Welding and brain damage link, Mayo Clinic
Due to ethical concerns, human trials with manganese fume exposure are not conducted. Most information about welding and health hazards is gleaned from animal studies or from analyzing patient cases in which exposure has occurred.
In the Mayo analysis, the researchers examined medical records from eight patients referred to the clinic between 1999 and 2005 for various nervous system complaints. All of their MRI scans showed an area of increased T1 signal intensity in the basal ganglia region of the brain, which appears as a bright spot on the MRI scan and is a biological indicator of manganese accumulation. All were men involved in welding for one to 25 years before symptoms developed. Initial symptoms varied, but multiple symptoms developed over time, including cognitive impairment, headaches and tremor in six of the patients, and balance problems in five patients. Each patient was diagnosed with neurotoxicity from welding fumes after undergoing testing appropriate to the patient's complaints, such as blood and urine testing, brain MRI and psychological testing of intelligence, aptitude and personality traits.
The increased T1 signal in the brains of the eight patients as revealed by MRI is an uncommon finding in brain imaging, according to Keith Josephs, M.D., Mayo Clinic neurologist who spearheaded the analysis. This is the first case series of welders with this abnormal signal highlighting such widespread neurological impairment.
"In the setting of prominent manganese exposure in the environment, as occurred in these otherwise healthy welders, there are no other reasonable explanations than the fume exposure for the damage present in the MRI findings," he says.
Syndromes
Dr. Josephs says previous case reports have linked manganese fumes generated by welding with various symptoms, but none has identified the syndromes or actual diagnoses, except parkinsonism. The syndromes identified in the Mayo Clinic analysis are:
-- Parkinsonian syndrome -- a form of parkinsonism, a group of diseases characterized by tremor, rigidity or stiffness, slow movements and difficulty maintaining balance. This syndrome can look like Parkinson's disease, yet is distinct.
-- Multifocal myoclonus -- lightning-fast twitches that occur all over the body.
-- Vestibular-auditory dysfunction -- problems with balance, hearing or dizziness.
-- Mild cognitive impairment -- concentration impairment characterized by a lack of attention. This is different from the mild cognitive impairment which is a precursor condition to Alzheimer's disease.
Patients also displayed minor symptoms of anxiety, irritability, shakiness and sleep disorder.
Dr. Josephs encourages physicians to think broadly regarding symptoms potentially associated with welding and manganese fume exposure. "When physicians consider welding and manganese exposure, they often think of a symptom known as 'cock walk' -- a staggering, strutting gait. Our analysis shows that symptoms are often more subtle. Damage from manganese exposure is also more common than we think."
Risk Factors
A common factor with all eight welders studied, according to Dr. Josephs, was inadequate fume-protective measures. This provides further evidence that unprotected welding leads to neurological damage.
"An important finding from our case series analysis is that these patients were not only all welders, but all had a lack of ventilation," says Dr. Josephs. "They didn't have a mask or were welding in confined spaces."
Dr. Josephs does not advocate against welding; rather, he encourages prudent safeguards. "Protection is the key ingredient here," he says. "I think that if you have good protection and follow the U.S. Department of Labor's Occupational Safety and Health Administration guidelines for protection while welding, you're probably safe." Further information on these guidelines is available at osha.gov/SLTC/weldingcuttingbrazing/index.html.
Treatment and Long-Term Outcomes
Mayo Clinic physicians treated seven of the eight patients with low-manganese diets and one with chelation therapy with ethylene diamine tetraacetic acid, a crystalline acid therapy designed to bind the acid with the excess metal in the body -- the manganese -- and neutralize the toxic effect.
Dr. Josephs explains, however, that there is no "home run" treatment for manganese neurotoxicity. "We don't have enough evidence that diet is absolutely the way to go; while diet modifications can decrease oral intake of manganese, their manganese exposure is due to another form of intake: inhalation. Chelation therapy has the inherent risk of removing metals important to the body."
Many of the patients studied still had symptoms after they stopped exposing themselves to welding fumes, leading the Mayo neurologists to postulate that the damage invoked by manganese exposure may be permanent. "It seems to be static or progressive, not reversible," says Dr. Josephs. "I think the best option is removal from welding."
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