 for RLS should be kept separate based upon the circadian studies, as had been the case previously based upon clinical grounds alone. To more fully prove the circadian rhythmicity of RLS, studies should be conducted to see if bright light shifts the signs and symptoms of RLS to a different circadian time in concert with circadian markers.

Periodic leg movements during sleep in narcoleptic patients with or without restless legs syndrome

We compared periodic and non-periodic leg movements during sleep and polysomnography in patients with narcolepsy with cataplexy (NC) with or without restless legs syndrome (RLS) with matched idiopathic RLS (iRLS) and control subjects. We enrolled 100 patients with NC: 17 having RLS were compared with 34 sex- and age-matched patients without RLS and with 17 normal controls and 17 iRLS subjects. Periodic leg movements were highest in iRLS and lowest in controls, with those in NC with RLS very close to iRLS, but higher than those in NC without RLS. The periodicity indexes showed the highest value in iRLS followed by NC with or without RLS and, finally, by controls. The inter-leg movement intervals peaked between 10 and 50 s in NC with RLS and in iRLS, the former did not display the nocturnal gradual decrease of periodic leg movements typical of iRLS. Periodic leg movements during sleep and polysomnography displayed specific features in RLS and NC, respectively, with NC with RLS showing an intermediate pattern. Even if RLS is only detected by targeted interview in NC, its frequency and impact on night-time sleep architecture and continuity suggest that this condition should be routinely searched for in NC.

Restless legs syndrome: differential diagnosis and management with rotigotine

RLS is a common sleep disorder with distinctive clinical features. The prevalence of RLS in Caucasians and North Americans ranges from 5% to 10%. However, only some of these subjects (almost the 3% of the general population) report being affected by a frequent and severe form of the sleep disorder. RLS is diagnosed clinically by means of four internationally recognized criteria that summarize the main characteristics of the sleep disorder. Besides the essential criteria, supportive and associated features of RLS have been established by experts in order to help physicians treat patients with doubtful symptoms. Several clinical conditions may mimic this sleep disorder. In order to increase the sensibility and specificity of RLS diagnosis, doctors should perform a meticulous patient history and then an accurate physical and neurological examination. Dopamine agonists are recognized as the preferred first-line treatment for RLS. Rotigotine is a non-ergoline dopamine agonist with selectivity for D1, D2 and D3 receptors. The drug is administered via transdermal patches which release rotigotine for 24 hours. Four clinical trials demonstrated that this compound is able to improve RLS symptomatology with few and moderate adverse events. Head to head trials are required to compare the efficacy and tolerability of rotigotine with other dopamine agonists administered via oral intake. Rotigotine has been approved by the FDA and EMEA for Parkinson's disease. For the treatment of moderate to severe idiopathic RLS, rotigotine has been recommended for approval by the EMEA and is under review by the FDA.

Inversion of melatonin circadian rhythm in chronic alcoholic patients during withdrawal: preliminary study on seven patients

AIMS

The inversion of melatonin circadian rhythm secretion in some alcoholics during both intake and acute withdrawal has been widely reported. In the same way, what happens to this inversion when these patients are in long-term withdrawal is not known. To document this abnormality in alcoholics after withdrawal we investigated melatonin secretion observed during chronic alcoholization and after withdrawal.

METHODS

We measured the urinary 6-sulfatoxymelatonin (6SM) (6SM/creatinine ratio), main metabolite of the hormone, in two fractions, one diurnal and the other nocturnal, in seven alcohol-dependent patients presenting with this abnormality during alcoholization at two times: in acute withdrawal phase (under benzodiazepines) and 15 days after beginning of withdrawal (free of any psychotropic treatment).

RESULTS

Our results show that this reversed rhythm of melatonin secretion as seen by the diurnal excretion of 6SM (6SM/creatinine ratio) persists during acute withdrawal in more than half of the patients and is still present 15 days after withdrawal in three patients.

CONCLUSION

It is remarkable that the inversion of the melatonin rhythms gets corrected in four out of seven patients after withdrawal. But, the circadian disorganization of melatonin secretion in three patients could underline a desynchronization in some alcoholic patients and may indicate more widespread circadian temporal structure disturbances in these patients.

Restless legs syndrome: pathophysiology, diagnosis and treatment

Restless legs syndrome (RLS) is clinically defined by the presence of (i) an urge to move the legs with or without an actual paraesthesia; (ii) a worsening of symptoms with inactivity; (iii) improvement with activity; and (iv) a worsening of symptoms in the evening and at night. Patients may use a variety of semantic phrases to describe their symptoms but all must have an urge to move. Most people with RLS also have periodic limb movements during sleep, although this is not part of the clinical diagnostic criteria. RLS is very common. About 10% of all Caucasian populations have RLS, although it may be mild in the majority of cases. Women generally outnumber men by about 2:1. As a general rule, RLS severity worsens through the first seven to eight decades of life, but may actually lessen in old age. The aetiology of RLS is only partly understood. There is a strong genetic component, and several genetic linkages and three causative genes have been identified worldwide. Several medical conditions, including renal failure, systemic iron deficiency and pregnancy, and possibly neuropathy, essential tremor and some genetic ataxias, are also associated with high rates of RLS. In all cases to date, the actual CNS pathology of RLS demonstrates reduced iron stores, in a pattern that suggests that the homeostatic control of iron is altered, not just that there is not enough iron entering the brain. The relationship between reduced CNS iron levels and the clinical phenotype or treatment response to dopaminergics is not known but generates promising speculation. Treatment of RLS is usually rewarding. Most patients respond robustly to dopamine receptor agonists. Over time, response may lessen, or the patients may develop 'augmentation', whereby they have a worsening of symptoms, usually in the form of an earlier onset. Other treatment options include gabapentin, or similar antiepileptic drugs, and opioids. High-dose intravenous iron is a promising but still experimental approach.

Circadian variation in restless legs syndrome

Restless legs syndrome (RLS) is a clinical disorder that currently is not characterized by a uniform pathophysiologiocal definition. The diagnosis of RLS requires circadian variation in symptoms, although no pathophysiological basis has been verified. Clinical observations and research studies confirm the variation in symptoms, of both sensory and motor components, over the course of the day. This contribution reviews the current literature on circadian variation in RLS and discusses potential intrinsic and extrinsic causes.

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.

Loss of normal circadian profile of urine excretion in idiopathic restless legs syndrome

BACKGROUND

This study was performed to elucidate preliminary observations of excessive nighttime urine excretion in idiopathic restless legs syndrome (iRLS).

METHODS

Seventeen patients, with normal serum creatinine, blood urea nitrogen, and urate, and 11 healthy controls were examined. We measured excretory renal function parameters (urine volume, osmolarity, sodium, chloride, potassium, calcium, phosphate, microalbumin, aldosterone, creatinine) between 7:00 am and 10:00 pm and between 10:00 pm and 7:00 am.

RESULTS

During the nighttime, volume (P=0.006), sodium (P=0.009), and chloride excretion (P=0.001) were significantly higher, and osmolarity (P=0.025) was significantly lower in patients as compared to controls. In comparing daytime to nighttime, controls showed the physiological reduced nocturnal excretion of volume (P=0.009) and chloride (P=0.023), and an increased osmolarity (P=0.026), but patients showed similar excretion rates of these parameters (all differences ns).

CONCLUSIONS

These data indicate a loss of normal circadian profile of urine excretion in iRLS. The elevated nighttime excretion, with values similar to those in the daytime, hint at a possibly elevated fluid, sodium, and chloride intake during daytime.

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.