Iron and manganese-related CNS toxicity: mechanisms, diagnosis and treatment

INTRODUCTION

Iron (Fe) and manganese (Mn) are essential nutrients for humans. They act as cofactors for a variety of enzymes. In the central nervous system (CNS), these two metals are involved in diverse neurological activities. Dyshomeostasis may interfere with the critical enzymatic activities, hence altering the neurophysiological status and resulting in neurological diseases. Areas covered: In this review, the authors cover the molecular mechanisms of Fe/Mn-induced toxicity and neurological diseases, as well as the diagnosis and potential treatment. Given that both Fe and Mn are abundant in the earth crust, nutritional deficiency is rare. In this review the authors focus on the neurological disorders associated with Mn and Fe overload. Expert commentary: Oxidative stress and mitochondrial dysfunction are the primary molecular mechanism that mediates Fe/Mn-induced neurotoxicity. Although increased Fe or Mn concentrations have been found in brain of patients, it remains controversial whether the elevated metal amounts are the primary cause or secondary consequence of neurological diseases. Currently, treatments are far from satisfactory, although chelation therapy can significantly decrease brain Fe and Mn levels. Studies to determine the primary cause and establish the molecular mechanism of toxicity may help to adapt more comprehensive and satisfactory treatments in the future.

Association of MRI T1 relaxation time with neuropsychological test performance in manganese- exposed welders

This study examines the results of neuropsychological testing of 26 active welders and 17 similar controls and their relationship to welders' shortened MRI T1 relaxation time, indicative of increased brain manganese (Mn) accumulation. Welders were exposed to Mn for an average duration of 12.25 years to average levels of Mn in air of 0.11±0.05mg/m3. Welders scored significantly worse than controls on Fruit Naming and the Parallel Lines test of graphomotor tremor. Welders had shorter MRI T1 relaxation times than controls in the globus pallidus, substantia nigra, caudate nucleus, and the anterior prefrontal lobe. 63% of the variation in MRI T1 relaxation times was accounted for by exposure group. In welders, lower relaxation times in the caudate nucleus and substantia nigra were associated with lower neuropsychological test performance on tests of verbal fluency (Fruit Naming), verbal learning, memory, and perseveration (WHO-UCLA AVLT). Results indicate that verbal function may be one of the first cognitive domains affected by brain Mn deposition in welders as reflected by MRI T1 relaxation times.

[Encephalopathy caused by intravenous potassium permanganate used for illegal production of methcathinone (ephedrone) from medicines containing pseudoephedrine]

Encephalopathy caused by manganese compounds used for illicit production of ephedrone (methcathinone) is described. The onset of disease could be observed after some months of regular intravenous use of ephedrone contaminated with manganese. In clinical picture dominate neurological signs and symptoms, mainly extrapyramidal syndromes: parkinsonism, tremor, muscle distonia, pro- and retropulsion. Some other symptoms may be observed: hypophonia or dysarthria, gain disturbances, impairment of precise movement, and micrographia. In cranial NMR often appears bilaterally an increase of an intensity of T1 signal in globus pallidus and in some other brain structures. Elimination of manganese with the use of chelating therapy as well as symptomatic treatment, mainly with the antyparkinsonic drugs, seems to be ineffective.

Repeated simultaneous cortical electrophysiological and behavioral recording in rats exposed to manganese-containing nanoparticles

Male Wistar rats wearing chronically implanted cortical electrodes were exposed to Mn-containing nanoparticles via the airways for 8 weeks following a 2-week pre-exposure period. The rats' cortical electrical activity and open field motility was recorded simultaneously, in weekly repetitions. It was supposed that this technique can provide better insight in the development of Mn-induced CNS damage. Decreased motility (less distance covered, longer periods of immobility) and increased total power of cortical electrical activity developed in parallel in the first 4-5 weeks of treatment but showed little change afterwards. Both the behavioral and the electrophysiological effect were in fair correlation with the rats' internal Mn exposure determined from brain samples. The results confirmed the non-linear dose- and time-dependence of Mn effects suggested by previous studies. Repeated simultaneous behavioral and electrophysiological recording during a longer treatment with neurotoxic metals (or other xenobiotics) seems to be a promising method.

Tremor, olfactory and motor changes in Italian adolescents exposed to historical ferro-manganese emission

BACKGROUND AND OBJECTIVE

Increased prevalence of Parkinsonism was observed in Valcamonica, Italy, a region impacted by ferroalloy plants emissions containing manganese and other metals for a century until 2001. The aim of this study was to assess neurobehavioral functions in adolescents from the impacted region and the reference area of Garda Lake.

METHODS

Adolescents age 11-14 years were recruited through the school system for neuro-behavioral testing. Metals including manganese, lead, iron, zinc, copper were measured in airborne particulate matter collected with 24-h personal samplers, and in soil, tap water, blood, urine and hair. Independent variables included parental education and socio-economic status, children's body mass index, number of siblings, parity order, smoking and drinking habits.

RESULTS

A total of 311 subjects (49.2% females), residing in either the exposed (n=154) or the reference (n=157) area participated. Average airborne and soil manganese were respectively 49.5 ng/m(3) (median 31.4, range 1.24-517) and 958 ppm (median 897, range 465-1729) in the impacted area, and 27.4 ng/m(3) (median 24.7, range 5.3-85.9) ng/m(3) and 427 ppm (median 409 range 160-734) in the reference area. Regression models showed significant impairment of motor coordination (Luria-Nebraska test, p=0.0005), hand dexterity (Aiming Pursuit test, p=0.0115) and odor identification (Sniffin' task, p=0.003) associated with soil manganese. Tremor intensity was positively associated with blood (p=0.005) and hair (p=0.01) manganese.

CONCLUSION

Historical environmental exposure to manganese from ferroalloy emission reflected by the concentration in soil and the biomarkers was associated with sub-clinical deficits in olfactory and motor function among adolescents.

[Value of manganese in human life (literature review)]

Manganese is an important element essential for human functioning. Pathogenesis of manganese intoxication remains unclear. Specification of differential diagnostic criteria is required for diagnosis of occupational manganese intoxication and ruling out Parkinson disease and secondary parkinsonism in the patients.

[Evaluating biomarkers of exposure to electric welding aerosol]

Biologic monitoring data in electric welders revealed reliable correlation between manganese concentration in the whole blood and manganese concentrations in the workplace air. The chronic manganese intoxication patients showed reliable lower levels of urinary iron, cobalt and manganese vs. those values in the reference group.

[Chronic manganese intoxication due to methcathinone (ephedron) abuse: a case report]

Known as an occupational disease, chronic manganese intoxication is recently being observed among abusers of psychoactive substances. Methcathinone hydrochloride is obtained by combining ephedrine/pseudoephedrine and potassium permanganate. Various neuropsychiatric symptoms have been reported among Efedron users. Our patient is a 29 year old male, who was referred to our hospital from a state general hospital with a diagnosis of Conversion Disorder. He was hospitalized and preliminary diagnoses of Facititous Disorder, Conversion Disorder, Psychiatric Disorder due to a General Medical Condition and Antisocial Personality Disorder. He was abstinent from any substance for five years upon referral to our hospital and had a history of methcathinone abuse for 4.5 years. The backache dated back to 6 years ago and a disturbance of gait was added to the clinical picture. A speech disturbance, falling while walking downhill and walking on tiptoe were added in the last 2-3 years. In the neurological examination, extrapyramidal system findings, gait disturbance and the report on use of manganese compunds were found. The setting was changed from psychiatric ward to neuorology ward and evaluated by consultant neurologist. The case was diagnosed as ?Manganese Intoxication'. The aim of this report is to demonstrate and emphasize the importance of questioning the presence of manganese compounds in case of history of substance abuse. Other areas of interest are the shortage of data on the intravenous use of manganese and the cases reported in the literature coming from the former Soviet Union.

Spectrum of movement disorders in professional welders

OBJECTIVE

To examine the clinical presentation of movement disorder in patients who reported a history of welding.

METHODS

A retrospective chart review during a three-year period was performed on all movement disorders and patients who had been welders were identified. The clinical presentation of these patients was categorized by the movement disorder at the time of the initial neurological evaluation and by the therapy response. A comparison group was created by randomly selecting four non-welders for each welder.

RESULTS

Among 1126 charts reviewed, eleven patients presented with a welder history. Parkinsonism was a common presentation in both groups: three of the eleven welders (27%) and five of the forty-one controls (12%). Dystonia was also common with 27% and 20%, respectively. Using the chi-squared analysis, the prevalence rates for both parkinsonism and dystonia were similar to controls. All of the welder patients with parkinsonism responded to dopaminomimetic therapy. Six of the eleven welders had elevated manganese levels in either blood or urine.

CONCLUSIONS

Welders who present with a movement disorder such as parkinsonism or dystonia, have the prevalence rates for these disorders similar to the non-welder population (Fig. 2, Ref. 15).

[Clinical cases of occupational chronic manganese intoxication]

Classic symptoms of manganese intoxication are very rarely seen nowadays. Clinic in Angarsk Research Institute for Occupational medicine and Human ecology registered two cases of stage I and II chronic manganese intoxication over 10 years among electric welders. The cases were diagnosed with consideration of long length of exposure to manganese with the ambient air level exceeding the MAC 1.5 times, the disease manifestation at middle age, high manganese level in serum and urine, characteristic neurologic symptoms in association with organic psychopathologic defects and polyneuropathy of limbs.

Differential deposition of manganese in the rat brain following subchronic exposure to manganese: a T1-weighted magnetic resonance imaging study

BACKGROUND

Manganism is a central nervous system disorder caused by toxic exposure to manganese. Manganism has been related to occupational exposures, liver diseases, prolonged parenteral nutrition, and abuse of illicit drugs. Initially manifested by a reversible neuropsychiatric syndrome (locura manganica), the main symptoms and signs of manganism are emotional lability, compulsive behavior and visual hallucinations. Locura manganica is followed by an irreversible extrapyramidal syndrome, the onset of which occurs years after chronic exposure.

OBJECTIVES

To characterize the regional distribution of Mn in the rat brain after subchronic exposure to Mn. This animal model holds special clinical relevance, reflecting the earlier clinical stages of manganism before chronic exposure to Mn exerts its irreversible effects.

METHODS

Sprague-Dawley rats were intravenously injected with MnCl2 weekly, for a total of 14 weeks - approximately 1/10 of the lifetime of the rat. T1-weighted magnetic resonance imaging was used to detect the distribution of Mn deposition in brain tissues, as evidenced by areas of T1-weighted hyperintense signals.

RESULTS

A consistent region-specific pattern of T1-weighted hyperintensities was observed in the brains of Mn-treated rats. Cortical hyperintensities were prominent in the hippocampus and dentate gyrus. Hyperintensities were also observed in the olfactory bulbs, pituitary gland, optic nerves and chiasma, pons, midbrain tegmentum, habenula, lentiform and caudate nuclei, thalamus, chorioid plexus and cerebellar hemispheres.

CONCLUSIONS

Prominent Mn depositions, evidenced by T1-weighted hyperintensities in the hippocampus after subacute exposure to Mn, are compatible with the clinical picture of manganism during its early stages, and may explain its pathophysiology.

Neuropsychological testing for the assessment of manganese neurotoxicity: a review and a proposal

BACKGROUND

Manganese exposure can cause neurobehavioral and neurological signs and symptoms. A review of the literature was carried out in order to identify the most sensitive and effective methods to assess these outcomes.

METHODS

Studies on manganese exposure performed with neuropsychological tests were reviewed using Medline. Test methods, obtained outcomes, and dose-response relationships were considered. Based on the review and additional considerations, a testing battery for adult and children was identified.

RESULTS

A total number of 31 studies were reviewed and divided in 18 occupational, 7 environmental, and 6 on children. A large variety of tests exploring motor and cognitive functions and mood were applied. Neurobehavioral effects were dose-dependent in several studies and determined by much lower exposure levels compared to 1 mg Mn/m(3) in total dust which is considered to be the minimum concentration able to induce the classical clinical features of "manganism." Although through a wide variety of tests, the observed outcomes support the knowledge that manganese exposure can cause neurobehavioral effects. Motor functions are mainly affected in adults, and cognitive functions and behavior are more affected in children.

CONCLUSIONS

Literature on manganese neurobehavioral effect is quite consistent, however, further improvement may be achieved by using better structured and more comparable evaluation methods. Based on the analysis of the existing experiences a test battery including tests of motor functions, response speed, cognitive functions, intellectual abilities, mood, and symptom questionnaires is suggested. We recommend that the tests indicated should always be included in future studies as a core battery.

Parkinsonism caused by chronic usage of intravenous potassium permanganate

INTRODUCTION

Chronic overexposure to manganese (Mn) may cause neuronal degeneration. Manganese intoxication is well known to induce parkinsonism. Manganese intoxication may be associated with abnormal magnetic resonance (MR) imaging (abnormal signal hyperintensity in the globus pallidus and substantia nigra on T1-weighted images).

CASES

We report an unusual presentation of manganese intoxication due to administration of a combination of acetylsalicylic acid and ephedrine HCl, potassium permanganate, and vinegar melted in tap water and administered parenterally as a psychostimulant substance in 2 cases who developed symptoms resembling parkinsonism. Neurologic examination of both cases revealed disturbances of the extrapyramidal system and a characteristic "cock walk." Tremor was present in the first case, whereas it was lacking in the second one. Cranial MRI showed bilateral symmetric T1-weighted hyperintense patterns in the globus pallidus, probably because of manganese accumulation. Different levels of response to levodopa were reported in the literature; in our cases, there was no response to levodopa.

CONCLUSION

Chronic overexposure to manganese may cause an atypical form of parkinsonism associated with increased T1 signal in the basal ganglia on magnetic resonance imaging.

Seizure associated with total parenteral nutrition-related hypermanganesemia

The trace element manganese is usually supplied when total parenteral nutrition is used. However, long-term parenteral administration of manganese, which bypasses the normal regulatory mechanism, may cause hypermanganesemia. Manganese poisoning presents clinically with parkinsonian-like symptoms and psychological changes. Seizures are a rare presentation of this disease. This report describes a 10-year-old female who had received total parenteral nutrition for 3 months because of short bowel syndrome, and presented with tonic-clonic seizure, decreased level of consciousness, and fever. The serum electrolytes, glucose and the cerebrospinal fluid examination were normal. The blood culture grew Pantoea agglomerans. The brain magnetic resonance imaging disclosed no evidence of central nervous system infection. However, symmetric high-intensity signal on T1-weighted images was documented in the basal ganglia, especially in the globus pallidus. Her whole blood manganese level was 3.7 microg/dL, which was significantly higher than the normal range (0.4-1.4 microg/dL). Diagnosis of hypermanganesemia related to total parenteral nutrition was made.

Effects of chronic manganese exposure on cognitive and motor functioning in non-human primates

Acute exposure to manganese is associated with complex behavioral/psychiatric signs that may include Parkinsonian motor features. However, little is known about the behavioral consequences of chronic manganese exposures. In this study, cynomolgus macaque monkeys were exposed to manganese sulfate (10-15 mg/kg/week) over an exposure period lasting 272+/-17 days. Prior to manganese exposure, animals were trained to perform tests of cognitive and motor functioning and overall behavior was assessed by ratings and by videotaped analyses. By the end of the manganese exposure period, animals developed subtle deficits in spatial working memory and had modest decreases in spontaneous activity and manual dexterity. In addition, stereotypic or compulsive-like behaviors such as compulsive grooming increased in frequency by the end of the manganese exposure period. Blood manganese levels measured at the end of the manganese exposure period ranged from 29.4 to 73.7 micro g/l (mean=55.7+/-10.8 (compared to levels of 5.1-14.2 micro g/l at baseline (mean=9.2+/-2.7)), placing them within the upper range of levels reported for human environmental, medical or occupational exposures. These results suggest that chronic exposure to levels of manganese achieved in this study may have detrimental effects on behavior, cognition and motor functioning.

Application of pharmacokinetic data to the risk assessment of inhaled manganese

There is increased interest within the scientific community concerning the neurotoxicity of manganese owing in part to the use of methylcyclopentadienyl manganese tricarbonyl (MMT) as a gasoline fuel additive and an enhanced awareness that this essential metal may play a role in hepatic encephalopathy and other neurologic diseases. Neurotoxicity generally arises over a prolonged period of time and results when manganese intake exceeds its elimination leading to increases in brain manganese concentration. Neurotoxicity can occur following high dose oral, inhalation, or parenteral exposure or when hepatobiliary clearance of this metal is impaired. Studies completed during the past several years have substantially improved our understanding of the health risks posed by inhaled manganese by determining exposure conditions that lead to increased concentrations of manganese within the central nervous system and other target organs. Many of these studies focused on phosphates, sulfates, and oxides of manganese since these are formed and emitted following MMT combustion by an automobile. These studies have evaluated the role of direct nose-to-brain transport of inhaled manganese and have examined differences in manganese toxicokinetics in potentially sensitive subpopulations (e.g., fetuses, neonates, individuals with compromised hepatic function or sub-optimal manganese intake, and the aged). This manuscript reviews the U.S. Environmental Protection Agency's current risk assessment for inhaled manganese, summarizes these contemporary pharmacokinetic studies, and considers how these data could inform future risk assessments of this metal following inhalation.

Occupational manganese neurotoxicity provoked by hepatitis C

Manganese neurotoxicity developed in a highly exposed worker after asymptomatic, moderate hepatic dysfunction from hepatitis C infection. Antiviral therapy was accompanied by resolution of increased blood manganese levels and neurologic improvement. Even asymptomatic hepatic dysfunction may impair manganese clearance and place highly exposed persons at risk for toxicity.

The emergence of manganese-related health problems in Quebec: An integrated approach to evaluation, diagnosis, management and control

This paper describes the strategy developed in Quebec to deal with an emerging problem: manganism in welders. Only two cases of manganism had been reported to the Commission de la santé et de la sécurité du travail (CSST, Workers Compensation Board in Quebec) before 2000. In the fall of 2001, the CSST was informed of a possible cluster of manganism and received 20 compensation claims from one plant. Action was rapidly taken to understand and tackle this emerging problem. Under the leadership of the CSST, a coordinating working group implemented medical and environmental subcommittees involving representatives of the different partners of the prevention network. After a literature review to document the health risks associated with manganese and the lack of some important information, a panel of international experts was formed to try to reach agreement on the parameters to consider in the diagnosis and management of manganism. The CSST compensation management policies would be adjusted accordingly. Simultaneously, all the available industrial hygiene data were analyzed to estimate where and at what levels workers were exposed to manganese. To complete these data, the exposure of workers in more than 50 industrial plants was evaluated and existing control measures were documented. All these data have been presented for a revision of the Quebec permissible exposure limit (PEL). In this integrated approach, the next step targets the formation of neurologists and neuropsychologists for a standardized medical evaluation, to complete workplace evaluation in the high risk sectors, inform workers and employers and recommend control measures where required, based on a revised PEL. Many strategies will be used to inform the prevention network (about 1000 people), employers and employees of the risks of overexposure to manganese and of the measures to control exposure in all the plants where workers are susceptible to be exposed to manganese.

Neuroimaging in manganism

Neuroimaging such as magnetic resonance imaging (MRI), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) have been used in the last decade for investigating the neurotoxicolgy of manganese (Mn). Increased signal intensities on a T1-weighted image may reflect increased Mn deposits (e.g., due to exposure to Mn) but not necessarily manganism. In a biologically based dose-response model, our recent results strongly suggest that signal intensities in T1-weighted MRI reflect a target site dose. However, the threshold of signal intensity associated with clinical symptoms of manganism remains to be solved. Functional neuroimaging such as PET or SPECT examines the integrity of the nigrostriatal dopaminergic system, and thus is very important for the differential diagnosis of manganism. However, neuroimaging research should also aim at developing specific and sensitive parameters for manganism in Mn-exposed individuals.

Neurologic manifestations in welders with pallidal MRI T1 hyperintensity

BACKGROUND

Neurologic symptoms have been attributed to manganese fumes generated during welding. Increased T1 MRI signal in the basal ganglia is a biologic marker of manganese accumulation. Recent studies have associated welding and parkinsonism, but generally without MRI corroboration.

OBJECTIVE

To characterize the clinical and neuropsychological features of patients with MRI basal ganglia T1 hyperintensity, who were ultimately diagnosed with neurotoxicity from welding fumes.

METHODS

The medical records of welders referred to the Department of Neurology with neurologic problems and basal ganglia T1 hyperintensity were reviewed.

RESULTS

All eight patients were male career welders with increased T1 basal ganglia signal on MRI of the brain. Several different clinical syndromes were recognized: a parkinsonian syndrome (three patients), a syndrome of multifocal myoclonus and limited cognitive impairment (two patients), a mixed syndrome with vestibular-auditory dysfunction (two patients), and minor subjective cognitive impairment, anxiety, and sleep apnea (one patient). Neuropsychometric testing suggested subcortical or frontal involvement. Inadequate ventilation or lack of personal respiratory protection during welding was a common theme.

CONCLUSIONS

Welding without proper protection was associated with syndromes of parkinsonism, multifocal myoclonus, mild cognitive impairment, and vestibular-auditory dysfunction. The MRI T1 hyperintensity in the basal ganglia suggests that these may have been caused by manganese neurotoxicity.

Quantifying postural tremor in workers exposed to low levels of manganese

The aim of this study was: (1) To determine the minimum number of characteristics necessary to discriminate between postural tremor recorded in control subjects (CO), in subjects exposed to manganese (MN), and in patients with Parkinson's disease (PD), and (2) to examine the continuum of changes between the three groups examined. Workers previously exposed to Mn (n = 10), patients with PD (n = 10), and control subjects (CO) (n = 11) underwent a clinical examination. Blood Mn was measured at the end of exposure time for the MN group and 12 months later at the beginning of the experiment for all groups. Postural tremor with visual feedback was recorded in the index finger with a laser system. Statistical criteria were used to reduce computed tremor characteristics to a minimal set of reliable discriminating variables. Two variables were retained namely corrected wobble (CW), describing the morphology of the tremor oscillations, and variability ratio (VR), describing proportional power of tremor. Both variables had an overall correct classification rate of 77.4%. Blood Mn levels at the time of the experiment were similar for all groups and had insignificant correlation with tremor variables. However, blood Mn levels in workers which were also measured at the end of exposure time (i.e., 12 months before) showed significant correlation (Spearman's rank coefficient) with both harmonic index (rho = 0.70, P = 0.03) and first maximum of the autocorrelation function (rho = 0.89, P = 0.001). We conclude that (1) the tremor of workers exposed to Mn could be adequately described with only two variables; (2) a continuum of changes between tremor recorded in control subjects, in subjects exposed to Mn and in patients with PD was observed, with the MN group always found in between the control (CO) and the PD groups; (3) while blood Mn levels in workers were back at control levels at the time of the experiment, the effect of Mn on postural tremor was still detected. Thus our method has the potential to detect the effect of Mn on tremor with only two variables even after Mn level in the blood is back to normal values.

High signal intensities on T1-weighted MRI as a biomarker of exposure to manganese

Increased signal in T1-weighted images was observed in the experimental manganese (Mn) poisoning of the non-human primate and a patient with Mn neurointoxication. However, our study showed that the increased signals in magnetic resonance images (MRI) were highly prevalent (41.6%) in Mn-exposed workers. Especially 73.5% of the welders showed increased signal intensities. Blood Mn concentration correlated with pallidal index. These changes in MRI tend to disappear following the withdrawal from the source of Mn accumulation, despite permanent neurological damage. Thus increased signal intensities on a T1-weighted image reflect exposure to Mn, but not necessarily manganism. Our study also showed that the concentration of Mn required to produce increased signal intensities on MRI is much lower than the threshold necessary to result in overt clinical signs of manganism. Increased signal intensities in the globus pallidus were determined by Mn accumulation in the animal experiment. All these results strongly suggest that signal intensities in T1-weighted MRI reflect a target site dose in a biologically-based dose-response model. At which increase of signal intensity, the progression of manganism from Mn exposure occurs, however, remains to be solved.

Effect of levodopa treatment for parkinsonism in welders: A double-blind study

BACKGROUND

Manganese is known to cause a parkinsonian syndrome similar clinically to Parkinson disease (PD). L-Dopa responsiveness is a hallmark of PD; however, L-dopa's effect on manganese-induced parkinsonism is not well defined.

OBJECTIVE

To access the efficacy and safety of L-dopa therapy in a double-blind, randomized, placebo-controlled trial.

METHODS

Thirteen patients with manganese-induced parkinsonism were evaluated in a cross-over study with a modified Unified PD Rating Scale (UPDRS), timed walk test, tapping, and global clinical impression scores. Adverse reactions were assessed.

RESULTS

There was no significant difference between placebo and L-dopa for any measure: motor UPDRS, 27.4 vs 28.8; walk time, 16.6 seconds vs 17.7 seconds; tapping right hand, 69.5 vs 64.7; and tapping left hand, 66.8 vs 64.4. There were no differences in the global impression scores. Adverse reactions occurred similarly in the two groups, including headaches, drowsiness, and diarrhea.

CONCLUSIONS

L-Dopa therapy is not effective for the management of parkinsonism in welders. L-dopa unresponsiveness may be useful to distinguish manganese-induced parkinsonism from Parkinson disease.

[Diagnostic and prognostic value of determining serum levels of cytokines and antibodies to basic myeloprotein in chronic manganese intoxication]

Findings are that progression of chronic manganese intoxication comes along with development of humoral immune response to antibodies of myelinic coating of nerve fibers. That is expressed by increased occurrence of reliable titers of antibodies to basic myeloprotein G and increased serum IL-6 level. The authors suggest using determination of serum antibodies to myeloprotein G and IL-1, IL-6 to specify severity of chronic manganese intoxication.

Dopamine transporter binding in chronic manganese intoxication

Chronic exposure to manganese may induce parkinsonism similar to idiopathic Parkinson's disease (PD). However, clinical manifestations of manganism also have some features different from PD. The mechanisms of manganese-induced parkinsonism remain not fully understood. (99m)Tc-TRODAT-1 is a cocaine analogue that can bind to the dopamine transporter (DAT) site reflecting the function of presynaptic dopaminergic terminals. The purpose of this study was to evaluate DAT function using (99m)Tc-TRODAT-1 to investigate the integrity of the presynaptic dopaminergic terminals in manganese-induced parkinsonism. Brain (99m)Tc-TRODAT-1 single photon emission computed tomography was performed in 4 patients with chronic manganese intoxication in a ferromanganese smelting plant in Taiwan. Twelve PD patients and 12 healthy volunteers served as abnormal and normal controls, respectively. Clinically, all manganism patients had a bradykinetic-rigid syndrome. The scores of the Unified Parkinson's Disease Rating Scale ranged between 19 and 64. The uptake values of the (99m)Tc-TRODAT-1 were 0.868+/-0.136 in the right corpus striatum and 0.865+/-0.118 in the left, as compared with 0.951+/-0.059 and 0.956+/-0.058, respectively for the normal controls. The data were significantly higher than 0.250+/-0.070 and 0.317+/-0.066 respectively for the PD patients. Interestingly, there was a mild decrease in the uptake of (99m)Tc-TRODAT-1 in the putamen and the ratio of putamen and caudate when compared with the normal controls. Although the DAT shows a slight decrease in the putamen of manganism patients as compared with that of the normal controls, the data indicate that the presynaptic dopaminergic terminals are not the main target of chronic manganese intoxication. In addition (99m)Tc-TRODAT-1 SPECT can provide a useful, convenient and inexpensive tool for differentiation between chronic manganism and PD.

Myoclonic involuntary movement associated with chronic manganese poisoning

We report a 17-year-old man showing myoclonic involuntary movement (IVM) associated with chronic manganese (Mn) poisoning. The patient, a welder, showed myoclonic IVM mainly in the right upper and lower extremities, elevated levels of Mn in the blood and hair and high-intensity signals in the globus pallidus on T1-weighted MR images. Chelation therapy resulted in improvement of the myoclonic IVM and MRI abnormalities. This is the first report of Mn poisoning characterized by myoclonic IVM without parkinsonism.

Non invasive quantification of manganese deposits in the rat brain by local measurement of NMR proton T1 relaxation times

Up to now, there is no reliable non invasive biomarker for the concentration of manganese (Mn) in the brain after intoxication to this metal. The aim of the present experimental study was to determine the predictive value of the localized measurement of the proton NMR relaxation time T1 as a quantitative estimation of the concentration of Mn in brain. The relationship of the proton relaxation rates (1/T1) was established in rat brain homogenates as a function of the Mn, iron, and copper concentration. Subsequently, an experimental model of Mn neurotoxicity was used: rats were stereotactically injected with increasing amounts of Mn2+ (as MnCl2) in the ventricles. After 3 weeks, local measurements of T1 were carried out in live rats. They were then sacrificed in order to sample the striatum, the cortex, and the cerebellum from the brain and to perform a quantitative determination of the concentration of Mn in these tissues by atomic absorption spectrometry (AAS). The results indicate excellent correlation coefficients between relaxation rates and tissue Mn concentrations (r= 0.84, 0.77 and 0.92 for the striatum, the cortex and the cerebellum, respectively). This methodology offers a unique toolfor monitoring the degree of Mn concentration in different areas of the brain in animal models of Mn intoxication. It will be useful for evaluating the efficacy of treatments aimed at decreasing the metal in the brain. The method could be potentially useful for being transposed in the clinical situation for monitoring Mn-exposed workers.

Manganese intoxication during intermittent parenteral nutrition: report of two cases

BACKGROUND AND METHODS

The administration of trace elements is thought to be needed in patients receiving long-term parenteral nutrition. Recently, manganese intoxication or deposition was documented in such patients. We report two cases of manganese intoxication during intermittent parenteral nutrition including manganese. Manganese had been administered for 4 years at a frequency of one or two times per week in one case and for 5 years at a frequency of one or two times per month in the other case. Both cases showed mild symptoms with headache and dizziness. One case had mild hepatic dysfunction and the other did not. The whole-blood manganese level increased in one case, but not in the other case. T1-weighted magnetic resonance images revealed symmetrical high-intensity areas in basal ganglia and thalamus in both cases. After the administration of manganese was stopped, these symptoms all disappeared and the magnetic resonance images abnormalities gradually improved in both patients. Mild long-term manganese intoxication is thus considered to occur regardless of the frequency of using a manganese supplement.

CONCLUSIONS

Patients should be carefully monitored when receiving long-term parenteral nutrition including manganese, even when the manganese dose is small and the frequency of receiving a manganese supplement is low.

Brain magnetic resonance imaging and manganese exposure

Due to its paramagnetic properties, manganese (Mn) can be effectively visualized by MRI. Mn accumulates selectively in the globus pallidus of basal ganglia, where it can produce high signals at brain magnetic resonance. These hyperintensities are bilateral, symmetrical, and visible in T1-weighted magnetic resonance imaging of different manganese overload conditions. A review of the literature shows identical findings in manganese exposed workers, hepatopatic patients, and patients undergoing total parenteral nutrition with excessive amount of manganese. Two indicators of exposure and hyperintensity were considered, represented respectively by the concentration of Mn in total blood (MnB), and the pallidal index (PI). These two indicators show a positive association, which indicates a possible continuum from normality to clinical stages both in workers occupationally exposed to Mn and in patients suffering from chronic liver disease. Since both MnB and PI show a high degree of variability, further research should be focused on the identification of more accurate indicators.

[Essential points to differentiate various diseases causing parkinsonism]

This review article deals with the cardinal features to differentiate various conditions which present with parkinsonism, other than Parkinson's disease, Lewy body disease, progressive supranuclear palsy and corticobasal degeneration. Special attention is paid to the distinctive clinical features, laboratory data and neuroimaging findings of frequent diseases as well as important ones including multiple system atrophies(MSA), drug-induced parkinsonism, vascular pseudo-parkinsonism and manganese intoxication due to parenteral nutrition. MRI is useful to diagnose MSA, vascular pseudo-parkinsonism and manganese intoxication. Benzamide derivatives including sulpiride, tiapride, metoclopramide and cisapride are the main causes of drug-induced parkinsonism in recent years in Japan.

[Magnetic resonance tomography of the brain in workers with chronic occupational manganese dioxide exposure]

AIM

Changes within the brain detected by MRI after chronic manganese poisoning raised the question whether morphological changes of the basal ganglia, particularly of the globus pallidus, could be detected after chronic occupational exposure to manganese dioxide.

METHOD

In a cross-sectional study, healthy workers (48 male and 27 female) at a dry cell battery factory were examined. Actual internal exposure was quantified by the analysis of manganese in the blood using atomic absorption spectrometry. Chronic exposure was defined as a cumulative index (CBI) including duration of exposure, individual workplace factors, and previously measured concentrations of MnO2 in dust samples. A Philips Gyroscan T5-II (0.5 T) was used for the MRI of the brain. The following indicators were taken to ascertain possible manganese-induced changes; Pallidum-Index (PI), width of 3rd ventricle and cella media index in addition to clinical examinations.

RESULTS

No cases of parkinsonism were detected in clinical examinations or by other means. The mean manganese concentration in blood was 12 micrograms/l (range: 3.9-23.3 micrograms/l). In comparison to the upper reference value of 10 micrograms/l, 42 workers (56%) had a higher body burden. A significant positive correlation between manganese levels in blood and the PI (indicated by T1-shortening) was observed as well as between the CBI and workplace-specific exposure. Brain atrophy was not detected in any of the observed cases.

CONCLUSIONS

Long-term exposure to manganese dioxide dust correlates with the Pallidum-Index in MRI scans. Although the MRI findings have no current clinical relevance for individuals, further studies are necessary to evaluate specificity and potential prognostic value.

Manganese intoxication

Manganese plays an important role as a cofactor in many enzymatic reactions in humans but in excess amounts can cause irreversible nervous system damage. Although manganism is a rare condition, it can be the cause of complex nervous system symptoms, especially in the setting of environmental exposure. Specifically, manganese is a well-known cause of dystonic parkinsonism. This article highlights several historical descriptions of the clinical manifestations, pathological changes, and attempted therapeutic intervention in manganese intoxication.

Manganese deposits in patients with biliary atresia after hepatic porto-enterostomy

PURPOSE

The aim of this study was to determine if there is latent manganese toxicity in patients with biliary atresia.

METHODS

Fifteen children with biliary atresia were examined postoperatively with regard to whole-blood manganese levels using brain magnetic resonance imaging (MRI) and I-123 iodoamphetamine (IMP) per rectal portal scintigraphy.

RESULTS

Nine (60%) of the 15 had high whole-blood manganese levels (mean, 4.1 microg/dL; range, 1.2 to 9.6; normal, 0.5 to 2.5), and these 9 had hyperintense globus pallidus on T1-weighted images, with no corresponding signal change in T2 sequences. I-123 IMP per rectal portal scintigraphy was done for 13 patients to evaluate portosystemic shunt flow. 12 (92%) of these patients had an increased flow. Mean shunt ratio was estimated to be 41% (range, 0.6 to 98; normal, <5%). Encephalopathy was evident in only 1 patient.

CONCLUSIONS

Some patients with biliary atresia in the postoperative period have manganese deposits in globus pallidus on T1-weighted images and high whole-blood manganese levels, possibly caused by increased portsystemic shunt, and a latent or subclinical encephalopathy is also present.