High-Resolution Nerve Ultrasound and Electrophysiological Findings in Restless Legs Syndrome

Median nerve ultrasonography in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

The cross-sectional area (CSA) of the median nerve in Parkinson's disease remains unclear.

OBJECTIVES

This meta-analysis assesses median nerve CSA changes in Parkinson's using ultrasonography.

METHODS

PubMed, Web of Science, Scopus, and EBSCO were selectively searched for literature on Parkinson's disease, Median nerve, and ultrasonography. Following full-text screening, three studies were included in this meta-analysis with 144 Parkinson's disease patients and 127 controls. The primary outcome was the cross-sectional area of the median nerve; other motor parameters were also evaluated.

RESULTS

The cross-sectional area of the median nerve was significantly increased in Parkinson's patients compared to controls (p = 0.007); the standardized mean difference was 0.79 [95% CI (0.21 - 1.37)]. The standardized mean difference of the motor parameters of the median nerve, amplitude, and latency was -0.04 [95% CI (-0.85 to 0.77)] and 0.30 [95% CI (-0.04 to 0.64)], respectively, with statistically insignificant (All p > 0.05).

CONCLUSION

This meta-analysis concluded that the cross-sectional area of the median nerve is increased in Parkinson's disease patients. The increase in the CSA of the median nerve might explain the higher prevalence of carpal tunnel syndrome in Parkinson's disease. Further studies are needed to quantify carpal tunnel syndrome prevalence accurately in Parkinson's.

LIMITATIONS

Heterogeneity exists due to non-standardized CSA calculation methods and varied disease stages. Finger movement during ultrasound may introduce artifacts, compromising CSA measurement accuracy. Establishing a definitive CSA cut-off for carpal tunnel syndrome in Parkinson's requires further investigation.

Prevalence and Characteristics of Polyneuropathy in Atypical Parkinsonian Syndromes: An Explorative Study

(1) Background: Peripheral nerve involvement is increasingly recognized in Parkinson's disease (PD). Although non-motor symptoms and postural instability are early features of atypical parkinsonian syndromes (APS), peripheral neuropathies in APS have not been addressed in detail thus far. Therefore, the aim of this study was to investigate the prevalence and characteristics of polyneuropathies (PNP) in multiple system atrophy (MSA) and progressive supranuclear palsy (PSP), as representative syndromes of APS. (2) Methods: In total, 8 MSA and 6 PSP patients were comprehensively analyzed regarding subjective, clinical (motor and non-motor) and paraclinical PNP features using nerve conduction studies and high resolution nerve ultrasounds (HRUS). (3) Results: A total of 87.5% of MSA and 66.7% of PSP patients complained of at least one neuropathic symptom, with electrophysiological confirmation of PNP in 50.0% of both, MSA and PSP patients. PNP symptom severity in PSP and motor nerve amplitude in MSA were associated with compromised motor function. Morphologic nerve examination by HRUS showed few alterations according to the axonal type of PNP. (4) Conclusions: The overall high PNP symptom burden may be partially credited to the significant prevalence of electrophysiologically diagnosed PNP, and impact motor aspects of APS. The findings of this exploratory study reinforce further investigations on a larger scale, in order to elucidate peripheral nerve involvement and the underlying pathophysiological mechanisms of APS.

Signs of sympathetic and endothelial cell activation in the skin of patients with restless legs syndrome

OBJECTIVES

To evaluate skin biopsies of patients with early- and late onset restless legs syndrome (RLS) for concomitant small fiber neuropathy (SFN) and to determine cutaneous sympathetic innervation and microvascularization in comparison to healthy individuals.

METHODS

Density of intraepidermal nerve fibers (IENFD), adrenergic nerve fibers and dermal capillaries was analyzed by immunofluorescence for PGP9.5, tyrosine hydroxylase and endothelial markers CD31 and CD105 in skin biopsies of 11 individuals with RLS and 8 age- and sex-matched controls.

RESULTS

IENFD did not differ between RLS and controls, but two RLS patients with comorbid impaired glucose metabolism fulfilled morphometric criteria of SFN according to published normative values. In contrast, dermal nerve bundles of RLS patients showed an increased density of tyrosine hydroxylase⁺ adrenergic nerve fibers (p < 0.005). Moreover, an increased ratio between immature CD105⁺ and mature CD31⁺ endothelial cells within dermal capillaries was observed in RLS (p < 0.02).

CONCLUSIONS

SFN, as a potential contributing factor for RLS, should be considered in patients with predisposing comorbidities presenting with burning or shooting pain, dysesthesias and impaired sensory and temperature perception. Evidence of an increased adrenergic innervation of the skin in RLS patients is in accordance with sympathetic hyperactivity while signs of endothelial cell activation may reflect an adaptive response to tissue hypoxia.

Association between restless legs syndrome and peripheral neuropathy: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

The coexistence of peripheral neuropathy (PN) and restless legs syndrome (RLS) or Willis-Ekbom disease is relatively frequent, but its prevalence has shown a high variability across studies. In addition, several reports have shown data suggesting the presence of PN in patients with idiopathic RLS.

METHODS

A search was undertaken using the PubMed, Embase and Web of Science Databases, from 1966 to 6 December 2020, crossing the search term 'restless legs syndrome' with 'neuropathy', 'polyneuropathy' (PNP) and 'peripheral neuropathy', and the references of interest for this topic were identified; a meta-analysis was performed, according to PRISMA guidelines, and a calculation of pooled prevalences, where appropriate, was made using standard methods.

RESULTS

Restless legs syndrome has been reported in 5.2%-53.7% of patients with PN (average 21.5%; 95% confidence interval 18.6%-24.5%), and PN has been reported in 0%-87.5% of patients with RLS (average 41.8%; 95% confidence interval 39.9%-43.6%), both being significantly more frequent than in controls. The heterogeneity across studies could be due to differences in the diagnostic criteria used for both RLS and PN. RLS is a frequent clinical complaint in patients with PN of different aetiologies, mainly diabetic PN, uraemic PNP, familial amyloid PNP, Charcot-Marie-Tooth disease and chronic dysimmune inflammatory PNP. Recent neurophysiological findings suggest the presence of small sensory fibre loss in patients diagnosed with idiopathic RLS, but it remains to be determined whether RLS associated with small sensory fibre loss and idiopathic RLS are different clinical entities.

CONCLUSIONS

Future studies including clinical and neurophysiological assessment and skin biopsy involving a large series of patients with PN and RLS are needed for a better understanding of the association between these two entities.

Correlates of polyneuropathy in Parkinson's disease

Objective

Previous studies in Parkinson’s disease (PD) patients have demonstrated a high prevalence of polyneuropathy (PNP) and pronounced alpha‐Synuclein pathology in dermal nerve fibers already at early disease stages. The aim of this study was to analyze associations between the prevalence and severity of PNP with nonmotor and motor symptoms in PD patients.

Methods

Fifty PD patients were characterized comprehensively for the presence of clinical symptoms (nonmotor and motor), electrophysiologic alterations and – for the first time – using high‐resolution ultrasound of peripheral nerves.

Results

Sixty‐two percent of PD patients showed electrophysiological pathology of PNP. The prevalence of patient‐reported PNP symptoms was 86% and was particularly present in patients with longer disease duration, compromised scores of nonmotor and motor symptoms as well as with a negative evaluation of quality of life. Seventy‐five percent of patients showed morphologic alterations similar to axonal PNP in high‐resolution ultrasound compared to healthy controls.

Interpretation

The study demonstrates the high burden of peripheral nervous system disease in Parkinson's disease. It advocates further studies to delineate the underlying pathophysiological mechanisms in order to optimize treatment approaches for PD, including the associated PNP.

Restless Legs Syndrome Among Sudanese Patients With Type 2 Diabetes Mellitus: A Case-Control Study

Background There is increasing awareness about the association of restless legs syndrome (RLS) with type 2 diabetes. This study assessed RLS and its associations among patients with diabetes. Material and methods This case-control study was conducted among 160 subjects (82 patients with diabetes and 78 controls) attending a diabetic clinic in Omdurman, Sudan, during the period from June 2018 to September 2019. A structured questionnaire was used to collect demographic factors, diabetic neuropathy, nephropathy, retinopathy, and macrovascular complications. The neck circumference was measured to assess adiposity, and a blood sample was taken for the glycated hemoglobin (HbA1_c) estimation. The local ethical committee approved the research, and the Statistical Package for Social Sciences (SPSS; IBM Corp., Armonk, NY) was used for data analysis. A P-value of <0.05 was considered significant. Results There were 82 patients with type 2 diabetes and 78 controls matched for age and sex. Restless legs syndrome was higher among patients with diabetes (31.7% vs. 10.3%%) with a significant statistical difference, P-<0.05. A direct positive relationship was found between restless legs syndrome and diabetic neuropathy (Wald=5.48, P-value=0.019, 95%CI 1.70-410.76), no relationship was found between RLS, diabetic retinopathy, glycated hemoglobin, sex, and neck circumference, P-values (0.757, 0.804, 0.317, and 0.361 respectively). Conclusion Restless legs syndrome was prevalent among patients with type 2 diabetes and was more common among patients with diabetic neuropathy, no relationship was found between restless legs syndrome, age, sex, neck circumference, HbA1_c, and retinopathy.

Restless Legs Syndrome across the Lifespan: Symptoms, Pathophysiology, Management and Daily Life Impact of the Different Patterns of Disease Presentation

Restless legs syndrome is a common but still underdiagnosed neurologic disorder, characterized by peculiar symptoms typically occurring in the evening and at night, and resulting in sleep disruption and daily functioning impairment. This disease can affect subjects of all age ranges and of both sexes, manifesting itself with a broad spectrum of severity and deserving special attention in certain patient categories, in order to achieve a correct diagnosis and an effective treatment. The diagnosis of restless legs syndrome can be challenging in some patients, especially children and elderly people, and an effective treatment might be far from being easy to achieve after some years of drug therapy, notably when dopaminergic agents are used. Moreover, the pathophysiology of this disorder offers an interesting example of interaction between genetics and the environment, considering strong iron metabolism involvement and its interaction with recognized individual genetic factors. Therefore, this syndrome allows clinicians to verify how lifespan and time can modify diagnosis and treatment of a neurological disorder.

The heterotetrameric structure of the adenosine A1-dopamine D1 receptor complex: Pharmacological implication for restless legs syndrome

Dopaminergic and purinergic signaling play a pivotal role in neurological diseases associated with motor symptoms, including Parkinson's disease (PD), multiple sclerosis, amyotrophic lateral sclerosis, Huntington disease, Restless Legs Syndrome (RLS), spinal cord injury (SCI), and ataxias. Extracellular dopamine and adenosine exert their functions interacting with specific dopamine (DR) or adenosine (AR) receptors, respectively, expressed on the surface of target cells. These receptors are members of the family A of G protein-coupled receptors (GPCRs), which is the largest protein superfamily in mammalian genomes. GPCRs are target of about 40% of all current marketed drugs, highlighting their importance in clinical medicine. The striatum receives the densest dopamine innervations and contains the highest density of dopamine receptors. The modulatory role of adenosine on dopaminergic transmission depends largely on the existence of antagonistic interactions mediated by specific subtypes of DRs and ARs, the so-called A_2AR-D₂R and A₁R-D₁R interactions. Due to the dopamine/adenosine antagonism in the CNS, it was proposed that ARs and DRs could form heteromers in the neuronal cell surface. Therefore, adenosine can affect dopaminergic signaling through receptor-receptor interactions and by modulations in their shared intracellular pathways in the striatum and spinal cord. In this work we describe the allosteric modulations between GPCR protomers, focusing in those of adenosine and dopamine within the A₁R-D₁R heteromeric complex, which is involved in RLS. We also propose that the knowledge about the intricate allosteric interactions within the A₁R-D₁R heterotetramer, may facilitate the treatment of motor alterations, not only when the dopamine pathway is hyperactivated (RLS, chorea, etc.) but also when motor function is decreased (SCI, aging, PD, etc.).