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Classic reports were given by Mena of Chilean miners in 1967 and by Rodier of Morroccan miners in 1955. Workers exposed to Mn have higher average urine and blood levels than unexposed workers, but these tests will not predict disease severity in a particular case. Similarly, abnormalities in the globus pallidus of the brain by MRI study reflect recent exposure to Mn, but are not diagnostic of disease. Neuropsychological testing can identify workers with advanced disease. Symptoms first appear after a chronic exposure of at least several months in duration:
1) Prodromal Phase: evidence of cognitive dysfunction and emotional disturbance begin to occur prior to severe motor and neurological dysfunction; symptoms may include fatigue, anorexia, muscle pain, nervousness, irritability, violent outbursts, insomnia, decreased libido, and labile affect; workers may also report headache, hypersomnia, spasms, weariness of the legs, and arthralgias;
2) Intermediate Phase: compulsive uncontrollable laughter or crying, clumsiness of movement, exaggeration of reflexes in lower limbs, speech disorders, visual hallucinations, excessive sweating, excessive salivation, and confusion;
3) Established Phase: muscular weakness, difficulty in walking, stiffness, impaired speech, mask-like face, increased muscular tone, slow and shuffling gait, micrographia, and resting tremors; the syndrome is indistinguishable from Parkinson's disease; [Sullivan, p. 930-7] Parkinsonism caused by manganese has the following that distinguish it from Parkinson's disease: psychiatric symptoms early in the disease; cock walk; tendency to fall backward; less frequent resting tremor; more frequent dystonia; lack of response to dopaminomimetics; abnormal MRI showing manganese in the pallidum and caudate nucleus; and normal fluorodopa positron emission tomography scan. [IRRST] Characteristic findings of manganese poisoning are poor steadiness of hands, difficulty doing rapid alternating movements, muscular rigidity, and postural instability. [PMID 17096374] Urine and plasma Mn levels are ineffective biomarkers. Blood Mn "may reflect average elevated daily air Mn levels when exposures are on-going and relatively consistent." [PMID 17924418] See "Parkinsonism."
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