Subclinical sensory neuropathy in late-onset restless legs syndrome

OBJECTIVE: To determine the prevalence of different forms of peripheral neuropathy in patients with restless legs syndrome (RLS) and correlate the findings with other clinical characteristics. BACKGROUND: RLS is characterized by a desire to move the extremities, often associated with paresthesias or dysesthesias, motor restlessness, worsening of symptoms with rest with relief by activity, and worsening of symptoms in the evening or night. The association between RLS and peripheral neuropathy remains controversial. The observation that many patients with small-fiber neuropathy also complain of RLS prompted this prospective case series. METHODS: Twenty-two consecutive patients with RLS were evaluated for evidence of large-fiber neuropathy (LFN) and small sensory fiber loss (SSFL). Results: In eight of the 22 (36%) patients, neuropathy was identified. Three patients had pure LFN; two had mixed LFN and SSFL; and three had isolated SSFL. The SSFL group had a later onset of RLS (p < 0.009), reported pain in their feet with RLS more frequently (p < 0.001), and tended to have no family history of RLS (p < 0.078). Patients with LFN did not have similar associations with age at onset, family history status, or presence of pain. CONCLUSION: The results suggest that two forms of RLS exist: one is triggered by painful dysesthesias associated with SSFL, has later onset, and no family history; and one without involvement of SSF, with an earlier onset age, positive family history for RLS, and no pain. The authors hypothesize that patients with the SSFL subtype of RLS will preferentially respond to neuropathic pain medications.     

Restless legs syndrome in diabetic neuropathy: a frequent manifestation of small fiber neuropathy

As the occurrence of restless legs syndrome (RLS) in diabetes is controversial, the aim of this study was to assess the prevalence of RLS in a cohort of patients with diabetic neuropathy and to analyze the features of the associated neuropathy. We investigated the occurrence of RLS diagnosed in accordance with the criteria of the International Restless Legs Syndrome Study Group in a cohort of patients with polyneuropathy and mononeuropathy multiplex associated with diabetes mellitus (DM), or impaired glucose tolerance (IGT), or impaired fasting glucose (IFG) in a retrospective study. RLS was present in 33/99 patients with neuropathy associated with DM/IGT/IFG (84 with distal polyneuropathy and 15 with multiple mononeuropathy). Comparing patients with or without RLS, small fiber sensory neuropathy was more common in the RLS patients (15/33 vs. 15/66), as were symptoms of burning feet (10/33 vs. 6/66). In several patients, RLS was responsive to neuropathic pain medications. The frequent occurrence of RLS in association with thermal dysesthesias may reflect the involvement of small sensory fibers in the form of hyperexcitable C fibers or A-delta fiber deafferentation. We suggest that RLS may be triggered by abnormal sensory inputs from small fibers, especially involved in neuropathy associated with DM/IGT/IFG. Our data show that RLS is a relevant feature of diabetic neuropathy, as a frequent and potentially treatable manifestation of small fiber involvement in the course of DM and IGT/IFG.     

Opioid and dopamine antagonist drug challenges in untreated restless legs syndrome patients

Background: The restless legs syndrome (RLS) is a common sensomotor disorder associated with severe sleep disturbances. Symptoms clearly improve following treatment with dopaminergic or opioidergic agonists.Objective: To further elucidate the involvement of opioidergic and dopaminergic mechanisms in the pathophysiology of RLS, the effects of specific antagonists on motor (periodic leg movements) and subjective (sensory) RLS-symptoms during daytime were assessed.Methods: A modified suggested immobilization test was performed in eight drug-naive RLS-patients. An infusion of either naloxone, metoclopramide or placebo was administered. In addition, the hormonal levels of adrenocorticotropic hormone, cortisol, prolactin and growth hormone were determined, to elucidate a possible involvement of the hypothalamic-pituitary-adrenocortical (HPA) system in RLS.Results: RLS sensory or motor symptoms could not be provoked. Hormonal responses showed no abnormal profiles.Conclusions: Rather than a general alteration of the opioidergic/dopaminergic tone and an involvement of the HPA system, it is more likely that specific neuronal dopaminergic or opioidergic pathways are altered in the pathophysiology of RLS.     

Painful polyneuropathy associated with restless legs syndrome. Clinical features and sensory profile

BackgroundThe association of restless legs syndrome (RLS) with polyneuropathy, and its prevalence, have been evaluated differently throughout various studies. As subtypes of polyneuropathy characterized by neuropathic pain seem to be preferentially associated with RLS, we intended to investigate the prevalence and the features of RLS occurring with painful neuropathy, and to define whether there is a specific sensory phenotype.MethodsWe prospectively investigated 58 consecutive patients with distal symmetric polyneuropathy and neuropathic pain or dysesthesia, using a bedside protocol for sensory assessment. RLS was diagnosed with an interview assessing the International RLS Study Group diagnostic criteria.ResultsOverall, RLS was reported by 21 patients (36.2%), but it was occurring at the time of the evaluation in 12 patients (20.7%), significantly more than in controls. RLS was chronic in nine patients and remitting–intermittent in 12 patients. No difference was demonstrated between patients with or without RLS. Comparing patients with chronic RLS and remitting-intermittent RLS, the latter had more severe electrophysiological changes, whereas hyperalgesia, suggesting central sensitization, was significantly more frequent in chronic RLS patients.ConclusionsRLS is frequently associated with painful polyneuropathy, in keeping with the hypothesis that its occurrence is favored by small fiber involvement. It represents a heterogeneous entity, differentiated in chronic and remitting-intermittent subtypes, possibly conditioned by indolent or aggressive neuropathy course and phenomena of central sensitisation.     

Cırcadian changes in cortical excitability in restless legs syndrome

Various investigations have revealed a widespread and somewhat controversial pattern of cerebral, cerebellar and brainstem involvement in the pathophysiology of restless legs syndrome (RLS). However, several studies which investigated functional or structural aspects indicated cortical involvement in RLS. In this study, we aimed to analyze circadian changes of cortical excitability in idiopathic RLS patients by means of transcranial magnetic stimulation (TMS). Eleven idiopathic RLS patients and eight healthy age and sex matched subjects were investigated using single-pulse TMS and motor nerve conduction studies during early afternoon when there were no symptoms and late at night (22:00-23:00) when the symptoms reappeared. Central motor conduction time, latencies and amplitudes of scalp and cervical motor evoked potentials, resting and active motor thresholds, and cortical silent period were measured. Measured parameters were similar between RLS patients and healthy subjects during the daytime. At night, cortical silent periods tended to shorten, and motor thresholds tended to decrease in the RLS group, whereas in controls they tended to increase. At night, active motor-threshold measurements were significantly lower in the RLS group (28.5 ± 6.2% vs 40.4 ± 8.4%, p=0.006). Therefore, we propose that in patients with RLS, conduction along the motor corticospinal axons is normal, with the possible loss of subcortical inhibition at nighttime.     

Neuropathies associated with excessive exposure to lead

Exposure to lead is a ubiquitous problem of the modern era. The majority of cases of all forms of lead intoxication, especially lead neuropathy, result from industrial exposure. In the Western world meticulous monitoring in industry has reduced the risk of overt lead neuropathy. The classic form of lead neuropathy consists of weakness that primarily involves the wrist and finger extensors but which later spreads to other muscles. There is only minimal sensory involvement. Less commonly, there is a more typical toxic neuropathy with distally accentuated sensory and motor involvement. The motor neuropathy is more likely to develop following relatively short-term exposure to high lead concentrations and evolves in a subacute fashion. Prognosis for recovery is good as long as exposure is terminated promptly. The distal sensory and motor neuropathy develops after many years of exposure, evolves more slowly, and recovery is less certain. There is a generally weak relationship between the development of lead neuropathy and blood lead levels, at least for the subacute motor neuropathy, leading to speculation that the metabolic basis for the neuropathy is interference with porphyrin metabolism. Lead intoxication in humans causes axonal degeneration, but in some other species it causes a primarily demyelinating neuropathy. It should be possible to prevent lead neuropathy by good industrial hygiene. Close monitoring should identify excessive lead exposure before it causes overt neuropathy. If evidence of excessive exposure is found or if overt neuropathy develops, exposure must be terminated immediately. The role of chelation therapy in the treatment of lead neuropathy is controversial.     

Sensory nerve pathology in multifocal motor neuropathy

The nosological status of multifocal motor neuropathy remains controversial. The clinical and electrodiagnostic hallmarks suggest selective motor fiber involvement. In this study, we asked to what extent sensory nerves might be involved pathologically in multifocal motor neuropathy. Examination of sensory nerve biopsy specimens from II patients did reveal pathological findings in all, but they were very mild. An increased number of thinly myelinated, large-caliber fibers was the unifying feature common to each specimen. By electron microscopy, each biopsy specimen had thinly myelinated fibers surrounded by minor onion bulbs. Active demyelination, though scant, was seen in 3 nerves. Myelinated fiber density was normal. Subperineurial edema and inflammation were not present. We conclude that multifocal motor neuropathy is not an exclusively motor abnormality, although it appears to be so clinically and electrophysiologically. The frequent, albeit mild, pathological abnormalities in sensory fibers suggest that the demyelinating pathophysiology also affects sensory fibers, but to a lesser degree than motor fibers. Some investigators maintain that multifocal motor neuropathy is within the spectrum of chronic inflammatory demyelinating polyneuropathy. The very mild degree of sensory fiber involvement, the absence of inflammation or edema, and the distinctive clinical features support the concept of multifocal motor neuropathy as distinct from chronic inflammatory demyelinating polyneuropathy.     

Diagnosis of motor neuropathy

Motor neuropathy is a clinical entity which leads to consideration of a wide spectrum of peripheral nerve disorders. Firstly, it may be distinguished from other causes of peripheral motor involvement such as muscle diseases and disorders of the neuromuscular junction. Secondly, it may be discussed in two different forms: acute and chronic. Acute chronic neuropathies are mainly observed in Guillain-Barré syndrome, in which electrophysiological studies allow us to recognize the classical demyelinating form and the axonal form. The other causes of acute motor neuropathy are mainly poliomyelitis and porphyrias. Chronic motor neuropathies are mainly observed in motor neuron diseases, mainly amyotrophic lateral sclerosis, but also Kennedy's disease and other lower motor neuron diseases which may be inherited or acquired. The other causes are multifocal motor neuropathy and the predominantly motor forms of chronic inflammatory demyelinating polyneuropathy. The characterization of these different types of chronic neuropathy is of major importance because of the therapeutic consequences which may lead to the proposal of specific treatments.     

Immune-mediated neuropathies in myeloma patients treated with bortezomib

OBJECTIVE: Bortezomib is a new chemotherapeutic drug available for the treatment of lymphoid disorders, including multiple myeloma. Although its primary mechanism of action is proteasome inhibition, other mechanisms can contribute to the therapeutic effects, including modulation of inflammatory cytokines and immune response. One of the main toxic effects of bortezomib is peripheral neuropathy, usually occurring in the form of a painful, sensory axonal neuropathy. The mechanisms of peripheral damage, however, are still unclear. We here report a series of patients treated with bortezomib, who developed a peripheral damage possibly related to immuno-mediated, rather than toxic, mechanisms. METHODS: Five patients who developed a peripheral neuropathy with severe motor involvement under bortezomib treatment underwent CSF, electrophysiological, and spinal cord MRI examinations. RESULTS: Peripheral damage was characterized by: demyelinating or mixed axonal-demyelinating neuropathy, with prominent motor involvement; albumin-cytological dissociation; lumbar root enhancement on MRI in 2/5 patients; favourable outcome in 4/5 patients after immune treatments, either steroids (2 patients) or IVIg (2 patients). CONCLUSIONS: In some instances, the peripheral damage associated with bortezomib may recognize immuno-mediated mechanisms. SIGNIFICANCE: This form of bortezomib-associated neuropathy needs to be recognized as treatable condition, as it may respond to immune therapies. Unexplained worsening of neurological dysfunction despite bortezomib discontinuation, with prominent motor involvement and CSF signs of inflammation, may be the clues to this complication.     

Rheumatologic serologies in secondary restless legs syndrome.

Diagnostic criteria for restless legs syndrome (RLS) have been established; however, the pathophysiology of this common condition remains elusive. Several secondary forms of RLS potentially include renal failure, iron deficiency, pregnancy, and neuropathy. RLS has also been reported in approximately 25% of patients diagnosed with rheumatoid arthritis and Sj?gren's syndrome. We performed clinical and serologic evaluations on 68 patients diagnosed with RLS to determine how many may have concurrent rheumatologic disease that could be causing their RLS symptoms. We compared these with other postulated secondary causes of RLS. No patient had clinical evidence of rheumatologic disease, and only four had any positive serologic evaluations (two positive SSA/SSB and two mildly elevated RF titers). Three of these had a positive family history for RLS. Patients without a family history of RLS did have lower ferritin levels, more cases of neuropathy, and an older age at symptom onset. We do not think rheumatologic disease represents a significant secondary cause of RLS and do not recommend serologic investigation unless there are overt clinical signs. In contrast, our study suggests that neuropathy and serum iron deficiency do represent secondary forms of RLS.     

Restless legs syndrome is frequently overlooked in patients being evaluated for polyneuropathies

Restless legs syndrome (RLS) often presents with paresthesias and dysesthesisas. We have investigated the prevalence and clinical features of RLS in a cohort of patients referred for clinical suspicion of peripheral neuropathy (PN). Sixty-four patients with sensory symptoms, and 101 age-matched controls were prospectively evaluated for RLS, PN and causes of both conditions. In the 64 patients (60 ± 14 years), none were referred with a suspicion of RLS. Forty-one had a sensori-motor PN of which 22 had a definite RLS (54%). When excluding other causes of RLS, 8 of 41 patients had a RLS associated with a neuropathy (20%). The proportion of RLS in the healthy controls was 10%, lower than in the cohort of patients. In patients without PN, 57% had a RLS, and 55% in the whole cohort, a higher proportion than in the healthy controls ( P  < 0.0001). Patients with PN and RLS had more sleep disorders ( P  < 0.04), and legs and calves symptoms ( P  = 0.09) than patients with PN without RLS. Toes symptoms were more frequently observed in patients with PN but without RLS ( P  < 0.02). We conclude that RLS frequently presents with symptoms suggestive of peripheral neuropathy, and therefore, is often overlooked.     

Varied electrophysiologic patterns in spinocerebellar ataxia type 2

The autosomal dominant ataxias are a heterogenous group of disorders. Almost 30 different genetic loci have been identified. Spinocerebellar ataxia type 2 (SCA2) is one of many autosomal dominant cerebellar ataxias. Electrophysiologic studies in SCA2 have shown mainly a sensory neuropathy or neuronopathy. To determine if electrophysiologic testing reveals concomitant or isolated involvement of motor nerves in SCA2 we reviewed historic and electrophysiologic data on all cases of genetically confirmed SCA2 who underwent nerve conduction studies and needle electromyographic during initial evaluation at our institution. We performed electrophysiologic studies in six genetically confirmed, unrelated, cases of SCA2 and discovered that in three patients, there were findings consistent with motor neuronopathy or neuropathy without sensory involvement. One patient had normal results and only one had a pure sensory neuropathy or neuronopathy. The sixth patients had mixed sensorimotor neuropathy. This is the first study that demonstrates isolated involvement of motor neurons and/or axons occur in SCA2. Therefore, electrophysiologic findings in SCA2 are not limited to mainly a sensory neuropathy but are varied and can even mimic slowly progressive motor neuron disease.     

Paraneoplastic encephalomyelitis/sensory motor peripheral neuropathy - an autopsy case study

Paraneoplastic neurological anti-Hu syndrome is one of the most frequent remote effects of cancer and usually manifests as encephalomyelitis combined with peripheral neuropathy. Subacute sensory neuronopathy, which results from the inflammatory destruction of sensory neurone cell bodies in the dorsal root ganglia, is thought to be the principal presentation of peripheral neuropathy. In addition to sensory involvement, evidence of motor nerve involvement is frequently found. The mechanisms of motor involvement remain largely unclear and there have been only a limited number of pathological studies. We present an autopsy case study of anti-Hu paraneoplastic encephalomyelitis/sensory-motor neuropathy, which confirms an inflammatory paraneoplastic destruction of sensory neuron cell bodies in the dorsal root ganglia and lower motor neurons in the spinal cord, as a cause of clinically rapidly progressive peripheral sensory-motor neuropathy.     

A novel p.Glu175X premature stop mutation in the C-terminal end of HSP27 is a cause of CMT2

Mutations in the gene HSPB1, encoding the small heat shock protein 27 (HSP27), are a cause of distal hereditary motor neuropathy (dHMN) and axonal Charcot-Marie-Tooth disease (CMT2). dHMN and CMT2 are differentiated by the presence of a sensory neuropathy in the latter although in the case of HSPB1 this division is artificial as CMT2 secondary to HSPB1 mutations is predominantly a motor neuropathy with only minimal sensory involvement. A recent study in mice has suggested that mutations in the C-terminus result in a motor only phenotype resembling dHMN, whereas mutations at the N-terminus result in a CMT2-like phenotype. However, we present a family with a novel mutation in the C-terminus of HSP27 (p.Glu175X) with a motor predominant distal neuropathy but with definite sensory involvement compatible with CMT2. This case highlights the artificial distinction between patients with motor predominant forms of CMT2 and dHMN and argues against the hypothesis that mutations in the C-terminus have no sensory involvement.     

Restless legs syndrome and periodic leg movements in sleep: the primary role of dopaminergic mechanism

We report here the possible effect of opiates on a patient exhibiting particularly severe restless legs syndrome (RLS) and periodic leg movements in sleep (PLMS). This patient was investigated in the sleep laboratory under three conditions, namely, unmedicated (baseline), medicated with codeine sulfate, and medicated with both codeine sulfate and pimozide. Codeine sulfate dramatically improved abnormal motor behavior in this patient. The addition of pimozide reversed the beneficial effect of codeine during the Forced Immobilization Test but not in spontaneous RLS or PLMS at night. These results are discussed in view of the possible involvement of the dopaminergic mechanism in RLS/PLMS syndrome.     

Restless leg syndrome in the differential diagnosis of entrapment and peripheral neuropathies

Restless leg syndrome (RLS) is an abnormal sensation disorder. Defining the syndrome is difficult. It is transmitted autosomal dominant genetically, is especially prevalent in the lower limbs, and is seen in both genders. In the differential diagnosis of RLS, nocturnal leg cramps, akathisia, peripheral neuropathy, entrapment neuropathy, and vascular disease (for example, deep vein thrombosis) should be considered. A 52-year-old woman was admitted to our clinic with signs of paresthesia, she had abnormal sensation disorder in both legs and the right arm, which she had difficulty defining. She had applied to another center with the same complaints and had been evaluated as entrapment neuropathy, carpal tunnel syndrome, and/or peripheral neuropathy. Her electromyographic examination carried out by us was normal. The history, neurological examination findings, and results of standard laboratory analyses provided a diagnosis of idiopathic RLS. After the diagnosis of RLS in the proband, we questioned other family members. Her large family had 63 members, 35 males, and 28 females. Of 63 members, 17 also had an RLS diagnosis.     

Monofocal motor neuropathy: Improvement with intravenous immunoglobulin

Multifocal motor neuropathy (MMN) is a chronic, immune-mediate, peripheral myelinopathy. Inherent in its name, MMN implies involvement of two or more motor nerves. We report three patients with weakness and partial motor conduction block restricted to a single nerve and localized to sites that are not at risk for entrapment or compression injury. None of the patients had sensory involvement and all showed a favorable response to intravenous immunoglobulin therapy. Based on these observations and reports of three additional patients, we believe that monofocal motor neuropathy is a partial form of MMN and should be treated as such.     

Abnormal motor behavior during sleep

Abnormal motor behaviors during sleep can be classified into four categories, ranging from myoclonic jerks to complex and integrated motor behaviors There have been recent developments in several of these conditions, in particular restless legs syndrome (RLS) and rapid-eye-movement sleep behavior disorder (RBD). RLS is one of the major causes of insomnia. Familial aggregation of RLS has been demonstrated by several groups, and molecular genetics studies have suggested the presence of susceptibility genes on chromosomes 12q and 14q. Pharmacologic and brain imaging studies suggest the involvement of dopaminergic mechanisms in RLS, but recent work has focused on brain iron metabolism. Studies indicate that RBD patients may eventually develop Parkinson's disease (PD). Conversely, RBD has been found in patients already diagnosed with PD. Single-photon emission computed tomography and positron emission tomography studies have shown a decrease in binding to presynaptic dopamine transporter in both idiopathic RBD and PD. Patients with RBD (associated or unassociated with PD) also have neuropsychological deficits. RBD may therefore represent the prodrome of a neurodegenerative disease leading to multiple system atrophy and Lewy body dementia. Understanding the underlying pathophysiology of abnormal sleep motor behaviors may prove useful in the management of insomnia.     

Restless-legs syndrome

Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movements and is exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to 3% of the general population in Western countries. Supportive criteria include a family history, the presence of periodic-leg movements (PLM) when awake or asleep and a positive response to dopaminergic treatment. The RLS phenotypes include an early onset form, usually idiopathic with a familial history and a late onset form, usually secondary to peripheral neuropathy. Recently, an atypical RLS phenotype without PLM and l-DOPA resistant has been characterized. RLS can occur in childhood and should be distinguished from attention deficit/hyperactivity disorder, growing pains and sleep complaints in childhood. RLS should be included in the diagnosis of all patients consulting for sleep complaints or discomfort in the lower limbs. It should be differentiated from akathisia, that is, an urge to move the whole body without uncomfortable sensations. Polysomnographic studies and the suggested immobilization test can detect PLM. Furthermore, an l-DOPA challenge has recently been validated to support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor quality of life, depressive and anxious symptoms and may be a risk factor for cardiovascular disease. In most cases, RLS is idiopathic. It may also be secondary to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drugs, such as antipsychotics and antidepressants. The small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with many neurological and sleep disorders including Parkinson's disease, but does not predispose to these diseases. The pathophysiology of RLS includes an altered brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain control systems and a genetic susceptibility with nine loci and three polymorphisms in genes serving developmental functions. RLS treatment begins with the elimination of triggering factors and iron supplementation when deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA or codeine; the first-line treatment for moderate to severe RLS is dopaminergic agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid (oxycodone, tramadol) drugs can be used.     

Acute intermittent porphyria with peripheral neuropathy: a follow-up study after hematin treatment

We report a patient with acute intermittent porphyria who presented with progressive motor neuropathy, particularly in the upper limbs. The electrophysiological studies showed an asymmetric motor neuropathy with a prominent involvement of both the radial and left peroneal nerves. During the 1-year follow-up period, 6 courses of hematin infusion, with 150 mg daily for 4 consecutive days every month, were administrated. The motor neuropathy showed a steady and gradual improvement following the hematin treatment. Molecular analysis of the porphobilinogen deaminase gene revealed a short segment deletion (1008–1019delCAGCCTGGCCAA) resulting in a truncated protein. The findings suggest that early hematin treatment is temporally associated with interval improvement of the patient's porphyric motor neuropathy.