Painful Restless Legs Syndrome: A Severe, Burning Form of the Disease

Nocturnal Leg Cramping Caused by Carnitine Deficiency Due to Long-Term Pivalate Antibiotics Administration in a Patient With Chronic Kidney Disease

Carnitine deficiency is a known cause of leg cramps and is sometimes observed in patients taking certain medications such as pivalate-containing antibiotics. A 69-year-old Japanese woman presented with a progression of painful involuntary nocturnal leg cramping. She had been taking cefcapene-pivoxil for six months. Serum-free carnitine (FC) and acylcarnitine levels were decreased. Then, carnitine deficiency due to long-term pivalate-containing antibiotics administration was diagnosed. After initiating oral L-carnitine treatment, her symptoms improved. It should be aware of carnitine deficiency if a patient taking pivalate-containing antibiotics presents with leg cramping.

Potential therapeutic benefit of spinal cord stimulation in restless legs syndrome: scoping review and mechanistic considerations

BACKGROUND

Restless legs syndrome (RLS) is a prevalent sensorimotor disorder that can dramatically impair sleep quality, daytime function, and quality of life. Although many patients benefit from standard pharmacological therapy, some patients suffer from insufficient treatment response or medication intolerance. Novel treatment approaches are therefore necessary.

OBJECTIVE

Given the overlap between RLS and pain syndromes in both pathophysiological mechanisms and certain treatment options, we aimed to perform a scoping review of the available evidence on spinal cord stimulation (SCS) for RLS and discuss potential mechanistic implications.

METHODS

We identified a total of 16 cases of patients with RLS who underwent SCS, all from case reports or case series.

DISCUSSION

The published evidence is insufficient to assess SCS efficacy in patients with RLS, but SCS remains a promising investigational therapy in RLS on the basis of its potential mitigatory effects in the central hyperexcitability of the sensorimotor cortex through neuromodulation of spinal, subcortical, and cortical areas. A call for further research in this field is presented, with suggestions for future directions and trial designs.

Myoclonus and other jerky movement disorders

Myoclonus and other jerky movements form a large heterogeneous group of disorders. Clinical neurophysiology studies can have an important contribution to support diagnosis but also to gain insight in the pathophysiology of different kind of jerks. This review focuses on myoclonus, tics, startle disorders, restless legs syndrome, and periodic leg movements during sleep. Myoclonus is defined as brief, shock-like movements, and subtypes can be classified based the anatomical origin. Both the clinical phenotype and the neurophysiological tests support this classification: cortical, cortical-subcortical, subcortical/non-segmental, segmental, peripheral, and functional jerks. The most important techniques used are polymyography and the combination of electromyography-electroencephalography focused on jerk-locked back-averaging, cortico-muscular coherence, and the Bereitschaftspotential. Clinically, the differential diagnosis of myoclonus includes tics, and this diagnosis is mainly based on the history with premonitory urges and the ability to suppress the tic. Electrophysiological tests are mainly applied in a research setting and include the Bereitschaftspotential, local field potentials, transcranial magnetic stimulation, and pre-pulse inhibition. Jerks due to a startling stimulus form the group of startle syndromes. This group includes disorders with an exaggerated startle reflex, such as hyperekplexia and stiff person syndrome, but also neuropsychiatric and stimulus-induced disorders. For these disorders polymyography combined with a startling stimulus can be useful to determine the pattern of muscle activation and thus the diagnosis. Assessment of symptoms in restless legs syndrome and periodic leg movements during sleep can be performed with different validated scoring criteria with the help of electromyography.

Improved definition of growing pains: A common familial primary pain disorder of early childhood

Background

Commonly applied diagnostic criteria for growing pains (GP) have evolved without determination by an authoritative representative body. GP and restless legs syndrome (RLS) share anatomical, distributional, temporal, and other clinical features and are associated in individuals over time, in families, and in population samples. In this study, we tested the hypothesis that GP, diagnosed by widely used criteria, is confounded by cases of painful restless legs syndrome (RLS‐Painful).

Methods

A twin family study of genetic influence and associations of GP using questionnaires was administered by Twins Research Australia. Twins (3–18 years; monozygous 503, dizygous 513), their oldest siblings, mothers, and fathers were randomly selected from the twin registry. Family members completed the questionnaires assessing lifetime prevalence of GP by commonly applied criteria and covariates including the history of iron deficiency and pediatric pain disorders. A GP‐Specific phenotype was defined as GP without urge to move the legs. We determined similarities in twin pairs for the GP and GP‐Specific phenotypes, family associations, and estimated familial and individual‐specific associations for each phenotype.

Results

Lifetime prevalence was one‐third lower for GP‐Specific than for GP among the twin and family members. Monozygous twin pairs were more similar than dizygous twin pairs for GP and for the derived GP‐Specific phenotype by three methods, consistent with genetic influence. There were familial associations, but the essential evidence for genetic influence was the twin‐cotwin data. GP was associated, in multivariable analyses, with migraine, headaches, recurrent abdominal pain, and iron deficiency, while GP‐Specific associations were limited to migraine and headaches.

Conclusions

GP is hybrid, one‐third of cases having symptoms and associations of RLS, necessarily RLS‐Painful. GP‐Specific (without symptoms and associations of RLS) could have a genetic etiology. We propose new criteria to facilitate etiological and therapeutic research.

Growing pains, a highly prevalent primary pain disorder of childhood, has been associated with restless legs syndrome in individuals over time, in families and in population samples. This conundrum has been clarified by the evidence in this twin family study that growing pains, as previously defined, has been confounded by symptoms of restless legs syndrome. An exclusion clause of urge to move the legs has resulted in criteria for a purer phenotype which retains evidence of heritability.

Baseline and 1-year longitudinal data from the National Restless Legs Syndrome Opioid Registry

STUDY OBJECTIVES

Restless legs syndrome (RLS) is a sensory-motor neurological disorder. Low dose opioid medications are prescribed for treatment-refractory RLS. We describe baseline and 1-year longitudinal dosing and symptom outcomes for the National RLS Opioid Registry.

METHODS

Individuals currently taking a prescribed opioid for diagnosed RLS are included in the registry. Information on initial and current opioid dosages, side effects, past and current concomitant RLS treatments, RLS severity, psychiatric history, and opioid abuse risk factors were collected at baseline. Follow-up online surveys were performed at 6 months and 1-year.

RESULTS

Participants (n = 500) are primarily white, elderly, educated, and retired. Half of all subjects are on opioid monotherapy. Nearly 50% of all subjects are taking methadone, and one-quarter are taking oxycodone formulations. The median total daily opioid dose is 30.0 morphine milligram equivalents (MME). At baseline, three-quarters of registry participants had been taking a prescribed opioid for RLS for more than 1 year and one-third for more than 5 years, and had mild-moderate RLS symptoms. At 1-year follow-up, 31.2% increased dose (median = 10 MME) and 16.0% decreased dose of their opioid. An MME increase ≥25 was associated with: opioid use for non-RLS pain, <1 year of opioid use, opioid switch to methadone, and discontinuation of non-opioid RLS medications which, combined, accounted for 91.7% of those with 1-year follow-up increases ≥25 MME.

CONCLUSIONS

In refractory RLS, prescribed opioids are generally used at low doses with good efficacy. Longitudinally over 1 year, roughly one-third of participants increased their prescribed opioid dose, though generally by small amounts, with larger dose increases accounted for by predictable features.

Characterization of painful Restless Legs Syndrome sensations in an English-speaking South African population

Background and aims Restless Legs Syndrome (RLS) is characterised by unusual sensations in the legs which can be described as painful in up to 60% of RLS patients. The purpose of this study was to characterise and examine whether the presence of pain influenced the words used to describe the sensations of RLS in an English speaking population. Methods RLS participants (n=55) were divided according to whether or not painful RLS sensations were reported upon questioning. They completed the McGill Pain Questionnaire (MPQ), the International Restless Legs Syndrome Severity Scale (IRLS) and selected descriptors from a list of previously published RLS terms. Results Thirty-five percent of the RLS patients had painful sensations. The participants with painful RLS had higher Pain Rating Index (PRI) scores [median (interquartile range) 21 (17-28) vs. 14 (7.5-21) p=0.0008] and IRLS scores [23 (17-28) vs. 18 (11.5-22.5) p=0.0175] than the participants with non-painful RLS. Patients with painful RLS symptoms selected more pain-related literature terms, chose significantly different words in eight of the MPQ subclasses (both sensory and affective) and selected more intense descriptors from certain MPQ subclasses than the non-painful RLS group. The terms that characterised painful RLS were "aching", "painful", "cramping" and "unbearable". Conclusions Descriptors of RLS sensations are changed by the presence of pain, which may indicate an aetiological difference in the patients who have painful RLS. Clinically, patients complaining of cramping and painful sensations may be diagnosed with a condition that mimics RLS. Thus, it is important that the most accurate set of descriptors for RLS are used to enable recognition of RLS and optimised treatment according to the RLS phenotype. Implications The diagnosis of RLS may be improved by overcoming language and cultural barriers and obtaining differential diagnostic terms for painful conditions mimicking RLS.

Restless arms syndrome: prevalence, impact, and management strategies

This literature review focuses on restless arms syndrome (RAS), an upper limb variant of restless legs syndrome (RLS). RLS, also known as Willis-Ekbom disease, is a frequently occurring neurological disorder characterized by an irresistible urge to move the lower limbs often accompanied by unpleasant sensations in the legs, worsened at rest and in the evening, improved by movement. Extension of leg restlessness to the upper limbs is frequently reported in typical patients who had RLS only in the legs and usually occurs later in the course of RLS, restlessness remaining most invalidating in the lower limbs. In RAS, the arms are predominantly affected with little or no involvement of the legs. Cases of restless shoulders syndrome or periodic arm movements without arm restlessness were not considered. A total of 9 articles with 10 cases were included and analyzed for the adherence to the five essential diagnostic criteria of the International RLS Study Group (IRLSSG) classification, as well as for the additional supportive features. All of the reported cases were classified as having definite RAS. The clinical history and disease evolution of two previously reported patients were completed and updated. Overall, the clinical picture of RAS does not differ from that of RLS, except for the symptoms localization on the upper limbs. Underlying mechanisms of the spread of RLS to upper limb restlessness and of RAS remain unknown. Whether RAS is a phenotypic variant of RLS or a separate entity needs further investigations. RAS likely remains underdiagnosed and according to IRLSSG diagnostic criteria RAS should be considered when RLS-like symptoms are present in one or both arms, especially when they have a circadian pattern and are improved by movement and dopaminergic therapy. Clinicians should be aware of this rare condition, especially as treatment using dopaminergic agonists proves to be very efficient.

French consensus: Pharmacoresistant restless legs syndrome

Dopaminergic agonists, α2δ ligands and opioids are, as single-drug therapy, the first line treatment for restless legs syndrome (RLS/Willis-Ekbom disease). However, despite treatment efficacy, exacerbations of RLS may occur with overall worsening in symptoms severity, development of pain and symptoms spreading to other parts of the body, without meeting augmentation syndrome criteria. This development of "drug-resistant" RLS can cause pain, severe insomnia and psychiatric disorders that affect considerably patients' quality of life. The lack of French recommendations for this form of RLS leave physicians with few options to help patients with physical and emotional distress. Our group of neurological experts and sleep specialists proposes a diagnostic and therapeutic strategy to provide better care and appropriate treatment through searching for the organic, psychiatric and/or iatrogenic causes of drug resistance. Once a drug-resistant RLS diagnosis has been confirmed, we recommend an obligatory work-up including: a video-polysomnogram, a biological evaluation including iron status, standard numeration and C-reactive protein level. Treatment will be comorbidity-dependent: dopaminergic agonist would be recommended in case of depression or associated periodic leg movements, α2δ ligand in case of insomnia, complaint of pain, or general anxiety, in association with low-dose opioids if necessary. Strong opioids should be preferred for multiresistant RLS.

Morning cortisol and fasting glucose are elevated in women with chronic widespread pain independent of comorbid restless legs syndrome

Background and aims:

Chronic widespread pain (CWP) is associated with poor quality of sleep, but the detailed underlying mechanisms are still not fully understood. In this study we investigated the influence of CWP on morning cortisol and fasting glucose concentrations as well as sleep disordered breathing.

Methods:

In this case-control study, subjects with CWP (n=31) and a control group without CWP (n=23) were randomly selected from a population-based cohort of women. Current pain intensity, sleep quality, excessive daytime sleepiness [Epworth sleepiness scale (ESS)], psychiatric comorbidity and occurrence of restless legs syndrome (RLS) were assessed. Overnight polygraphy was applied to quantify sleep apnoea, airflow limitation and attenuations of finger pulse wave amplitude (>50%) as a surrogate marker for increased skin sympathetic activity. Morning cortisol and fasting glucose concentrations were determined. Generalised linear models were used for multivariate analyses.

Results:

CWP was associated with higher cortisol (464±141 vs. 366±111 nmol/L, p=0.011) and fasting glucose (6.0±0.8 vs. 5.4±0.7 mmol/L, p=0.007) compared with controls. The significance remained after adjustment for age, body mass index, RLS and anxiety status (β=122±47 nmol/L and 0.89±0.28 mmol/L, p=0.009 and 0.001, respectively). The duration of flow limitation in sleep was longer (35±22 vs. 21±34 min, p=0.022), and pulse wave attenuation was more frequent (11±8 vs. 6±2 events/h, p=0.048) in CWP subjects compared with controls. RLS was associated with higher ESS independent of CWP (β=3.1±1.3, p=0.018).

Conclusions:

Elevated morning cortisol, impaired fasting glucose concentration and increased skin sympathetic activity during sleep suggested an activated adrenal medullary system in subjects with CWP, which was not influenced by comorbid RLS.

Implications:

CWP is associated with activated stress markers that may deteriorate sleep.

Central and peripheral nervous system excitability in restless legs syndrome

Neurophysiological techniques have been applied in restless legs syndrome (RLS) to obtain direct and indirect measures of central and peripheral nervous system excitability, as well as to probe different neurotransmission pathways. Data converge on the hypothesis that, from a pure electrophysiological perspective, RLS should be regarded as a complex sensorimotor disorder in which cortical, subcortical, spinal cord, and peripheral nerve generators are all involved in a network disorder, resulting in an enhanced excitability and/or decreased inhibition. Although the spinal component may have dominated in neurophysiological assessment, possibly because of better accessibility compared to the brainstem or cerebral components of a hypothetical dysfunction of the diencephalic A11 area, multiple mechanisms, such as reduced central inhibition and abnormal peripheral nerve function, contribute to the pathogenesis of RLS similarly to some chronic pain conditions. Dopamine transmission dysfunction, either primary or triggered by low iron and ferritin concentrations, may also bridge the gap between RLS and chronic pain entities. Further support of disturbed central and peripheral excitability in RLS is provided by the effectiveness of nonpharmacological tools, such as repetitive transcranial magnetic stimulation and transcutaneous spinal direct current stimulation, in transiently modulating neural excitability, thereby extending the therapeutic repertoire. Understanding the complex interaction of central and peripheral neuronal circuits in generating the symptoms of RLS is mandatory for a better refinement of its therapeutic support.