The epidemiology and risk factors of chronic polyneuropathy

[Diagnostic workup for polyneuropathy]

Polyneuropathy is a disease of the peripheral nervous system that usually results in distally emphasized, often symmetrical sensory and motor stimulation and deficits. These are often extremely painful. They can be divided into hereditary and acquired causes; inflammatory and infectious causes should be further differentiated among the acquired causes. A careful diagnostic workup is essential. Clinical signs and distribution patterns of symptoms can often already provide clues to the underlying aetiology. This review describes this workup, which in addition to the medical history and clinical examination always includes thorough laboratory diagnostics, electrophysiological examination and cerebrospinal fluid diagnostics. In individual cases, further diagnostic steps may be necessary in order to make the correct diagnosis.

Factors correlating to decisions for prescribing pharmacological treatment and referrals in suspected peripheral neuropathy cases in chat consultation-based application

Introduction

Since the COVID-19 pandemic, there has been increasing use ofchat-based telemedicine, including for patients with neuropathy complaints. It is imperative to learn how to effectively use telemedicine. This study describes the characteristics of patients with neuropathy complaints in chat-based telemedicine services in Indonesia and their influence on treatment decisions and referrals.

Methods

This is a retrospective cross-sectional study during the COVID-19 pandemic era (March 2020 to December 2021) using anonymous secondary data from patient chat databases on Indonesian application-based telemedicine services (Halodoc, Alodokter, Good Doctor, and Milvik). We applied bivariate and multivariate analysis.

Results

We obtained 1051 patients with suspected peripheral nerve complaints (4 per 10,000) from a total of 2,199,527 user consultations, with the majority being 40-64 years old females and diabetes mellitus was the leading comorbid (90.7%). Most patients received treatment (90.7%) and only 11.4% patients were referred. Multivariate analysis showed that treatment was more likely to be given by a neurologist (p < 0.01). Chronic symptoms (p < 0.01) and previous laboratory/other tests (p = 0.01) decreased the likelihood of medication prescription. Referrals were more likely to be given to chronic onset (p = 0.02), hypertension and heart disease (p < 0.01), and previous laboratory/other tests (p = 0.02). The opposite was true for age≥65 years, female (p = 0.04), and neurologists or other specialists as responders (p < 0.01).

Conclusion

We identified several factors that influence the treatment decision such as female patients and onset. Meanwhile, age, sex, chronic symptoms, history of hypertension and heart disease, and previous laboratory/other tests may influence the referral decisions. General practitioners were more likely to refer the patients whereas neurologists or other specialists were more likely to give treatment. Chat-based telemedicine services can still be developed in the future to be better.

Interoception, Affect, and Cognition in Older Adults

Interoception is the detection of signals that arise from within the body. Interoceptive sensitivity has been found to be associated with affect and cognition among younger adults, and examination of these relationships in older adult samples is beginning to emerge. Here, we take an exploratory approach to determine how demographic, affective, and cognitive variables relate to interoceptive sensitivity in neurologically normal older adults, aged 60-91 years old. Ninety-one participants completed a comprehensive neuropsychological battery, self-report questionnaires, and a heartbeat counting task to measure interoceptive sensitivity. Our findings revealed several relationships: 1) interoceptive sensitivity was inversely correlated with measures of positive emotionality: participants with higher interoceptive sensitivity tended to have lower levels of positive affect and trait extraversion; 2) interoceptive sensitivity was found to positively correlate with cognition: participants who performed better on the heartbeat-counting task also tended to perform better on a measure of delayed verbal memory; and 3) when examining the predictors of interoceptive sensitivity in a single hierarchical regression model, higher interoceptive sensitivity was related to: higher time estimation, lower positive affect, lower extraversion, and higher verbal memory. In total, the model accounted for 38% of the variability in interoceptive sensitivity (R2 = .38). These results suggest that, among older adults, interoceptive sensitivity is facilitative for aspects of cognition but perhaps disruptive for certain aspects of emotional experience.

[Retrospective Long-Term Results After Dellon's Nerve Decompression In The Lower Leg For Polyneuropathy]

BACKGROUND

Patients affected by polyneuropathy often report pain, paraesthesia and numbness and are at risk of having an increased propensity to fall with the corresponding complications. In case of persistent symptoms after all conservative and medical treatment options have been exhausted, a nerve decompression in the lower leg as described by Dellon can lead to an improvement of the discomfort for many patients. This article presents our long-term results with Dellon's operation.

METHODS

In this retrospective study, we included 33 patients with diabetic or idiopathic polyneuropathy in whom we performed Dellon's nerve decompression in the lower leg in the years 2011-2013. In 29 out of the 33 patients, we investigated the level of pain (according to the numeric rating scale NRS 0-10), paraesthesia, numbness, Hoffman-Tinel sign, and Semmes-Weinstein monofilaments three months postoperatively. 88 months postoperatively (range 78-111 months), we were able to contact 20 of the 33 patients with a questionnaire asking about their present pain level (NRS 0-10), satisfaction with the postoperative result (NRS 0-10, 0=most satisfied, 10=not satisfied at all) and whether the patients would recommend the surgical procedure to their friends or family.

RESULTS

1. Significant pain reduction three months postoperatively, NRS 4.5 to 2.2, (p=0.000). 2. Significant reduction of paraesthesia three months postoperatively from 84.8 to 24.2% (p=0.000) 3. Significant reduction of numbness three months postoperatively from 97% to 39% (p=0.000). 4. Significant improvement of sensitivity three months postoperatively from 91% no sensitivity to 28% no sensitivity (p=0.000). 5. Significant improvement of Hoffmann-Tinel sign three months postoperatively from 76% to 13% (p=0.000). 88 months postoperatively, we saw a significant pain reduction from an average preoperative pain level of NRS 4.5 to a postoperative pain level of 2.7 (p=0.048). 88 months postoperatively, 65% of the patients would recommend the surgical procedure to their family and friends, and patient satisfaction was high (NRS 3,4).

CONCLUSION

Our long-term results show that Dellon's nerve decompression in the lower extremities leads to a marked, lasting pain reduction and a functional improvement.

Nerve Decompression in the Lower Leg Results in an Improvement in Symptoms in Patients With Both Diabetic and Idiopathic Polyneuropathy

BACKGROUND

Patients suffering from polyneuropathy often complain of pain, tingling, and numbness sensations, as well as an increased risk of falling with the corresponding subsequent complications. If symptoms persist after conservative treatment options have been exhausted, nerve decompression in the lower extremity, as described by Dellon, can bring about an improvement in symptoms in many patients. Dellon originally reported that this surgery led to very successful outcomes in patients with diabetic polyneuropathy. In this study, we compare our postsurgical results in patients with diabetic versus idiopathic polyneuropathy.

METHODS

Thirty-three patients with idiopathic or diabetic polyneuropathy who had undergone Dellon nerve decompression in the lower extremity between 2011 and 2013 were included in the retrospective study. Pain (numeric rating scale [NRS] 0-10; 0, no pain; 10, worst imaginable pain), tingling, numbness, Hoffmann-Tinel sign, and Semes-Weinstein monofilament were assessed in 20 patients with diabetic polyneuropathy and in 13 patients with idiopathic polyneuropathy.

RESULTS

Three months after surgery, a significant reduction in pain was evident in patients with diabetic polyneuropathy, from a preoperative level of NRS 4.9 (minimum, 0; maximum, 10) to 2 (minimum, 0; maximum, 8; P = 0.005). Ninety percent of patients complained of tingling ( P = 0.000) before surgery and 18% after surgery, whereas 100% complained of numbness before surgery and 41% ( P = 0.000) after surgery. One hundred percent of patients had no measurable surface sensitivity before surgery (measured with the Semes-Weinstein monofilament), whereas 3 months after surgery, only 24% of patients still had no measurable surface sensitivity ( P = 0.000). A positive Hoffmann-Tinel sign was recorded in 85% of patients before surgery and only in 11% 3 months after surgery ( P = 0.000). In the case of patients with idiopathic polyneuropathy, a reduction in pain was evident 3 months after surgery, from a preoperative level of NRS 3.9 (minimum, 0; maximum, 9) to 2.2 (minimum, 0; maximum, 9; P = 0.058). Seventy-seven percent of patients complained of tingling before surgery and 42% after surgery ( P = 0.111), whereas 92% complained of numbness before surgery and 50% after surgery ( P = 0.030). Seventy-seven percent of patients had no measurable surface sensitivity before surgery (measured with the Semes-Weinstein monofilament), whereas 3 months after surgery, only 33% of patients still had no measurable surface sensitivity ( P = 0.047). A positive Hoffmann-Tinel sign was recorded in 62% of patients before surgery and only in 17% 3 months after surgery ( P = 0.041).

CONCLUSIONS

Not only patients with diabetic polyneuropathy but also those with idiopathic polyneuropathy benefit from Dellon nerve decompression surgery in the lower extremities.

Engineering Neurotoxin-Functionalized Exosomes for Targeted Delivery to the Peripheral Nervous System

The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the blood-nerve barrier (BNB). Therefore, there is a pressing need to enhance delivery effectiveness and implement targeted delivery methods. Recently, erythrocyte-derived exosomes (Exos) have gained widespread attention as biocompatible vehicles for therapeutics in clinical applications. However, engineering targeted Exos for the peripheral nervous system (PNS) is still challenging. This study aims to develop a targeted Exo delivery system specifically designed for presynaptic terminals of peripheral nerve tissue. The clostridium neurotoxin, tetanus toxin-C fragment (TTC), was tethered to the surface of red blood cell (RBC)-derived Exos via a facile and efficient bio-orthogonal click chemistry method without a catalyst. Additionally, Cyanine5 (Cy5), a reactive fluorescent tag, was also conjugated to track Exo movement in both in vitro and in vivo models. Subsequently, Neuro-2a, a mouse neuronal cell line, was treated with dye-labeled Exos with/without TTC in vitro, and the results indicated that TTC-Exos exhibited more efficient accumulation along the soma and axonal circumference, compared to their unmodified counterparts. Further investigation, using a mouse model, revealed that within 72 h of intramuscular administration, engineered TTC-Exos were successfully transported into the neuromuscular junction and sciatic nerve tissues. These results indicated that TTC played a crucial role in the Exo delivery system, improving the affinity to peripheral nerves. These promising results underscore the potential of using targeted Exo carriers to deliver therapeutics for treating peripheral neuropathies.

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

Characteristics of Abnormalities in Somatosensory Submodalities Observed in Residents Exposed to Methylmercury

Hundreds of thousands of people living along the Yatsushiro Sea coast have been exposed to methylmercury from the contaminated water of the Chisso factory in Minamata. The most common neurological disorder caused by methylmercury is somatosensory disturbance, but very few studies have been conducted in the world to determine its pathophysiology and origin, including the Japanese cases, which have produced numerous intoxicated individuals. We have already shown in previous studies the body part where the disorder occurs and that its cause is not peripheral nerve damage but damage to the parietal lobes of the cerebrum. We reanalyzed the results of subjective symptoms, neurological findings, and quantitative sensory measurements in 197 residents (63.2 ± 10.7 years old) from contaminated areas exposed to methylmercury from seafood and 130 residents (63.7 ± 9.3 years old) from control areas, the same subjects as in previous studies, to determine the characteristics of somatosensory disturbance in detail. The most commonly affected sensory modalities were superficial peripheral touch and pain in the extremities, followed by two-point discrimination and deep senses, and in the most severe cases, full-body sensory dysfunction and impairment of all sensory submodalities. The severity of sensory submodalities correlated with each other but not with peripheral nerve conduction test indices, further confirming the correctness of our assertion about the responsible foci of sensory disturbance. The health effects of chronic methylmercury toxicosis can be elucidated by a detailed examination of sensory deficits.

Epidemiology and Functional Impact of Early Peripheral Neuropathy Signs in Older Adults from a General Population

INTRODUCTION

Peripheral neuropathy (PN) becomes more common with increasing life expectancy, but general population prevalence estimates are lacking. We investigated an epidemiological distribution of signs of PN among 2,996 community-dwelling participants in Good Aging in Skåne Study, age 60-97, and their impact on physical and autonomic function.

METHODS

Signs of PN were measured with Utah Early Neuropathy Scale (UENS). Associations between UENS and physical tests, pain, and dysautonomic phenomena were calculated for each sex, adjusted for age, with estimated marginal means (EMM) and odds ratios (ORs) in four UENS quantiles (Q1-Q4).

RESULTS

Participants in Q4 had worse EMM for: time to complete Timed Up and Go test (Q4-Q1: male 10.8-9.6 s; female 11.7-10.2 s), 15 m Walk test (Q4-Q1: male 11.1-9.9 s; female 11.2-10.4 s), and fewer repetitions in Step test (Q4-Q1: male 15.2-17.0 steps; female 14.5-15.8 steps). Higher OR of failing one-leg balance 60 s test {male 2.5 (confidence interval [CI] 95%: 1.7-3.8); female 2.1 (1.1-3.2)}, Foam Pad Balance test (male 4.6 [CI 95%: 3.2-6.7]; female 1.8 [1.3-2.6]), and lower physical quality of life were seen in Q4 compared to Q1. Participants in Q4 had higher OR for walking aid usage, falls, fear of falling, pain, and urinary incontinence, while in males, higher OR for orthostatic intolerance, fecal incontinence, and constipation.

CONCLUSIONS

In a general population, 20-25% of older adults who have highest UENS scores, a sensitive measure of early PN, express slower gait, worse balance, lower quality of life, pain, falls and fear of falling, and autonomic symptoms.

Monotherapy Versus Combination Therapy in the Treatment of Painful Diabetic Neuropathy: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

Painful peripheral neuropathy is a common and challenging complication of diabetes mellitus. Combination therapy is used widely by clinicians, although strong evidence for efficacy and safety is lacking. The goal of this study is to compare the efficacy and safety of combination versus monotherapy of first-line medications for peripheral diabetic neuropathy.

METHODS

PubMed, Embase, Cochrane Central, and clinicaltrials.gov databases were searched on December 5, 2022, for randomized clinical trials comparing combined therapy with gabapentinoids and either tricyclic antidepressants (TCAs) or serotonin and norepinephrine reuptake inhibitors (SNRIs) versus monotherapy with any of these drugs. Pooled mean differences (MD) with a 95% confidence interval (CI) were computed for pain outcomes, measured on an 11-point numeric rating scale averaging pain scores in the last 7 days. Risk ratios (RRs) were computed for binary endpoints. Risk assessment was performed using the Risk of Bias 2 tool.

RESULTS

A total of five randomized studies and 916 patients were included. Follow-up ranged from 6 to 12 weeks. Mean pain reduction was greater for combination therapy than monotherapy (MD - 0.39; 95% CI - 0.67 to - 0.12; p = 0.005). Similarly, there was an improvement in ≥ 30% reduction in average pain (RR 1.16; 95% CI 1.07-1.26; p < 0.01) with combination therapy. In contrast, there was no significant difference between groups in ≥ 50% reduction in average pain (RR 1.21; 95% CI 0.99-1.49; p = 0.06). When comparing combination therapy versus gabapentinoid monotherapy, there was also a significant reduction in average pain (MD - 0.61; 95% CI - 0.85 to - 0.37; p < 0.01) with combination therapy.

CONCLUSION

In patients with painful diabetic peripheral neuropathy, the combination of gabapentinoids with TCAs or SNRIs is associated with a greater reduction in pain as compared with monotherapy, although this difference may not translate into a clinically important difference.

Transdermal Magnesium for the Treatment of Peripheral Neuropathy in Chronic Kidney Disease: A Single-Arm, Open-Label Pilot Study

Introduction: Peripheral neuropathy is common in chronic kidney disease (CKD) and may be multifactorial in origin, resulting from uremia, hyperkalemia, and diabetes. Previous studies have suggested that magnesium plays a crucial role in chronic pain. Studies evaluating magnesium in neuropathy have demonstrated mixed results. Aims: To provide preliminary data on the effectiveness of transdermal magnesium in treating peripheral neuropathy related to CKD. Methods: Twenty participants with advanced CKD were enrolled from a major teaching hospital clinic in Sydney, Australia. Each participant was provided with a spray bottle containing magnesium chloride and instructed to apply five sprays to each limb affected by neuropathy daily for 12 weeks. Participants completed the Neuropathy Total Symptom Score-6 (NTSS-6) every 4 weeks during follow-up. Serum magnesium concentrations were measured at 4-week intervals. Results: Twenty participants were recruited, of which 14 completed the 12-week follow-up period. Mean age was 78.90 years, 80.00% were female and mean estimated glomerular filtration rate was 9.78 mL/min/1.73 m2. With intention to treat analysis (mean [95% confidence interval]), NTSS-6 was significantly reduced at weeks 8 (4.04 [2.43-5.65]) and 12 (4.26 [2.47-6.05]), compared with baseline (6.92 [5.29-8.55]), p < 0.05. Serum magnesium concentration did not change significantly during the study. Conclusion: This pilot study suggests that transdermal magnesium may be beneficial in reducing frequency and severity of peripheral neuropathic symptoms in patients with advanced CKD. Trial Registration: australianclinicaltrials.gov.au. Identifier: ACTRN12621000841875. Date first registered January 7, 2021.

Dorsal Root Ganglion Stimulation in Chronic Painful Polyneuropathy: A Potential Modulator for Small Nerve Fiber Regeneration

OBJECTIVES

Neuromodulatory treatments like spinal cord stimulation and dorsal root ganglion stimulation (DRGS) have emerged as effective treatments to relieve pain in painful polyneuropathy. Animal studies have demonstrated that neurostimulation can enhance nerve regeneration. This study aimed to investigate if DRGS may impact intraepidermal nerve fiber regeneration and sensory nerve function.

MATERIALS AND METHODS

Nine patients with chronic, intractable painful polyneuropathy were recruited. Intraepidermal nerve fiber density (IENFD) quantification in 3 mm punch skin biopsy was performed 1 month before DRGS (placed at the level of the L5 and S1 dorsal root ganglion) and after 12- and 24-month follow-up. Quantitative sensory testing, nerve conduction studies, and a clinical scale score were also performed at the same time points.

RESULTS

In 7 of 9 patients, DRGS was successful (defined as a reduction of ≥ 50% in daytime and/or night-time pain intensity), allowing a definitive implantable pulse generator implantation. The median baseline IENFD among these 7 patients was 1.6 fibers/mm (first and third quartile: 1.2; 4.3) and increased to 2.6 fibers/mm (2.5; 2.9) and 1.9 fibers/mm (1.6; 2.4) at 1- and 2-years follow-up, respectively. These changes were not statistically significant (p = 1.000 and 0.375). Sensory nerve tests did not show substantial changes.

CONCLUSIONS

Although not significant, the results of this study showed that in most of the patients with implants, there was a slight increase of the IENFD at the 1- and 2-year follow-up. Larger-scale clinical trials are warranted to explore the possible role of DRGS in reversing the progressive neurodegeneration over time.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT02435004; Swiss National Clinical Trials Portal: SNCTP000001376.

Towards a practical use of text mining approaches in electrodiagnostic data

Healthcare professionals produce abounding textual data in their daily clinical practice. Text mining can yield valuable insights from unstructured data. Extracting insights from multiple information sources is a major challenge in computational medicine. In this study, our objective was to illustrate how combining text mining techniques with statistical methodologies can yield new insights and contribute to the development of neurological and neuromuscular-related health information. We demonstrate how to utilize and derive knowledge from medical text, identify patient groups with similar diagnostic attributes, and examine differences between groups using demographical data and past medical history (PMH). We conducted a retrospective study for all patients who underwent electrodiagnostic (EDX) evaluation in Israel's Sheba Medical Center between May 2016 and February 2022. The data extracted for each patient included demographic data, test results, and unstructured summary reports. We conducted several analyses, including topic modeling that targeted clinical impressions and topic analysis to reveal age- and sex-related differences. The use of suspected clinical condition text enriched the data and generated additional attributes used to find associations between patients' PMH and the emerging diagnosis topics. We identified 6096 abnormal EMG results, of which 58% (n = 3512) were males. Based on the latent Dirichlet allocation algorithm we identified 25 topics that represent different diagnoses. Sex-related differences emerged in 7 topics, 3 male-associated and 4 female-associated. Brachial plexopathy, myasthenia gravis, and NMJ Disorders showed statistically significant age and sex differences. We extracted keywords related to past medical history (n = 37) and tested them for association with the different topics. Several topics revealed a close association with past medical history, for example, length-dependent symmetric axonal polyneuropathy with diabetes mellitus (DM), length-dependent sensory polyneuropathy with chemotherapy treatments and DM, brachial plexopathy with motor vehicle accidents, myasthenia gravis and NMJ disorders with botulin treatments, and amyotrophic lateral sclerosis with swallowing difficulty. Summarizing visualizations were created to easily grasp the results and facilitate focusing on the main insights. In this study, we demonstrate the efficacy of utilizing advanced computational methods in a corpus of textual data to accelerate clinical research. Additionally, using these methods allows for generating clinical insights, which may aid in the development of a decision-making process in real-life clinical practice.

Diagnostic accuracy of the 5.07 monofilament test for diabetes polyneuropathy: influence of age, sex, neuropathic pain and neuropathy severity

INTRODUCTION

There is a need for simple and cheap diagnostic tools for diabetic polyneuropathy (DPN). We aimed to assess the diagnostic accuracy of the 5.07/10 g monofilament test in patients referred to polyneuropathy assessments, as well as to examine how disease severity, age, sex and neuropathic pain (NP) impact diagnostic accuracy.

RESEARCH DESIGN AND METHODS

Five Norwegian university hospitals recruited patients with diabetes aged 18-70 referred to neurological outpatient clinics for polyneuropathy assessments. The 5.07/10 g Semmes-Weinstein monofilament examination (SWME) was validated against the Toronto consensus for diagnosing diabetic neuropathies; the results were stratified by age, sex and NP. Disease severity was graded by a combined nerve conduction study (NCS) Z-score, and logistic regression was applied to assess whether disease severity was a predictor of diagnostic accuracy.

RESULTS

In total, 506 patients were included in the study. Global sensitivity was 0.60 (95% CI 0.55, 0.66), specificity 0.82 (95% CI 0.75, 0.87), positive and negative predictive values were 0.86 (95% CI 0.81, 0.90) and 0.52 (95% CI 0.46, 0.58), respectively, positive and negative likelihood ratios were 3.28 (95% CI 2.37, 4.53) and 0.49 (95% CI 0.42, 0.57), respectively. The SWME was less sensitive in females (0.43), had lower specificity in patients with NP (0.56), and performed worse in patients ≥50 years. NCS-based disease severity did not affect diagnostic accuracy (OR 1.15, 95% CI 0.95, 1.40).

CONCLUSIONS

This multicenter study demonstrates poor diagnostic performance for the 5.07/10 g SWME in patients with diabetes referred to polyneuropathy assessments; it is particularly unsuited for female patients and those with NP. The diagnostic accuracy of the SWME was not influenced by NCS-based disease severity, demonstrating that it does not perform better in patients with later stages of DPN. We do not recommend the use of the 5.07/10 g monofilament in the evaluation of patients with diabetes referred to polyneuropathy assessments.

Red flags and adjusted suspicion index for distinguishing hereditary transthyretin amyloid polyneuropathy from idiopathic axonal polyneuropathy

BACKGROUND

Early diagnosis of hereditary ATTR polyneuropathy (ATTRv-PN) is important since treatment options have become available, which are most effective early in the disease course. ATTRv-PN is likely underdiagnosed as patients might be misdiagnosed with idiopathic polyneuropathy. It is uncertain if it is useful to test for TTR gene mutations in patients with a typical presentation for chronic idiopathic axonal polyneuropathy (CIAP) and which are the distinguishing clinical features.

METHODS

We carried out a retrospective cohort study to assess the yield of TTR gene sequencing in patients with polyneuropathy and assessed if the identified patients with ATTRv-PN had a clinical presentation typical of CIAP. Additionally, we assessed which clinical features, including previously defined red flag symptoms, can differentiate between patients with CIAP and ATTRv-PN and assessed the performance of the TTR suspicion index.

RESULTS

Out of 338 patients with polyneuropathy, 10 patients had a pathogenic TTR gene mutation (all p.Val50Met) and none had a clinical presentation typical of CIAP. Patients with ATTRv-PN more often had bilateral CTS, motor involvement of arms, cardiac involvement, family history suggestive of hATTRv, and autonomic symptoms than patients with CIAP. All patients with ATTRv-PN as well as 70% of patients with CIAP fulfilled the suspicion index.

CONCLUSION

Routine TTR gene sequencing in patients with a typical presentation for CIAP is not useful. However, red flag symptoms can differentiate patients with ATTRv-PN from patients with CIAP. We propose an adjusted version of the TTR suspicion index to increase diagnostic yield.

Systematic Comparison of Muscle Ultrasound Thickness in Polyneuropathies and Other Neuromuscular Diseases

BACKGROUND

We have aimed to assess whether muscle thickness ultrasound (US) shows differences between patients with chronic inflammatory demyelinating polyneuropathy (CIDP), chronic axonal polyneuropathy (CAP), and other neuromuscular (NM) diseases compared to controls and to each other.

METHODS

We performed a cross-sectional study from September 2021 to June 2022. All subjects underwent quantitative sonographic evaluation of muscle thickness in eight relaxed muscles and four contracted muscles. Differences were assessed using multivariable linear regression, correcting for age and body mass index (BMI).

RESULTS

The study cohort consisted of 65 healthy controls, and 95 patients: 31 with CIDP, 34 with CAP, and 30 with other NM diseases. Both relaxed and contracted muscle thickness in all patient groups were lower than in the healthy controls, after controlling for age and body mass index (BMI). Regression confirmed that the differences persisted between patient groups and healthy controls. Differences between patient groups were not apparent.

CONCLUSION

The current study shows that muscle ultrasound thickness is not specific in NM disorders, but shows a global reduction in thickness compared with healthy controls after corrections for age and BMI.

"PNP slows down" - linearly-reduced whole body joint velocities and altered gait patterns in polyneuropathy

Introduction

Gait disturbances are a common consequence of polyneuropathy (PNP) and a major factor in patients' reduced quality of life. Less is known about the underlying mechanisms of PNP-related altered motor behavior and its distribution across the body. We aimed to capture whole body movements in PNP during a clinically relevant mobility test, i.e., the Timed Up and Go (TUG). We hypothesize that joint velocity profiles across the entire body would enable a deeper understanding of PNP-related movement alterations. This may yield insights into motor control mechanisms responsible for altered gait in PNP.

Methods

20 PNP patients (61 ± 14 years) and a matched healthy control group (CG, 60 ± 15 years) performed TUG at (i) preferred and (ii) fast movement speed, and (iii) while counting backward (dual-task). We recorded TUG duration (s) and extracted gait-related parameters [step time (s), step length (cm), and width (cm)] during the walking sequences of TUG and calculated center of mass (COM) velocity [represents gait speed (cm/s)] and joint velocities (cm/s) (ankles, knees, hips, shoulders, elbows, wrists) with respect to body coordinates during walking; we then derived mean joint velocities and ratios between groups.

Results

Across all TUG conditions, PNP patients moved significantly slower (TUG time, gait speed) with prolonged step time and shorter steps compared to CG. Velocity profiles depend significantly on group designation, TUG condition, and joint. Correlation analysis revealed that joint velocities and gait speed are closely interrelated in individual subjects, with a 0.87 mean velocity ratio between groups.

Discussion

We confirmed a PNP-related slowed gait pattern. Interestingly, joint velocities in the rest of the body measured in body coordinates were in a linear relationship to each other and to COM velocity in space coordinates, despite PNP. Across the whole body, PNP patients reduce, on average, their joint velocities with a factor of 0.87 compared to CG and thus maintain movement patterns in terms of velocity distributions across joints similarly to healthy individuals. This down-scaling of mean absolute joint velocities may be the main source for the altered motor behavior of PNP patients during gait and is due to the poorer quality of their somatosensory information.

Clinical Trial Registration

https://drks.de/search/de, identifier DRKS00016999.

What's New in Neuropathy?

Neuropathic pain presents diagnostic and treatment challenges. Despite recent advances in our understanding of the diagnosis and treatment of neuropathy, much remains to be elucidated. Familiar with neuropathy is the paradox that aberrant nerve signaling causes both sensory loss and pain. Voltage-gated sodium channels play an important role in neuronal electrogenesis and communication among neurons, and their dysregulation leads to hyperexcitability and pain. While numerous validated diagnostic assessment tools are available for neuropathy, patients often experience a diagnostic delay about the cause of their neuropathy. New research is defining more specific types of neuropathy beyond peripheral and central forms. The prevalence of pain varies by type of neuropathy, with chronic idiopathic axonal polyneuropathy associated with the highest proportion of patients experiencing pain. In the majority of types, it exceeds 50%. Gluten neuropathy, a form of peripheral neuropathy, is a new diagnostic consideration. It may require electrochemical conductance testing of hands and feet to test for sudomotor dysfunction. Among those with serologically confirmed gluten sensitivity or celiac disease, gluten neuropathy is a common neurological manifestation and may be addressed at least partially by a gluten-free diet. In Greece, a new neuropathic pain registry was created in 2014 in order to help gather data from real-world neuropathic pain patients. While still in its earliest phase, this registry has already produced demographic and treatment data that suggest suboptimal prescribing and less than recommended use of interventional procedures. Awareness campaigns are underway to encourage more Greek pain clinics to participate in this important registry.

People's experiences living with peripheral neuropathy: a qualitative study

Introduction

Peripheral neuropathy is a neurological disorder characterised by pain, numbness, or tingling due to nerve damage. Peripheral neuropathy is one of the main health issues in Kuwait and is a rising concern which affects a large proportion of the population, therefore the lived experience needs to be explored to identify areas for improvement in care. This qualitative study explored the experiences of people living with peripheral neuropathy in Kuwait.

Methods

Semi-structured interviews were conducted with 25 participants recruited from the Neurology Outpatient Clinic of the Ibn Sina Hospital in Kuwait. The interview questions explored their experiences and understanding of pain along with the impact on their daily life. The interviews were audio recorded, transcribed and translated into English then coded using NVivo 12. Thematic analysis was conducted to identify patterns and themes in the data.

Results

Three major themes were identified including treatment beliefs (perceived effectiveness of treatment and seeking alternative treatments), the barriers to pain management (medication side effects, relationships with healthcare professionals and lack of information and access to healthcare), and the impact on quality of life (impact on work and social, physical, and psychological consequences). Self-efficacy was a key construct and over-arching theme that was discussed in all aspects, which finds reflection in the protection motivation theory.

Discussion

This paper presents the experiences of people living with peripheral neuropathy and highlights there is scope for improvement of current treatments in Kuwait. Self-management strategies are recommended alongside prescribed medication and healthcare professionals are encouraged to use a patient-centered approach. More importantly, information and support on the condition to promote coping strategies and self-efficacy should be adopted to improve quality of life. These findings can be implemented locally and globally to improve the quality of care provided to people living with peripheral neuropathy.

Association of reproductive factors and exogenous hormone use with distal sensory polyneuropathy among postmenopausal women in the United States: results from 1999 to 2004 NHANES

Postmenopausal status is a risk factor for distal sensory polyneuropathy-the most common type of peripheral neuropathy. We aimed to investigate associations between reproductive factors and history of exogenous hormone use with distal sensory polyneuropathy among postmenopausal women in the United States using data from the National Health and Nutrition Examination Survey 1999-2004, and to explore the modifying effects of ethnicity on these associations. We conducted a cross-sectional study among postmenopausal women aged ≥ 40 years. Women with a history of diabetes, stroke, cancer, cardiovascular disease, thyroid disease, liver disease, weak or failing kidneys, or amputation were excluded. Distal sensory polyneuropathy was measured using a 10-g monofilament test, and a questionnaire was used to collect data on reproductive history. Multivariable survey logistic regression was used to test the association between reproductive history variables and distal sensory polyneuropathy. In total, 1144 postmenopausal women aged ≥ 40 years were included. The adjusted odds ratios were 8.13 [95% confidence interval (CI) 1.24-53.28] and 3.18 (95% CI 1.32-7.68) for age at menarche < 11 years and time since menopause > 20 years, respectively, which were positively associated with distal sensory polyneuropathy; adjusted odds ratios were 0.45 for the history of breastfeeding (95% CI 0.21-0.99) and 0.41 for exogenous hormone use (95% CI 0.19-0.87) were negatively associated. Subgroup analysis revealed ethnicity-based heterogeneity in these associations. Age at menarche, time since menopause, breastfeeding, and exogenous hormone use were associated with distal sensory polyneuropathy. Ethnicity significantly modified these associations.

The efficacy of flexor tenotomy to prevent recurrent diabetic foot ulcers (DIAFLEX trial): Study protocol for a randomized controlled trial

Foot ulcers are a frequent and costly problem in people with diabetes mellitus and can lead to amputations. Prevention of these ulcers is therefore of paramount importance. Claw/hammer toe deformities are commonly seen in people with diabetes. These deformities increase the risk of ulcer development specifically at the (tip of) the toe. Percutaneous needle tenotomy of the tendon of the m. flexor digitorum longus (tendon tenotomy) can be used to reduce the severity of claw/hammer toe deformity with the goal to prevent ulcer recurrence. The main objective of this randomized controlled trial is to assess the efficacy of flexor tenotomy to prevent recurrence of toe ulcers in people with diabetes and a history of toe (pre-)ulcers. Additionally, we aim to assess interphalangeal joints (IPJ) and metatarsophalangeal joint (MTPJ) angles in a weight-bearing and non-weight-bearing position, barefoot plantar pressure during walking, cost-effectiveness and quality of life before and after the intervention and compare intervention and control study groups. Sixty-six subjects with diabetes and claw/hammer toe deformity and a recent history of (pre-)ulceration on the tip of the toe will be included and randomized between flexor tenotomy of claw/hammer toes (intervention) versus standard of care including orthosis and shoe offloading (controls) in a mono-center randomized controlled trial.

Clinicaltrialsgov registration

NCT05228340.

In situ delivery of a curcumin-loaded dynamic hydrogel for the treatment of chronic peripheral neuropathy

Patients with peripheral nerve injuries would highly likely suffer from chronic neuropathic pain even after surgical intervention. The primary reasons for this involve sustained neuroinflammatory and dysfunctional changes in the nervous system after the nerve injury. We previously reported an injectable boronic ester-based hydrogel with inherent antioxidative and nerve protective properties. Herein, we first explored the anti-neuroinflammatory effects of Curcumin on primary sensory neurons and activated macrophages in vitro. Next, we incorporated thiolated Curcumin-Pluronic F-127 micelles (Cur-M) into our boronic ester-based hydrogel to develop an injectable hydrogel that serves as sustained curcumin release system (Gel-Cur-M). By orthotopically injecting the Gel-Cur-M to sciatic nerves of mice with chronic constriction injuries, we found that the bioactive components could remain on the nerves for at least 21 days. In addition, the Gel-Cur-M exhibited superior functions compared to Gel and Cur-M alone, which includes ameliorating hyperalgesia while simultaneously improving locomotor and muscular functions after the nerve injury. This could stem from in situ anti-inflammation, antioxidation, and nerve protection. Furthermore, the Gel-Cur-M also showed extended beneficial effects for preventing the overexpression of TRPV1 as well as microglial activation in the lumbar dorsal root ganglion and spinal cord, respectively, which also contributed to its analgesic effects. The underlying mechanism may involve the suppression of CC chemokine ligand-2 and colony-stimulating factor-1 in the injured sensory neurons. Overall, this study suggests that orthotopic injection of the Gel-Cur-M is a promising therapeutic strategy that especially benefits patients with peripheral neuropathy who require surgical interventions.

Local Inflammatory Mediators Involved in Neuropathic Pain

Polyneuropathy (PNP) is a term to describe diseases of the peripheral nervous system, 50% of which present with neuropathic pain. In some types of PNP, pain is restricted to the skin distally in the leg, suggesting a local regulatory process leading to pain. In this study, we proposed a pro-inflammatory pathway mediated by NF-κB that might be involved in the development of pain in patients with painful PNP. To test this hypothesis, we have collected nerve and skin samples from patients with different etiologies and levels of pain. We performed RT-qPCR to analyze the gene expression of the proposed inflammatory pathway components in sural nerve and in distal and proximal skin samples. In sural nerve, we showed a correlation of TLR4 and TNFα to neuropathic pain, and an upregulation of TNFα in patients with severe pain. Patients with an inflammatory PNP also presented a lower expression of TRPV1 and SIRT1. In distal skin, we found a reduced expression of TLR4 and miR-146-5p, in comparison to proximal skin. Our findings thus support our hypothesis of local inflammatory processes involved in pain in PNP, and further show disturbed anti-inflammatory pathways involving TRPV1 and SIRT1 in inflammatory PNP.

A prospective case-control study of excessive fragmentary myoclonus in the upper and lower extremities: Clinical characteristics and electrophysiological correlates

BACKGROUND

Excessive fragmentary myoclonus (EFM) is an incidental finding in video-polysomnography (VPSG) and listed among "Sleep Related Movement Disorders - Isolated symptoms and normal variants" in the ICSD-3. We aimed to prospectively evaluate EFM in the upper and lower extremities in a large sleep laboratory cohort and to investigate clinical characteristics and peripheral nerve pathology in patients with and without EFM.

METHODS

Two-hundred consecutive sleep laboratory patients with EFM according to ICSD-3 criteria were included and matched to 100 patients without EFM for age, sex and presence or absence of sleep-related breathing disorder. Patients additionally underwent peripheral neurophysiological work-up.

RESULTS

In 31/200 (15.5%) patients EFM was present not only in the lower extremities, but also in the upper extremities. Patients with EFM had less REM sleep (%/SPT; median (IQR); 13.8 (9.1-18.2) vs. 17.1 (10.1-20.5); p = 0.008) and the PLMS-Index was higher in patients with EFM than in those without (16.2 vs. 8.8/h; p = 0.009). Polyneuropathy (PNP) and nerve root lesions L5 and S1 were more frequent in patients with than in those without EFM (31.5% vs. 21% and 5% vs. 0%; p = 0.003).

CONCLUSIONS

In this large cohort we systematically investigated upper and lower extremities with surface electromyography during sleep and show that EFM is much more frequent in the lower extremities than in the upper extremities and corroborate the association of EFM with peripheral nerve pathology and PLMS.

Prevalence and associated factors with peripheral neuropathies in the general population in the rural area of Adjohoun in Benin

BACKGROUND

Peripheral neuropathies (PN) are a group of neurological conditions related to damage to the peripheral nervous system. Due to their wide diversity, few studies in sub-Saharan Africa have explored their epidemiology in general population. Our objective was to study the prevalence and associated factors with PN in general population in Adjohoun in Benin.

METHODS

A cross-sectional study has been conducted from February to March 2019 and included people aged ≥ 18 years old living in Adjohoun, Benin. Following a screening phase for PN (using World Health Organization questionnaire for major neurological diseases), a neurologist made a diagnosis after in-depth clinical examinations completed in some cases by electroneuromyography. The EFNS (European Federation of Neurological Societies) 2010 criteria was used for chronic inflammatory demyelinating polyneuropathy diagnosis. Data such as age, occupation, consanguinity, alcohol consumption, diabetes, hypertension were collected. Association between independent variables and PN were investigated using multivariable logistic regression models.

RESULTS

In total, 1 655 participants were included, mean age 41.4 ± 16.7 years; 64.8 % are female. The overall prevalence of PN was 6.9 % (95 %CI: 5.7 %-8.2 %). The main types of PN were: polyneuropathies 4.8 % (95 %CI: 3.8 %-5.9 %); polyradiculoneuropathies 1.6 % (95 %CI: 1.0 %-2.2 %). Factors independently associated with PN were age ≥ 40 years (adjusted Odds Ratio aOR = 19.6; 95 %CI: 8.2-46.3), diabetes (aOR = 1.8; 95 %CI: 1.08-2.99) and hypertension (aOR = 1.6; 95 %CI: 1.02-2.5).

CONCLUSION

The prevalence of PN was high in the rural commune of Adjohoun in Benin. Actions on its modifiable associated factors such as diabetes and hypertension could help reduce the proportion of PN and their potential harmful consequences.

Sex differences in neuromuscular disorders

The prevalence, onset, pathophysiology, and clinical course of many neuromuscular disorders (NMDs) may significantly differ between males and females. Some NMDs are more frequently observed in females, and characterized to show a higher grade of severity during or after the pregnancy. Meanwhile, others tend to have an earlier onset in males and exhibit a more variable progression. Prevalently, sex differences in NMDs have a familiar character given from genetic inheritance. However, they may also influence clinical presentation and disease severity of acquired NMD forms, and are represented by both hormonal and genetic factors. Consequently, to shed light on the distinctive role of biological factors in the different clinical phenotypes, we summarize in this review the sex related differences and their distinctive biological roles emerging from the current literature in both acquired and inherited NMDs.

The Relationship between Numbness and Quality of Life

BACKGROUND

Numbness is a term commonly used in clinical practice to describe an abnormal sensory experience that is produced by a stimulus or is present even without a stimulus. However, there is still much that remains obscure in this field, and also, few reports have focused on its symptoms. In addition, while pain itself is known to have a significant impact on quality of life (QOL), the relationship between numbness and QOL is often unclear. Therefore, we conducted an epidemiological survey and analyzed the relationship between painless numbness and QOL, using type, location, and age as influencing factors, respectively.

METHODS

A nationwide epidemiological survey was conducted by mail using a survey panel designed by the Nippon Research Center. Questionnaires were sent to 10,000 randomly selected people aged 18 and over from all over Japan. Out of the 5682 people who responded, the relationship between numbness and QOL was analyzed using the EuroQol 5 Dimension-3L (EQ5D-3L) for patients who are currently experiencing painless numbness.

FINDINGS

The results suggest that painless numbness affects QOL and that QOL decreases as its intensity increases. Furthermore, the two factors of numbness of feet and numbness among the young may be less likely to affect QOL. This study may be of great significance in the field of numbness research.

Peripheral Neuropathy and Vision and Hearing Impairment in US Adults With and Without Diabetes

We aimed to assess the associations of peripheral neuropathy (PN) with vision and hearing impairment among adults aged ≥40 years who attended the lower-extremity disease exam for the National Health and Nutrition Examination Survey (United States, 1999-2004). Overall, 11.8% (standard error (SE), 0.5) of adults had diabetes, 13.2% (SE, 0.5) had PN (26.6% (SE, 1.4) with diabetes, 11.4% (SE, 0.5) without diabetes), 1.6% (SE, 0.1) had vision impairment, and 15.4% (SE, 1.1) had hearing impairment. The prevalence of vision impairment was 3.89% (95% CI: 2.99, 5.05) among adults with PN and 1.29% (95% CI: 1.04, 1.60) among adults without PN (P < 0.001). After adjustment, PN was associated with vision impairment overall (odds ratio (OR) = 1.48, 95% confidence interval (CI): 1.03, 2.13) and among adults without diabetes (OR = 1.80, 95% CI: 1.17, 2.77) but not among adults with diabetes (P for interaction = 0.018). The prevalence of hearing impairment was 26.5% (95% CI: 20.4, 33.7) among adults with PN and 14.2% (95% CI: 12.4, 16.3) among adults without PN (P < 0.001). The association of PN with moderate/severe hearing impairment was significant overall (OR = 2.55, 95% CI: 1.40, 4.64) and among adults without diabetes (OR = 3.26, 95% CI: 1.80, 5.91). Overall, these findings suggest an association between peripheral and audiovisual sensory impairment that is unrelated to diabetes.

Pattern and implications of neurological examination findings in autosomal dominant Alzheimer disease

INTRODUCTION

As knowledge about neurological examination findings in autosomal dominant Alzheimer disease (ADAD) is incomplete, we aimed to determine the frequency and significance of neurological examination findings in ADAD.

METHODS

Frequencies of neurological examination findings were compared between symptomatic mutation carriers and non mutation carriers from the Dominantly Inherited Alzheimer Network (DIAN) to define AD neurological examination findings. AD neurological examination findings were analyzed regarding frequency, association with and predictive value regarding cognitive decline, and association with brain atrophy in symptomatic mutation carriers.

RESULTS

AD neurological examination findings included abnormal deep tendon reflexes, gait disturbance, pathological cranial nerve examination findings, tremor, abnormal finger to nose and heel to shin testing, and compromised motor strength. The frequency of AD neurological examination findings was 65.1%. Cross-sectionally, mutation carriers with AD neurological examination findings showed a more than two-fold faster cognitive decline and had greater parieto-temporal atrophy, including hippocampal atrophy. Longitudinally, AD neurological examination findings predicted a significantly greater decline over time.

DISCUSSION

ADAD features a distinct pattern of neurological examination findings that is useful to estimate prognosis and may inform clinical care and therapeutic trial designs.

Environmental risk factors of incident distal sensorimotor polyneuropathy: Results from the prospective population-based KORA F4/FF4 study

Distal sensorimotor polyneuropathy (DSPN) is a common condition in older populations with high prevalence of obesity and type 2 diabetes. We hypothesised that the risk of DSPN is increased by multiple ubiquitous environmental risk factors, particularly in people with obesity. This study was based on 423 individuals aged 62-81 years without DSPN who participated in the population-based Cooperative Health Research in the Region of Augsburg (KORA) F4 survey (2006-2008) in Southern Germany. During 6.5 years of follow-up, 188 participants developed clinical DSPN as assessed by the Michigan Neuropathy Screening Instrument. Environmental exposures, including air temperature, surrounding greenness (assessed with the normalized difference vegetation index [NDVI]), long-term road traffic noise and air pollution, were assessed at participants' residences. The cumulative risk index (CRI) evaluated the joint effects of co-occurring exposures on DSPN risk based on effect estimates from multi-exposure Poisson regression models. The models were adjusted for age, sex, height, waist circumference, smoking, alcohol consumption, physical activity, education and neighbourhood socioeconomic status. In the entire cohort, the co-occurrence of an interquartile range (IQR) decrease in temperature of the warm season and NDVI in a 100-m buffer and of an IQR increase in night-time average traffic noise and in annual average particle number concentration (PNC) was positively associated with incident DSPN (CRI [95 % CI] 1.39 [1.02, 1.91]). Effect estimates for exposure combinations were generally higher in individuals with obesity (CRI 1.34-2.01) than in those without obesity (CRI 0.90-1.33). The four-exposure model showed a twofold increased risk of DSPN among obese (CRI [95 % CI] 2.01 [1.10, 3.67]), but not among non-obese individuals (CRI [95 % CI] 1.18 [0.83, 1.67]). Thus, ubiquitous environmental exposures jointly augment the risk of DSPN in the older population. Lower air temperature in the warm season, less greenness, and higher noise levels and ultrafine particle concentrations identified people with obesity as a particularly vulnerable subgroup.

Diagnostic yield of nerve biopsy in the evaluation of peripheral neuropathies

BACKGROUND

With progress made in neurogenetics and neuroinflammation, the indications and value of nerve biopsies in the diagnostic evaluation of peripheral neuropathies are less clear. In this study, we aimed to evaluate the diagnostic yield of nerve biopsies in patients with peripheral neuropathies.

METHODS

We performed a retrospective review of nerve biopsy reports from April 1998 to June 2021 of patients with peripheral neuropathies presenting to the Department of Pathology, University of Malaya Medical Centre, Kuala Lumpur, Malaysia. The diagnostic value of the biopsies was determined based on the criteria by Midroni and Bilbao as follows: contributive (essential and helpful), non-contributive and inadequate.

RESULTS

A total of 107 nerve biopsies were analysed. Sixty-four (60 %) were males and the mean age was 52 years, ranging from 13 to 86 years. Ninety-four (88 %) were sural nerve biopsies; and only one patient (1 %) each had superficial peroneal and superficial radial nerve biopsy. The indications for the procedure were vasculitis (34 %), peripheral neuropathy of unknown aetiology (34 %), amyloidosis (14 %) and chronic inflammatory demyelinating polyneuropathy (10 %). In 68 (63 %) biopsies, the diagnostic value was contributive. Of these, 28 (26 %) were essential and 40 (37 %) were helpful. In contrast, 35 (33 %) biopsies were non-contributive and 4 (4 %) were inadequate. In 66 % (71/107) of cases, the nerve biopsy did not reveal a definite pathological diagnosis. However, in the remainder, a diagnosis of vasculitis (18 %, 19/107), followed by amyloidosis (10 %, 11/107) could be determined. For 32/71 biopsies with undetermined pathological diagnosis, neuropathy remained cryptogenic in 22 % (7/32) upon follow up.

CONCLUSIONS

With the exception of vasculitis and amyloidosis, there is limited value in performing nerve biopsies in the evaluation of patients with peripheral neuropathy. However, this should be interpreted with caution as the number of patients with a clinical diagnosis of vasculitis and amyloidosis were relatively larger than patients with other diagnosis. Refinement and careful selection of cases are required to increase the diagnostic yield of nerve biopsy.

Association Between Breastfeeding and Reduced Distal Sensory Polyneuropathy in Postmenopausal Women Aged 40-70 Years: Analysis of Data from the 1999-2004 National Health and Nutrition Examination Survey

Background: Distal sensory polyneuropathy (DSP) is a common peripheral neuropathy subtype. We aimed to determine the association between breastfeeding and DSP among postmenopausal women aged 40-70 years, and the effect modification of obesity on this association. Methods: A cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey 1999-2004. Postmenopausal women aged 40-70 years were included. Women with diabetes, stroke, cancer, cardiovascular disease, thyroid disease, liver disease, weak/failing kidneys, or amputation were excluded. Binary logistic regression was used to analyze the association between breastfeeding and DSP. Results: Among 798 participants, 386 (44.30%) reported breastfeeding history and 51 (5.29%) were defined as having DSP using the monofilament test. A significant inverse association was observed between breastfeeding and DSP (odds ratio [OR] = 0.29; 95% confidence interval [CI]: 0.11-0.79; p = 0.017) after adjusting for other confounding variables. In subgroup analysis, this adjusted association was observed only in the obese group (OR = 0.21; 95% CI: 0.06-0.73, p = 0.013). Conclusions: Breastfeeding was found to have potential benefits in the presence of DSP in postmenopausal women aged 40-70 years, and obesity modified the association between breastfeeding and DSP. Promoting breastfeeding may reduce the burden of peripheral neuropathy in middle-aged postmenopausal women.

Types and Concentrations of Blood-Based Biomarkers in Adults With Peripheral Neuropathies: A Systematic Review and Meta-analysis

Importance

Peripheral neuropathies are common conditions and can result in numbness, paresthesia, motor deficits, and pain. There is increasing evidence for the use of biomarkers as clinical indicators of the presence, severity, and prognosis of nerve lesions; however, biomarker identification has largely been focused on disorders of the central nervous system, and less is known about their role in the peripheral nervous system.

Objective

To assess blood-based biomarker concentrations associated with nerve involvement in patients with peripheral neuropathy compared with control participants.

Data Sources

Ovid, MEDLINE, Embase, and CINAHL were searched from inception to September 23, 2021.

Study Selection

Observational studies reporting on blood biomarkers in patients diagnosed with peripheral neuropathy were included. This review was preregistered on PROSPERO and followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. Data were abstracted by 1 investigator and independently reviewed by a second.

Data Extraction and Synthesis

Data were meta-analyzed when at least 2 studies reported the same biomarker with comparable methodology. Fixed-effects models were used when only 2 studies were included; random-effects models were used when more than 2 studies were included.

Main Outcomes and Measures

The outcome of interest was concentration of biomarkers.

Results

This review included 36 studies reporting on 4414 participants, including 2113 control participants and 2301 patients with peripheral neuropathy with 13 distinct peripheral neuropathy diagnoses. Diabetic neuropathy was the most common neuropathy diagnosis (13 studies), followed by Charcot-Marie-Tooth disease (6 studies) and Guillain-Barre syndrome (6 studies). Overall, 16 different blood-based biomarkers associated with nerve involvement were evaluated. The most used were neurofilament light chain, S100B, brain-derived neurotrophic factor, and neuron-specific enolase. Patients with peripheral neuropathy demonstrated significantly higher levels of neurofilament light chain compared with controls (standardized mean difference [SMD], 0.93 [95% CI, 0.82 to 1.05]; P < .001). There were no significant differences in levels of S100B (SMD, 1.10 [95% CI, -3.08 to 5.28]; P = .38), brain-derived neurotrophic factor (SMD, -0.52 [95% CI, -2.23 to 1.19]; P = .40), or neuron-specific enolase (SMD, -0.00 [95% CI, -1.99 to 1.98]; P = .10) in patients with peripheral neuropathy compared with control participants.

Conclusions and Relevance

The findings of this systematic review and meta-analysis support the use of neurofilament light chain as a blood-based measure associated with the presence of neuronal injury in patients with peripheral neuropathy.

Towards Substitution of Hexane as Extraction Solvent of Food Products and Ingredients with No Regrets

Hexane is a solvent used extensively in the food industry for the extraction of various products such as vegetable oils, fats, flavours, fragrances, colour additives or other bioactive ingredients. As it is classified as a "processing aid", it does not have to be declared on the label under current legislation. Therefore, although traces of hexane may be found in final products, especially in processed products, its presence is not known to consumers. However, hexane, and in particular the n-hexane isomer, has been shown to be neurotoxic to humans and has even been listed as a cause of occupational diseases in several European countries since the 1970s. In order to support the European strategy for a toxic-free environment (and toxic-free food), it seemed important to collect scientific information on this substance by reviewing the available literature. This review contains valuable information on the nature and origin of the solvent hexane, its applications in the food industry, its toxicological evaluation and possible alternatives for the extraction of natural products. Numerous publications have investigated the toxicity of hexane, and several studies have demonstrated the presence of its toxic metabolite 2,5-hexanedione (2,5-HD) in the urine of the general, non-occupationally exposed population. Surprisingly, a tolerable daily intake (TDI) has apparently never been established by any food safety authority. Since hexane residues are undoubtedly found in various foods, it seems more than necessary to clearly assess the risks associated with this hidden exposure. A clear indication on food packaging and better information on the toxicity of hexane could encourage the industry to switch towards one of the numerous other alternative extraction methods already developed.

Polyneuropathy Associated with IgM Monoclonal Gammopathy; Advances in Genetics and Treatment, Focusing on Anti-MAG Antibodies

With increasing age, the chances of developing either MGUS or polyneuropathy increase as well. In some cases, there is a causative relationship between the IgM M-protein and polyneuropathy. In approximately half of these cases, IgM targets the myelin-associated glycoprotein (MAG). This results in chronic polyneuropathy with slowly progressive, predominantly sensory neurological deficits and distally demyelinating features in nerve conduction studies. Despite the disease being chronic and developing slowly, it can cause considerable impairment. We reviewed English medical publications between 1980 and May 2022 on IgM gammopathy-associated polyneuropathy, with special attention to studies addressing the pathophysiology or treatment of anti-MAG polyneuropathy. Treatment options have been limited to a temporizing effect of intravenous immunoglobulins in some patients and a more sustained effect of rituximab but in only 30 to 55 percent of patients. An increase in our knowledge concerning genetic mutations, particularly the MYD88L265P mutation, led to the development of novel targeted treatment options such as BTK inhibitors. Similarly, due to the increasing knowledge of the pathophysiology of anti-MAG polyneuropathy, new treatment options are emerging. Since anti-MAG polyneuropathy is a rare disease with diverse symptomatology, large trials with good outcome measures are a challenge.

Obesity-Associated Neuropathy: Recent Preclinical Studies and Proposed Mechanisms

Significance: The prevalence of metabolic syndrome (MetS) and associated obesity has increased in recent years, affecting millions worldwide. One of the most common complications of obesity is damage to the peripheral nerve system, referred to as neuropathy. The lack of disease-modifying therapy for this complication is largely due to a poor understanding of the complex neurobiology underlying neuropathy. Recent preclinical studies suggest that in addition to glucotoxic events, other mechanisms, including lipid signaling, microbiome, or inflammation, may be viable targets to prevent nerve damage and neuropathic pain in obesity. Recent Advances: Clinical and preclinical studies using diet-induced obesity rodent models have identified novel interventions that improve neuropathy. Notably, mechanistic studies suggest that lipid, calcium signaling, and inflammation are converging pathways. Critical Issues: In this review, we focus on interventions and their mechanisms that are shown to ameliorate neuropathy in MetS obese models, including: (i) inhibition of a sensory neuron population, (ii), modification of dietary components, (iii) activation of nuclear and mitochondrial lipid pathways, (iv) exercise, and (v) modulation of gut microbiome composition and their metabolites. Future Directions: These past years, novel research increased our knowledge about neuropathy in obesity and discovered the involvement of nonglucose signaling. More studies are necessary to uncover the interplay between complex metabolic pathways in the peripheral nerve system of obese individuals. Further mechanistic studies in preclinical models and humans are crucial to create single- or multitarget interventions for this complex disease implying complex metabolic phenotyping. Antioxid. Redox Signal. 37, 597-612.

Peripheral neuropathy: A neglected cause of disability in COPD - A narrative review

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory syndrome with systemic involvement leading to various cardiovascular, metabolic, and neurological comorbidities. It is well known that conditions associated with oxygen deprivation and metabolic disturbance are associated with polyneuropathy, but current data regarding the relationship between COPD and peripheral nervous system pathology is limited. This review summarizes the available data on the association between COPD and polyneuropathy, including possible pathophysiological mechanisms such as the role of hypoxia, proinflammatory state, and smoking in nerve damage; the role of cardiovascular and metabolic comorbidities, as well as the diagnostic methods and screening tools for identifying polyneuropathy. Furthermore, it outlines the available options for managing and preventing polyneuropathy in COPD patients. Overall, current data suggest that optimal screening strategies to diagnose polyneuropathy early should be implemented in COPD patients due to their relatively common association and the additional burden of polyneuropathy on quality of life.

Prevalence and predictors of neurological manifestations in systemic AL amyloidosis

INTRODUCTION

Immunoglobulin light chain (AL) amyloidosis is a life-threatening systemic disease due to plasma cell dyscrasias, which is characterized by amyloid deposition in various tissues. Neurological manifestations, in particular peripheral nervous system involvement, play a major role for quality of life and treatment decisions as frequently potentially neurotoxic drugs are used.

METHODS

We retrospectively investigated the prevalence of neurological manifestations, its risk factors and prognostic value in 155 consecutive patients with AL amyloidosis in a single German tertiary center between 2010 and 2021. Multiple logistic regression was performed to identify predictors of amyloid neuropathy and the impact of peripheral neuropathy on patient survival was assessed by Cox proportional hazard regression analysis.

RESULTS

Nearly half of patients showed at least one of four neurological manifestations of AL amyloidosis which were frequent in our study: peripheral neuropathy (36.8%), carpal tunnel syndrome (12.9%), lumbar spinal stenosis (7.1%), and amyloid myopathy (3.9%). Male sex (OR 2.943, CI 1.152-8.139, p = 0.029) and cardiac involvement (OR 6.186, CI 1.449-43.38, p = 0.028) were independent predictors of peripheral neuropathy which was closely related to autonomic dysfunction in patients with AL amyloidosis. Peripheral neuropathy had no impact on survival (HR 0.952, CI 0.517-1.754, p = 0.876).

CONCLUSIONS

Neurological involvement is common in systemic AL amyloidosis. Treatment decisions should take into account peripheral neuropathy, in particular in male patients with amyloid cardiomyopathy, but also amyloid myopathy that seems to be not as rare as previously suggested.

A Bibliometric Analysis of Leprosy during 2000-2021 from Web of Science Database

In recent years, after the essential elimination of leprosy (the prevalence of which is <1/100,000), the trends, research hotpots, and frontiers of leprosy research are not clear. This study provides a detailed overview of leprosy in terms of papers, journal, language, year, citations, h-index, author keywords, institution, and country through bibliometrics. The results are as follows: (1) The publication rate has increased in recent years, and 8892 papers were obtained. Most of the publications are in English, and the subject categories are mainly focused on “Dermatology.” The “leprosy review” published the most significant number of papers on leprosy, followed by “Plos Neglected Tropical Disease” and “International Journal of Leprosy and Other Mycobacterial Diseases.” (2) Leprosy-related research was contributed to by 24,672 authors, and the ten authors with the most significant number of publications were identified. (3) The University of London (including the London School of Hygiene and Tropical Medicine) has the highest h-index, and Fundacao Oswaldo Cruz is the most productive institution. (4) Brazil, India, the United States, the United Kingdom, and the Netherlands are the most productive countries, and the collaborative network reveals that they have established close cooperation with other countries. France has the highest average number of citations. (5) The keyword co-occurrence network identifies five highly relevant clusters representing topical issues in leprosy research (public health, leprosy vaccine, immune mechanisms, treatment, and genomics research). Overall, these results provide valuable insights for scholars, research institutions, and policymakers to better understand developments in the field of leprosy.

Epidemiology of chronic inflammatory demyelinating polyradiculoneuropathy in The Netherlands

BACKGROUND AND AIMS

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a rare but disabling disorder that often requires long-term immunomodulatory treatment. Background incidence rates and prevalence and risk factors for developing CIDP are still poorly defined. In the current study, we used a longitudinal population-based cohort study in The Netherlands to assess these rates and demographic factors and comorbidity associated with CIDP.

METHODS

We determined the incidence rate and prevalence of CIDP between 2008-2017 and the occurrence of potential risk factors in a retrospective Dutch cohort study using the Integrated Primary Care Information (IPCI) database. Cases were defined as CIDP if the diagnosis of CIDP was described in the electronic medical file.

RESULTS

In a source population of 928,030 persons with a contributing follow-up of 3,525,686 person-years, we identified 65 patients diagnosed with CIDP. The overall incidence rate was 0.68 per 100,000 person-years (95% CI 0.45-0.99). The overall prevalence was 7.00 per 100,000 individuals (95% CI 5.41-8.93). The overall incidence rate was higher in men compared to woman (IRR 3.00, 95% CI 1.27-7.11), and higher in elderly of 50 years or older compared to people <50 years of age (IRR 17 95% CI 4-73). Twenty percent of CIDP cases had DM and 9% a co-existing other autoimmune disease.

INTERPRETATION

These background rates are important to monitor changes in the frequency of CIDP following infectious disease outbreaks identify potential risk factors, and to estimate the social and economic burden of CIDP.

Associations of Lower Extremity Peripheral Nerve Impairment and Risk of Dementia in Black and White Older Adults

BACKGROUND AND OBJECTIVES

Peripheral nerve impairments and dementia are common among older adults and share risk factors. However, few studies have examined whether peripheral nerve function and dementia are associated. We evaluated whether lower extremity peripheral nerve impairments were associated with higher incidence of dementia and whether associations differed by comorbidity subgroups (diabetes, low vitamin B12, and APOE ε4 allele carriers).

METHODS

We studied Black and White Health, Aging, and Body Composition Study participants 70 to 79 years of age and without dementia at enrollment. Lower extremity sensory and motor peripheral nerve function was measured at year 4 (the analytic baseline of this study). Sensory nerve impairments were measured with monofilament (1.4 g, 10 g) and vibration threshold of the toe. Monofilament insensitivity was defined as unable to detect monofilament (3 of 4 touches), and vibration detection impairment was defined as >130 μm. Fibular motor impairments were defined as <1 mV compound motor action potential (CMAP) amplitude and slow nerve conduction velocity <40 m/s. Incident dementia over the following 11 years was determined from medical records, cognitive scores, and medications. Cox proportional hazard models adjusted for demographics and health conditions assessed associations of nerve impairments with incident dementia.

RESULTS

Among 2,174 participants (52% women, 35% Black), 45% could not detect monofilament 1.4 g, 9% could not detect monofilament 10 g, 6% could not feel vibration, 10% had low CMAP amplitude, and 24% had slow conduction velocity. Monofilament 10 g (hazard ratio [HR] 1.35, 95% CI 0.99-1.84) and vibration detection insensitivity (HR 1.73, 95% CI 1.24-2.40) were associated/borderline associated with a higher risk of dementia after covariate adjustment. Estimates were elevated but not significant for monofilament 1.4 g, CMAP amplitude, and conduction velocity (p > 0.05). Increasing number of peripheral nerve impairments was associated with higher risk of dementia in a graded fashion; for ≥3 impairments, the HR was 2.37 (95% CI 1.29-4.38). In subgroup analyses, effect estimates were generally higher among those with diabetes, low vitamin B12, and APOE ε4 allele except for vibration detection.

DISCUSSION

Peripheral nerve impairments, especially sensory, were associated with a higher risk of dementia even after adjustment for age and other health factors. These associations may represent a shared susceptibility to nervous system degeneration.

Peripheral Neuropathies Derived from COVID-19: New Perspectives for Treatment

Peripheral neuropathies constitute a group of disorders affecting the peripheral nervous system. Neuropathies have multiple causes such as infections (i.e., COVID-19), diabetes, and nutritional (low vitamin levels), among others. Many micronutrients, such as vitamins (A, C, D, E, B6, B12, and folate), certain minerals (Fe, Mg, Zn, Se, and Cu), and ω-3 fatty acids have immunomodulatory effects. Therefore, they may play an instrumental role in the treatment of COVID-19 infection. However, many COVID-19 patients can undergo neuropathy. In this context, there is a wealth of information on a variety of first-, second-, and third-line treatment options. This review focuses on the application of nutraceutical strategies in order to improve the symptomatology of neuropathy and neuropathic pain in patients that suffered from COVID-19. Our aim is to provide an alternative vision to traditional medical-pharmacological treatment through nutraceuticals.

Comparison of diabetic and idiopathic sensory polyneuropathies with respect to nerve fibre affection and risk factors

Background and purpose

Chronic distal sensory or sensorimotor polyneuropathy is the most common pattern of polyneuropathy. The cause of this pattern is most often diabetes or unknown. This cross-sectional study is one of the first studies to compare the demographics, cardiovascular risk factors and clinical characteristics of diabetic polyneuropathy (DPN) with idiopathic polyneuropathy (IPN).

Methods

Patients with DPN were included from a sample of 389 patients with type 2 diabetes mellitus (T2DM) enrolled from a national cohort of patients with recently diagnosed T2DM (Danish Centre for Strategic Research in Type 2 Diabetes cohort). Patients with IPN were included from a regional cohort of patients with symptoms of polyneuropathy referred for workup at a combined secondary and tertiary neurological centre (database cohort).

Results

A total of 214 patients with DPN were compared with a total of 88 patients with IPN. Patients with DPN were older (67.4 vs 59 years) and had a longer duration of neuropathy symptoms. Patients with DPN had greater body mass index (32 vs 27.4 kg/m²) and waist circumference (110 cm vs 97 cm); higher frequency of hypertension diagnosis (72.9% vs 30.7%); lower total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels; and a higher prevalence of use of statins (81.8% vs 19.3%). DPN was associated with a slightly higher autonomic score and total score on the Neuropathy Symptom Score; lower frequency of hyperalgesia, allodynia and decreased vibration on quantitative sensory testing; lower intraepidermal nerve fibre density count and higher frequency of small-fibre neuropathy.

Conclusion

DPN and IPN showed clear differences in neuropathy characteristics, indicating that these two entities are to be regarded as aetiologically and pathogenetically distinct.

Genetic evidence for the most common risk factors of chronic axonal polyneuropathy in the general population

Background and purpose

Chronic axonal polyneuropathy is a common disease, but the etiology remains only partially understood. Previous etiologic studies have identified clinical risk factors, but genetic evidence supporting causality between these factors and polyneuropathy are largely lacking. In this study, we investigate whether there is a genetic association of clinically established important risk factors (diabetes, body mass index [BMI], vitamin B12 levels, and alcohol intake) with chronic axonal polyneuropathy.

Methods

This study was performed within the population‐based Rotterdam Study and included 1565 participants (median age = 73.6 years, interquartile range = 64.6–78.8, 53.5% female), of whom 215 participants (13.7%) had polyneuropathy. Polygenic scores (PGSs) for diabetes, BMI, vitamin B12 levels, and alcohol intake were calculated at multiple significance thresholds based on published genome‐wide association studies.

Results

Higher PGSs of diabetes, BMI, and alcohol intake were associated with higher prevalence of chronic axonal polyneuropathy, whereas higher PGS of vitamin B12 levels was associated with lower prevalence of polyneuropathy. These effects were most pronounced for PGSs with lenient significance thresholds for diabetes and BMI (odds ratio [OR]_{diabetes, p < 1.0} = 1.21, 95% confidence interval [CI] = 1.05–1.39 and OR_{BMI, p < 1.0} = 1.21, 95% CI = 1.04–1.41) and for the strictest significance thresholds for vitamin B12 level and alcohol intake (OR _{vitamin B12, p < 5e‐6} = 0.79, 95% CI = 0.68–0.92 and OR_{alcohol, p < 5e‐8} = 1.17, 95% CI = 1.02–1.35). We did not find an association between different PGSs and sural sensory nerve action potential amplitude, nor between individual lead variants of PGS_p < 5e‐8 and polyneuropathy.

Conclusions

This study provides evidence for polygenic associations of diabetes, BMI, vitamin B12 level, and alcohol intake with chronic axonal polyneuropathy. This supports the hypothesis of causal associations between well‐known clinical risk factors and polyneuropathy.

LXR agonist improves peripheral neuropathy and modifies PNS immune cells in aged mice

Background

Peripheral neuropathy is a common and progressive disorder in the elderly that interferes with daily activities. It is of importance to find efficient treatments to treat or delay this age-related neurodegeneration. Silencing macrophages by reducing foamy macrophages showed significant improvement of age-related degenerative changes in peripheral nerves of aged mice. We previously demonstrated that activation of the cholesterol sensor Liver X receptor (LXR) with the potent agonist, GW3965, alleviates pain in a diet-induced obesity model. We sought to test whether LXR activation may improve neuropathy in aged mice.

Methods

21-month-old mice were treated with GW3965 (25 mg/Kg body weight) for 3 months while testing for mechanical allodynia and thermal hyperalgesia. At termination, flow cytometry was used to profile dorsal root ganglia and sciatic nerve cells. Immune cells were sorted and analyzed for cholesterol and gene expression. Nerve fibers of the skin from the paws were analyzed. Some human sural nerves were also evaluated. Comparisons were made using either t test or one-way ANOVA.

Results

Treatment with GW3965 prevented the development of mechanical hypersensitivity and thermal hyperalgesia over time in aged mice. We also observed change in polarization and cholesterol content of sciatic nerve macrophages accompanied by a significant increase in nerve fibers of the skin.

Conclusions

These results suggest that activation of the LXR may delay the PNS aging by modifying nerve-immune cell lipid content. Our study provides new potential targets to treat or delay neuropathy during aging.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02423-z.

Long-term association of pregnancy and maternal brain structure: the Rotterdam Study

The peripartum period is the highest risk interval for the onset or exacerbation of psychiatric illness in women’s lives. Notably, pregnancy and childbirth have been associated with short-term structural and functional changes in the maternal human brain. Yet the long-term effects of pregnancy on maternal brain structure remain unknown. We investigated a large population-based cohort to examine the association between parity and brain structure. In total, 2,835 women (mean age 65.2 years; all free from dementia, stroke, and cortical brain infarcts) from the Rotterdam Study underwent magnetic resonance imaging (1.5 T) between 2005 and 2015. Associations of parity with global and lobar brain tissue volumes, white matter microstructure, and markers of vascular brain disease were examined using regression models. We found that parity was associated with a larger global gray matter volume (β = 0.14, 95% CI = 0.09–0.19), a finding that persisted following adjustment for sociodemographic factors. A non-significant dose-dependent relationship was observed between a higher number of childbirths and larger gray matter volume. The gray matter volume association with parity was globally proportional across lobes. No associations were found regarding white matter volume or integrity, nor with markers of cerebral small vessel disease. The current findings suggest that pregnancy and childbirth are associated with robust long-term changes in brain structure involving a larger global gray matter volume that persists for decades. Future studies are warranted to further investigate the mechanism and physiological relevance of these differences in brain morphology.

The additional diagnostic value of motor nerve excitability testing in chronic axonal neuropathy

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Nerve excitability testing was correlated with conventional nerve conduction studies.

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Nerve excitability testing was similar in patients with and without neuropathy and normal nerve conduction.

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There is no support for the potential additional diagnostic value of nerve excitability testing in mixed etiology neuropathy.

Objective

To explore potential differences in motor nerve excitability testing (NET) variables at group levels between patients with a clinical diagnosis of polyneuropathy (PNP), which did not fulfil diagnostic criteria of conventional nerve conduction studies (NCS) and patients without polyneuropathy. Such differences could support a role for NET in increasing the diagnostic sensitivity of NCS in chronic axonal PNP.

Methods

Motor NET was performed using the median nerve in patients with a clinical suspicion of PNP in addition to conventional NCS, skin biopsies, corneal confocal microscopy and structured clinical evaluation including scoring of neuropathy symptoms and signs.

Results

Of the 57 patients included, 32 had PNP, half of which had NCS, which fulfilled criteria for PNP (NCS+ PNP). There were no significant differences for any of the NET variables between PNP patients with non-diagnostic conventional NCS (NCS− PNP) and patients without PNP. Rheobase was increased, and Ted (undershoot) and subexcitability were decreased in NCS+ PNP. Sural amplitude, peroneal nerve F-wave latency and tibial nerve F-wave-latency were correlated with subexcitability, and tibial nerve motor amplitude was correlated with rheobase.

Conclusions

NET was correlated with conventional NCS and no differences were found between NCS− PNP patients and patients without PNP.

Significance

NET does not seem to offer any additional diagnostic value in chronic mixed etiology neuropathy.

Genome-Wide Association Study of 2,093 Cases With Idiopathic Polyneuropathy and 445,256 Controls Identifies First Susceptibility Loci

Background: About one third of patients with chronic polyneuropathy have no obvious underlying etiology and are classified as having idiopathic polyneuropathy. The lack of knowledge about pathomechanisms and predisposing factors limits the development of effective prevention and treatment for these patients. We report the first genome-wide association study (GWAS) of idiopathic polyneuropathy.

Methods: Cases with idiopathic polyneuropathy and healthy controls were identified by linkage to hospital records. We performed genome-wide association studies using genetic data from two large population-based health studies, the Trøndelag Health Study (HUNT, 1,147 cases and 62,204 controls) and UK Biobank (UKB, 946 cases and 383,052 controls). In a two-stage analysis design, we first treated HUNT as a discovery cohort and UK Biobank as a replication cohort. Secondly, we combined the two studies in a meta-analysis. Downstream analyses included genetic correlation to other traits and diseases. We specifically examined previously reported risk loci, and genes known to cause hereditary polyneuropathy.

Results: No replicable risk loci were identified in the discovery-replication stage, in line with the limited predicted power of this approach. When combined in a meta-analysis, two independent loci reached statistical significance (rs7294354 in B4GALNT3, P-value 4.51 × 10⁻⁸) and (rs147738081 near NR5A2, P-value 4.75 × 10⁻⁸). Idiopathic polyneuropathy genetically correlated with several anthropometric measures, most pronounced for height, and with several pain-related traits.

Conclusions: In this first GWAS of idiopathic polyneuropathy we identify two risk-loci that indicate possible pathogenetic mechanisms. Future collaborative efforts are needed to replicate and expand on these findings.