Neuroimaging, Cognitive, and Neurobehavioral Outcomes Following Carbon Monoxide Poisoning

Carbon monoxide poisoning with hippocampi lesions on MRI: cases report and literature review

BACKGROUND

Carbon monoxide (CO) poisoning is now one of the leading causes of poisoning-related mortality worldwide. The central nervous system is the most vulnerable structure in acute CO poisoning. MRI is of great significance in the diagnosis and prognosis of CO toxic encephalopathy. The imaging features of CO poisoning are diverse. We report atypical hippocampal lesions observed on MRI in four patients after acute CO exposure.

CASE PRESENTATIONS

We report four patients who presented to the emergency department with loss of consciousness. The diagnosis of CO poisoning was confirmed on the basis of their detailed history, physical examination and laboratory tests. Brain MRI in all of these patients revealed abnormal signal intensity in hippocampi bilaterally. They all received hyperbaric oxygen therapy. The prognosis of all four patients was poor.

CONCLUSION

Hippocampi, as a relatively rare lesion on MRI of CO poisoning, is of important significance both in the early and delayed stages of acute CO poisoning. In this article, we summarize the case reports of hippocampal lesions on MRI in patients with CO poisoning in recent years, in order to provide reference for the diagnosis and prognosis of CO poisoning.

Clinical significance of fractional anisotropy in cerebral white matter regional vulnerability caused by carbon monoxide poisoning: A systematic review and meta-analysis

Carbon monoxide poisoning (COP) can lead to various cerebral white matter (WM) lesions across different disease phases and clinical manifestations, and fractional anisotropy (FA) of diffusion tensor imaging has been widely applied to investigate WM injury in these patients. Here we conduct a systematic review and meta-analysis to investigate the utility of FA in evaluating the regional vulnerability of WM injury caused by COP and explore differences between different disease phases and patient subtypes. We systematically searched PubMed, Medline, Scopus and reference lists of appropriate publications to identify relevant studies. Eight studies with 217 COP patients and 207 healthy controls (HCs) were included. Eight regions of interest were available to investigate regional vulnerability. The results showed the most significant decrease in FA in orbitofrontal subcortical regions. Comparisons of different disease phases revealed lower FA in the centrum semiovale and corpus callosum in the acute phase, while in the chronic phase, only FA in the centrum semiovale remained significantly decreased. Analysis of different patient subtypes showed that the FA values in the splenium of the corpus callosum were significantly decreased in the patients with delayed neurologic sequelae (DNS) but not in the mixed population (with and without DNS). In conclusion, this meta-analysis highlights the frontal-subcortical regional vulnerability in COP. FA changes in the corpus callosum across different disease phases reflect alterations in underlying microstructures. Extended corpus callosum injury involving the splenium could be an imaging biomarker of the occurrence of DNS.

Quantitative pupillary light reflex assessment for prognosis of carbon monoxide poisoning

Background

A non-reactive pupil in standard pupillary light reflex (sPLR) is regarded as a factor predicting neurological sequelae at 1-month after carbon monoxide (CO) poisoning. An automated pupillometer is used in the intensive care unit to quantitatively assess PLR. Quantitative PLR (qPLR) was superior to sPLR using penlight for prognosis of various neurological diseases. Therefore, this study aimed to analyze whether quantitative pupillary variables (neurological Pupil index [NPi] and qPLR) are superior to sPLR in predicting 1-month neurocognitive sequelae after acute CO poisoning.

Methods

We performed a prospective observational study of consecutive patients with acute CO poisoning admitted to an emergency department (ED) between August 2019 and December 2020 in a single academic medical center. sPLR and pupillometer examinations (qPLR and NPi) were performed by emergency physicians at the ED on hospital days 0-2. The lowest values among those recorded within 24 h and during the total measurement period were considered the 24-h and total lowest values, respectively. Global Deterioration Scale scores were measured at 1 month as an outcome and were dichotomized into favorable (1-4) or poor (5-7) outcomes.

Results

We analyzed the data of 104 adult patients with acute CO poisoning. qPLR was significantly higher in the favorable outcome group than in the poor outcome group 24-h and total lowest values (21.2% vs. 15.0%, p = 0.006 and 21.0% vs. 14.8%, p = 0.006). qPLR <18% had fair predictive power for poor neurocognitive outcomes [area under the curve (AUC), 0.70; 95% confidence interval (0.60-0.78)]. Among the patients with decreased mental status (Glasgow Coma Scale ≤12), the power of NPi and qPLR increased [AUC, 0.72 and AUC, 0.80]. NPi < 1 and qPLR <18% showed sensitivity (9.5% vs. 76.2%) and specificity (98.8% vs. 67.5%) for the prediction of poor outcomes. qPLR was significantly superior to sPLR in predicting poor neurocognitive outcomes at 1 month after CO poisoning (p = 0.007).

Conclusion

qPLR and NPi were superior to sPLR in terms of predicting poor neurocognitive outcomes. qPLR and NPi measured from hospital days 0-2 may be valuable in predicting neurocognitive outcome.

Abnormal Brain Functional Network Dynamics in Acute CO Poisoning

Aims: Carbon monoxide poisoning is a common condition that can cause severe neurological sequelae. Previous studies have revealed that functional connectivity in carbon monoxide poisoning is abnormal under the assumption that it is resting during scanning and have focused on studying delayed encephalopathy in carbon monoxide poisoning. However, studies of functional connectivity dynamics in the acute phase of carbon monoxide poisoning may provide a more insightful perspective for understanding the neural mechanisms underlying carbon monoxide poisoning. To our knowledge, this is the first study that explores abnormal brain network dynamics in the acute phase of carbon monoxide poisoning.

Methods: Combining the sliding window method and k-means algorithm, we identified four recurrent dynamic functional cognitive impairment states from resting-state functional magnetic resonance imaging data from 29 patients in the acute phase of carbon monoxide poisoning and 29 healthy controls. We calculated between-group differences in the temporal properties and intensity of dFC states, and we also performed subgroup analyses to separately explore the brain network dynamics characteristics of adult vs. child carbon monoxide poisoning groups. Finally, these differences were correlated with patients’ cognitive performance in the acute phase of carbon monoxide poisoning and coma duration.

Results: We identified four morphological patterns of brain functional network connectivity. During the acute phase of carbon monoxide poisoning, patients spent more time in State 2, which is characterized by positive correlation between SMN and CEN, and negative correlation between DMN and SMN. In addition, the fractional window and mean dwell time of State 2 were positively correlated with coma duration. The subgroup analysis results demonstrated that the acute phase of childhood carbon monoxide poisoning had greater dFNC time variability than adult carbon monoxide poisoning.

Conclusion: Our findings reveal that patients in the acute phase of carbon monoxide poisoning exhibit dynamic functional abnormalities. Furthermore, children have greater dFNC instability following carbon monoxide poisoning than adults. This advances our understanding of the pathophysiological mechanisms underlying acute carbon monoxide poisoning.

Neurocognitive sequelae after carbon monoxide poisoning and hyperbaric oxygen therapy

Carbon monoxide (CO) has been the leading cause of poisoning mortality in many countries and hyperbaric oxygen (HBO) is a widely accepted treatment for CO poisoning. However, some patients with CO poisoning will still develop neurocognitive sequelae regardless of HBO therapy, which can persist since CO poisoning or be present days to weeks after a recovery from CO poisoning. HBO has been used in the prevention and treatment of neurocognitive sequelae after CO poisoning, and some mechanisms are also proposed for the potential neuroprotective effects of HBO on the neurocognitive impairment after CO poisoning, but there is still controversy on the effectiveness of HBO on neurocognitive sequelae after CO poisoning. In this paper, we briefly introduce the neurocognitive sequelae after CO poisoning, summarize the potential predictive factors of neurocognitive sequelae, and discuss the use of HBO in the treatment and prevention of neurocognitive sequelae after CO poisoning.

Short- and long-term exposure to air pollution and lack of sunlight are associated with an increased risk of depression: A nested case-control study using meteorological data and national sample cohort data

Previous studies have suggested an increased risk of depression related to air pollutants. This study investigated the relationship of air pollutant exposure and meteorological factors with depression. The Korean National Health Insurance Service-Health Screening Cohort from 2002 to 2013 was analyzed. In total, 25,589 depression participants were 1:4 matched with 102,356 control participants for age, sex, income, and region of residence. Depression was defined based on a diagnosis (ICD-10: F31-33) by a psychiatric physician. Meteorological factors and air pollutants including sulfur dioxide (SO₂) (ppm), nitrogen dioxide (NO₂) (ppm), ozone (O₃) (ppm), carbon monoxide (CO) (ppm), and particulate matter with an aerodynamic diameter <10 μm (PM₁₀) (μg/m³) during the 30 days and 365 days before the index date were analyzed for associations with depression using conditional logistic regression. Subgroup analyses were performed according to age, sex, income, and region of residence. The odds ratios (ORs) for depression were 1.05 (95% CI = 1.02-1.08) at 365 days for 1 h less of sunshine. The ORs for depression were 1.02 (95% CI = 1.01-1.03) and 1.03 (95% CI = 1.00-1.05) at 30 days and 365 days for PM₁₀ (10 μg/m³), respectively. The ORs for depression were 1.18 (95% CI = 1.04-1.35) and 1.25 (95% CI = 1.07-1.47) at 30 days and 365 days for CO (ppm), respectively. In the subgroup analyses, the overall results were consistent. However, statistical significance diminished in the younger, high-income, and urban resident subgroups. Both short- and long-term exposure to PM₁₀ and CO and a reduced duration of sunshine were related to an increased risk of depression.

Altered regional homogeneity in delayed encephalopathy after carbon monoxide poisoning: A resting-state fMRI study

OBJECTIVE

To investigate alternations in spontaneous brain activities reflected by regional homogeneity (ReHo) in patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) using resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

Twenty-one patients with DEACMP and 21 age, sex and education matched healthy controls (HCs) received rs-fMRI scanning and clinical assessment. We used the ReHo method to analyze the interregional synchronized activity of all participants. Two sample t-tests were performed to compare the ReHo maps between the two groups. Pearson correlation analysis was then used to assess the correlations between clinical measures and abnormal ReHo in DEACMP patients.

RESULTS

Compared with HCs, DEACMP patients showed significantly decreased ReHo in bilateral cerebellum posterior lobe, pons, bilateral basal ganglia, while increased in the posterior cingulate, calcarine, bilateral occipital lobe(GRF correction, voxel P value <0.001, cluster P value <0.05). Negative correlation was found between Mini-mental State Examination (MMSE) scores and the ReHo values of posterior cingulate gyrus (r = -0.672, p < 0.05) in the DEACMP group, while positively related to the time from CO poisoning to MRI scan (r = 0.428, p < 0.05).

CONCLUSION

Patients with DEACMP exhibited altered ReHo in the multiple functional brain regions, which provide evidence for local brain dysfunctions and may help to understand the neuropathologic mechanism for the disease.

Nonmotor Symptoms in Vascular and Other Secondary Parkinsonism

Vascular parkinsonism (VP) is a relatively frequent variant of secondary parkinsonism caused by ischemic or hemorrhagic lesions of basal ganglia, midbrain, or their links with frontal cortex. According to different investigations, various forms of cerebrovascular disease cause 1%-15% of parkinsonism cases. Nonmotor symptoms are frequently found in VP and may negatively influence on quality of life. However, nonmotor symptoms such as hallucinations, orthostatic hypotension, REM-sleep behavior disorder, and anosmia are rarely revealed in VP, which may be noted to another diagnosis or mixed pathology. Clinical value of nonmotor symptoms in normal pressure hydrocephalus, toxic, and drug-induced parkinsonism is also discussed.

Advanced neuroimaging of carbon monoxide poisoning

Carbon monoxide (CO) inhalation is nowadays the most common cause of fatal poisoning worldwide. CO binds to haemoglobin 230-270 times more avidly than oxygen, thus leading to formation of carboxyhaemoglobin with subsequent reduction of tissue oxygenation. Brain is mainly affected due to its high oxygen requirement. Up to two-thirds of patients who survive the acute phase of this pathology present a delayed leukoencephalopathy, usually in a period ranging from two to 40 days. White matter damage closely relates to long-term prognosis of these patients. On the other hand CO seems to play a fundamental role as a possible neuro-protective agent in ischaemic stroke. Diagnostic imaging, with computed tomography and magnetic resonance imaging, especially magnetic resonance spectroscopy, is very useful to depict the presence and extension of this pathology, in both acute and late phase. Nevertheless, a correlation of imaging studies with clinical history and laboratory data is fundamental to perform the correct diagnosis. The purpose of this article is to highlight the imaging features of brain CO poisoning in acute and late phase, describing a case report of a 56-year-old man found unconscious at home.

Mitochondrial oxidative stress in female and male rat brain after ex vivo carbon monoxide treatment

Carbon monoxide (CO) is the most common cause of fatal poisoning all over the world. At the cellular level, a combination of tissue hypoxia and direct cellular damage underlie the pathophysiology of CO toxicity. The purpose of this study was to determine the effect of CO treatment on oxidative stress parameters in mitochondria isolated from male and female rat brains. Mitochondria prepared from frontal cortex, hippocampus and corpus striatum were treated with 0.1% CO at 37°C for 30 minutes; control samples were not exposed to CO. Cytochrome c oxidase activity (COX), lipid peroxidation (thiobarbituric acid reactive species = TBARS), protein oxidation (protein carbonyls) and glutathione (GSH) levels were measured in CO treated and control samples. Our results confirmed previous studies reporting the inhibition of cytochrome c oxidase activity by CO in rat brain. Additionally, protein carbonyl levels in the hippocampus and striatum significantly increased after CO treatment in male rats. While CO treatment caused a significant decrease in GSH levels in the cortex and striatum in male rats, reduced GSH levels were observed in the cortex and hippocampus in female rats following CO exposure. Taken together, our data suggest a role for mitochondrial oxidative stress in CO toxicity at the cellular level during CO poisoning. Human & Experimental Toxicology (2007) 26, 645—651

Carbon monoxide poisoning and risk of deep vein thrombosis and pulmonary embolism: a nationwide retrospective cohort study

BACKGROUND

Few studies have investigated the relationship between carbon monoxide (CO) poisoning and risk of deep vein thrombosis (DVT) and pulmonary embolism (PE). Therefore, we conducted a nationwide longitudinal cohort study in Taiwan to determine whether patients with CO poisoning are associated with increased risk of developing DVT and PE.

METHODS

This study investigated the incidence and risk factors for DVT and PE in 8316 patients newly diagnosed with CO poisoning from the Taiwan National Health Insurance Research Database between 2000 and 2011. The comparison cohort contained 33 264 controls without CO poisoning from the general population. Follow-up was initiated on the date of initial diagnosis of CO poisoning and continued until the date of a DVT or PE event, censoring or December 31, 2011. Cox proportional hazard regression models were used to analyse the risk of DVT and PE according to sex, age and comorbidities.

RESULTS

The incidences of DVT and PE were higher in the patients with CO poisoning than in the controls (5.67 vs 1.47/10 000 person-years and 1.97 vs 1.02/10 000 person-years, respectively). After adjusting for age, sex and comorbidities, the patients with CO poisoning were associated with a 3.85-fold higher risk of DVT compared with the comparison cohort, and non-significantly associated with risk of PE. CO poisoning patients with a coexisting comorbidity or acute respiratory failure were associated with significantly and substantially increased risk of DVT.

CONCLUSION

Risk of DVT is significantly higher in patients with CO poisoning than in the general population.

Structural and cognitive deficits in chronic carbon monoxide intoxication: a voxel-based morphometry study

BACKGROUND

Patients with carbon monoxide (CO) intoxication may develop ongoing neurological and psychiatric symptoms that ebb and flow, a condition often called delayed encephalopathy (DE). The association between morphologic changes in the brain and neuropsychological deficits in DE is poorly understood.

METHODS

Magnetic resonance imaging and neuropsychological tests were conducted on 11 CO patients with DE, 11 patients without DE, and 15 age-, sex-, and education-matched healthy subjects. Differences in gray matter volume (GMV) between the subgroups were assessed and further correlated with diminished cognitive functioning.

RESULTS

As a group, the patients had lower regional GMV compared to controls in the following regions: basal ganglia, left claustrum, right amygdala, left hippocampus, parietal lobes, and left frontal lobe. The reduced GMV in the bilateral basal ganglia, left post-central gyrus, and left hippocampus correlated with decreased perceptual organization and processing speed function. Those CO patients characterized by DE patients had a lower GMV in the left anterior cingulate and right amygdala, as well as lower levels of cognitive function, than the non-DE patients.

CONCLUSIONS

Patients with CO intoxication in the chronic stage showed a worse cognitive and morphologic outcome, especially those with DE. This study provides additional evidence of gray matter structural abnormalities in the pathophysiology of DE in chronic CO intoxicated patients.

Carbon monoxide poisoning

Carbon monoxide (CO) poisoning is the leading cause of death as a result of unintentional poisoning in the United States. CO toxicity is the result of a combination of tissue hypoxia-ischemia secondary to carboxyhemoglobin formation and direct CO-mediated damage at a cellular level. Presenting symptoms are mostly nonspecific and depend on the duration of exposure and levels of CO. Diagnosis is made by prompt measurement of carboxyhemoglobin levels. Treatment consists of the patient's removal from the source of exposure and the immediate administration of 100% supplemental oxygen in addition to aggressive supportive measures. The use of hyperbaric oxygen is controversial.

National carbon monoxide poisoning surveillance framework and recent estimates

OBJECTIVES

Unintentional, non-fire-related (UNFR) carbon monoxide (CO) poisoning is a leading cause of poisoning in the United States. A comprehensive national CO poisoning surveillance framework is needed to obtain accurate estimates of CO poisoning burden and guide prevention efforts. This article describes the current national CO poisoning surveillance framework and reports the most recent national estimates.

METHODS

We analyzed mortality data from the National Vital Statistics System multiple cause-of-death file, emergency department (ED) and hospitalization data from the Healthcare Cost and Utilization Project's Nationwide Emergency Department Sample and Nationwide Inpatient Sample, hyperbaric oxygen treatment (HBOT) data from HBOT facilities, exposure data from the National Poison Data System, and CO alarm prevalence data from the American Housing Survey and the National Health Interview Survey.

RESULTS

In the United States, 2,631 UNFR CO deaths occurred from 1999 to 2004, an average of 439 deaths annually. In 2007, there were 21,304 (71 per one million population) ED visits and 2,302 (eight per one million population) hospitalizations for confirmed cases of CO poisoning. In 2009, 552 patients received HBOT, and from 2000 to 2009, 68,316 UNFR CO exposures were reported to poison centers. Most nonfatal poisonings were among children (<18 years of age) and females; hospitalizations and deaths occurred more frequently among males and elderly people (>65 years of age). More poisonings occurred during winter months and in the Midwest and Northeast.

CONCLUSIONS

UNFR CO poisoning poses a significant public health burden. Systematic evaluation of data sources coupled with modification and expansion of the surveillance framework might assist in developing effective prevention strategies.

Hospital burden of unintentional carbon monoxide poisoning in the United States, 2007

BACKGROUND

Unintentional, non-fire-related (UNFR) carbon monoxide (CO) poisoning is a leading cause of poisoning in the United States, but the overall hospital burden is unknown. This study presents patient characteristics and the most recent comprehensive national estimates of UNFR CO-related emergency department (ED) visits and hospitalizations.

METHODS

Data from the 2007 Nationwide Inpatient and Emergency Department Sample of the Hospitalization Cost and Utilization Project were analyzed. The Council of State and Territorial Epidemiologists' CO poisoning case definition was used to classify confirmed, probable, and suspected cases.

RESULTS

In 2007, more than 230,000 ED visits (772 visits/million) and more than 22,000 hospitalizations (75 stays/million) were related to UNFR CO poisoning. Of these, 21,304 ED visits (71 visits/million) and 2302 hospitalizations (8 stays/million) were confirmed cases of UNFR CO poisoning. Among the confirmed cases, the highest ED visit rates were among persons aged 0 to 17 years (76 visits/million) and 18 to 44 years (87 visits/million); the highest hospitalization rate was among persons aged 85 years or older (18 stays/million). Women visited EDs more frequently than men, but men were more likely to be hospitalized. Patients residing in a nonmetropolitan area and in the northeast and midwest regions of the country had higher ED visit and hospitalization rates. Carbon monoxide exposures occurred mostly (>60%) at home. The hospitalization cost for confirmed CO poisonings was more than $26 million.

CONCLUSION

Unintentional, non-fire-related CO poisonings pose significant economic and health burden; continuous monitoring and surveillance of CO poisoning are needed to guide prevention efforts. Public health programs should emphasize CO alarm use at home as the main prevention strategy.

Smoking and everyday prospective memory: a comparison of self-report and objective methodologies

AIMS

To examine whether persistent smoking leads to impairments in self-reported and objective measures of prospective memory (PM: the cognitive ability to remember to carry out activities at some future point in time).

METHODS

An opportunity sample of 18 existing smokers and 22 who had never smoked were compared. An existing-groups design was utilised, comparing a smoking group with a never-smoked control group as the independent factor. Scores on the sub-scales of the Prospective and Retrospective Memory Questionnaire (PRMQ) and scores on the Cambridge Prospective Memory Test (CAMPROMPT) constituted the dependent factors. Age, mood, other drug use, strategy scores and IQ were also measured. Each participant was tested in a laboratory setting. Self-reported PM lapses were measured using the PRMQ. The CAMPROMPT was used as an objective measure of PM. Alcohol and other drug use were assessed by a Recreational Drug Use Questionnaire. The Hospital Anxiety and Depression Scale gauged levels of anxiety and depression. A strategy scale measured the number of strategies used to aid memory. The National Adult Reading Test measured IQ.

RESULTS

After observing no between-group differences on age, mood, alcohol use, strategy use, and IQ, smokers and the never-smoked did not differ on the self-reported lapses measured on the PRMQ. However, smokers recalled significantly fewer items on the CAMPROMPT than the never-smoked group.

CONCLUSION

The results of the present study suggest that persistent smoking leads to impairments in everyday PM.

Damage of white matter tract correlated with neuropsychological deficits in carbon monoxide intoxication after hyperbaric oxygen therapy

Carbon monoxide (CO) intoxication can result in cognitive deficits and demyelinating changes of the white matter (WM), for which hyperbaric-oxygen (HBO) treatment is considered effective in reducing neuropsychiatric symptoms. This study aimed to analyze cognitive functions and WM diffusion properties in CO intoxication after standard HBO treatment. Seventeen CO intoxicated patients were evaluated 4-6 months after HBO treatment. They also underwent diffusion tensor imaging (DTI) and cognitive assessment, and the results were compared with those from 34 age-matched controls. DTI was transformed into fractional anisotropy (FA) and mean diffusivity (MD) and assessed at every voxel level with tract-based spatial statistics across the brain. Correlation between reduced FA and increased MD with neuropsychological deficits were performed. Cognitive results showed that impairment in executive function, as well as verbal and visual memories, were most prominent. There were extensive areas of increased MD and decreased FA. Correlation analyses showed that memory retrieval, judgment, and verbal generation tasks were related to FA of the frontotemporal WM. MD showed weaker correlation with cognitive deficits. These data suggest that neurologic deficits and WM changes are detectable 4-6 months after HBO therapy. The correlation of WM diffusion with cognitive deficits also suggests that reduced connectivity between different cortical regions is a pathophysiologic mechanism.

Carbon monoxide-related hospitalizations in the U.S.: evaluation of a web-based query system for public health surveillance

OBJECTIVE

Carbon monoxide (CO) poisoning is preventable, yet it remains one of the most common causes of poisoning in the U.S. In the absence of a national data reporting system for CO-poisoning surveillance, the burden of CO-related hospitalizations is unknown. Our objective was to generate the first national estimates of CO-related hospitalizations and to evaluate the use of a Web-based query system for public health surveillance.

METHODS

The Healthcare Cost and Utilization Project's (HCUP's) 2005 Nationwide Inpatient Sample (NIS) data were used for CO-related hospitalization estimates. Data for confirmed, probable, and suspected cases were generated using the HCUPnet Web-based query system. We used data from 1993 through 2005 NIS to describe trends in CO-related hospitalizations. We used the Centers for Disease Control and Prevention's surveillance evaluation guidelines to evaluate the system.

RESULTS

In 2005, there were 24,891 CO-related hospitalizations nationwide: 16.9% (n=4,216) were confirmed, 1.1% (n=279) were probable, and 81.9% (n=20,396) were suspected CO-poisoning cases. Of the confirmed cases (1.42/100,000 population), the highest hospitalization rates occurred among males, older adults (aged > or = 85 years), and Midwestern residents. CO-related hospitalization rates declined from 1993 through 2000 and plateaued from 2001 through 2005. The simplicity, acceptability, sensitivity, and representativeness of the HCUPnet surveillance system were excellent. However, HCUPnet showed limited flexibility and specificity.

CONCLUSIONS

Nationwide, the burden of CO exposure resulting in hospitalization is substantial. HCUPnet is a useful surveillance tool that efficiently characterized CO-related hospitalizations for the first time. Public health practitioners can utilize this data source for state-level surveillance.

Air pollution and daily emergency department visits for depression

OBJECTIVES

To investigate the potential correlation between ambient air pollution exposure and emergency department (ED) visits for depression.

MATERIALS AND METHODS

A hierarchical clusters design was used to study 27 047 ED visits for depression in six cities in Canada. The data used in the analysis contain the dates of visits, daily numbers of diagnosed visits, and daily mean concentrations of air pollutants as well as the meteorological factors. The generalized linear mixed models technique was applied to data analysis. Poisson models were fitted to the clustered counts of ED visits with a single air pollutant, temperature and relative humidity.

RESULTS

Statistically significant positive correlations were observed between the number of ED visits for depression and the air concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2) and particulate matter (PM10). The percentage increase in daily ED visits was 15.5% (95% CI: 8.0-23.5) for CO per 0.8 ppm and 20.0% (95% CI: 13.3-27.2) for NO2 per 20.1 ppb, for same day exposure in the warm weather period (April-September). For PM10, the largest increase, 7.2% (95% CI: 3.0-11.6) per 19.4 ug/m3, was observed for the cold weather period (October-March).

CONCLUSIONS

The results support the hypothesis that ED visits for depressive disorder correlate with ambient air pollution, and that a large majority of this pollution results from combustion of fossil fuels (e.g. in motor vehicles).

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.

Longitudinal study of carbon monoxide intoxication by diffusion tensor imaging with neuropsychiatric correlation

BACKGROUND

White matter damage is common after carbon monoxide (CO) intoxication, but in vivo follow-up studies about the mechanism of white matter damage are not possible in pathology series. Diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) can quantify diffusion parameters and volumetric changes in white matter that can be correlated with neuropsychological performances in longitudinal studies.

METHODS

We examined 9 patients with CO intoxication using DTI, VBM and neuropsychologic tests at an average of 3 and 10 months after CO exposure. We used data from 18 age- and sex-matched controls for comparison.

RESULTS

We found that cognitive recovery at 10 months after CO intoxication was not significant, although it was after 3 months. The neuropsychologic tests correlated better for the fibre tract of the semicentrum ovale and not the periventricular fibres. Diffusion measures suggest increases in fractional anisotropy, mean diffusivity and axial eigenvalues over time, while increases in radial eigenvalue were evident at 3 months compared with controls. Periventricular white matter atrophy was observed 10 months after CO intoxication.

LIMITATIONS

Our study included few cases, and the interpretation of the putative changes on neuroimaging findings cannot be confirmed by histology.

CONCLUSION

Our study showed that the evolution of white matter injury in CO encephalopathy occurred over time. Cognitive recovery was not evident in the follow-up period because of white matter injuries.

Impaired grasping in a patient with optic ataxia: primary visuomotor deficit or secondary consequence of misreaching?

Optic ataxia is defined as a spatial impairment of visually guided reaching, but it is typically accompanied by other visuomotor difficulties, notably a failure to scale the handgrip appropriately while reaching to grasp an object. This impaired grasping might reflect a primary visuomotor deficit, or it might be a secondary effect arising from the spatial uncertainty associated with poor reaching. To distinguish between these possibilities, we used a new paradigm to tease apart the proximal and distal components of prehension movements. In the "far" condition objects were placed 30 cm from the hand so that subjects had to make a reaching movement to grasp them, whereas in the "close" condition objects were placed adjacent to the hand, thereby removing the need for a reaching movement. Stimulus eccentricity was held constant. We tested a patient with optic ataxia (M.H.), whose misreaching affects only his right hand within the right visual hemifield. M.H. showed a clear impairment in grip scaling, but only when using his right hand to grasp objects in the right visual hemifield. Critically, this grip-scaling impairment was absent in M.H. in the "close" condition. These data suggest that M.H.'s grip scaling is impaired as a secondary consequence of making inaccurate reaching movements, and not because of any intrinsic visuomotor impairment of grasping. We suggest that primary misgrasping is not a core symptom of the optic ataxia syndrome, and that patients will show a primary deficit only when their lesion extends anteriorly within the intraparietal sulcus to include area aIPS.

Imaging for neuro-ophthalmic and orbital disease - a review

A literature review was performed by content experts in neuro-ophthalmology and neuroradiology using a systematic English-language Medline search (1994-2008) limited to articles with relevance to neuro-ophthalmic and orbital imaging. The information covered in this review includes: (i) the basic mechanics, indications and contraindications for cranial and orbital computed tomography and magnetic resonance (MR) imaging; (ii) the utility and indications for intravenous contrast, (iii) the use of specific MR sequences; (iv) the techniques and ophthalmic indications for computed tomography/MR angiography and venography; and (v) the techniques and indications for functional MR imaging, positron emission tomography scanning and single photon emission computed tomography. Throughout the review accurate and timely communication with the neuroradiologist regarding the clinical findings and suspected location of lesions is emphasized so as to optimize the ordering and interpretation of imaging studies for the ophthalmologist.

Carbon monoxide poisoning at motels, hotels, and resorts

BACKGROUND

Each year, more than 200 people in the United States die from carbon monoxide (CO) poisoning. Poisoning has occurred at motels, hotels, and resorts. Congressional mandate requires smoke alarms in all guest rooms; however, smoke alarms do not detect CO.

METHODS

Data on patients poisoned at hotels, motels, and resorts were evaluated at a hyperbaric medicine service. In 2005, legal databases and online news databanks were searched to discover additional incidents. Only victims evaluated in hospitals or declared dead at the scene were included. Cases of intentional poisoning and poisoning from fires were excluded.

RESULTS

Between 1989 and 2004, 68 incidents of CO poisoning occurring at hotels, motels, and resorts were identified, resulting in 772 accidentally poisoned: 711 guests, 41 employees or owners, and 20 rescue personnel. Of those poisoned, 27 died, 66 had confirmed sequelae, and 6 had sequelae resulting in a jury verdict. Lodging-operated, faulty room heating caused 45 incidents, pool/spa boilers 16, CO entrained from outdoors 5, and unreported sources caused 2 incidents. Public verdicts have averaged $4.8 million per incident (range, $1 million to $17.5 million). Poisoning occurred at hotels of all classes. Despite these incidents, most properties did not install CO alarms, and requirements for CO alarms at hotels, motels, and resorts are rare.

CONCLUSIONS

Guests of motels, hotels, and resorts remain at risk for injury or death from CO poisoning. Measures to prevent CO poisoning of guests and employees of the lodging industry should be evaluated.