Magnetic resonance detects brainstem changes in chronic, active heavy drinkers

Imaging neuroinflammation in individuals with substance use disorders

Increasing evidence suggests a role of neuroinflammation in substance use disorders (SUDs). This Review presents findings from neuroimaging studies assessing brain markers of inflammation in vivo in individuals with SUDs. Most studies investigated the translocator protein 18 kDa (TSPO) using PET; neuroimmune markers myo-inositol, choline-containing compounds, and N-acetyl aspartate using magnetic resonance spectroscopy; and fractional anisotropy using MRI. Study findings have contributed to a greater understanding of neuroimmune function in the pathophysiology of SUDs, including its temporal dynamics (i.e., acute versus chronic substance use) and new targets for SUD treatment.

Brain metabolite alterations related to alcohol use: a meta-analysis of proton magnetic resonance spectroscopy studies

Alcohol misuse and alcohol use disorder (AlUD) have neurobiological consequences. This meta-analysis of proton magnetic resonance spectroscopy (MRS) studies aimed to assess the differences in brain metabolite levels in alcohol misuse and AUD relative to controls (PROSPERO registration: CRD42020209890). Hedge's g with random-effects modeling was used. Sub-group and meta-regression techniques explored potential sources of demographic and MRS parameter heterogeneity. A comprehensive literature review identified 43 studies, resulting in 69 models across gray and white matter (GM, WM). Lower N-acetylaspartate levels were found in frontal, anterior cingulate cortex (ACC), hippocampal, and cerebellar GM, and frontal and parietal WM, suggesting decreased neuronal and axonal viability. Lower choline-containing metabolite levels (all metabolites contributing to choline peak) were found in frontal, temporal, thalamic, and cerebellar GM, and frontal and parietal WM, suggesting membrane alterations related to alcohol misuse. Lower creatine-containing metabolite levels (Cr; all metabolites contributing to Cr peak) were found in temporal and occipital cortical GM, while higher levels were noted in midbrain/brainstem GM; this finding may have implications for using Cr as an internal reference. The lack of significant group differences in glutamate-related levels is possibly related to biological and methodological complexities. The few studies reporting on GABA found lower levels restricted to the ACC. Confounding variables were age, abstinence duration, treatment status, and MRS parameters (echo time, quantification type, data quality). This first meta-analysis of proton MRS studies consolidates the numerous individual studies to identify neurometabolite alterations within alcohol misuse and AUD. Future studies can leverage this new formalized information to investigate treatments that might effectively target the observed disturbances.

Shapes of subcortical structures in adolescents with and without familial history of substance use disorder

It has been suggested that intergenerational transmission of risk for substance use disorder (SUD) manifests in the brain anatomy of substance naïve adolescents. While volume and shapes of subcortical structures (SSS) have been shown to be heritable, these structures, especially the pallidum, putamen, nucleus accumbens, and hippocampus, have also been associated with substance use disorders. However, it is not clear if those anatomical differences precede substance use or are the result of that use. Therefore, we examined if volume and SSS of adolescents with a family history (FH+) of SUD differed from adolescents without such a history (FH−). Because risk for SUD is associated with anxiety and impulsivity, we also examined correlations between these psychological characteristics and volume/SSS. Using structural MRI and FSL software, we segmented subcortical structures and obtained indices of SSS and volumes of 64 FH+ and 58 FH− adolescents. We examined group differences in volume and SSS, and the correlations between volume/SSS and trait anxiety and impulsivity. FH+ adolescents had a significant inward deformation in the shape of the right anterior hippocampus compared to FH− adolescents, while the volume of this structure did not differ between groups. Neither shape nor volume of the other subcortical structures differed between groups. In the FH+ adolescents, the left hippocampus shape was positively correlated with both trait anxiety and impulsivity, while in FH− adolescents a negative correlation pattern of SSS was seen in the hippocampus. SSS appears to capture local anatomical features that traditional volumetric analysis does not. The inward shape deformation in the right anterior hippocampus in FH+ adolescents may be related to the known increased risk for behavioral dysregulation leading to SUD in FH+ offspring. Hippocampus shape also exhibits opposite patterns of correlation with anxiety and impulsivity scores across the FH+ and FH− adolescents. These novel findings may reveal neural correlates, not captured by traditional volumetric analysis, of familial transmission of increased vulnerability to SUD.

Alterations of Metabolites in the Frontal Cortex and Amygdala Are Associated With Cognitive Impairment in Alcohol Dependent Patients With Aggressive Behavior

BACKGROUND

Alcohol dependence (AD) patients have a high prevalence of aggressive behavior (AB). The frontal cortex and amygdala contains various neurotransmitter systems and plays an important role in AB, which is also associated with cognitive deficits. However, to date, no study has addressed the association of metabolites in the frontal cortex and amygdala with cognitive deficits in Chinese aggressive behavior-alcohol dependent patients(AB-ADs).

METHODS

We recruited 80 male AD and 40 male healthy controls (HCs), who completed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), the Modified Overt Aggression Scale (MOAS), and the proton magnetic resonance spectroscopy (¹H MRS) scan using 3.0T Siemens. The ¹H MRS data were automatically fitted with a linear combination model for quantification of metabolite levels of n-acetyl-aspartate (NAA), glutamate (Glu), Choline (Cho) and creatine (Cr). Metabolite levels were reported as ratios to Cr.

RESULTS

The AB-ADs group scored significantly lower than the non-aggression-alcohol dependent patients (NA-ADs) on these two RBANS subscales (immediate memory and attention function indices). The AB-ADs group showed a significant reduction in NAA/CR ratio in the left frontal cortex and Cho/Cr ratio in the left amygdala, and elevation in Glu/Cr ratio in the bilateral amygdala, compared with the NA-ADs group. The NAA/Cr ratio in the left frontal cortex was positively associated with immediate memory (r=0.60, P<0.05), and the Glu/Cr ratio in the right amygdala was negatively associated with delayed memory (r=-0.44,P<0.05) in AB-ADs group.

CONCLUSIONS

Metabolite alterations in the frontal cortex and amygdala may be involved in the pathophysiology of AB in AD and its associated cognitive impairment, especially immediate memory and delayed memory.

Imaging the Addicted Brain: Alcohol

Alcohol use disorder (AUD) represents a major public health issue due to its prevalence and severe health consequences. It may affect several aspects of an individual's life including work and relationships, and it also increases risk for additional problems such as brain injury. The causes and outcomes of AUD are varied; thus, attempting to understand this complex phenomenon requires investigation from multiple perspectives. Magnetic resonance imaging (MRI) is a powerful means to investigate brain anatomical and functional alterations related to AUD. Recent advances in MRI methods allow better investigation of the alterations to structural and functional brain networks in AUD. Here, we focus on findings from studies using multiple MRI techniques, which converge to support the considerable vulnerability of frontal systems. Indeed, MRI studies provide evidence for a "disconnection syndrome" which could be involved in the poor behavioral control observed in AUD.

Quantitative assessment of neurochemical changes in a rat model of long-term alcohol consumption as detected by in vivo and ex vivo proton nuclear magnetic resonance spectroscopy

The aim of present study was to quantitatively investigate the neurochemical profile of the frontal cortex region in a rat model of long-term alcohol consumption, by using in vivo proton magnetic resonance spectroscopy ((1)H-MRS) at 4.7 T and ex vivo(1)H high-resolution magic angle spinning (HR-MAS) technique at 11.7 T. Twenty male rats were divided into two groups and fed a liquid diet for 10 weeks. After 10 weeks, in vivo(1)H MRS spectra were acquired from the frontal cortex brain region. After in vivo(1)H MRS experiments, all animals were sacrificed and 20 frontal cortex tissue samples were harvested. All tissue examinations were performed with the 11.7 T HR-MAS spectrometer and high-resolution spectra were acquired. The in vivo and ex vivo spectra were quantified as absolute metabolite concentrations and normalized ratios of total signal-intensity (i.e., metabolitesNorm), respectively. The absolute quantifications of in vivo spectra showed significantly higher glycerophosphocholine plus phosphocholine (GPC+PCh) and lower myo-inositol (mIns) concentrations in ethanol-treated rats compared to controls. The quantifications of ex vivo spectra showed significantly higher PChNorm, ChoNorm and tChoNorm, and lower GPCNorm and mInsNorm ratio levels in ethanol-treated rats compared to controls. Our findings suggest that reduced mIns concentrations caused by the long-term alcohol consumption may lead to hypo-osmolarity syndrome and astrocyte hyponatremia. In addition, increased choline-containing compound concentrations may reflect an increased cell turnover rate of phosphatidylcholine and other phospholipids, indicating an adaptive mechanism. Therefore, these results might be utilized as key markers in chronic alcohol intoxication metabolism.

Ex vivo detection for chronic ethanol consumption-induced neurochemical changes in rats

The aim of this study was to quantitatively investigate the chronic ethanol-induced cerebral metabolic changes in various regions of the rat brain, using the proton high resolution magic angle spinning spectroscopy technique. The rats were divided into two groups (control group: N=11, ethanol-treated group: N=11) and fed with the liquid diets for 10 weeks. In each week, the mean intake volumes of liquid diet were measured. The brain tissues, including cerebellum (Cere), frontal cortex (FC), hippocampus (Hip), occipital cortex (OC) and thalamus (Thal), were harvested immediately after the end of experiments. The ex vivo proton spectra for the five brain regions were acquired with the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence at 500-MHz NMR spectrometer. All of the spectra were processed using the LCModel software, with simulated basis-set file, and the metabolite levels were referenced to total creatine. In the ethanol liquid diet group, there were significant increases in the metabolites ratio levels, as compared to control (Cere: alanine, glutathione, and N-acetlyaspartate; FC: phosphocholine and taurine; Hip: alanine, glutamine, and N-acetylaspartate; OC: glutamine; Thal: alanine, γ-aminobutyric acid, glutamate, glycerophosphocholine, phosphocholine, taurine, and free choline). However, in the ethanol liquid diet group, the myo-inositol levels of the OC were significantly lower. The present study demonstrates how chronic ethanol consumption affects cerebral metabolites in the chronic ethanol-treated rat. Therefore, this result could be useful to pursue clinical applications for quantitative diagnosis in human alcoholism.

Alcohol and the human brain: a systematic review of different neuroimaging methods

BACKGROUND

Imaging techniques have been in widespread use in the scientific community for more than 3 decades. They facilitate noninvasive, in vivo studies of the human brain in both healthy and diseased persons. These brain-imaging techniques have contributed significantly to our understanding of the effects of alcohol abuse and dependence on structural and functional changes in the human brain. A systematic review summarizing these contributions has not previously been conducted, and this is the goal of the current paper.

METHODS

The databases PubMed, PsycINFO, and PSYNDEX were searched using central key words. Fulfilling the inclusion criteria were 140 functional and structural imaging studies, together comprising data from more than 7,000 patients and controls. The structural imaging techniques we considered were cranial computerized tomography and various magnetic resonance imaging-based techniques, including voxel-based morphometry, deformation-based morphometry, diffusion tensor magnetic resonance imaging, and diffusion-weighted magnetic resonance imaging. The functional methods considered were magnetic resonance spectroscopy, positron emission tomography, single photon emission computed tomography, and functional magnetic resonance imaging.

RESULTS

Results from studies using structural imaging techniques have revealed that chronic alcohol use is accompanied by volume reductions of gray and white matter, as well as microstructural disruption of various white matter tracts. These changes are partially reversible following abstinence. Results from functional imaging methods have revealed metabolic changes in the brain, lower glucose metabolism, and disruptions of the balance of neurotransmitter systems. Additionally, functional imaging methods have revealed increased brain activity in the mesocorticolimbic system in response to alcohol-themed pictures relative to nondrug-associated stimuli, which might be of predictive value with regard to relapse.

CONCLUSIONS

There has been tremendous progress in the development of imaging technologies. Use of these technologies has clearly demonstrated the structural and functional brain abnormalities that can occur with chronic alcohol use. The study of the alcoholic brain provides an heuristic model which furthers our understanding of neurodegenerative changes in general, as well as their partial reversibility with sustained abstinence. Additionally, functional imaging is poised to become an important tool for generating predictions about individual brain functioning, which can then be used as a basis for personalized medicine.

Morphology of the adult midsagittal brainstem in relation to the reference systems MRI-based variability study

RATIONALE AND OBJECTIVES

Anterior/posterior commissure reference system (AC/PC reference system) and the fastigium/ventricular floor plane reference system (FFL/VFL reference system) are two reference systems used in the stereotactic localization of the invisible nuclei of the brainstem in magnetic resonance (MR) images. This study investigated the variation of the midsagittal brainstem in relation to the AC/PC and VFL/FFL reference systems with respect to age and gender.

MATERIALS AND METHODS

High-resolution T1-weighted structural MR images were acquired from 64 adults (age range 21-60 years, 32 males and 32 females). The AC/PC and VFL/FFL reference systems were identified automatically. A set of landmarks of the midsagittal brainstem were defined and localized interactively.

RESULTS

Results illustrated that there was significant difference between the variance of the anteroposterior coordinate of the landmarks in relation to the AC/PC reference system and that in relation to the FFL/VFL reference system (P < .05), the former is larger than the latter. The positions of the landmarks in the females are more anterior than those in the males in relation to the AC/PC reference (P < .05); the difference in relation to the FFL/VFL reference system was not found.

CONCLUSION

Either the FFL/VFL reference system or the AC/PC reference system has its own advantage in the stereotactic localization of the structure in the brainstem.

The effect of ethanol on human brain metabolites longitudinally characterized by proton MR spectroscopy

The effect ethanol exerts on the human brain has not yet been addressed by longitudinal magnetic resonance (MR) spectroscopic experiments. Therefore, we longitudinally characterized cerebral metabolite changes in 15 healthy individuals by proton magnetic resonance spectroscopy ((1)H-MRS) subsequent to the ingestion of a standard beverage (mean peak blood alcohol concentration (BAC): 51.43 +/- 10.27 mg/dL). Each participant was examined before, over 93.71 +/- 11.17 mins immediately after and 726.36 +/- 94.96 mins (12.11 +/ -1.58 h) past per os alcohol exposure. Fronto-mesial and cerebellar ethanol concentrations over time were similar as determined by the LCModel analysis of spectral data. Alcohol-induced changes of fronto-mesial creatine, choline, glucose, inositol and aspartate levels at 5.79 +/- 2.94 [corrected] mins upon ingestion as well as cerebellar choline and inositol levels at 8.64 +/- 2.98 [corrected] mins past exposure. Closely associated with ethanol concentrations, supratentorial creatine, choline, inositol and aspartate levels decreased after ethanol administration, whereas glucose levels increased. Similarly, infratentorial choline and inositol concentrations were negatively correlated with ethanol levels over time. There were no changes in N-acetyl-aspartate levels upon alcohol exposure. Furthermore, no influence of ethanol on brain water integrals was detected. Ethanol consumption may directly increase oxidative stress and the neuronal vulnerability to it. In addition, our results are compatible with ethanol-induced cell membrane modifications and alternative energy substrate usage upon alcohol exposure.

Degradation of association and projection white matter systems in alcoholism detected with quantitative fiber tracking

BACKGROUND

Excessive alcohol use can cause macrostructural tissue shrinkage with regional preference for frontal systems. The extent and locus of alcoholism's effect on white matter microstructure is less known.

METHODS

Quantitative fiber tracking derived from diffusion tensor imaging (DTI) assessed the integrity of samples of 11 major white matter bundles in 87 alcoholics (59 men, 28 women) and 88 healthy control subjects (42 men, 46 women). Fiber integrity was expressed as fractional anisotropy (FA) and apparent diffusion coefficient (ADC), quantified separately for longitudinal diffusivity (lambdaL), a putative index of axonal integrity, and transverse diffusivity (lambdaT), a putative index of myelin integrity.

RESULTS

Alcoholism affected FA and diffusivity, particularly lambdaT, of several fiber bundles. Frontal and superior sites (frontal forceps, internal and external capsules, fornix, and superior cingulate and longitudinal fasciculi) showed greatest abnormalities in alcoholics relative to control subjects. More posterior and inferior bundles were relatively spared. Lifetime alcohol consumption correlated with regional DTI measures in alcoholic men but not women. When matched for alcohol exposure, alcoholic women showed more DTI signs of white matter degradation than alcoholic men in several fiber bundles. Among all alcoholics, poorer performance on speeded tests correlated with DTI signs of regional white matter degradation.

CONCLUSIONS

This survey of multiple brain fiber systems revealed a differential pattern of alcoholism's effect on regional FA and diffusivity with functional consequences attributable in part to compromised fiber microstructure with prominence in signs of myelin degradation. Sex-based differences suggest that women are at enhanced risk for alcoholism-related degradation in selective white matter systems.

Neuroimmunity, drugs of abuse, and neuroAIDS

It has long been postulated that drugs of abuse may represent significant cofactors in the progression of human immunodeficiency virus (HIV)-induced disease. Both HIV infection and drugs of abuse have significant effect on the immune system as well as on the nervous system. In HIV infection, abnormalities in these systems intersect to lead to a constellation of symptoms known as neuroAIDS. Drugs of abuse may synergize with such damage, acting on immune and/or neural cells. However, definitive epidemiological evidence for such an interaction is lacking. Here we review such studies as well as the use of the nonhuman primate/simian immunodeficiency virus system to investigate the interaction of neuroAIDS with drugs of abuse. Furthermore, recent findings on mechanisms of actions of selected drugs reveal the possibility of protective as well as detrimental effects on the central nervous system damage induced by HIV.

Deformation-based morphometry reveals brain atrophy in frontotemporal dementia

OBJECTIVE

To compare deformation-based maps of local anatomical size between subjects with frontotemporal dementia (FTD) and healthy subjects to identify regions of the brain involved in FTD.

DESIGN

Structural magnetic resonance images were obtained from 22 subjects with FTD and 22 cognitively normal, age-matched controls. We applied deformation-based morphometry and compared anatomy between groups using an analysis of covariance model that included a categorical variable denoting group membership and covaried for head size.

SETTING

University of California, San Francisco, Memory and Aging Center, and the San Francisco Veterans Affairs Medical Center.

PATIENTS

Twenty-two subjects with FTD and 22 cognitively normal, age-matched controls.

INTERVENTIONS

Neurological, neuropsychological, and functional evaluations and magnetic resonance imaging.

MAIN OUTCOME MEASURE

Deformation maps of local anatomical size.

RESULTS

Patients with FTD showed extensive, significant atrophy of the frontal lobes, affecting both gray matter and white matter. Atrophy of similar magnitude but less significance was observed in the anterior temporal lobes. The subcortical and midbrain regions, particularly the thalamus, pons, and superior and inferior colliculi, showed strongly significant atrophy of smaller magnitude.

CONCLUSIONS

We confirmed frontal and anterior temporal gray matter atrophy in FTD. The observed white matter loss, thalamic involvement, and midbrain atrophy are consistent with pathological findings in late-stage FTD. Dysfunction of ventral-frontal-brainstem circuitry may underlie some of the unique clinical features of FTD.

A widespread distinct pattern of cerebral atrophy in patients with alcohol addiction revealed by voxel-based morphometry

BACKGROUND

Patients with alcohol addiction show a number of transient or persistent neurological and psychiatric deficits. The complexity of these brain alterations suggests that several brain areas are involved, although the definition of the brain alteration patterns is not yet accomplished.

AIM

To determine brain atrophy patterns in patients with alcohol dependence.

METHODS

Voxel-based morphometry (VBM) of grey matter (GM) and white matter (WM) was performed in 22 patients with alcohol dependence and in 22 healthy controls matched for age and sex.

RESULTS

In patients with alcohol dependence, VBM of GM revealed a significant decrease in density (p<0.001) in the precentral gyrus, middle frontal gyrus, insular cortex, dorsal hippocampus, anterior thalamus and cerebellum compared with controls. Reduced density of WM was found in the periventricular area, pons and cerebellar pedunculi in patients with alcohol addiction.

CONCLUSIONS

Our findings provide evidence that alcohol addiction is associated with altered density of GM and WM of specific brain regions. This supports the assumption that alcohol dependence is associated with both local GM dysfunction and altered brain connectivity. Also, VBM is an effective tool for in vivo investigation of cerebral atrophy in patients with alcohol addiction.

Supratentorial profile of white matter microstructural integrity in recovering alcoholic men and women

BACKGROUND

Postmortem and in vivo studies consistently report degeneration of brain white matter in alcohol-dependent men and women. The full extent of the white matter involvement in uncomplicated alcoholism, however, is unknown, yet knowledge of the distribution of white matter degradation might provide clues to mechanisms underlying the pathology.

METHODS

To examine whether the white matter involvement is widespread or, alternatively, is regionally restricted in uncomplicated alcoholism, we used in vivo magnetic resonance diffusion tensor imaging (DTI) to quantify the microstructure of brain tissue. Accordingly, we acquired DTI data in 57 alcoholics (40 men, 17 women) who had been sober, on average, for 3 months and 74 demographically-matched control subjects (32 men, 42 women). Alcoholic men had consumed about twice as much alcohol in their lifetimes as the alcoholic women. Supratentorial white matter fractional anisotropy (FA), a DTI measure of intravoxel orientational coherence of tissue, was calculated across the full anterior-posterior extent of the brain in coronal sections, and a slice profile of the mean white matter FA was created for each subject. Group differences between alcoholics and control subjects were tested for each slice in three regions: the left and right hemispheres and a midsagittal sample; men and women were tested separately.

RESULTS

Alcoholic men and women each showed widespread FA deficits in all three regions relative to their gender-matched control subjects that were evident on a slice-by-slice basis. Furthermore, the number of slices showing FA deficits was significantly greater in the alcoholic men than women.

CONCLUSIONS

The widespread distribution of white matter deficits is in contrast to the highly regional-specific deficits seen in nutritional deficiency syndromes that can accompany alcoholism.