A Child with Elemental Mercury Poisoning and Unusual Brain MRI Findings

Dementia, epilepsy and polyneuropathy in a mercury-exposed patient: investigation, identification of an obscure source and treatment

We present a patient aged 54 years with early onset of dementia, epilepsy and peripheral polyneuropathy. A mercury intoxication was diagnosed in 2010, chelation therapy with 2,3-dimercaptopropane-1-sulfonate had failed. A source of exposure could not be identified. MRI showed unspecific hyperintense brain lesions in 2015. She was referred for diagnosis and treatment. Neuropsychological testing indicated severe memory loss and nerve conduction speed measurements showed chronic neurogenically changed potentials. Mercury levels in blood and urine and neuron-specific enolase (NSE) were elevated. A detailed patient history revealed a daily application of mercury-containing skin lightening creams for 6 years. Treatment with 2,3-dimercaptosuccinic acid (DMSA) was started, blood mercury levels were falling during treatment. She was discharged with DMSA prescriptions. A renewed MRI revealed unchanged brain lesions. Blood and urine mercury levels and NSE were falling. Memory function had improved qualitatively and quantitatively.

Acute mercury poisoning among children in two provinces of Turkey

Elemental mercury exposure occurs frequently and is potentially a toxic, particularly in children. Children are often attracted to elemental mercury because of its color, density, and tendency to form beads. Clinical manifestations of elemental mercury intoxication vary depending on its form, concentration, route of ingestion, and the duration of exposure. We present data on 179 pediatric cases of elemental mercury poisoning from exposure to mercury in schools in two different provinces of Turkey. Of all patients, 160 children had both touched/played with the mercury and inhaled its vapors, while 26 children had only inhaled the mercury vapor, two children reported having tasted the mercury. The median duration of exposure was 5 min (min 1-max 100), and 11 (6 %) children were exposed to the mercury for more than 24 h at home. More than half of the children (51.9 %) were asymptomatic at admission. Headache was the most common presenting complaint. The results of physical and neurological examinations were normal in 80 (44.6 %) children. Mid-dilated/dilated pupils were the most common neurological abnormality, and this sign was present in 90 (50.2 %) children. Mercury levels were measured in 24-h urine samples daily, and it was shown that the median urinary level of mercury was 29.80 μg/L (min, 2.40 μg/L; max, 4,687 μg/L). A positive correlation was also found between the duration of exposure and urinary mercury levels (r = 0.23, p = 0.001). All patients were followed up for 6 months. On the first follow-up visit performed 1 month after discharge, the neurological examinations of all patients were normal except for those patients with peripheral neuropathy and visual field defects. On the last follow-up visit at the sixth month, only two children still experienced visual field defects. In conclusion, this study is one of the largest case series of mercury intoxication of students in schools. Elemental mercury exposure can be potentially toxic, and its symptomatology is variable, particularly in children. Therefore, school staff and children should be aware of the risk of mercury toxicity. Pediatricians also need to warn parents and children about the hazards of playing with any chemical.

Dose-response relationship between cumulative mercury exposure index and specific uptake ratio in the striatum on Tc-99m TRODAT SPECT

PURPOSE

Tc-99m TRODAT is an agent for dopamine transporters and measuring dopamine innervation of the striatum. An association between Parkinson disease and body burden mercury level has been reported in the scientific published data. The purpose of this study was to investigate the effect of mercury exposure on dopamine transporters in the striatum measured by Tc-99m TRODAT single-photon emission computed tomography (SPECT).

METHOD AND MATERIALS

Study subjects included 17 workers who worked in a lamp factory at risk for mercury vapor exposure and 15 age-matched healthy controls. All subjects received Tc-99m TRODAT SPECT, brain computed tomography scan, and neurologic examinations. Biologic urine mercury levels at the end of a work week were assessed for workers.

RESULTS

There were significant differences in specific uptake ratio (SUR) in the striatum, caudate, and putamen between mercury exposure workers and healthy controls on Tc-99m TRODAT SPECT (all P < 0.001). The results showed a significantly negative correlation between urine and cumulative mercury levels and SUR in the striatum on Tc-99m TRODAT SPECT by Pearson analysis (r = -0.501, P = 0.040; r = -0.563, P = 0.019). After adjusting for age, gender, and body mass index, cumulative mercury exposure index (Cum Hg) was demonstrated to be the statistically significant predictor for SUR in the striatum, caudate, and putamen on Tc-99m TRODAT SPECT by multiple linear regression analysis (β = -0.543, P = 0.018; β = -0.521, P = 0.033; β = -0.465, P = 0.048).

CONCLUSION

Mercury exposure has significantly negative effect on dopamine transporters in the striatum. There is dose-response relationship between cumulative mercury exposure index (Cum Hg) and SUR in the striatum on Tc-99m TRODAT brain SPECT.

Hyperintense lesions in brain MRI after exposure to a mercuric chloride-containing skin whitening cream

Exposure to inorganic mercury (Hg) is a serious problem presenting with a combination of neurological and psychiatric symptoms along with weight loss, pruritus, erythema, arterial hypertension, tachycardia, and renal tubular dysfunction. We report a 4-year-old girl with chronic intoxication of inorganic mercury secondary to the accidental use of an Hg₂Cl₂- and HgCl₂-containing skin whitening cream (urine level of Hg, 41.1 μg/l; reference level, < 25 μg/l). Under treatment with dimercapto-1-propansulficacid, Hg level in the urine raised to 1,175.5 μg/l, neurological deterioration occurred, and brain magnetic resonance imaging (MRI) showed on fluid attenuated inversion recovery sequences new hyperintense lesions in the subcortical white matter. After 4 months, clinical signs and symptoms and brain MRI findings resolved. This is a first case of inorganic mercury poisoning showing hyperintense lesions in brain MRI and confirms earlier cases showing transient deterioration during chelation therapy. Although urinary excretion could be enhanced during chelation therapy, signs and symptoms of intoxication could be worsened.

Electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication

Contrast sensitivity (CS) was evaluated in 41 former workers from a lamp manufacturing plant who were on disability retirement due to exposure to mercury and 14 age-matched controls. The CS was measured monocularly using the sweep visual evoked potential (sVEP) paradigm at 6 spatial frequencies (0.2, 0.8, 2.0, 4.0, 15.0, and 30 cpd). Statistical difference (p<0.05) was found between the controls and the patient right and left eyes for 2.0 and 4.0 cpd. According the results in those spatial frequencies the eyes were classified in best and worst. Statistical differences were found between the controls and the best eyes for 2.0 and 4.0 cpd and for 0.8, 2.0, and 4.0 cpd for their worst eyes. No correlation was found between CS results and the time of exposure (mean=8.9 yr+/-4.1), time away from the mercury source (mean=6.0 yr+/-3.9), urinary mercury level at the time of work (mean=40.6 microg/g+/-36.3) or with the mercury level at the CS measurement time (mean=1.6 microg/g+/-1.1). We show the first evidence of a permanent impairment in CS measured objectively with the sVEP. Our data complement the previous psychophysical works reporting a diffuse impairment in the CS function showing a CS reduction in the low to middle spatial frequencies. In conclusion, non-reversible CS impairment was found in occupational exposure to mercury vapor. We suggest that CS measurement should be included in studies of the mercury effects of occupational exposure.

Psychiatric issues in toxic exposures

Military, occupational, and environmental events can cause toxic injuries that require psychiatric diagnosis and treatment. This article reviews the psychiatric effects of neurotoxins, including nerve gases, ionizing radiation, insecticides, heavy metals, solvents, and other toxic agents. Diagnostic considerations and clinical tests for further evaluation of the numerous psychiatric conditions and symptoms caused by toxic exposures are discussed.