[Parkinsonism in chronic occupational metallic mercury intoxication]

Parkinson syndrome occurs in the course of chemical intoxication, especially Mn, CS2, CO. It is rarely caused by chronic mercury intoxication. We present the case of 55 year old man who was exposed to metallic mercury vapor during 33 years of working in the chemical plant at the production of chlorine. On several occassions patient was removed from contact with Hg because of the symptoms of increased Hg absorption. At the age of 52 he developed hand tremor, balance and gait disturbance with bradykinesia, paresthesias of the upper extremities, neurobehavioral abnormalities, slight memory loss, and spatial disorientation. Psychoneurological examination revealed dementia, Parkinson's syndrome and ataxia of the lower limbs. Mercury excretion in the urine, which equaled 18.3 mu\g creatinine, confirmed exposure to Hg. MRI of the head revealed cortical and cerebellar atrophy. Electroneurography examination found features of subclinical peripheral sensory axonopathy of the upper limbs. Despite atypical clinical course (parkinsonismus) chronic mercury encephalopathy was diagnosed based on documented occupational exposure and diagnostic test results.