Detection of Gray Matter Damage Using Brain MRI and SPECT in Carbon Monoxide Intoxication: A Comparison Study With Neuropsychological Correlation

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.

Surface-based morphometry study of brain in patients with carbon monoxide poisoning

PURPOSE

Although cortical volume abnormalities are frequently detected in patients with carbon monoxide poisoning (COP), particularly delayed neurological sequelae (DNS), the associated changes in cortical thickness and shape patterns remain unknown.

MATERIALS & METHODS

Using surface-based morphometry, we investigated the differences in cortical thickness and shape indices between a COP group (n = 44) vs healthy controls (HCs, n = 36), and between the DNS (n = 21) vs non-DNS (n = 23) subgroups. Additionally, the influence of cortical damage on neurological disorders was explored.

RESULTS

The COP group exhibited significant cortical thinning mainly in the bilateral fronto-parietal lobes (P < 0.05, family-wise error corrected). When cortical thinning in the bilateral parietal lobes, bilateral primary motor areas, left primary sensory areas, and bilateral paracentral lobules was explored in the DNS subgroups compared to the non-DNS subgroup (P < 0.05, FWE corrected), no differences in shape indices between the two subgroups were noted. In the COP group, there were significant positive correlations between the Mini-Mental State Examination (MMSE) score and cortical thickness in the right superior frontal gyrus (SFG) and bilateral rostral middle frontal gyrus (rMFG) (P < 0.05, false discovery rate corrected). There was no any significant correlation between cortical thickness and Neuropsychiatric inventory (NPI), UPDRS III scores (P > 0.05, FDR-corrected).

CONCLUSION

Cortical thickness is a more sensitive index than shape for measuring cortical damage in patients with COP exposure, as cortical thinning in the right SFG and bilateral rMFG is related to cognitive impairment.

Early gray matter atrophy and neurological deficits in patients with carbon monoxide poisoning

PURPOSE

To investigate early neurological deficits-related change patterns in gray matter (GM) volume in patients with carbon monoxide poisoning (COP) and GM volume differences between patients with and without delayed neurological sequelae (DNS) and those with and without T2 hyperintense lesions after COP.

METHODS

Forty-one COP patients (24 patients with DNS) and 36 sex- and age-matched healthy controls (HC) were enrolled in this study. The neurological assessments were administered within 24 h after MRI scans. Voxel-based morphometry analysis was used to detect regional GM volume change.

RESULTS

The COP group had statistically significant GM atrophy in the bilateral prefrontal and temporal lobes, anterior cingulate (ACC), thalamus, posterior cerebellum, and right hippocampus compared to the HC group. Atrophy in the left medial orbital superior frontal gyrus (SFG), bilateral ACC, and bilateral thalamus were related to lower Mini-Mental State Examination (MMSE) scores and higher Unified Parkinson's Disease Rating Scale subsection III and neuro-psychiatric inventory scores. Atrophy in the hippocampus and posterior cerebellum were also related to decrease MMSE scores. The DNS subgroup had greater GM atrophy in the limbic system than the non-DNS subgroup. Compared to the subgroup without T2 hyperintense lesions, greater GM atrophy in the limbic system, motor and visual cortex, and default network was observed in the subgroup with T2 hyperintense lesions.

CONCLUSION

GM atrophy in the medial orbital SFG, ACC, thalamus, hippocampus, and posterior cerebellum is associated with early neurological deficits in patients with COP. Greater atrophy occurred in patients with DNS and those with T2 hyperintense lesions.

The Legacy of the TTASAAN Report-Premature Conclusions and Forgotten Promises: A Review of Policy and Practice Part I

Brain perfusion single photon emission computed tomography (SPECT) scans were initially developed in 1970's. A key radiopharmaceutical, hexamethylpropyleneamine oxime (HMPAO), was originally approved in 1988, but was unstable. As a result, the quality of SPECT images varied greatly based on technique until 1993, when a method of stabilizing HMPAO was developed. In addition, most SPECT perfusion studies pre-1996 were performed on single-head gamma cameras. In 1996, the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (TTASAAN) issued a report regarding the use of SPECT in the evaluation of neurological disorders. Although the TTASAAN report was published in January 1996, it was approved for publication in October 1994. Consequently, the reported brain SPECT studies relied upon to derive the conclusions of the TTASAAN report largely pre-date the introduction of stabilized HMPAO. While only 12% of the studies on traumatic brain injury (TBI) in the TTASAAN report utilized stable tracers and multi-head cameras, 69 subsequent studies with more than 23,000 subjects describe the utility of perfusion SPECT scans in the evaluation of TBI. Similarly, dementia SPECT imaging has improved. Modern SPECT utilizing multi-headed gamma cameras and quantitative analysis has a sensitivity of 86% and a specificity of 89% for the diagnosis of mild to moderate Alzheimer's disease-comparable to fluorodeoxyglucose positron emission tomography. Advances also have occurred in seizure neuroimaging. Lastly, developments in SPECT imaging of neurotoxicity and neuropsychiatric disorders have been striking. At the 25-year anniversary of the publication of the TTASAAN report, it is time to re-examine the utility of perfusion SPECT brain imaging. Herein, we review studies cited by the TTASAAN report vs. current brain SPECT imaging research literature for the major indications addressed in the report, as well as for emerging indications. In Part II, we elaborate technical aspects of SPECT neuroimaging and discuss scan interpretation for the clinician.

Incidence Rate and Predictors of Globus Pallidus Necrosis after Charcoal Burning Suicide

Objective: This study examined predictors of globus pallidus necrosis as there was a paucity of literature of globus pallidus necrosis resulted from carbon monoxide poisoning after charcoal burning suicide. Methods: A total of 67 patients who had attempted charcoal burning suicide were recruited and stratified into two subgroups based on either presence (n = 40) or absence (n = 27) of globus pallidus necrosis. Demographic, clinical, laboratory, and radiographic data were obtained for cross-sectional analysis. All patients were followed to investigate the risks for mortality. Results: The patients aged 36.8 ± 11.1 years (67.2%) were male. Patients with globus pallidus necrosis were younger (p = 0.044) and had less hypertension (p = 0.015) than patients without globus pallidus necrosis. Furthermore, patients with globus pallidus necrosis suffered from severer medical complications, i.e., fever (p = 0.008), acute myocardial injury (p = 0.022), acute rhabdomyolysis (p = 0.022), and neuropsychiatric symptoms (p < 0.001) than patients without globus pallidus necrosis. Moreover, patients with globus pallidus necrosis received less hyperbaric oxygen therapy than without necrosis (p = 0.024). Two patients (3.0%) died on arrival. In a multivariable regression model, it was revealed that acute myocardial injury (odds ratio 4.6, confidence interval 1.1–18.9, p = 0.034) and neuropsychiatric symptoms (odds ratio 8.0, confidence interval 2.0–31.4, p = 0.003), decreased blood bicarbonate level (odds ratio 0.8, confidence interval 0.7–1.0, p = 0.032), and younger age (odds ratio 0.9, confidence interval 0.9–1.0, p = 0.038) were significant predictors for globus pallidus necrosis. Conclusion: Although patients who had attempted charcoal burning suicide had a low mortality rate (3.0%), globus pallidus necrosis was not uncommon (59.7%) in this population. Further studies are warranted.

Diffusion kurtosis imaging as a neuroimaging biomarker in patients with carbon monoxide intoxication

Attempting suicide by burning charcoal can lead to carbon monoxide (CO) intoxication and cognitive deficits. Changes in white matter (WM) quantified by diffusion tensor imaging (DTI)-derived parameters have been validated to reflect cognitive test scores. As diffusion kurtosis imaging (DKI) measures biological microstructures using non-Gaussian diffusivity, we assessed the added-information of DKI with neuropsychological test scores as the major outcome measure. A total of 45 patients were enrolled and compared with 30 age-matched controls. The patients were stratified into acute or chronic phase according to the intervals of intoxication and assessments. WM status was assessed using tract-based spatial statistics for DKI and DTI topographies, and the sensitivity/specificity of either model was tested using area under the curve (AUC) analysis. To evaluate their clinical significance, values of DKI- and DTI-derived parameters were extracted from seven regions of interest (ROI) and correlated with neuropsychiatric scores. The kurtosis parameters were lower in the patients than in the controls but none of the parameters provided differentiations between the acute or chronic phase. Kurtosis fractional anisotropy (KFA) had a higher AUC than fractional anisotropy while the other 3 DTI parameters had higher AUC than the corresponding DKI ones. In clinical correlations, KFA value of right posterior WM correlated with visual memory (r = 0.326, p = 0.029), and KFA values of bilateral posterior WM correlated with the digit forward score (right: r = 0.302, p = 0.043; left: r = 0.314, p = 0.036). Although DTI was more sensitive in reflecting disease status, KFA may be more sensitive and specific than fractional anisotropy in cognitive test score predictions.

N-Butylphthalide Improves Cognitive Function in Rats after Carbon Monoxide Poisoning

Cognitive impairment is the most common neurologic sequelae after carbon monoxide (CO) poisoning, and the previous investigations have demonstrated that N-Butylphthalide (NBP) could exert a broad spectrum of neuroprotective properties. The current study aimed to investigate the effect of NBP on cognitive dysfunction in rats after acute severe CO poisoning. Rats were randomly divided into a normal control group, a CO poisoning group and a CO+NBP group. The animal model of CO poisoning was established by exposure to CO in a chamber, and then all rats received hyperbaric oxygen therapy once daily, while rats in CO+NBP group were administered orally NBP (6 mg/ 100g) by gavage twice a day additionally. The results indicated that CO poisoning could induce cognitive impairment. The ultrastructure of hippocampus was seriously damaged under transmission electron microscopy, and the expressions of calpain 1 and CaMK II proteins were significantly elevated after CO exposure according to the analysis of immunofluorescence staining and western blot. NBP treatment could evidently improve cognitive function, and maintain ultrastructure integrity of hippocampus. The expression levels of both calpain 1 and CaMK II proteins in CO+NBP group were considerably lower than that of CO poisoning group (P < 0.05). Taken together, this study highlights the molecular mechanism of cognitive dysfunction in rats after CO exposure via the upregulation of both calpain 1 and CaMK II proteins. The administration of NBP could balance the expressions of calpain 1 and CaMK II proteins and improve cognitive function through maintaining ultrastructural integrity of hippocampus, and thus may play a neuroprotective role in brain tissue in rats with CO poisoning.

Cognitive severity-specific neuronal degenerative network in charcoal burning suicide-related carbon monoxide intoxication: a multimodality neuroimaging study in Taiwan

While carbon monoxide (CO) intoxication often triggers multiple intraneuronal immune- or inflammatory-related cascades, it is not known whether the pathological processes within the affected regions evolve equally in the long term. To understand the neurodegenerative networks, we examined 49 patients with a clinical diagnosis of CO intoxication related to charcoal burning suicide at the chronic stage and compared them with 15 age- and sex-matched controls. Reconstructions of degenerative networks were performed using T1 magnetic resonance imaging, diffusion-tensor imaging, and fluorodeoxyglucose positron emission tomography (PET). Tract-specific fractional anisotropy (FA) quantification of 11 association fibers was performed while the clinical significance of the reconstructed structural or functional networks was determined by correlating them with the cognitive parameters. Compared with the controls, the patients had frontotemporal gray matter (GM) atrophy, diffuse white matter (WM) FA decrement, and axial diffusivity (AD) increment. The patients were further stratified into 3 groups based on the cognitive severities. The spatial extents within the frontal-insular-caudate GM as well as the prefrontal WM AD increment regions determined the cognitive severities among 3 groups. Meanwhile, the prefrontal WM FA values and PET signals also correlated significantly with the patient's Mini-Mental State Examination score. Frontal hypometabolic patterns in PET analysis, even after adjusted for GM volume, were highly coherent to the GM atrophic regions, suggesting structural basis of functional alterations. Among the calculated major association bundles, only the anterior thalamic radiation FA values correlated significantly with all chosen cognitive scores. Our findings suggest that fronto-insular-caudate areas represent target degenerative network in CO intoxication. The topography that occurred at a cognitive severity-specific level at the chronic phase suggested the clinical roles of frontal areas. Although changes in FA are also diffusely distributed, different regional changes in AD suggested unequal long-term compensatory capacities among WM bundles. As such, the affected WM regions showing irreversible changes may exert adverse impacts to the interconnected GM structures.

Salvianolic acids attenuate rat hippocampal injury after acute CO poisoning by improving blood flow properties

Carbon monoxide (CO) poisoning causes the major injury and death due to poisoning worldwide. The most severe damage via CO poisoning is brain injury and mortality. Delayed encephalopathy after acute CO poisoning (DEACMP) occurs in forty percent of the survivors of acute CO exposure. But the pathological cause for DEACMP is not well understood. And the corresponding therapy is not well developed. In order to investigate the effects of salvianolic acid (SA) on brain injury caused by CO exposure from the view point of hemorheology, we employed a rat model and studied the dynamic of blood changes in the hemorheological and coagulative properties over acute CO exposure. Compared with the groups of CO and 20% mannitol + CO treatments, the severe hippocampal injury caused by acute CO exposure was prevented by SA treatment. These protective effects were associated with the retaining level of hematocrit (Hct), plasma viscosity, fibrinogen, whole blood viscosities and malondialdehyde (MDA) levels in red blood cells (RBCs). These results indicated that SA treatment could significantly improve the deformation of erythrocytes and prevent the damage caused by CO poisoning. Meanwhile, hemorheological indexes are good indicators for monitoring the pathological dynamic after acute CO poisoning.

¹⁸F-FP-(+)-DTBZ positron emission tomography detection of monoaminergic deficient network in patients with carbon monoxide related parkinsonism

BACKGROUND AND PURPOSE

Although parkinsonism after carbon monoxide (CO) intoxication is well known, neurotransmitter deficient networks that are responsible for the severity of parkinsonism have rarely been systemically evaluated.

METHODS

Eighteen patients with CO-related parkinsonism and nine age- and sex-matched controls were enrolled for detailed neurological examinations, three-dimensional T1-weighted images, diffusion tensor imaging and (18)F-9-fluoropropyl-(+)-dihydrotetrabenzazine ((18)F-FP-(+)-DTBZ) positron emission tomography (PET). The structural analysis included voxel-based morphometry to assess grey matter atrophy and tract-based spatial statistics related to white matter involvement. For presynaptic monoaminergic assessment, volume of interest analysis in six subcortical regions and non-parametric voxel-wise comparison were performed on PET images with estimation of registration parameters from magnetic resonance images. All the imaging modalities were compared between the patients and controls. For the patients, a regression model for correlation with cognitive behaviour and Unified Parkinson's Disease Rating Scale (UPDRS) score was used.

RESULTS

In the patients, monoaminergic deficit networks were found in the caudate, anterior putamen, anterior insular, thalamus and anterior cingulate cortex. The UPDRS revealed significant correlations with the prefrontal white matter fractional anisotropy values and with the (18)F-FP-(+)-DTBZ uptake values in the caudate nucleus, insular, medial prefrontal and dorsomedial thalamus. The neuropsychiatric inventory score correlated with the (18)F-FP-(+)-DTBZ uptake values in the anterior cingulate cortex and dorsolateral prefrontal cortex.

CONCLUSIONS

Our study demonstrated monoaminergic deficits and white matter damage networks in CO-related parkinsonism that determined the severity of parkinsonism or behaviour changes. As the substantia nigra was spared, the monoaminergic topography of involvement suggests a different pathophysiology in CO-related parkinsonism.

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.

Combined treatment of methylprednisolone pulse and memantine hydrochloride prompts recovery from neurological dysfunction and cerebral hypoperfusion in carbon monoxide poisoning: a case report

A 49-year-old healthy man developed sudden unconsciousness under inadequate ventilation. Blood gas analysis showed carboxyhemoglobin of 7.3%. After normobaric oxygen therapy, he recovered completely 7 days later. At 3 weeks after carbon monoxide (CO) exposures, memory and gait disturbances appeared. Neurological examination revealed Mini-Mental State Examination (MMSE) score of 5 of 30 points, leg hyper-reflexia with Babinski signs, and Parkinsonism. Brain fluid-attenuated inversion recovery imaging disclosed symmetric hypointense lesions in the thalamus and the globus pallidus, and hyperintense lesions in the cerebral white matter. Brain single-photon emission tomography (SPECT) scanning with (99m)Technesium-ethyl cysteinate dimer displayed marked hypoperfusion in the cerebellum, the thalamus, the basal ganglia, and the entire cerebral cortex. He was diagnosed as CO poisoning and treated with hyperbaric oxygen therapy. The neurological deficits were not ameliorated. At 9 weeks after neurological onset, methylprednisolone (1000 mg/day, intravenous, 3 days) and memantine hydrochloride (20 mg/day, per os) were administered. Three days later, MMSE score was increased from 3 to 20 points. Neurological examination was normal 3 weeks later. Brain SPECT exhibited 20% increase of regional cerebral blood flows in the cerebellum, the thalamus, the basal ganglia, and the entire cerebral cortex. These clinicoradiological changes supported that the treatment with steroid pulse and memantine hydrochloride could prompt recovery from neurological dysfunction and cerebral hypoperfusion. Further clinical trials are warranted whether such combined therapy can attenuate neurological deficits and cerebral hypoperfusion in patients with CO poisoning.