A cross sectional study was conducted to investigate the effects of pesticide exposure (organophosphate and carbamate) using nerve conductive velocity, current perception threshold (CPT). Cluster random sampling was employed to recruit 64 paddy farmers and 22 fishermen in June 2006. The duration of pesticide exposure was between (5-20) years. The CPT values were measured using Neurometer CPT/Eagle, on the index finger and the great toe with three neuroselective frequencies range (2000, 250, and 5 Hz). The results showed that at the three different frequencies, the CPT values were significantly elevated among farmers on both the medial and peroneal nerves (P < .002). The measurement of CPT can be used as a biomarker to determine and monitor the effects of organophosphate and carbamate exposure among workers who may have been exposed.
Recent studies have advocated the use of serial nerve conduction studies (NCS) in the electrodiagnosis of Guillain-Barré syndrome (GBS). The current study aims to elucidate when and how frequent NCS can be performed to reflect the disease pathophysiology.
BACKGROUND: The role of endothelial injury and circulating adhesion molecule in the development and progression of diabetic peripheral neuropathy in the long-term has been established previously.
AIMS: To study the effects of short-term glycemic control using insulin and oral hypoglycemic agent therapy (OHA) on the peroneal nerve function and vascular cell adhesion molecule-1 (VCAM-1) and advanced glycation endproducts (AGE) levels in type 2 diabetic patients.
SETTINGS AND DESIGN: A randomized controlled study involving poorly controlled (HbA1c, 7.5%-11%) type 2 diabetic patients attending the endocrinology outpatient center in a tertiary hospital in Kuala Lumpur.
MATERIALS AND METHODS: Twenty-nine patients were randomized to receive insulin (n=15) or OHA (n=14) for 8 weeks. The glycemic variables (HbA1c, fasting plasma glucose [FPG], fructosamine), VCAM-1, serum AGE and the peroneal motor conduction velocity (PMCV) were measured at baseline and at 4-week intervals.
STATISTICAL ANALYSIS USED: Paired 't' test or Kruskal Wallis test; and the unpaired 't' test or Mann-Whitney U test were used for within-group and between-group analyses, respectively. Correlation was analyzed using Spearman's correlation coefficient.
RESULTS: Within-group analysis showed significant progressive improvement in HbA1c at weeks 4 and 8 in the insulin group. The PMCV improved significantly in both groups by week 8, and by week 4 (P = 0.01) in the insulin group. PMCV correlated negatively with VCAM-1 (P = 0.031) and AGE (P = 0.009) at week 8.
CONCLUSION: Aggressive glycemic control with insulin improves the peroneal nerve function within 4 weeks. Improvement in the serum VCAM-1 and AGE levels correlated significantly with improvement in peroneal nerve conduction velocity only in the insulin group.
Study site: Tertiary endocrinology outpatient center in Kuala Lumpur, Malaysia
Diabetic peripheral neuropathy (DPN) is the most common microvascular complication of diabetes that affects approximately half of the diabetic population. Up to 53% of DPN patients experience neuropathic pain, which leads to a reduction in the quality of life and work productivity. Tocotrienols have been shown to possess antioxidant, anti-inflammatory, and neuroprotective properties in preclinical and clinical studies. This study aimed to investigate the effects of tocotrienol-rich vitamin E (Tocovid SuprabioTM) on nerve conduction parameters and serum biomarkers among patients with type 2 diabetes mellitus (T2DM). A total of 88 patients were randomized to receive 200 mg of Tocovid twice daily, or a matching placebo for 12 months. Fasting blood samples were collected for measurements of HbA1c, renal profile, lipid profile, and biomarkers. A nerve conduction study (NCS) was performed on all patients at baseline and subsequently at 2, 6, 12 months. Patients were reassessed after 6 months of washout. After 12 months of supplementation, patients in the Tocovid group exhibited highly significant improvements in conduction velocity (CV) of both median and sural sensory nerves as compared to those in the placebo group. The between-intervention-group differences (treatment effects) in CV were 1.60 m/s (95% CI: 0.70, 2.40) for the median nerve and 2.10 m/s (95% CI: 1.50, 2.90) for the sural nerve. A significant difference in peak velocity (PV) was also observed in the sural nerve (2.10 m/s; 95% CI: 1.00, 3.20) after 12 months. Significant improvements in CV were only observed up to 6 months in the tibial motor nerve, 1.30 m/s (95% CI: 0.60, 2.20). There were no significant changes in serum biomarkers, transforming growth factor beta-1 (TGFβ-1), or vascular endothelial growth factor A (VEGF-A). After 6 months of washout, there were no significant differences from baseline between groups in nerve conduction parameters of all three nerves. Tocovid at 400 mg/day significantly improve tibial motor nerve CV up to 6 months, but median and sural sensory nerve CV in up to 12 months of supplementation. All improvements diminished after 6 months of washout.
Attention has been paid to neurobehavioral effects of occupational and environmental exposures to chemicals such as pesticides, heavy metals and organic solvents. The area of research that includes neurobehavioral methods and effects in occupational and environmental health has been called "Occupational and Environmental Neurology and Behavioral Medicine." The methods, by which early changes in neurological, cognitive and behavioral function can be assessed, include neurobehavioral test battery, neurophysiological methods, questionnaires and structured interview, biochemical markers and imaging techniques. The author presents his observations of neurobehavioral and neurophysiological effects in Tokyo subway sarin poisoning cases as well as in pesticide users (tobacco farmers) in Malaysia in relation to Green Tobacco Sickness (GTS). In sarin cases, a variety effects were observed 6-8 months after exposure, suggesting delayed neurological effects. Studies on pesticide users revealed that organophosphorus and dithiocarbamate affected peripheral nerve conduction and postural balance; subjective symptoms related to GTS were also observed, indicating the effects of nicotine absorbed from wet tobacco leaves. In addition, non-neurological effects of pesticides and other chemicals are presented, in relation to genetic polymorphism and oxidative stress.