OBJECTIVETo investigate the changes of mercury (Hg) levels in cerebrospinal fluid (CSF) in patients with chronic mercury poisoning and elucidate the neurotoxic mechanism of mercury.

METHODSNine patients with chronic mercury poisoning (poisoning group) as well as eight patients without exposure to mercury were included in this study. Mercury concentrations of 24 hour urine (U-Hg) and CSF (CSF-Hg) were measured with cold-vapor atomic absorption spectrometry-alkali stannous chloride method. The concentration of blood (B-Hg) at the same day was measured with cold-vapor atomic absorption spectrometry-acidic stannous chloride method. In five patients of poisoning group, these concentrations before chelation therapy were compared with those after chelation therapy.

RESULTSThe levels of B-Hg, U-Hg, and CSF-Hg in poisoning group (250.00 +/- 48.54, 160.07 +/- 91.15, 20.22 +/- 10.21 nmol/L, respectively) were significantly higher than those in control group (81.04 +/- 63.01, 24.73 +/- 9.96 nmol/L, undetectable, respectively; P < 0.01). In nine patients of poisoning group, CSF-Hg concentrations were correlated with B-Hg (r = 0.675, P < 0.05), but not U-Hg. After chelation therapy with dimercaptopropane sulfonate in five patients of poisoning group, the levels of B-Hg, U-Hg, and CSF-Hg were decreased significantly (P < 0.05). The reduction of CSF-Hg was not related with B-Hg and U-Hg.

CONCLUSIONCSF-Hg concentration in chronic mercury poisoning patient is increased with the rise of B-Hg, but not U-Hg. When the levels of B-Hg and U-Hg drop to normal, the CSF-Hg level is still high enough to be detected. It indicates that mercury is combined with protein after entering brain and this complex is difficult to cross through blood-cerebral barrier. The complex may cause neuromuscular disorder and fremitus in chronic mercury poisoning.