Toxic encephalopathy

Myoclonus, Uremia, and Delirium in a Liver Transplant Recipient: A Case Report and Literature Review

BACKGROUND

Consultation-liaison (CL) psychiatrists are frequently asked to consult on various abnormal movements (1). CL psychiatrists can be instrumental in aiding the primary teams to identify and manage these movement disorders. In this manuscript, we provide an illustrative case of a patient presenting with myoclonus and offer a review on this important topic. Myoclonus accompanied by delirium represents a rare post-transplant complication and can be associated with heightened morbidity and mortality. The incidence of this complication in solid organ transplant recipients is scarcely documented, and its pathophysiology remains inadequately understood. Potential etiologies in the intensive care unit are numerous and likely multifactorial. The literature lacks detailed descriptions of the correlation and association between myoclonus and uremia. Management of this condition requires a multimodal approach, focusing on resolving underlying metabolic disturbances and providing symptomatic treatment.

OBJECTIVE

This manuscript describes the clinical presentation of myoclonus in a liver transplant recipient accompanied by delirium and precipitated by uremia. We aim to highlight the diagnostic and therapeutic complexities, help providers distinguish myoclonus from other movement disorders, and aid appropriate management.

METHODS AND RESULTS

We present a case of acute myoclonus in an elderly female liver transplant recipient precipitated by uremia and improved after continuous renal replacement treatment. In addition, we conducted a systematic review utilizing EMBASSE and PubMed of reported cases of myoclonus, delirium, and/or encephalopathy accompanied by uremia. We included 12 manuscripts in our review and discussed their findings.

CONCLUSIONS

CL psychiatrists are frequently consulted for a range of movement disorders in the intensive care unit, including myoclonus. Accurate diagnosis and identification of contributing etiologies are critical in these cases. Management typically involves addressing the underlying disorder, such as using dialysis for uremia, alongside symptomatic treatment with benzodiazepines to mitigate the frequency and amplitude of myoclonus. This approach helps to alleviate both the physical burden and psychological distress associated with the condition. This case underscores the pivotal role of the CL psychiatrist within a complex multidisciplinary team, contributing to diagnostic precision and optimization of management strategies for movement disorders.

Mortality rates for men and women from cerebrovascular and nervous diseases in the regions of Russia in 2013 and 2022

In recent years, researchers have noted an increase in mortality from neurodegenerative diseases and a decrease in mortality from strokes. There have been no studies comparing mortality from these causes in the regions of the Russian Federation.

Aim:comparative analysis of regional (age-) standardized death rate (SDR) among men and women from cerebrovascular diseases (CVD) and nervous system diseases (NSD) in 2013 and 2022 and discussion of factors influencing SDR.

Materials and methods.Rosstat data obtained upon request were used. SDR was calculated using software (state registration number of computer program 216661114) using the European Standard Population using the direct standardization method per 100 thousand population; The average regional SDR values were calculated for the class of NSD and individual groups from this class, CVB (codes I60–69).

Results.A decrease in the regional average SDR from CVD was revealed among men (218.09 ± 60.81 in 2013 and 159.41 ± 51.20 per 100 thousand people in 2022) and women (144.30 ± 39.33 and 103.51 ± 32.63 respectively) and the increase in SDR from LBP (19.77 ± 17.70 and 65.99 ± 56.67 for men, 10.99 ± 11.32 and 52.81 ± 46.13 for women). Only in 4 regions was there a decrease in SDR from both NSD and CVD in both men and women. The dispersion of regional SDRs from NSD and CVB in 2022 compared to 2013 increased by more than 10 times, which indicates a significant and growing regional variability of indicators. In the stroke group, the most significant decrease occurred from “Stroke not specified as hemorrhage or infarction” (code I64). The regional average contribution of acute stroke (codes I60–64) to the SCS from NSD and CVB (in total) decreased (in 2013 among women 51.57 ± 16.26 %, in 2022 33.96 ± 14.95 %; among men 54.0 ± 15.01 and 39.82 ± 14.26 respectively). Alzheimer’s disease makes a negligible contribution to mortality; In men in certain regions, alcohol-associated LBP is significant.

Conclusions.Significant regional variability of SDR from individual groups of causes and a general trend towards a decrease in SDR from CVD and an increase in SDR from NSD were revealed, which is due to many factors. To eliminate the influence of different approaches to determining the cause of death, a unified protocol of criteria for their establishment is necessary.

Review of the Brain's Behaviour after Injury and Disease for Its Application in an Agent-Based Model (ABM)

The brain is the most complex organ in the human body and, as such, its study entails great challenges (methodological, theoretical, etc.). Nonetheless, there is a remarkable amount of studies about the consequences of pathological conditions on its development and functioning. This bibliographic review aims to cover mostly findings related to changes in the physical distribution of neurons and their connections-the connectome-both structural and functional, as well as their modelling approaches. It does not intend to offer an extensive description of all conditions affecting the brain; rather, it presents the most common ones. Thus, here, we highlight the need for accurate brain modelling that can subsequently be used to understand brain function and be applied to diagnose, track, and simulate treatments for the most prevalent pathologies affecting the brain.

Assessment of rehabilitation treatment for patients with acute poisoning-induced toxic encephalopathy

BACKGROUND

Poisoned patients often suffer damage to multiple systems, and those experiencing central nervous system disorders present more severe conditions, prolonged hospital stays, and increased mortality rates. We aimed to assess the efficacy of rehabilitation interventions for patients with toxic encephalopathy.

METHODS

This retrospective, observational, comparative cohort study was performed at the teaching hospital affiliated of Nanjing Medical University, from October 2020 to December 2022. Patients who met the diagnostic criteria for toxic encephalopathy and exclusion criteria were included, and patients were divided into three subgroups according to Glasgow Coma Scale (GCS). Demographic and clinical characteristics were collected. The effect of the rehabilitation intervention on patients were assessed in the improvement of consciousness status (Glasgow Coma Scale [GCS] score), muscle strength and movement and swallowing function (Fugl-Meyer Assessment [FMA] scale, Water Swallow Test [WST], and Standardized Swallowing Assessment [SSA]). Subgroup analysis was based on different toxic species.

RESULTS

Out of the 464 patients with toxic encephalopathy, 184 cases received rehabilitation treatments. For the severe toxic encephalopathy patients, patients without rehabilitation intervention have a 2.21 times higher risk of death compared to patients with rehabilitation intervention (Hazard ratio [HR]=2.21). Subgroup analysis revealed that rehabilitation intervention significantly increased the survival rate of patients with pesticide poisoning (P=0.02), while no significant improvement was observed in patients with drug/biological agent poisoning (P=0.44). After rehabilitation intervention, significant improvement in GCS and FMA were observed in severe patients with toxic encephalopathy (P<0.01).

CONCLUSION

Active rehabilitation intervention for patients exposed to poisons that can potentially cause toxic encephalopathy may improve the prognosis and reduce the mortality rate in clinical practice.

Toxic leukoencephalopathies

Toxic-metabolic encephalopathies are a group of disorders in which an exogenous or endogenous substance leads to transient or permanent neuronal damage. It is an important cause of potentially reversible acute encephalopathy syndrome. The signs and symptoms of toxic encephalopathies may be relatively nonspecific, and toxicologic tests are not always widely available. Imaging plays a key role in determining the most probable diagnosis, pointing to the next steps of investigation, and providing prognostic information. In this chapter, we review the main acquired toxic-metabolic leukoencephalopathies, commenting on their pathophysiology, imaging patterns, and rationale for an adequate diagnosis in detail.

Acute 1,2-Dichloropropane Poisoning due to Ingestion of Rubber Cement: An Autopsy Case Report and Review

ABSTRACT

1,2-Dichloropropane (1,2-DCP) is a common industrial solvent and chemical intermediate that can cause acute poisoning to humans through exposure during its production and industrial use. The target organs of 1,2-DCP include the eyes, respiratory system, liver, kidney, central nervous system, and skin. Forensic identification of 1,2-DCP poisoning is difficult because of the lack of characteristic pathological changes. This article reports an autopsy case of acute 1,2-DCP poisoning caused by self-ingestion of rubber cement. A woman developed seizures and coagulation dysfunction after ingesting approximately 10 mL of rubber cement and died 43 hours later. Autopsy revealed generalized subcutaneous hemorrhage, cardiopulmonary multifocal hemorrhage, bronchopneumonia, severe cerebral edema, focal hepatic necrosis, granular deposition in the glomerular capsule and renal tubules, and delipidation of the adrenal cortex. These findings indicate that 1,2-DCP poisoning can induce central nervous system dysfunction, respiratory system damage, liver and kidney function damage, hemolytic anemia, disseminated intravascular coagulation, and adrenal damage. This case may provide useful perspectives for forensic identification of 1,2-DCP poisoning in the future.

Acute Toxic Encephalopathy in Occupational Exposure with Polyvinyl Chloride (PVC) Fumes: A Case Series

BACKGROUND

Toxic encephalopathy is a spectrum of central nervous system disorders caused by exposure to toxins, especially from occupational workplace. Polyvinylchloride (PVC) is a synthetic chemical polymer that is used widely in daily activities of living. PVC is produced by polymerization of monomer units of vinyl chloride. Its manufacturing requires multiple procedures and additives for heat and light stabilization involving heavy metals.

OBJECTIVE

In this novel case series, we present the diverse clinical presentation of 10 patients, working in plastic recycling factory having inhalational exposure to PVC fumes, manifesting as acute toxic encephalopathy.

MATERIALS AND METHODS

All the patients were screened for the causes of acute encephalopathy including heavy metals, methanol poisoning, and organotins along with arterial blood gas analysis, brain imaging, and electroencephalogram. Memory loss, confusion, vertigo, headache, and nausea were complained in all the patients while seizure occurred in three patients. Neurocognitive status was grossly impaired in all the patients. Metabolic acidosis in presence of hyponatremia and/or hypokalemia was observed in nine cases. Five of the patients were having evidence of white matter involvement in brain imaging. The screening for heavy metal, methanol, and organotin were negative. Hemodialysis was done in six patients. Recovery was good in everyone and the average discharge was by 10.8 days (range: 2-25 days). All the patients were symptom-free at 3-months follow-up.

CONCLUSION

Early suspicion and aggressive management can have favorable outcome in PVC toxic encephalopathy. Occupational hazards due to PVC toxicity are increasing in the present industrial era but it is very less identified.

Implementing traditional ayurveda treatment as a primary care management in a survivor of gas geyser syndrome - A case report

Domestically, gas geysers are used in developing countries like India to supply hot water in bathrooms. These are of low economic value, with no requirement of electricity and easy installation, hence they are high in demand. A female patient of 14 year visited to a private Ayurved clinic on 27/12/2021 with complaints of difficulty in dysgraphia, dyslexia, dysphonia and fall (sometimes) while walking on uneven and unknown pathway. Four years ago, the patient landed into a vegetative state and was bed ridden, her condition was further diagnosed as Gas Geyser Syndrome. Here an effort has been put forth to reveal the concept of ayurvedic management adopted in a survivor of Gas Geyser Syndrome which is found to be effective. In Ayurveda the symptoms of Acute Gas Geyser syndrome can be correlated with Visha (Toxins) and its vishalakshana (Toxicity symptoms) wherein Murcha (Unconsciousness) and Sanyasa (Stage of Coma) are seen. The long term side effects of Gas Geyser Syndrome can be correlated with Vatavyadhi (Neurological disorders) as the stages of the disease manifestation presents with more neurological deficits. Ayurvedic intervention with internal medications along with the panchakarma procedures in the treatment of Gas geyser syndrome exhibits encouraging results which were seen in improving her cognition, memory and essential skills like writing, verbal communication, thinking skills, use of technology in socializing with the community.

THE NEUROLOGICAL MANIFESTATIONS AND FUNCTIONAL INDEPENDENCE IN PATIENTS WITH ENCEPHALOPATHIES OF DIFFERENT TYPES

OBJECTIVE

Aim: To access the neurological manifestations and activities of daily living in patients with encephalopathy of one of the following types: post-infectious, chronic traumatic encephalopathy, alcohol-induced, and microvascular ischemic disease of the brain.

PATIENTS AND METHODS

Materials and Methods: In the period of 2021-2022 we examined 520 patients, who signed the informed consent, taking into account their age, sex, occupation, the cause, and the disease duration. Such parameters were evaluated, as the data of neurological manifestations, the activities of daily living (Barthel index), cognitive functioning (MoCA-test), and statistical methods (Statistica 13.0).

RESULTS

Results: A probable influence of the age factor on the frequency of occurrence of different types of encephalopathies was established (χ2=235.05; p<0.001). The cognitive impairment was diagnosed in 53.79 % of patients with CTE, 66.21% with SVD, and 58.82% with AE. 40% of patients with CTE are dependent on their activities of daily living, among patients with SVD - 31,72 %, among patients with AE - 44.12%, among patients with PIE - 53.91%. 17.97% of patients with PIE had moderate dependence by the Barthel index. Thus, the severity of disability doesn't depend on the age or sex of patients but is correlating with the duration of the disease.

CONCLUSION

Conclusions: The neurological manifestations in patients with encephalopathies and their activities of daily living were studied profoundly and the data obtained opened new directions in the following research.

Capecitabine related neurotoxicity: Clinical and radiologic features

AIM

To study the clinical and radiologic features of patients with capecitabine neurotoxicity.

METHODS

We performed a retrospective analysis and systematic review on the clinical and radiologic characteristics of all patients with capecitabine neurotoxicity reported in literature between 2003 and 2020.

RESULTS

24 cases including our patient were retrospectively analysed, with their clinical and radiologic features summarized. Their median age was 59 years old (ranges from 31 to 82 years old). Encephalopathy was the predominant clinical symptom affecting more than half (15/24, 63%) of the patients. This was followed by cerebellar ataxia (10/24, 42%). Amongst the patients who had magnetic resonance imaging(MRI) brain imaging performed, majority of them (18/23, 78%) had acute radiologic abnormalities. Leukoencephalopathy was the commonest radiologic abnormality seen in more than half of the patients (15/23,65%). Despite the preponderance of female patients in our study, there were no significant statistical differences in the clinical and radiologic features. Short term prognosis was excellent with complete resolution of neurologic symptoms observed in nearly all of the patients (22/23, 96%).

CONCLUSION

Capecitabine-related neurotoxicity is an uncommon cause of toxic encephalopathy, with a predilection for females. Clinical features are non-specific, with encephalopathy being the commonest. Prognosis remains good with timely recognition, and cessation of capecitabine. Future research looking into other pathogenic pharmacogenetic processes should be conducted for further elucidation of these associations.

A molecular view of amyotrophic lateral sclerosis through the lens of interaction network modules

Background

Despite the discovery of familial cases with mutations in Cu/Zn-superoxide dismutase (SOD1), Guanine nucleotide exchange C9orf72, TAR DNA-binding protein 43 (TARDBP) and RNA-binding protein FUS as well as a number of other genes linked to Amyotrophic Lateral Sclerosis (ALS), the etiology and molecular pathogenesis of this devastating disease is still not understood. As proteins do not act alone, conducting an analysis of ALS at the system level may provide new insights into the molecular biology of ALS and put it into relationship to other neurological diseases.

Methods

A set of ALS-associated genes/proteins were collected from publicly available databases and text mining of scientific literature. We used these as seed proteins to build protein-protein interaction (PPI) networks serving as a scaffold for further analyses. From the collection of networks, a set of core modules enriched in seed proteins were identified. The molecular biology of the core modules was investigated, as were their associations to other diseases. To assess the core modules’ ability to describe unknown or less well-studied ALS biology, they were queried for proteins more recently associated to ALS and not involved in the primary analysis.

Results

We describe a set of 26 ALS core modules enriched in ALS-associated proteins. We show that these ALS core modules not only capture most of the current knowledge about ALS, but they also allow us to suggest biological interdependencies. In addition, new associations of ALS networks with other neurodegenerative diseases, e.g. Alzheimer’s, Huntington’s and Parkinson’s disease were found. A follow-up analysis of 140 ALS-associated proteins identified since 2014 reveals a significant overrepresentation of new ALS proteins in these 26 disease modules.

Conclusions

Using protein-protein interaction networks offers a relevant approach for broadening the understanding of the biological context of known ALS-associated genes. Using a bottom-up approach for the analysis of protein-protein interaction networks is a useful method to avoid bias caused by over-connected proteins. Our ALS-enriched modules cover most known biological functions associated with ALS. The presence of recently identified ALS-associated proteins in the core modules highlights the potential for using these as a scaffold for identification of novel ALS disease mechanisms.

Movement Disorders and Dementia in a Woman With Chronic Aluminium Toxicity: Video-MRI Imaging

Background:

Aluminium encephalopathy results from exposure to aluminium from occupational, recreational, and environmental sources. Movement disorders, cerebellar ataxia, pyramidal tract signs, dementia, microcytic anemia and bone disease are typical manifestations.

Case Report:

A 55-year-old woman had clinical manifestations, persistent hyperaluminemia without magnetic resonance imaging (MRI) scan changes of toxic encephalopathy following a prolonged exposure to marine grade paints containing 30% aluminium. Chelation therapy with ethylenediaminetetraacetic acid (EDTA) demonstrated decreased levels of aluminemia and significant neurological improvement over time.

Discussion:

This diagnosis should be entertained in patients with movement disorders, cerebellar ataxia, pyramidal signs, and dementia of unknown etiology.

Highlights:

Aluminium encephalopathy (AE) is a neurological syndrome caused by aluminium neurotoxicity. Manifestations include cognitive impairment, motor dysfunction, microcytic anemia and bone disease. This case illustrates AE with hyperaluminemia associated with chronic exposure to industrial paints and clinical and biochemical reversibility after chelation therapy with ethylenediaminetetraacetic acid. Movement disorders are highlighted.

F-18 FDG PET brain imaging in symptomatic arthroprosthetic cobaltism

PURPOSE

Imaging studies of cobalt toxicity from cobalt-chromium alloy arthroprosthetics have focused on the local intra-articular and peri-articular presentation from failing joint replacements. Most studies investigating neurological findings have been small case series focused on the clinical findings of memory loss, diminished executive function, tremor, hearing and vision loss, depression, and emotional lability. This study utilizes software-based quantitative analysis of brain metabolism to assess the degree of hypometabolism and areas of susceptibility, determine if a pattern of involvement exists, and measure reversibility of findings after prosthetic revision to cobalt-free appliances.

METHODS

Over 48 months, 247 consecutive patients presenting to an orthopedic clinic with an arthroprosthetic joint containing any cobalt-chromium part were screened with whole blood and urine cobalt levels. A clinically validated inventory of 10 symptoms was obtained. Symptomatic patients with a blood cobalt level above 0.4 mcg/L or urine cobalt greater than 1 mcg/L underwent F-18 FDG PET brain imaging. Analysis was performed with FDA-approved quantitative brain analysis software with the pons as the reference region. Control group was the normal brain atlas within the software.

RESULTS

Of the 247 consecutively screened patients, 123 had blood and urine cobalt levels above the threshold. The 69 scanned patients had statistically significant regional hypometabolism and higher symptoms inventory. Fifty-seven patients were retained in the study. Distribution of hypometabolism was in descending order: temporal, frontal, Broca's areas, anterior cingulate, parietal, posterior cingulate, visual, sensorimotor, thalamic, and lastly caudate. Metal-on-metal (MoM) and metal-on-plastic (MoP) joint replacements produced similar patterns of hypometabolism. Of 15 patients with necessary revision surgery, 8 demonstrated improved metabolism when later re-scanned.

CONCLUSION

All scanned patients had regions of significant hypometabolism. Neurological toxicity from elevated systemic cobalt levels following arthroprosthetic joint replacement has a pattern of regional susceptibility similar to heavy metals and solvents, differing from classical dementias and may occur at blood and urine cobalt levels as low as 0.4 mcg/L and 1 mcg/L, respectively. Presently accepted thresholds for cobalt exposure and monitoring may need revision. Quantitative F-18 FDG PET brain imaging may aid in the decision process for treatment options and timing of possible medical versus surgical intervention.

Specific EEG Encephalopathy Pattern in SARS-CoV-2 Patients

We used quantified electroencephalography (qEEG) to define the features of encephalopathy in patients released from the intensive care unit after severe illness from COVID-19. Artifact-free 120-300 s epoch lengths were visually identified and divided into 1 s windows with 10% overlap. Differential channels were grouped by frontal, parieto-occipital, and temporal lobes. For every channel and window, the power spectrum was calculated and used to compute the area for delta (0-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) bands. Furthermore, Shannon's spectral entropy (SSE) and synchronization by Pearson's correlation coefficient () were computed; cases of patients diagnosed with either infectious toxic encephalopathy (ENC) or post-cardiorespiratory arrest (CRA) encephalopathy were used for comparison. Visual inspection of EEGs of COVID patients showed a near-physiological pattern with scarce anomalies. The distribution of EEG bands was different for the three groups, with COVID midway between distributions of ENC and CRA; specifically, temporal lobes showed different distribution for EEG bands in COVID patients. Besides, SSE was higher and hemispheric connectivity lower for COVID. We objectively identified some numerical EEG features in severely ill COVID patients that can allow positive diagnosis of this encephalopathy.

Acute toxic encephalopathy induced by occupational exposure to 1,2-dichloropropane

1,2-Dichloropropane (1,2-DCP) is used widely in Korea as a substitute for trichloroethylene or methylene chloride. Some companies mistakenly consider that 1,2-DCP is an eco-friendly detergent because its use is not regulated, but 1,2-DCP is known to inhibit the central nervous system in animals; a few cases of accidental exposure have been reported in humans. We present a case of acute encephalopathy caused by exposure to 1,2-DCP. A 41 yr-old male presented with dizziness, headache, and diplopia after exposure to the detergent without protective equipment. Brain magnetic resonance imaging suggested metabolic encephalopathy, but the patient had no thiamine deficiency and no other metabolic disorder. As the symptoms had commenced after exposure to a large amount of solvent while skimming rust from the surface, and as the symptoms were more severe during the work week, improved on weekends, and disappeared after solvent exposure ceased, the toxic encephalopathy was likely induced by inhalation of the detergent.

An aggravated return-to-work case of organic solvent induced chronic toxic encephalopathy

Background

Organic solvent-induced chronic toxic encephalopathy (CTE) is known as a non-progressive disorder that does not progress after diagnosis. The authors present a case those symptoms worsened after continued exposure to organic solvent after returning to work. Because such a case has not been reported in South Korea to the best of our knowledge, we intend to report this case along with literature review.

Case presentation

A 59-year-old man, who performed painting job at a large shipyard for 20 years, was receiving hospital treatment mainly for depression. During the inpatient treatment, severe cognitive impairment was identified, and he visited the occupational and environmental medicine outpatient clinic for assessing work relatedness. In 1984, at the age of 27, he began performing touch-up and spray painting as a shipyard painter. Before that he had not been exposure to any neurotoxic substances. In 2001, at the age of 44, after 15 years of exposure to mixed solvents including toluene, xylene and others, he was diagnosed with CTE International Solvent Workshop (ISW) type 2A. After 7 years of sick leave, he returned to work in 2006. And he repeated return-to-work and sick leave in the same job due to worsening of depressive symptoms. He had worked four times (2006–2010, 2011–2011, 2011–2011, 2016–2017) for a total of 5 years as a shipyard painter after first compensation. During the return-to-work period, the mean values of the mixed solvent index ranged from 0.57 to 2.15, and except for a one semiannual period, all mean values were above the standard value of 1. We excluded other diseases that can cause cognitive impairment like central nervous system diseases, brain injury, psychological diseases and metabolic diseases with physical examinations, laboratory tests, and brain image analysis. And finally, throughout neuropsychological tests, an overall deterioration in cognitive function was identified compared to 2002, and the deterioration types was similar to that often shown in the case of CTE; thus a diagnosis of CTE (ISW) type 3 was made.

Conclusion

This case is showing that CTE can go on with continued exposure to mixed solvents. Appropriate “fitness to work” should be taken to prevent disease deterioration especially for the sick leave workers.

Malaria Prevention, Mefloquine Neurotoxicity, Neuropsychiatric Illness, and Risk-Benefit Analysis in the Australian Defence Force

The Australian Defence Force (ADF) has used mefloquine for malaria chemoprophylaxis since 1990. Mefloquine has been found to be a plausible cause of a chronic central nervous system toxicity syndrome and a confounding factor in the diagnosis of existing neuropsychiatric illnesses prevalent in the ADF such as posttraumatic stress disorder and traumatic brain injury. Overall health risks appear to have been mitigated by restricting the drug's use; however serious risks were realised when significant numbers of ADF personnel were subjected to clinical trials involving the drug. The full extent of the exposure, health impacts for affected individuals, and consequences for ADF health management including mental health are not yet known, but mefloquine may have caused or aggravated neuropsychiatric illness in large numbers of patients who were subsequently misdiagnosed and mistreated or otherwise failed to receive proper care. Findings in relation to chronic mefloquine neurotoxicity were foreseeable, but this eventuality appears not to have been considered during risk-benefit analyses. Thorough analysis by the ADF would have identified this long-term risk as well as other qualitative risk factors. Historical exposure of ADF personnel to mefloquine neurotoxicity now also necessitates ongoing risk monitoring and management in the overall context of broader health policies.

Iron deficiency increases blood concentrations of neurotoxic metals in children

Iron deficiency affects approximately one-third of the world's population, occurring most frequently in children aged 6 months to 3 years. Mechanisms of iron absorption are similar to those of other divalent metals, particularly manganese, lead, and cadmium, and a diet deficient in iron can lead to excess absorption of manganese, lead, and cadmium. Iron deficiency may lead to cognitive impairments resulting from the deficiency itself or from increased metal concentrations caused by the deficiency. Iron deficiency combined with increased manganese or lead concentrations may further affect neurodevelopment. We recently showed that blood manganese and lead concentrations are elevated among iron-deficient infants. Increased blood manganese and lead levels are likely associated with prolonged breast-feeding, which is also a risk factor for iron deficiency. Thus, babies who are breast-fed for prolonged periods should be given plain, iron-fortified cereals or other good sources of dietary iron.

Sex-specific Profiles of Blood Metal Levels Associated with Metal-Iron Interactions

The mechanisms by which iron is absorbed are similar to those of divalent metals, particularly manganese, lead, and cadmium. These metals, however, show different toxicokinetics in relation to menarche or menopause, although their interaction with iron is the same. This review focuses on the kinetics of these three toxic metals (manganese, lead, and cadmium) in relation to menarche, pregnancy, and menopause. The iron–manganese interaction is the major factor determining sex-specific differences in blood manganese levels throughout the whole life cycle. The effects of estrogen overshadow the association between iron deficiency and increased blood lead concentrations, explaining why women, despite having lower ferritin concentrations, have lower blood lead concentrations than men. Iron deficiency is associated with elevated cadmium levels in premenopausal women, but not in postmenopausal women or men; these findings indicate that sex-specific differences in cadmium levels at older ages are not due to iron–cadmium interactions, and that further studies are required to identify the source of these differences. In summary, the potential causes of sex-specific differences in the blood levels of manganese, lead, and cadmium differ from each other, although all these three metals are associated with iron deficiency. Therefore, other factors such as estrogen effects, or absorption rate as well as iron deficiency, should be considered when addressing environmental exposure to toxic metals and sex-specific differences in the blood levels of these metals.

Iron Deficiency is Not Associated with Increased Blood Cadmium in Infants

OBJECTIVES

To determine whether blood cadmium concentration is elevated in iron-deficient infants.

METHODS

Blood cadmium and serum ferritin concentrations, serum iron/total iron-binding capacity (Fe/TIBC) and complete blood counts were measured in 31 iron deficient and 36 control infants, aged 6-24 months. All 31 iron-deficient infants received iron supplementation for 1-6 months.

RESULTS

Blood cadmium concentrations were measured again in 19 of the iron deficient infants after their ferritin levels returned to the normal range. The mean blood cadmium concentration did not differ significantly in iron deficient and control infants. The mean blood cadmium concentration in the 19 iron-deficient infants was not significantly altered by ferric hydroxide treatment, while their hemoglobin, ferritin, and Fe/TIBC (%) concentrations were significantly higher after than before treatment.

CONCLUSION

These findings indicate that iron deficiency does not increase blood cadmium concentrations in infants, in contrast with the effects of iron deficiency on manganese and lead concentrations.

Blood manganese concentration is elevated in infants with iron deficiency

The present study was done to determine whether blood Mn concentration is elevated in iron-deficient infants. Thirty-one infants with iron deficiency and thirty-six control subjects (6-24 months of age) were tested for blood Mn concentration, complete blood counts, serum ferritin, and serum iron/transferring iron-binding capacity (Fe/TIBC). All the 31 iron-deficient infants were treated with iron supplement; however, 19 of them underwent blood Mn checkup again in compliance with follow-up schedule when their ferritin levels returned to the normal range. Iron therapies were done for 1-6 months (mean, 2.8; standard deviation, 1.6) using ferric hydroxide-polymaltose complex (6 mg/kg Fe(3+) daily). Infants with iron deficiency had a higher mean blood Mn concentration than controls (2.550 vs. 1.499 μg/dL, respectively). After iron therapy, the blood Mn levels of iron-deficient infants significantly decreased compared to their pre-therapy levels (2.045 vs. 2.971 μg/dL, respectively), and their hemoglobin and ferritin levels significantly increased. After adjustment for covariates (e.g., age and breast-feeding), multiple linear regression models showed that increased blood Mn levels were significantly associated with low serum ferritin and hemoglobin levels, whereas with Fe/TIBC there was only a tendency. Our results indicate that iron deficiency increases blood Mn levels in infants, presumably by increasing Mn absorption.