Clinical, physiological and pathological characterisation of the sensory predominant peripheral neuropathy in copper deficiency

U-shaped nonlinear relationship between dietary copper intake and peripheral neuropathy

BACKGROUND

Dietary copper intake is a promising predictor of peripheral neuropathy. There is no research exploring the potential link between dietary copper intake and peripheral neuropathy.

METHODS

The information utilized in our research was collected from the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004. The relationship between dietary copper intake and peripheral neuropathy was analyzed using a multivariate logistic regression model and restricted cubic spline (RCS).

RESULTS

The RCS analysis results showed a U-shaped nonlinear relationship between dietary copper intake and peripheral neuropathy (P for nonlinearity < 0.001). The threshold effect analysis results indicated that when dietary copper intake was less than 0.889 mg/d, the risk of peripheral neuropathy decreased with increasing copper intake (OR: 0.388, 95% CI: 0.200-0.753). When dietary copper intake was ≥ 0.889 mg/d, the risk of peripheral neuropathy increased with increasing copper intake (OR: 1.129, 95% CI: 1.006-1.266). And the incidence rate of peripheral neuropathy in the first quantile (OR: 1.421, 95% CI: 1.143-1.766), the third quantile (OR: 1.358, 95% CI: 1.057-1.744), and the fourth quantile (OR: 1.676, 95% CI: 1.250-2.248) of dietary copper intake were significantly higher than that in the second quantile (where the inflection point was located).

CONCLUSION

Our study suggests that both insufficient and excessive dietary copper intake may be associated with an increased incidence of peripheral neuropathy. However, further research is needed to provide definitive evidence and confirm these findings.

Manganese- and Platinum-Driven Oxidative and Nitrosative Stress in Oxaliplatin-Associated CIPN with Special Reference to Ca4Mn(DPDP)5, MnDPDP and DPDP

Platinum-containing chemotherapeutic drugs are efficacious in many forms of cancer but are dose-restricted by serious side effects, of which peripheral neuropathy induced by oxidative-nitrosative-stress-mediated chain reactions is most disturbing. Recently, hope has been raised regarding the catalytic antioxidants mangafodipir (MnDPDP) and calmangafodipir [Ca4Mn(DPDP)5; PledOx®], which by mimicking mitochondrial manganese superoxide dismutase (MnSOD) may be expected to overcome oxaliplatin-associated chemotherapy-induced peripheral neuropathy (CIPN). Unfortunately, two recent phase III studies (POLAR A and M trials) applying Ca4Mn(DPDP)5 in colorectal cancer (CRC) patients receiving multiple cycles of FOLFOX6 (5-FU + oxaliplatin) failed to demonstrate efficacy. Instead of an anticipated 50% reduction in the incidence of CIPN in patients co-treated with Ca4Mn(DPDP)5, a statistically significant increase of about 50% was seen. The current article deals with confusing differences between early and positive findings with MnDPDP in comparison to the recent findings with Ca4Mn(DPDP)5. The POLAR failure may also reveal important mechanisms behind oxaliplatin-associated CIPN itself. Thus, exacerbated neurotoxicity in patients receiving Ca4Mn(DPDP)5 may be explained by redox interactions between Pt2+ and Mn2+ and subtle oxidative-nitrosative chain reactions. In peripheral sensory nerves, Pt2+ presumably leads to oxidation of the Mn2+ from Ca4Mn(DPDP)5 as well as from Mn2+ in MnSOD and other endogenous sources. Thereafter, Mn3+ may be oxidized by peroxynitrite (ONOO-) into Mn4+, which drives site-specific nitration of tyrosine (Tyr) 34 in the MnSOD enzyme. Conformational changes of MnSOD then lead to the closure of the superoxide (O2•-) access channel. A similar metal-driven nitration of Tyr74 in cytochrome c will cause an irreversible disruption of electron transport. Altogether, these events may uncover important steps in the mechanism behind Pt2+-associated CIPN. There is little doubt that the efficacy of MnDPDP and its therapeutic improved counterpart Ca4Mn(DPDP)5 mainly depends on their MnSOD-mimetic activity when it comes to their potential use as rescue medicines during, e.g., acute myocardial infarction. However, pharmacokinetic considerations suggest that the efficacy of MnDPDP on Pt2+-associated neurotoxicity depends on another action of this drug. Electron paramagnetic resonance (EPR) studies have demonstrated that Pt2+ outcompetes Mn2+ and endogenous Zn2+ in binding to fodipir (DPDP), hence suggesting that the previously reported protective efficacy of MnDPDP against CIPN is a result of chelation and elimination of Pt2+ by DPDP, which in turn suggests that Mn2+ is unnecessary for efficacy when it comes to oxaliplatin-associated CIPN.

Nutritional peripheral neuropathies

Nutritional peripheral neuropathies are a global problem, heavily influenced by geopolitical, cultural and socioeconomic factors. Peripheral neuropathy occurs most frequently secondary to B-vitamin deficiencies, which is suspected to increase in years to come due to the popularity of vegan and vegetarian diets and increased use of bariatric surgery.This review will focus on the common B-vitamins for which a causal link to peripheral neuropathy is more established (vitamins B1, B2, B6, B9 and B12). We will review the historical human and animal data on which much of the clinical descriptions of vitamin deficiencies are based and summarise current available tools for accurately diagnosing a nutritional deficiency. We will also review recently described genetic diseases due to pathogenic variants in genes involved in B-vitamin metabolism that have helped to inform the phenotypes and potential causality of certain B-vitamins in peripheral neuropathy (B2 and B9).Endemic outbreaks of peripheral neuropathy over the last two centuries have been linked to food shortages and nutritional deficiency. These include outbreaks in Jamaican sugar plantation workers in the nineteenth century (Strachan's syndrome), World War two prisoners of war, Cuban endemic neuropathy and also Tanzanian endemic optic neuropathy, which remains a significant public health burden today. An improved understanding of lack of which vitamins cause peripheral neuropathy and how to identify specific deficiencies may lead to prevention of significant and irreversible disability in vulnerable populations.

Approach to diagnosis, evaluation, and treatment of generalized and nonlocal dysesthesia: A review

Dysesthesia is an abnormal sensation in the skin that occurs in the absence of any extraordinary stimulus or other primary cutaneous disorders, excluding any delusions or tactile hallucinations. Clinicians have characterized dysesthesias to include sensations such as burning, tingling, pruritus, allodynia, hyperesthesia, or anesthesia. The etiology and pathogenesis of various generalized dysesthesias is largely unknown, though many dysesthesias have been associated with systemic pathologies including malignancy, infection, autoimmune disorders, and neuropathies. Dermatologists are often the first-line clinicians for patients presenting with such cutaneous findings, thus it is crucial for these physicians to be able to methodically work-up generalized dysesthesias to build a working differential diagnosis, follow up with key labs and/or imaging, and offer patients evidence-based treatment to relieve their symptoms. This broad literature review is an attempt to centralize key studies, cases, and series to help guide dermatologists in their assessment and evaluation of complaints of abnormal cutaneous sensations.

Nutritional Neuropathies

OBJECTIVE

This article reviews the etiologies, presentations, and management of neuropathies related to nutritional deficiencies.

LATEST DEVELOPMENTS

Peripheral neuropathy can be the predominant or only manifestation of certain nutrient deficiencies. Cognitive difficulties or involvement of other parts of the central nervous system, such as the optic nerve and spinal cord, may accompany nutritional peripheral neuropathies. In most patients, the nutritional deficiency may have a single predominant cause, but in some cases, multiple causes may coexist. Obesity, for unclear reasons, can be associated with nutrient deficiencies. The rising rates of bariatric surgery and the incidence of nutrient deficiencies following bariatric surgery make this a particularly relevant topic for neurologists.

ESSENTIAL POINTS

Neuropathies caused by nutrient deficiencies are preventable with appropriate supplementation in high-risk situations. Early recognition and prompt treatment are essential to ensure an optimal outcome and minimize neurologic morbidity.

Composite nerve conduction scores and signs for diagnosis and somatic staging of diabetic polyneuropathy: Mid North American ethnic cohort survey

INTRODUCTION/AIMS

In the Diabetes Control and Complications Trial (DCCT), the minimal nerve conduction (NC) criterion for diabetic sensorimotor polyneuropathy (DSPN) was abnormality of NC in more than one peripheral nerve without specifying the attributes of NCs to be evaluated. In the present study, we assess individual and composite scores of NCs meeting the DCCT criterion and signs for improved diagnosis and assessment of DSPN severity.

METHODS

Evaluated were 13 attributes and 6 composite NC scores and signs and symptoms in 395 healthy subjects (HS) and 388 persons with diabetes (DM).

RESULTS

Percent abnormality between subjects with DM and HS was remarkably different among individual attributes and the six composite NC scores. For diagnosis of DSPN using the DCCT criterion, assessment of conduction velocities (CVs) and distal latencies (DLs) provided sensitive diagnoses of DSPN. NC amplitudes provided stronger measures of severity. In studied cohorts, DSPN was staged: N0, no NC abnormality using NC score 2 (CVs and DLs), 60.0%; N1, NC abnormality only, 18.4%; N2, NC abnormality and signs of feet or legs, 16.3%; and N3, NC abnormality and signs of thighs, 5.3%.

DISCUSSION

For sensitive and standard diagnosis of DSPN using the DCCT NC criterion, specifically defined composite scores of CVs and DLs, e.g., score 2, is recommended. A composite score of amplitudes, e.g., score 4, provides a stronger measure of neuropathy severity. Also, provided are HS reference values of evaluated attributes of NCs and estimates of staged severity of DSPN of mid North American DM cohorts.

Electrophysiologic Characteristics of Nitrous-Oxide-Associated Peripheral Neuropathy: A Retrospective Study of 76 Patients

BACKGROUND AND PURPOSE

The electrophysiologic characteristics of peripheral neuropathy secondary to nitrous oxide (N₂O) abuse remain unclear. The paper therefore aimed to summarize the electrophysiologic characteristics of N₂O-associated peripheral neuropathy and identify the risk factors of severe nerve injury.

METHODS

The electrophysiologic results and clinical data of patients with peripheral neuropathy secondary to N₂O abuse at our hospital between 2018 and 2020 were analyzed retrospectively, and their electrophysiologic changes were summarized.

RESULTS

Most patients exhibited decreased sensory and motor nerve conduction velocities (75% and 76%), decreased sensory nerve and compound motor action potentials (57% and 59%), and prolonged distal motor latency (59%), while a response was absent in 36%. These findings indicate that N₂O abuse can result in generalized injury to sensory and motor nerves. Electrophysiologic results indicated axonal neuropathy in 37 cases (49%), demyelinating peripheral neuropathy in 4 (5%), and mixed neuropathy in 12 (16%). Peripheral nerve injury was more common in the lower limbs (72%) than in the upper limbs (42%, p<0.0001). The upper and lower limbs were primarily affected by sensory nerve demyelination (35%) and motor axonal injury (67%), respectively. Subgroup analysis indicated that longer N₂O exposure and longer disease course were associated with more-severe motor axonal injury in the lower limbs.

CONCLUSIONS

N₂O-associated peripheral neuropathy can lead to sensory and motor nerve injury, with axonal injury being the most common. Injuries were more severe in the lower limbs. Prolonged N₂O exposure and disease course increased the severity of motor axonal injury in the lower limbs.

Current View of Diagnosing Small Fiber Neuropathy

Small fiber neuropathy (SFN) is a disorder of the small myelinated Aδ-fibers and unmyelinated C-fibers [5, 6]. SFN might affect small sensory fibers, autonomic fibers or both, resulting in sensory changes, autonomic dysfunction or combined symptoms [7]. As a consequence, the symptoms are potentially numerous and have a large impact on quality of life [8]. Since diagnostic methods for SFN are numerous and its pathophysiology complex, this extensive review focusses on categorizing all aspects of SFN as disease and its diagnosis. In this review, sensitivity in combination with specificity of different diagnostic methods are described using the areas under the curve. In the end, a diagnostic work-flow is suggested based on different phenotypes of SFN.

Clinical Manifestations of Copper Deficiency: A Case Report and Review of the Literature

BACKGROUND

Copper is a mineral that is absorbed in the stomach, duodenum, and jejunum. Gastric bypass surgery, gastrectomy, and short-bowel syndrome commonly lead to copper malabsorption. Copper deficiency primarily presents with hematological and neurological sequelae, including macrocytic anemia and myelopathy. Although hematological disturbances often correct with copper supplementation, neurological manifestations of copper deficiency may be irreversible. We present the case of copper deficiency secondary to malabsorption and management strategies to prevent irreversible neurological sequelae.

PRESENTATION

A 48-year-old female with a history of hypothyroidism, ischemic stroke, and Crohn's disease, complicated by subtotal colectomy and small-bowel resections, was admitted for fatigue and progressive neurological deficiencies. Her vital signs were stable, and physical examination was remarkable for weakness of both upper and lower extremities, ataxia, and upper extremities paresthesia. Computed tomography scan of the head without contrast was unremarkable. Magnetic resonance imaging enterography revealed a focal area of narrowing of the remaining small bowel. Copper level was low at 39 µg/dL. After 5 days of intravenous replacement using trace element within parenteral nutrition, her copper level corrected to 81 µg/dL. Her ataxia improved after intravenous copper supplementation and did not recur.

CONCLUSIONS

Our patient presented with copper deficiency secondary to malabsoprtion. This case highlights the importance of copper testing in the bariatric surgery population and in patients with short-bowel syndrome. Given the irreversible nature of neurological symptoms when compared with the expense of nutrition supplements, routine copper testing should be considered in patients with malabsorptive states or altered anatomy, regardless of initial presentation.

Peripheral Neuropathies Due to Vitamin and Mineral Deficiencies, Toxins, and Medications

PURPOSE OF REVIEW

Vitamin and mineral deficiencies, neurotoxins, and, particularly, prescription medications, are some of the most common causes of peripheral neuropathy. Recognition and prompt treatment of these neuropathies require a high index of suspicion and an accompanied detailed history. This article provides a comprehensive approach and list of items that must be considered in the setting of new-onset neuropathy.

RECENT FINDINGS

Although many of the neuropathies described in this article have decreased in prevalence in developed countries because of public health interventions and occupational/environmental regulations, new causes for this class of neuropathy continue to be uncovered.

SUMMARY

The peripheral nervous system is susceptible to a broad array of metabolic and toxic abnormalities, which most often lead to a length-dependent sensory-predominant axonal peripheral neuropathy. A careful history accompanied by recognition of multisystem clues can increase recognition of these neuropathies, which is important as many have specific treatments that may either improve the neuropathy or halt its progression.

Nutritional neuropathies

Neuropathies associated with nutritional deficiencies are routinely encountered by the practicing neurologist. Although these neuropathies assume different patterns, most are length-dependent, sensory axonopathies. Cobalamin deficiency neuropathy is the exception, often presenting with a non-length-dependent sensory neuropathy. Patients with cobalamin and copper deficiency neuropathy characteristically have concomitant myelopathy, whereas vitamin E deficiency is uniquely associated with a spinocerebellar syndrome. In contrast to those nutrients for which deficiencies produce neuropathies, pyridoxine toxicity results in a non-length-dependent sensory neuronopathy. Deficiencies occur in the context of malnutrition, malabsorption, increased nutrient loss (such as with dialysis), autoimmune conditions such as pernicious anemia, and with certain drugs that inhibit nutrient absorption. When promptly identified, therapeutic nutrient supplementation may result in stabilization or improvement of these neuropathies.

Recent update on basic mechanisms of spinal cord injury

Spinal cord injury (SCI) is a life-shattering neurological condition that affects between 250,000 and 500,000 individuals each year with an estimated two to three million people worldwide living with an SCI-related disability. The incidence in the USA and Canada is more than that in other countries with motor vehicle accidents being the most common cause, while violence being most common in the developing nations. Its incidence is two- to fivefold higher in males, with a peak in younger adults. Apart from the economic burden associated with medical care costs, SCI predominantly affects a younger adult population. Therefore, the psychological impact of adaptation of an average healthy individual as a paraplegic or quadriplegic with bladder, bowel, or sexual dysfunction in their early life can be devastating. People with SCI are two to five times more likely to die prematurely, with worse survival rates in low- and middle-income countries. This devastating disorder has a complex and multifaceted mechanism. Recently, a lot of research has been published on the restoration of locomotor activity and the therapeutic strategies. Therefore, it is imperative for the treating physicians to understand the complex underlying pathophysiological mechanisms of SCI.