Cognitive Dysfunction Associated with Elemental Mercury Ingestion and Inhalation: A Case Study

Abstract

A 63-year-old man with a history of alcohol dependence ingested elemental mercury as a suicide gesture. Serial abdominal X-rays showed gradual but incomplete clearance of mercury from the colon. Routine chest X-ray showed evidence of punctate radiopaque materials in the lower lobe of the right lung. Blood and urine mercury levels both exceeded thresholds considered to be associated with cognitive dysfunction. Elicited cognitive deficits were most prominent in processing speed, flexibility, and response inhibition. Semantic fluency, visuospatial processing, and recall memory for visual and low-context verbal material were also affected. The deficits may have been attributable primarily to alcohol abuse. Elemental mercury is not readily absorbed from the gastrointestinal tract; however, mercury vapor, which was inhaled inadvertently, readily crosses the blood-brain barrier and is neurotoxic. We argue, therefore, that mercury toxicity is more likely than not to have been a factor contributing to the patient's cognitive dysfunction.

Key words:

• alcohol abuse
• cognitive disorders
• dementia
• mercury
• mercury toxicity

Notes

Note. T1 = first admission for mercury ingestion, T2 = second admission for mercury ingestion, + n = n days following day of admission, NA = not assessed, WNL = within expected limits; laboratory assays in italics reflect abnormal elevations, laboratory assays in bold reflect abnormal low levels; ALP = alkaline phosphatase, BUN = blood urea nitrogen, SGOT = serum glutamic-oxacloacetic transaminase, SGPT = serum glutamate-pyruvate transaminase, T. BILI = total bilirubin, TSH = thyroid stimulating hormone; fL = femtoliters, IU/L = international units per liter, µIU/mL = micro international units per milliliter, mg/24 hr = milligrams per 24 hours, mg/dL = milligrams per deciliter, U/L = units per liter.

WTAR = Wechsler Test of Adult Reading; MMSE = Mini-Mental State Examination; WAIS-III = Wechsler Adult Intelligence Scale—Third Edition; TMT = Trail Making Test; SDMT = Symbol Digit Modalities Test; CDT = Clock Drawing Test, MCST = Modified Card Sorting Test; Stroop = Stroop Color and Word Test; SPE = Sensory-Perceptual Examination; COWA-FAS = Controlled Oral Word Association (letters F, A, S); BNT = Boston Naming Test, ROCFT = Rey-Osterrieth Complex Figure Test; WMS-R = Wechsler Memory Scale-Revised, LM = Logical Memory; HVLT-R = Hopkins Verbal Learning Test-Revised; GDS = Geriatric Depression Scale; FSIQ = Full Scale IQ; WNL = within expected limits.