March 30, 2006

NeuroScience Insights for Health Care Professionals

The physicians and staff of The Neuroscience Group are providing this physician and provider communication to help you stay abreast of issues and updates in the dynamic field of neurosciences, with the goal of helping you provide better overall healthcare services to your patients.

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Update: Neurological Diseases and Work-Related Factors

Did you know clergy, teachers and hairdressers all have elevated risk for work-related. neurodegenerative diseases? Annual neurodegenerative disease (NDD) deaths in the US are projected to increase significantly. Genetics-related causes are a major focus of current research. However, mounting evidence has linked other contributing factors, such as environmental and occupational factors, with increased incidence of disease and mortality rates. Patients presenting with any neurological complaints or evidence of neurological compromise should be questioned regarding work-related and environmental exposure to suspected neurodegenerative exposures.

The National Institute for Occupational Safety and Health (NIOSH) recently released information linking neurodegenerative diseases with various occupations. Park, et. al. Am. Journal of Industrial Medicine 48:63-77 (2005). Based on death certificate data from 22 states between 1992 and 1998, specific occupations and exposures to pesticides, solvents, oxidative stressors, magnetic fields and welding fumes were evaluated. Elevated mortality odds ratios (MOR) were statistically significant for one-third 26/87 of the occupations hypothesized to have neurodegenerative associations. Those occupations with the largest MORs (greatest statistical risk) were grouped around 4 diagnoses: pre-senile dementia (PSD), Alzheimer’s disease (AD), Parkinson’s disease (PD), and motor neuron disease (MND). Teachers had significantly elevated MOR’s in all four diseases and hairdressers for three of the four. Occupations linked to pre-senile dementia included dentists, non-agricultural graders/sorter and clergy. Occupations linked to Alzheimer’s disease included bank tellers, clergy, aircraft mechanics and hairdressers. Occupations linked to Parkinson’s disease included biological scientists, clergy, religious workers, post-secondary teachers. The highest associations with motor neuron disease included veterinarians, hairdressers, and non-agricultural graders/sorters.

Work-related exposures related to neurodegenerative diseases are linked to pesticides in farming occupations, solvents and oxidative stress, magnetic fields and welding were noted. One of the limitations of this study is that mortality does not address onset of disease, nor does “usual occupation” characterize time course of exposure. NDD occupational risk factors could differ across race and gender. Of importance to primary care providers is the elevated odds ratio for specific occupations. Hairdressers are at increased risk of pre senile dementia, Alzheimer’s disease and motor neuron disease, which may link to exposure to dyes, components in hair care products, solvents. All four NDD elevations were highest among farmers, which may be liked to pesticide exposure. For all 4 NDD outcomes, teachers at all levels had elevated risks. This may be a result of stress and contact with infectious agents. Magnetic field exposure was noted as an issue. Welding and exposure to manganese fumes has been implicated in elevated Parkinson’s disease incidence.

In addition to the usual patient history screening questions, when a patient presents with poorly-defined neurological complaints, integrating pertinent questions regarding occupational and environmental exposures may help in your differential diagnosis. A comprehensive occupational/environmental assessment helps to identify a symptomatic occupational/environmental illness; provides epidemiologic correlation between symptoms and activities/exposures; aids in diagnosis, treatment plan, and counseling and prevention activities. It may also help to determine ways to prevent aggravation of existing injury/illness and assess for synergistic risks.

Pertinent questions to ask include: name of workplace, dates worked, part time vs. fulltime, type of industry, job duties, known health hazards in work place, contact with chemicals, noise, vibration, radiation exposure. Does the spouse have contact with pesticides/asbestos? Other questions to ask- use of personal protective equipment, time off work for health problems, changed jobs for health reasons. Other pertinent questions include symptoms, such as coughing, wheezing, breathing problems, back/extremity pain, sensation disturbances, integument.

Work-related neurodegenerative disease changes are insidious. Solvents are frequently found in the work environment for hairdressers. Solvents are defined by their ability to dissolve other substances, some are chemical reactants (i.e. hair coloring and perm solutions). Hairdressers are at increased risk for PSD, AD and MND. Chronic effects associated with solvents include neurobehavioral dysfunction and peripheral neuropathy, as well as liver disease, renal disease, dermatitis and reproductive disorders. Chronic exposure to carbon disulfide can lead to nervous system effects or peripheral neuropathy, Parkinson’s –like effects, cranial neuropathies and optic neuritis.

A few chemicals to ask about in the patient history include: n-Hexane, methyl chloride, toluene, trichloroethylene and pesticides. N-Hexane is used in thinners, glues and the manufacturing of rubber products. Toxic effects include sensorimotor polyneuropathy. Distal portions of long nerves are most susceptible. A stocking-glove sensory loss is often noted, along with impaired motor function. Methylene chloride is used as a degreaser and an active ingredient in furniture strippers. Acute exposure leads to CNS depression. Toluene is used as a substitute for benzene in many household products, such as inks, aerosol paints and dyes. Long-term exposure can lead to neurobehavioral dysfunction and cerebellar symptoms such as ataxia and poor coordination. Trichloroethylene is used in degreasing operations and can cause trigeminal neuropathy with facial numbness and masseter muscle weakness.

Symptoms are worse in the presence of ethanol, precipitating what is known as “degreaser’s flush”. Pesticides, which have parathion and mevinphos, inhibit acetylcholinesterase, allowing accumulation of acetylcholine at synapses. Signs of exposure include weakness, paralysis, muscle twitching and CNS effects.

Sorting out origins and exposures related to neurodengenerative diseases can be confusing and consume large amounts of office visit time. The specialists at the Neuroscience Group are available to help with these complex patient presentations.

Information Resources

At the work site Material Safety Data Sheets (MSDS) provide information regarding chemical make-up, health hazard data and other pertinent information regarding exposure and treatment.

Websites for further information:

www.epa.gov

www.cdc.gov/niosh/

www.niehs.nih.gov

www.acoem.org

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