Partial conduction blocks in N-hexane neuropathy

Another brick in the wall: is hexane neuropathy a 'nodo-paranodopathy'?

n-Hexane gives cause to one of the most common toxic polyneuropathies seen in poorly ventilated factories. It is a sensory-motor polyneuropathy ending up with axonal degeneration. Nerve biopsy reveals paranodal axonal swelling and secondary myelin retraction in early stages. Myelin retraction imitates demyelination causing focal conduction block and failure before axonal degeneration emerges. This brings to mind the new category of nodo-paranodopathy described first for anti-ganglioside antibody-mediated neuropathies, which can be proved by electrophysiological re-evaluations. We, herein, discuss the clinical and electrophysiological follow-up of three patients with n-hexane neuropathy and remark overlaps with new concept nodo-paranodopathy.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Pulmonary Toxicity Induced by N-Hexane in Wistar Male Rats After Oral Subchronic Exposure

Studies of pulmonary toxicity induced by oral exposure to n-hexane are very few, in contrast to those studying the exposure by inhalation. This research tackles the oral toxic effect of n-hexane solvent on the lungs after subchronic exposure of Wistar male rats at 300, 600, and 1200 mg/kg, respectively, each day for 8 weeks. The pneumotoxicity observed in this study was marked by an immune toxicity in the form of a significant increase in the levels of white blood cells, lymphocytes, granulocytes, and eosinophils, as well as a significant increase in relative and absolute lung weight in both groups treated at the doses of 600 and 1200 mg/kg. n-Hexane also resulted in a significant increase in serum total proteins and acid phosphatase in the 3 doses tested daily for 8 weeks. In addition, we found a significant increase in total protein and a decrease in glutathione at 600 and 1200 mg/kg, in the pulmonary homogenate. Furthermore, the rate of lipid peroxidation increased in the 3 doses tested. Histological findings revealed a pneumonia characterized by bronchopneumonia, fibronecrotic lesions, congestion, hemorrhage, type II pneumocyte hyperplasia, alveolar lesions, bronchial epithelium degradation, and inflammation.

Clinical description of toxic neuropathies

Toxic neuropathy, although rare, is an important consideration in the setting of a known or suspected toxic exposure in the workplace or other environment. This chapter discusses the clinical and electrodiagnostic evaluation of peripheral neuropathies, highlighting findings that direct further workup and may point to specific toxins as etiology. The difficulty of establishing causality of a toxin in relation to peripheral neuropathy is discussed; guidelines for establishing causality are presented. Examples of common industrial toxins are listed, including their typical industrial uses and their mechanisms of action in producing neuropathy. Characteristic clinical presentations of specific toxic neuropathies are highlighted with selected case studies.

Not all neuropathy in diabetes is of diabetic etiology: differential diagnosis of diabetic neuropathy

Diabetic peripheral neuropathy is the most common peripheral neuropathy in the developed world; however, not all patients with diabetes and peripheral nerve disease have a peripheral neuropathy caused by diabetes. Several (although not all) studies have drawn attention to the presence of other potential causes of a neuropathy in individuals with diabetes; 10% to 50% of individuals with diabetes may have an additional potential cause of a peripheral neuropathy and some may have more than one cause. Neurotoxic medications, alcohol abuse, vitamin B(12) deficiency, renal disease, chronic inflammatory demyelinating neuropathy, inherited neuropathy, and vasculitis are the most common additional potential causes of a peripheral neuropathy in these series. The most common disorders in the differential diagnosis of a generalized diabetic peripheral neuropathy are discussed in this article. Prospective studies to investigate the prevalence of other disorders that might be responsible for a peripheral neuropathy in individuals with diabetes are warranted.

Toxic neuropathy due to N-hexane: report of three cases

Chronic exposure to n-hexane is one of the well known causes of peripheral neuropathy. This type of neuropathy is commonly seen among individuals employed in shoe and bag factories with inadequate ventilation. We describe three patients with acute and sub-acute neuropathy following n-hexane exposure via inhalation of glue. All of the patients had history of working in the same place. The results of laboratory examinations were in normal ranges except the electroneuromyographic (ENMG) findings which were showing the neuropathy. All patients were hospitalized and rehabilitation programs were carried out. Symptomatic relief was achieved following this treatment, however the pathologic ENMG findings still persisted.

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed ton-hexane: A preliminary study

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR=?.58, 95% CI=1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.

Toxic neuropathies

Many substances, organic and manufactured, may induce peripheral nerve damage when exposed to them. The expected clinical phenotype is of a distal, sensory or sensorimotor polyneuropathy, often painful, with axonal characteristics on electrodiagnostic and histopathologic analysis. Treatment is limited; often, the only effective management is supportive care and avoidance from or removal of the offending toxin. Fortunately, the majority of toxic neuropathies are self-limited and improves gradually after toxin elimination.

Free and total 2,5-hexanedione in biological monitoring of workers exposed to n-hexane in the shoe industry

OBJECTIVES

To analyse the role of total 2,5-hexanedione (2,5-HD) compared with free 2,5-HD as a biological indicator of exposure to n-hexane at work.

METHODS

One-hundred and thirty two workers in contact with this solvent during their occupation in the shoe industry in the province of Alicante (Spain) were studied. Environmental and biological tests were carried out analysing variations of the concentration of the metabolite in urine corresponding to different working conditions. Environmental exposure was evaluated in each work place using active personal monitors and measured by gas chromatography (GC). Dichloromethane extracts of the urine samples collected at the end of the working shifts were analysed, before (determining free 2,5-HD, the toxic metabolite) and after acid hydrolysis (pH 0.1) (yielding the total 2,5-HD) and also by GC. The concentration of conjugated metabolite 4,5-dihydroxy-2-hexanone was calculated from the difference between total and free 2,5-HD.

RESULTS

Free 2,5-HD represented an average of 14.2% of the total 2,5-HD determined in urine, and this percentage increased significantly (P<0.01) with higher environmental levels of acetone. Other factors, such as absorption through the skin (depending on the use of gloves) and the day on which samples were taken also significantly affected the relation between the two indicators and their respective relationships with environmental concentrations of n-hexane.

CONCLUSION

Although analyses of the relationship between the levels of atmospheric n-hexane and those of metabolites in urine show a greater correlation for total 2,5-HD than for free 2,5-HD, our results suggest that free 2,5-HD could be a better indicator in evaluating risk of exposure to n-hexane, since the concentration is directly related to the neurotoxic effect.