Welding and Parkinsonism

The debate continues over the existence of an association between welding and parkinsonism with two recent articles in Neurology. One report of the findings in eight patients suggests that welding without proper protection contributes to the development of parkinsonism, whereas authors of a literature review say that there is no convincing evidence that welding is a risk factor for the condition. The report describes the findings in eight patients who were career welders and had been referred to the Mayo Clinic for a variety of neurologic complaints. Each had MRI basal ganglia T1 hyperintensity, indicating manganese accumulation within the CNS. Based on their presenting symptoms, the authors recognised a number of different clinical syndromes in the welders, although symptoms such as cognitive impairment, headaches, imbalance and tremor were experienced in most patients. Three of the patients were described as having a parkinsonian syndrome, two had a syndrome of multifocal myoclonus and cognitive impairment, two had vestibular-auditory dysfunction and one had subjective cognitive impairment, anxiety and sleep apnoea. The authors say, "The reason for the heterogeneity of the clinical phenotypes was unclear but may relate to the varied chronicity and intensity of exposure plus other metabolic factors such as the body burden of other metals that share transport and metabolism with manganese." The authors list four findings that suggest welding-related manganese neurotoxicity could be the cause of the symptoms: the MRI T1 basal ganglia hyperintensity in each patient, indicating high levels of manganese in the CNS; overlapping symptoms and signs among the patients; similar clinical features to other reported cases of manganese neurotoxicity; and inadequate ventilation during welding, predisposing the welders to manganese toxicity. In the same issue of Neurology, Dr Jankovic reviews the evidence linking manganese, welding and Parkinson's disease. He says that, "despite attempts linking welding to manganese neurotoxicity, there is little or no evidence that welding fumes contain sufficient amounts of free and soluble manganese to actually enter the blood and brain, strongly arguing against any neurotoxic effects of manganese from welding."An editorial accompanying the articles suggests that the reader should take care to recognise the potential conflicts of interest of experts researching and writing on the topic, as many have been involved on one side or the other of litigation surrounding welding and Parkinson's disease. Reference...