Carbon Monoxide Brain Toxicity: Clinical, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, and Neuropsychological Effects in 9 People

The role of carbon monoxide in aerotoxic syndrome

Chronic low-level exposure to toxic compounds in airplane cabin air may result in Aerotoxic Syndrome (AS). Aetiologic agents are organophosphates and numerous volatile organic hydrocarbons originating from leaks of engine oil and hydraulic fluids. Despite a documented history spanning decades, the role of carbon monoxide remains controversial. What evidence exists that carbon monoxide (CO), present in the cocktail of toxic compounds in bleed air, contributes to the AS? We selected 22 publications encompassing 888 flights with 18 different aircraft types. In one study of 100 flights, fume events were confirmed in 38. Four studies were initialized after air quality incidents. The cabin CO concentrations could be categorized in three levels, 1) low (<5 ppm), without health implications, 2) moderate (5-10 ppm) with probably health implications in case of chronic exposure, and 3) high > 10 ppm, with health effects in case of acute and chronic exposure. These levels were recorded in 12, 6 and 4 studies respectively. In the six studies in category 2, max CO concentrations ranged from 5.8-9.4 ppm. The four studies with CO > 10 ppm comprised 376 of the 888 flights (42%) with six aircraft types. Toxic CO levels ranging between 13-60 ppm were identified in at least 129 of 888 (14.5%) flights. In one study with high CO levels four flight attendants were diagnosed with CO poisoning with elevated HbCO levels. Max CO levels in aviation are either the same or higher than current occupational exposure limits (OEL) for ground-based workplace exposures or levels for urban street transport environments. Specific aspects of aviation should be taken into consideration: the effect of low(er) air pressure at high altitudes increasing the toxicity of CO, and the binding of CO to CYP enzymes, leading to impaired organophosphate detoxification. We conclude that CO must be considered an important factor in the lubrication derived cocktail of airborne toxic compounds causing AS. In line with the WHO advice, a reduction of the OEL to 5 ppm over 8 hr time weighted average (TWA) for aircrew is strongly recommended. And we advocate continuous monitoring during all phases of flight and installation of CO detectors in the air supply ducts to the aircraft cabin.

The efficiency of continuous positive airway pressure therapy in carbon monoxide poisoining in the emergency department

OBJECTIVE

To determine whether oxygen therapy with continuous positive airway pressure (CPAP) is superior to normobaric oxygen therapy in carbon monoxide poisoning.

METHODS

The study participants were 43 patients diagnosed with carbon monoxide poisoning between the dates 15 March and 30 June 2016 at the emergency department of an urban teaching hospital. The control group comprised patients who received normobaric oxygen therapy. The case group consisted of patients who underwent one-hour CPAP therapy. The primary outcome was the determination of the half-life of carboxyhemoglobin (COHb) with CPAP treatment. The CPAP and control groups were compared in terms of the reduction in COHb levels after 60 minutes of therapy.

RESULTS

The COHb level among patients in the CPAP group was lower in the 30th and 60th minutes. The half-life of COHb was apparently decreased in the CPAP group compared with the control group (control and case groups mean plasma half-life of COHb were 80.26 ± 12.70 and 36.20 ± 4.58 minutes, respectively).

CONCLUSION

The results of the present study demonstrate that CPAP therapy may be an effective option for oxygen therapy among patients with carbon monoxide intoxication; this is achieved by decreasing the half-life of COHb.

Isotopic biomonitoring of anthropic carbon emissions in a megalopolis

Atmospheric pollution has become a serious threat for human health and the environment. However, the deployment, operation and maintenance of monitoring networks can represent a high cost for local governments. In certain locations, the use of naturally occurring plants for monitoring pollution can be a useful supplement of existing monitoring networks, and even provide information when other types of monitoring are lacking. In this work, we (i) determined the tissue carbon content and the δ13C values for the epiphytic CAM bromeliad Tillandsia recurvata and the relationship of both parameters with the existing CO concentrations in the Valley of Mexico basin and (ii) mapped the spatial distribution of such elemental and isotopic composition for this plant within the basin, in order to assess its potential as an atmospheric biomonitor of carbon monoxide, a pollutant with important repercussions on public health. The CO concentrations in the basin ranged from 0.41 ppm at rural locations to 0.81 ppm at urban sites. The carbon content of T. recurvata, which averaged 42.9 ± 0.34% (dry weight), was not influenced by the surrounding CO concentration. In contrast, the δ13C depended on the sites where the plants were collected. For example, the values were -13.2‰ in rural areas and as low as -17.5‰ in an urban site. Indeed, the isotopic values had a positive linear relationship with the atmospheric CO concentrations. Given the close relationship observed between the isotopic composition of T. recurvata with the CO concentrations in the Valley of Mexico, the δ13C values can be useful for the detection of atmospheric carbonaceous emissions.

Simultaneous exposure to noise and carbon monoxide increases the risk of Alzheimer's disease: a literature review

Dementia is a syndrome of cognitive and functional decline, commonly occurring in later life as a result of neurodegenerative and cerebrovascular processes beginning earlier in the life course. An excess of free radicals has an essential role in neurodegenerative diseases and aging. This paper aims to review the effects of noise and carbon monoxide as a risk factor in Alzheimer's disease as well as the role of free radicals in the progress of Alzheimer's disease. Articles included in this review were identified through a search of the databases PubMed, Scopus, and Google Scholar using the search terms Alzheimer's disease, dementia, noise, reactive oxygen species, and Carbon Monoxide. The literature search was restricted to the years 1982 to 2020 and articles published in the English language. The metabolism rate of the body is very high when exposed to noise and carbon monoxide; this leads to overproduction of reactive oxygen species and oxidative stress conditions. Oxidative stress has an essential role in the mechanisms concerned in Alzheimer's disease. In addition to the consequences of noise and a chemical substance on the auditory system, they also have non-auditory effects that affect the brain and induced neurodegenerative disease.

Secondary parkinsonism due to drugs, vascular lesions, tumors, trauma, and other insults

In addition to neurodegenerative disorders, there are many secondary forms of parkinsonism. The most common cause for secondary parkinsonism is the intake of distinct drugs. Neuroleptics and calcium channel blockers have been mainly described to induce parkinsonism, but also other drugs were suspected to cause or worsen parkinsonism. Another common cause for secondary parkinsonism are vascular lesions (i.e. vascular parkinsonism). Furthermore, also brain tumors have been described as rare causes for parkinsonism. Moreover, parkinsonism can be caused by chronic traumatic encephalopathy, which is a special case, since secondary insults to the brain leads to the occurrence of a neuropathologically defined disease. Other rare causes for secondary parkinsonism are lesions caused by infectious or immunological diseases as well as toxins or street drugs.

Early white matter injuries associated with dopamine transporter dysfunction in patients with acute CO intoxication: A diffusion kurtosis imaging and Tc-99m TRODAT-1 SPECT study

PURPOSE

Patients with CO intoxication were demonstrated to exhibit white matter (WM) injuries, changes in substantia nigra, dopamine transporter dysfunctions of striatum and Parkinsonism symptoms. We aimed to investigate the relationship between WM injuries of dopaminergic pathways and dopamine transporter dysfunctions of the striatum in patients with acute CO intoxication using both diffusion kurtosis imaging (DKI) and single photon-emission computed tomography (SPECT).

MATERIALS AND METHODS

Seventeen patients with acute CO intoxication and 19 age- and gender-matched healthy subjects were enrolled. DKI data were acquired from all participants and Tc-99m-TRODAT-1 SPECT scan was performed on each patient. DKI datasets were fitted to obtain axial, radial and mean diffusivity, fractional anisotropy, axial, radial and mean kurtosis for voxel-based comparison. In addition, the TRODAT-1 binding ratio of the striatum was calculated using the occipital cortices as a reference. In significant regions, correlational analysis was performed to understand the relationship between DKI indices and TRODAT-1 binding ratio.

RESULTS

The results showed that DKI indices were significantly altered in multiple WM regions broadly involving the basal ganglia-thalamocortical circuit and nigrostriatal pathway. The correlation analysis further revealed significant correlations between DKI indices and the TRODAT-1 binding ratio in the nigrostriatal pathway (absolute correlation coefficients ranged from 0.5992 to 0.6950, p<0.05), suggesting that CO-induced early WM injuries were associated with dopamine transporter dysfunctions of striatum.

CONCLUSION

We concluded that DKI and Tc-99m-TRODAT-1 SPECT scans were helpful in early detection of global WM injuries associated with dysfunctions of dopamine transporter in patients with acute CO intoxication.

KEY POINTS

• Voxel-based diffusion kurtosis imaging analysis was helpful in globally detecting early white matter injuries in patients with acute CO intoxication. • CO-induced early white matter injuries were broadly located in basal ganglia-thalamocortical circuit and nigrostriatal pathway. • Early white matter injuries in dopaminergic pathways were significantly correlated with dopamine transporter dysfunctions of the striatum.

Delayed neurologic sequelae of carbon monoxide intoxication

Altered consciousness and accompanying neurological symptoms are both complex and challenging cases for emergency physicians. These are not specific and may be a sign of a variety of medical conditions including stroke and delayed neurological sequelae (DNS) is a recurrent transient neuropsychiatric consequence of CO intoxication. DNS produces a spectrum of varying symptoms and the diagnosis is primarily made on the basis of clinical features and radiological findings from CT and conventional MRI. In clinical practice, serious CO intoxication is treated only with oxygen therapy although no effective treatment exists. Emergency physicians play a major role in managing patients presenting with CO intoxication and preventing DNS.

Neuroimaging, Cognitive, and Neurobehavioral Outcomes Following Carbon Monoxide Poisoning

Carbon monoxide is a colorless, odorless gas produced as a byproduct of combustion. Carbon monoxide is the leading cause of poisoning injury and death worldwide. Morbidity following CO poisoning includes neurologic sequelae, neuropathologic abnormalities on brain imaging, neurobehavioral changes, and cognitive impairments. It is estimated that as high as 50% of individuals with carbon monoxide poisoning will develop neurologic, neurobehavioral, or cognitive sequelae. Carbon monoxide related cognitive impairments included impaired memory, attention, executive function, motor, visual spatial, and slow mental processing speed. Given the high rate of brain related morbidity and the fact that the majority of carbon monoxide is avoidable, awareness and prevention of carbon monoxide poisoning is warranted.

Erythropoietin Protects Rat Brain Injury from Carbon Monoxide Poisoning by Inhibiting Toll-Like Receptor 4/NF-kappa B-Dependent Inflammatory Responses

Inflammatory responses play critical roles in carbon monoxide (CO) poisoning-induced cerebral injury. The present study investigated whether erythropoietin (EPO) modulates the toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) inflammatory signaling pathways in brain injury after acute CO poisoning. EPO (2500 and 5000 U/kg) was injected subcutaneously twice a day after acute CO poisoning for 2 days. At 48 h after treatment, the expression levels of TLR4 and NF-κB as well as the levels of inflammatory cytokines in the hippocampal tissues were measured. Our results showed that CO poisoning induced a significant upregulation of TLR4, NF-κB, and inflammatory cytokines in the injured rat hippocampal tissues. Treatment with EPO remarkably suppressed the gene and protein expression levels of TLR4 and NF-κB, as well as the concentrations of TNF-α, IL-1β, and IL-6 in the hippocampal tissues. EPO treatment ameliorated CO poisoning-induced histological edema and neuronal necrosis. These results suggested that EPO protected against CO poisoning-induced brain damage by inhibiting the TLR4-NF-κB inflammatory signaling pathway.

Altered white matter metabolism in delayed neurologic sequelae after carbon monoxide poisoning: A proton magnetic resonance spectroscopic study

Proton magnetic resonance spectroscopy ((1)H-MRS) was recently used to examine altered metabolism in the white matter (WM) of patients experiencing carbon monoxide (CO) poisoning; however, only a small number of patients with delayed neurologic sequelae (DNS) were analyzed. We aimed to detect altered metabolism in the WM of patients with DNS using (1)H-MRS; to explore its clinical relevance in the management of patients experiencing CO poisoning. Patients experiencing acute CO poisoning underwent (1)H-MRS and cerebrospinal fluid (CSF) examination within 1week and at 1month after acute poisoning. Metabolites including choline-containing compounds (Cho), creatine (Cr), N-acetylaspartate (NAA), and lactate were measured from the periventricular WM. Myelin basic protein (MBP) concentrations were measured in CSF. Fifty-two patients experiencing acute CO poisoning (15 with DNS, 37 without DNS; median age, 49years; 65% males) underwent (1)H-MRS. Within 1week, NAA/Cr ratios, reflecting neuroaxonal viability, were lower in patients with DNS than in those without DNS (P<0.05). At 1month, when 9 of 15 patients (60%) developed DNS, Cho/Cr ratios were higher, and NAA/Cr and NAA/Cho ratios lower in patients with DNS (P=0.0001, <0.0001, and <0.0001, respectively), indicating increased membrane metabolism and decreased neuroaxonal viability. (1)H-MRS parameter abnormalities correlated with the elevation of MBP in CSF. The presence of a lactate peak was a predictor for a poor long-term outcome. (1)H-MRS within 1week may be useful for predicting DNS development; (1)H-MRS at 1month may be useful for discriminating patients with DNS and predicting long-term outcomes.

Carbon monoxide intoxication

Carbon monoxide (CO) is a colorless, odorless, nonirritant gas that accounts for numerous cases of CO poisoning every year from a variety of sources of incomplete combustion of hydrocarbons. These include poorly functioning heating systems, indoor propane-powered forklifts, indoor burning of charcoal burning briquettes, riding in the back of pick-up trucks, ice skating rinks using propane-powered resurfacing machines, and gasoline-powered generators that are not in correct locations. Once CO is inhaled it binds with hemoglobin to form carboxyhemoglobin (COHb) with an affinity 200 times greater than oxygen that leads to decreased oxygen-carrying capacity and decreased release of oxygen to tissues leading to tissue hypoxia. Ischemia occurs with CO poisoning when there is loss of consciousness that is accompanied by hypotension and ischemia in the arterial border zones of the brain. Besides binding to many heme-containing proteins, CO disrupts oxidative metabolism leading to the formation of free radicals. Once hypotension and unconsciousness occur with CO poisoning, lipid peroxidation and apoptosis follow. Because COHb has a short half-life, examination of other biomarkers of CO neurotoxicity that reflect inflammation or neuronal damage has not demonstrated consistent results. The initial symptoms with CO exposure when COHb is 15-30% are nonspecific, namely, headache, dizziness, nausea, fatigue, and impaired manual dexterity. However individuals with ischemic heart disease may experience chest pain and decreased exercise duration at COHb levels between 1% and 9%. COHb levels between 30% and 70% lead to loss of consciousness and eventually death. Following resolution of acute symptoms there may be a lucid interval of 2-40 days before the development of delayed neurologic sequelae (DNS), with diffuse demyelination in the brain accompanied by lethargy, behavior changes, forgetfulness, memory loss, and parkinsonian features. Seventy-five percent of patients with DNS recover within 1 year. Neuropsychologic abnormalities with chronic CO exposure are found even when magnetic resonance imaging (MRI) and magnetic resonance spectroscopy are normal. White-matter damage in the centrum semiovale and periventricular area and abnormalities in the globus pallidus are most commonly seen on MRI following CO exposure. Though not as common, toxic or ischemic peripheral neuropathies are associated with CO exposure in humans and animals. The cornerstone for treatment for CO poisoning is 100% oxygen using a tight-fitting mask for greater than 6 hours. The indications for treatment with hyperbaric oxygen to decrease the half-life of COHb remain controversial.

Cerebral proton magnetic resonance spectroscopy demonstrates reversibility of N-acetylaspartate/creatine in gray matter after delayed encephalopathy due to carbon monoxide intoxication: a case report

Introduction

Predictive markers for long-term outcome in carbon monoxide-intoxicated patients with late encephalopathy are desired. Here we present the first data demonstrating a full reversibility pattern of specific brain substances measured by cerebral proton magnetic resonance spectroscopy in a carbon monoxide-intoxicated victim. This may provide clinicians with important information when estimating patient outcome.

Case presentation

We report the case of a 40-year-old Caucasian woman with severe carbon monoxide poisoning who was treated with five repetitive sessions of hyperbaric oxygen therapy in a multiplace chamber (100 percent oxygen with a ventilator, 90 minutes exposure to 2.8 atmospheres absolute). Initially, our patient recovered completely after three days of hospitalization, but became encephalopathic after a lucid interval of four weeks. An examination of the brain with cerebral proton magnetic resonance spectroscopy showed a dramatically decrease in N-acetylaspartate to total creatine ratios and elevated lactate levels in the gray matter. Subsequently, our patient received six additional sessions of hyperbaric oxygen therapy with only minimal recovery. At six-month follow-up our patient showed significant improvement in cognition and neuromuscular coordination. Extraordinarily, the cerebral proton magnetic resonance spectroscopy measurements at relapse compared to measurements at follow-up (217 days post insult) revealed full reversal of the severe abnormalities in mid-occipital gray matter and partial reversal in white matter.

Conclusions

The present case indicates that cerebral proton magnetic spectroscopy provides valuable information on brain metabolism in patients presenting with delayed encephalopathy after acute carbon monoxide intoxication. The full reversal of N-acetylaspartate to total creatine ratios in gray matter has, to our knowledge, never been described before and shows that severe, initial measurements may not predict poor long-term patient outcome.

Delayed parkinsonism after CO intoxication: evaluation of the substantia nigra with inversion-recovery MR imaging

PURPOSE

To quantitatively investigate signal alterations of the substantia nigra in patients with delayed parkinsonism following CO intoxication, as seen on gray matter (GM)-suppressed inversion-recovery (IR) magnetic resonance (MR) images.

MATERIALS AND METHODS

This prospective study was approved by the local institutional review board, and written informed consent was obtained from all subjects. Thirteen patients with delayed onset of CO-induced parkinsonism (nine men and four women; mean age, 40.3 years), 13 age-matched CO-intoxicated patients without parkinsonism, and 13 age-matched healthy volunteers were examined with GM-suppressed IR MR imaging. The signal intensity of the substantia nigra was normalized to the adjacent normal-appearing white matter in the temporal lobe, followed by semiautomatic segmentation into medial, middle, and lateral parts by using a skeleton-based algorithm. Multivariate and univariate analyses and Spearman rank correlation test were performed to examine the relationships between variables. Clinical severity was assessed with the modified Hoehn and Yahr rating scale.

RESULTS

The normalized signal ratios in the middle and lateral segments of the substantia nigra were significantly higher in those with CO-induced parkinsonism, compared with those with CO intoxication without parkinsonism or normal volunteers (P=.02). For the medial segments, the ratios showed no significant differences among the groups. The normalized signal ratios of substantia nigra were correlated with the severity of parkinsonism, particularly in the lateral segments (ρ=0.927, P<.001).

CONCLUSION

CO toxicity to the substantia nigra plays a role in pathophysiologic mechanisms of CO-induced parkinsonism. GM-suppressed IR MR imaging is a useful tool in depicting substantia nigra injury following CO intoxication.

The association of physical examination abnormalities and carboxyhemoglobin concentrations in 21 dogs trapped in a kennel fire

OBJECTIVE

To evaluate physical examination findings and their association with carboxyhemoglobin (COHb) concentrations in 21 dogs that were exposed to smoke during a kennel fire.

SERIES SUMMARY

Twenty-one dogs were exposed to a kennel fire. Physical exam findings, presenting, and posttherapy COHb concentrations as well as therapeutic interventions were evaluated. COHb concentrations upon presentation were increased in all smoke inhalation exposed dogs. These dogs were compared to a small set of clinically normal staff-owned dogs who were not exposed to fire. Physical parameters significantly associated with higher COHb concentrations included lower body temperature, increased respiratory effort, abnormal respiratory auscultation, altered neurologic status, and length of hospital stay. Oxygen therapy resulted in a more rapid decline in COHb concentrations although 5 dogs still had mildly increased COHb concentrations 24-hour postadmission.

UNIQUE INFORMATION PROVIDED

This study describes the relationship of admitting clinical findings of dogs exposed to a kennel fire with their initial blood COHb concentrations. It also describes the resolution of increased COHb concentrations with use of oxygen therapy and hospitalization. Additionally, COHb concentrations for a control group of dogs was evaluated and compared to the dogs exposed to smoke inhalation.

Application of principal component analysis to study topography of hypoxic-ischemic brain injury

The regions at risk of ischemia following cardio-respiratory arrest have not been systematically analysed. This knowledge may be of use in determining the mechanism of ischemic injury at vulnerable sites. The aim of this study is to evaluate the use of principal component analysis to analyse the covariance patterns of hypoxic ischemic injury. The inclusion criteria were: age ≥ 17 years, cardio-respiratory arrest and coma on admission (2003-2011). Regions of ischemic injury were manually segmented on fluid attenuated inversion recovery (FLAIR) and diffusion weighted (DWI) sequences and linearly registered into common stereotaxic coordinate space. Topography of ischemic injury was assessed using principal component analysis (covariance data) and compared qualitatively against current method of topography analysis, the probabilistic method (frequency data). For the probabilistic data, subgroup analyses were performed using t-statistics while for the covariance data, subgroup analyses were performed by calculating the angle between the principle components. To account for bias due to a higher frequency of coma survivors in the studied group, we performed sensitivity analysis by sequentially removing coma survivors such that the final data set contained higher rate of death. Quantitative analysis between these methods could not be performed as they have different units of measurement. Forty one patients were included in this series (mean age ± SD=51.5 ± 18.9 years). In our probabilistic map, the highest frequency of ischemic injury on the DWI and FLAIR sequences was putamen (0.250), caudate (0.225), temporal lobes (0.175), occipital (0.150) and hippocampus (0.125). The first 6 principal components contained 77.7% of the variance of the data. The first component showed covariance between the deep grey matter nuclei and posterior cortical structures (contains 50.2% of the variance of the data). There was similarity in the findings of the subgroup analyses by the downtime whether it was assessed by t-statistics for probabilistic data or angle between the principal components for the covariance data. The sensitivity analysis showed that the pattern of ischemic injury did not change when the analysis was restricted to patients who died. In conclusion, PCA method has many advantages over probabilistic method. In the context of this dataset, PCA showed covariance between deep grey matter nuclei and the posterior cortical structures whereas the probabilistic map provided complementary information on the frequency of occurrence at these locations.

Imaging features of acquired pediatric metabolic and toxic white matter disorders

Acquired white matter abnormalities in children may be due to a broad spectrum of disorders, with the most significant related to metabolic and toxic etiologies. Recognition of the imaging appearance of neonatal hypoglycemia, nonketotic hyperglycemia, hyperammonemia, hepatic encephalopathy, and central pontine myelinolysis (CPM) is essential because prompt correction of the underlying metabolic abnormality may limit and, in some cases, reverse the cerebral damage. Toxic leukoencephalopathies encompass disorders caused by iatrogenic administration of pharmacologic agents and radiation therapy, poisoning by household substances, and recreational drug use. Although medication-induced leukoencephalopathies often show a propensity for reversibility of clinical and radiologic findings upon discontinuation of the offending substance, recreational drugs may cause white matter toxicity that often portends a poorer prognosis. Our discussion focuses on the clinical aspects, pathophysiological mechanisms, and imaging features of commonly encountered acquired metabolic and toxic leukoencephalopathies in the pediatric population.

Movement disorder emergencies in childhood

The literature on paediatric acute-onset movement disorders is scattered. In a prospective cohort of 52 children (21 male; age range 2mo-15y), the commonest were chorea, dystonia, tremor, myoclonus, and Parkinsonism in descending order of frequency. In this series of mainly previously well children with cryptogenic acute movement disorders, three groups were recognised: (1) Psychogenic disorders (n = 12), typically >10 years of age, more likely to be female and to have tremor and myoclonus (2) Inflammatory or autoimmune disorders (n = 22), including N-methyl-d-aspartate receptor encephalitis, opsoclonus-myoclonus, Sydenham chorea, systemic lupus erythematosus, acute necrotizing encephalopathy (which may be autosomal dominant), and other encephalitides and (3) Non-inflammatory disorders (n = 18), including drug-induced movement disorder, post-pump chorea, metabolic, e.g. glutaric aciduria, and vascular disease, e.g. moyamoya. Other important non-inflammatory movement disorders, typically seen in symptomatic children with underlying aetiologies such as trauma, severe cerebral palsy, epileptic encephalopathy, Down syndrome and Rett syndrome, include dystonic posturing secondary to gastro-oesophageal reflux (Sandifer syndrome) and Paroxysmal Autonomic Instability with Dystonia (PAID) or autonomic 'storming'. Status dystonicus may present in children with known extrapyramidal disorders, such as cerebral palsy or during changes in management e.g. introduction or withdrawal of neuroleptic drugs or failure of intrathecal baclofen infusion; the main risk in terms of mortality is renal failure from rhabdomyolysis. Although the evidence base is weak, as many of the inflammatory/autoimmune conditions are treatable with steroids, immunoglobulin, plasmapheresis, or cyclophosphamide, it is important to make an early diagnosis where possible. Outcome in survivors is variable. Using illustrative case histories, this review draws attention to the practical difficulties in diagnosis and management of this important group of patients.

The role of heart-type fatty acid-binding protein in the evaluation of carbon monoxide poisoning in rats

Acute carbon monoxide (CO) poisoning can cause early and persistent damages in tissues sensitive to hypoxia. This study investigated serum heart-type fatty acid-binding protein (H-FABP) levels as a biomarker of acute CO poisoning in rats. The rats were exposed to a mixture of either 3000 (group A) or 5000 (group B) parts per million (ppm) CO in air, or to ambient air (group C, control group). Blood samples were taken just before, immediately after and 6 hours after the exposure, and serum H-FABP and troponin-I levels were measured. The consciousness level was evaluated just after the exposure. The survival rate was monitored for 7 days. Serum H-FABP levels increased just after the CO exposure in both groups A and B. Additionally, H-FABP level was higher in group B than in group A, immediately after the exposure. However, serum troponin-I levels only increased at 6 hours after the CO exposure in groups A and B. Consciousness and survival rates in group B were lower than that in group A. Our results suggest that H-FABP might have potential to be an early and quantitative parameter of clinical severity and prognosis in CO poisoning.

S-100beta and neuron-specific enolase levels in carbon monoxide-related brain injury

INTRODUCTION

Carbon monoxide (CO) toxicity may cause persistent injuries in tissues sensitive to hypoxia. Neuropsychiatric sequelae may be observed in about 67% of cases after severe CO exposure.

AIM

The aims of this study were to demonstrate the usefulness of S-100beta and neuron-specific enolase (NSE) in CO intoxications, show the degree of neurological response, and determine the indications for hyperbaric oxygen treatment (HBOT) as biochemical markers.

RESULTS

The S-100beta and NSE levels of the sera of 30 patients were studied upon admittance and at the third and sixth hours. S-100beta levels were found to be high in all 3 analyses. There was no significant change in NSE levels. When the S-100beta levels were compared with Glasgow Coma Scale levels, a strong negative correlation was found for all hours (r = -0.7, -0.8; P = .00). The correlation between S-100beta and carboxyhemoglobin levels at the initial hour was found to be statistically significant (r = 0.4; P = .01). The S-100beta levels in patients receiving HBOT showed a considerable decrease compared with those in patients not receiving the treatment. The same decrease was valid for NSE, although it was insignificant.

CONCLUSION

S-100beta may be useful in evaluating intoxications as an early biochemical marker in CO intoxications, as well as in the differential diagnosis due to other causes, and in determining HBOT indications.

Accidental carbon monoxide poisoning presenting without a history of exposure: a case report

Introduction

Carbon monoxide poisoning is easy to diagnose when there is a history of exposure. When the exposure history is absent, or delayed, the diagnosis is more difficult and relies on recognising the importance of multi-system disease. We present a case of accidental carbon monoxide poisoning.

Case presentation

A middle-aged man, who lived alone in his mobile home was found by friends in a confused, incontinent state. Initial signs included respiratory failure, cardiac ischaemia, hypotension, encephalopathy and a rash, whilst subsequent features included rhabdomyolysis, renal failure, amnesia, dysarthria, parkinsonism, peripheral neuropathy, supranuclear gaze palsy and cerebral haemorrhage. Despite numerous investigations including magnetic resonance cerebral imaging, lumbar puncture, skin biopsy, muscle biopsy and electroencephalogram a diagnosis remained elusive. Several weeks after admission, diagnostic breakthrough was achieved when the gradual resolution of the patient's amnesia, encephalopathy and dysarthria allowed an accurate history to be taken for the first time. The patient's last recollection was turning on his gas heating for the first time since the spring. A gas heating engineer found the patient's gas boiler to be in a dangerous state of disrepair and it was immediately decommissioned.

Conclusion

This case highlights several important issues: the bewildering myriad of clinical features of carbon monoxide poisoning, the importance of making the diagnosis even at a late stage and preventing the patient's return to a potentially fatal toxic environment, and the paramount importance of the history in the diagnostic method.

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.

Brain injury after acute carbon monoxide poisoning: early and late complications

OBJECTIVE

The purposes of this article are to illustrate the variable CT and MRI features of carbon monoxide-induced brain injury and to discuss the underlying pathogenesis.

CONCLUSION

Carbon monoxide can produce different patterns of brain injury in the acute and delayed stages. CT and MRI are valuable in the delineation of disease extent and helpful for understanding the pathophysiologic mechanisms.

The allegory of a mountain: an environmental introduction to neurotoxicology

Overall, the area of human neurotoxicity offers significant difficulties as well as challenges in our attempts to maintain or enhance human well being. Many of the substances to which humans are being exposed are relatively new to the environment, i.e., the products of a sophisticated industrial development. As a result humans are exposed to volatile organic compounds not previously present in our environment in significant amounts. It is important to maintain our industrial complex and the economic growth of our society. The use of volatile organic compounds is often important to the success of the industry. However, it is also important for us to determine what concentration of a given substance may produce short-term effects or chronic long-term effects. Human exposure to these potentially toxic levels could then be prevented. This is especially true because once irreversible damage occurs there is no medical treatment that can lead to improvement. Therefore, prevention of neurotoxic injury is essential.

Carbon monoxide intoxication: an updated review

Carbon monoxide (CO), a highly toxic gas produced by incomplete combustion of hydrocarbons, is a relatively common cause of human injury. Human toxicity is often overlooked because CO is tasteless and odorless and its clinical symptoms and signs are non specific. The brain and the heart may be severely affected after CO exposure with carboxyhemoglobin (COHb) levels exceeding 20%. Damage occurs because the affinity of hemoglobin for CO is 210 times higher than for O(2). Hypoxic brain damage predominates in the cerebral cortex, cerebral white matter and basal ganglia, especially in the globus pallidus. Diagnosis requires clinical acumen and a high index of suspicion, combined with epidemiological data, clinical examination, analysis of ambient air CO and patient COHb levels; also required are cardiology evaluation including ECG as well as neurological evaluation including brain imaging (CT and/or MRI, MR spectroscopy), and neuropsychological testing. Although immediate O(2) breathing is sometimes an adequate treatment, hyperbaric oxygen therapy (HBO) is favored. Subsequently, only symptomatic therapy is available for the long-term sequelae of CO poisoning.

Diffusion-tensor MR imaging for evaluation of the efficacy of hyperbaric oxygen therapy in patients with delayed neuropsychiatric syndrome caused by carbon monoxide inhalation

The purpose of this study is to assess the efficacy of hyperbaric oxygen therapy (HBOT) in patients with delayed neuropsychiatric syndrome (DNS) caused by carbon monoxide (CO) inhalation using diffusion tensor magnetic resonance (MR) imaging and neuropsychological test. Conventional and diffusion tensor brain MR imaging exams were performed in six patients with DNS immediately before and 3 months after the HBOT to obtain fractional anisotropy (FA) values. Six age- and sex-matched normal control subjects also received MR exams for comparison. Mini-Mental State Examination (MMSE) was also performed in patients immediately before and 3 months after the HBOT. A significantly higher mean FA value was found in control subjects as compared with the patients both before and 3 months after the HBOT (P < 0.001). The mean FA value 3 months after the HBOT was also significantly higher than that before the HBOT in the patient group (P < 0.001). All of the patients regained full scores in the MMSE 3 months after the HBOT. Diffusion tensor MR imaging can be a quantitative method for the assessment of the white matter change and monitor the treatment response in patients of CO-induced DNS with a good clinical correlation. HBO may be an effective therapy for DNS.

Pyramidal and extrapyramidal dysfunction as a sequela of hypoxic injury: case report

Background

The clinical and radiological aspects of hypoxic brain injury without ischemia are not well characterized. A spectrum of clinical manifestations have been observed in patients that recover from hypoxic brain injury, including a subset that demonstrate persistent motor system disturbances. Early Magnetic Resonance Imaging (MRI) studies have shown abnormalities in basal ganglia, cerebral and cerebellar cortex.

Case presentation

A 23-year-old man was affected by acute respiratory failure after drug overdose. His clinical condition progressed from coma to partial recovery with persistent lack of control and stiffness in the lower extremities. MRI of the brain showed evolving lesions in the cerebellum, globus pallidus and motor cortex that correlated with neurological signs.

Conclusion

A careful analysis of this case and a review of the relevant literature indicate that the clinical residua after recovery from hypoxic injury to the brain is predominantly disorders of the motor system, and the MRI manifestations as well as the clinical presentation can evolve over time. Understanding more of the factors that affect hypoxic brain injury can be helpful in determining the clinical outcome and management of these patients.

Accumulation of oxidatively generated DNA damage in the brain: a mechanism of neurotoxicity

Unrepaired or erroneously repaired DNA lesions drive genomic instability and contribute to cellular and organ decline. Since delayed neuropathologies are common in survivors of smoke inhalation injuries, we asked whether the integrity of brain DNA might be compromised by acute exposure to combustion smoke. Although many studies demonstrate that the brain is equipped to repair oxidatively damaged DNA, to date, the capacity for accurate DNA repair under conditions of disrupted oxygenation and oxidative stress has not been defined. We show that DNA adducts detectable by their ability to block PCR amplification form in the rat hippocampus after acute exposure to smoke. To identify the different types of adducts and to dissect their temporal formation and repair profiles in vivo in the brain, we used DNA-modifying enzymes to convert specific adducts into strand breaks prior to PCR amplification. Using this strategy, we detected formation of oxidative DNA adducts early on after smoke inhalation, while mismatched bases emerged at the later recovery times, potentially due to an erroneous DNA repair process. Erroneous repair can be mutagenic and because the initial smoke-induced oxidative damage to DNA is extensive, compromised fidelity of DNA repair may underlie neurotoxicity and contribute to delayed death of hippocampal neurons.

Troubles cognitifs dus à l’intoxication oxycarbonée: étude neuropsychologique et IRM de 5 cas

INTRODUCTION

Carbon monoxide (CO) poisoning has been shown to result in cognitive impairments. These disorders have rarely been reported. The present study aimed to evaluate these disturbances in five patients with a neuroanatomical study.

METHODS

There were two men and three women with an average of 25 years old. Patients were explored several months after acute CO poisoning. Neuropsychological testing was administered to assess memory, intellectual, executive, visual-spatial and constructional functions, language, praxis and gnosis. Cerebral magnetic resonance imaging (MRI) was performed in all patients using axial, sagittal and coronal slides with T1 and T2 weighted and flair images. None of the subjects had hyperbaric oxygen. They received 7, 5 mg bromocriptine per day.

RESULTS

All patients presented cognitive disorders including marked impairment in long term memory with a severe defect in recall performance in comparison to recognition memory. Visual memory was more affected than the verbal one. There were also moderate disturbances in intellectual, executive, visual-spatial and constructional functions. One patient presented alexia agraphia, severe visual disturbances, constructional and dressing apraxia. Four patients had depression and one psychic akinesia. Cerebral MRI studies revealed that all patients had bilateral pallidal necrosis, bilateral hippocampal and moderate cortical atrophy. Fornix atrophy was found in 2 patients and corpus mammillary atrophy in 3 patients. Others lesions were also found: bilateral cerebellar in two cases and cortical in three cases. Treatment with bromocriptine was effective in three cases. There was no improvement in the patients treated 14 months and 5 years following CO poisoning.

CONCLUSION

Neuropsychological impairments in CO poisoned subjects include memory, intellectual, executive, and visuospatial defects. In addition to pallidal necrosis, which is a typical feature of CO poisoning, hippocampal and cortical atrophy are often present. Bromocriptine can improve the cognitive disorders.

The Value of Morphological Neuroimaging after Acute Exposure to Toxic Substances

Many toxic agents induce brain dysfunction and/or lesions. Modern neuroimaging techniques, such as CT and more recently magnetic resonance imaging (MRI), are able to demonstrate toxic brain lesions at both early and delayed phases of disease progression. In the early phase, neuroimaging enables the detection of acutely injured brain areas responsible for sudden onset of neurological dysfunction, but the severity and the extension of brain lesions on neuroimages do not necessarily parallel the severity of the clinical status. In the chronic phase, when neurological dysfunction has become permanent, neuroimaging allows precise identification of neuroanatomical sequelae that do not necessarily match the severity of the chronic neurological impairment. Papers in the medical imaging literature have dealt mainly with the brain changes induced by 'chronic exposure' to toxic substances such as solvents or heavy metals. This article selectively reviews the main radiological changes observed on CT/magnetic resonance (MR) neuroimages after 'acute exposure' to industrial products (methanol [methyl alcohol], ethylene glycol), environmental agents (cyanide, carbon monoxide), pharmaceuticals (insulin, valproic acid) and illicit substances (heroin, cocaine). Different kinds of lesions, which lack specificity for toxic injury, can be observed on radiological images, but deep grey matter lesions with symmetrical distribution throughout basal ganglia are most often seen. However, such findings have also been reported after anoxic-ischaemic insults or during severe metabolic disturbances. Lesions in the white matter may also be present in the case of acute exposure to toxic agents. The true prognostic value of toxic-induced brain changes in the acute phase in CT or MR studies is unclear, although serial MRI may add new information as may quantitative or molecular imaging techniques such as the MR diffusion-weighted imaging or MR spectroscopy.