Lack of association between hippocampal volume reduction and first-onset alcohol withdrawal seizure. A volumetric MRI study

A combination of support vector machine and voxel-based morphometry in adult male alcohol use disorder patients with cognitive deficits

Cognitive performance deteriorates with drinking. However, the neural basis of cognitive deficits in alcohol use disorder (AUD) is still incompletely understood. Here we examined the relationship between overall drinking, brain structural alterations and cognitive deficits in AUD. A total of 40 middle-aged AUD males and 40 healthy controls (HC) underwent high-resolution anatomical imaging scans, and the data were analyzed using voxel-based morphometry, support vector machine (SVM) classification and mediation analysis. The AUD patients demonstrated reduced gray matter (GM) volumes that included left amygdala, thalamus, hippocampus, precentral gyrus, cerebellum, calcarine, right supplementary motor area and bilateral superior temporal gyri (voxel-wise p < 0.05, FWE corrected). The SVM results could distinguish AUD from HC with satisfactory classification results (0.8275). GM volumes in the bilateral cerebellum and thalamus, left anterior medial temporal lobe, left nucleus ambiguus + parahippocampus gyrus, left fusiform gyrus, left lingual gyrus, left hippocampus, and right nucleus accumbens had positive correlations with the Montreal Cognitive Assessment (MoCA) scores. Further mediation analysis showed that left cerebellum crus 1 partially mediated the relationship between overall drinking and MoCA scores (standardized beta coefficient = -0.0973, SE = 0.0002, 95% CI = (-0.0006, 0.0000)). Our findings showed widespread GM atrophies and many of these atrophies also mirrored cognitive deficits and were robustly distinguishable. Critically, the left cerebellum crus 1 partially mediated the relationship betweem overall drinking and MoCA scores, suggesting a pathway by which alcohol abuse impairs cognition and accelerates brain ageing in middle-aged AUD males.

Grey matter structural differences in alcohol-dependent individuals with and without comorbid depression/anxiety-an MRI study

Although depression and anxiety disorders are common comorbid conditions in alcohol dependence, few structural brain imaging studies have compared alcohol-dependent subjects with and without such comorbidity. In the current study, brain scans of 35 alcohol-dependent with and 40 individuals without diagnosis of a comorbid ICD-10 depressive or anxiety disorder receiving detoxification inpatient treatment were evaluated. Thickness and volumes of automatically segmented neuroanatomical structures were measured in FreeSurfer. Furthermore, associations of brain structure with biological markers and clinical severity markers of alcohol dependence were assessed. Despite comparable addiction severity, the non-comorbid group had evidence of higher cytotoxic effects of alcohol use on hepatic and haematological markers, and showed significantly smaller volumes of total cerebral, and cerebellar grey matter. Similarly, they showed unexpected smaller hippocampal and nucleus accumbens volumes, and thinner frontal, temporal and occipital cortices. Smaller brain volumes correlated with increased markers of hepatic and haematological dysfunction, and with longer duration of alcohol dependence in the non-comorbid group. Evidence of higher biomarkers of alcohol use may be indicative of more severe alcohol dependence or higher vulnerability to ethanol toxicity in this group. Furthermore, psychopathology-related drug treatment, which occurred in 53% of the comorbid group over the recent years, or tissue inflammation may have a moderate effect on the grade of cerebral atrophy in alcohol-dependent patients. Longitudinal studies are needed to investigate this issue more fully.

Problematic alcohol use and reduced hippocampal volume: a meta-analytic review

BACKGROUND

A number of studies reports reduced hippocampal volume in individuals who engage in problematic alcohol use. However, the magnitude of the difference in hippocampal volume between individuals with v. without problematic alcohol use has varied widely, and there have been null findings. Moreover, the studies comprise diverse alcohol use constructs and samples, including clinically significant alcohol use disorders and subclinical but problematic alcohol use (e.g. binge drinking), adults and adolescents, and males and females.

METHODS

We conducted the first quantitative synthesis of the published empirical research on associations between problematic alcohol use and hippocampal volume. In total, 23 studies were identified and selected for inclusion in the meta-analysis; effects sizes were aggregated using a random-effects model.

RESULTS

Problematic alcohol use was associated with significantly smaller hippocampal volume (d = -0.53). Moderator analyses indicated that effects were stronger for clinically significant v. subclinical alcohol use and among adults relative to adolescents; effects did not differ among males and females.

CONCLUSIONS

Problematic alcohol use is associated with reduced hippocampal volume. The moderate overall effect size suggests the need for larger samples than are typically included in studies of alcohol use and hippocampal volume. Because the existing literature is almost entirely cross-sectional, future research using causally informative study designs is needed to determine whether this association reflects premorbid risk for the development of problematic alcohol use and/or whether alcohol has a neurotoxic effect on the hippocampus.

Volume of hippocampal subfields in patients with alcohol dependence

Alcohol-induced hippocampal atrophy has been well documented in many studies and is known to affect various subfields. Given the functional heterogeneity of these subfields, we investigated the precise effects of alcohol-induced damage in these areas. Twenty-six male patients with alcohol dependence (alcohol group) and twenty-six age-matched male healthy social drinkers were recruited from a mental health hospital and the community respectively, with the aim of comparing the hippocampal subfields between groups. Each participant underwent a 3T MRI scan. Hippocampal subfield volumes were estimated using an automated procedure and drinking history recorded using Lifetime Drinking History, Alcohol Use Disorder Identification Test, and the Brief Michigan Alcoholism Screening Test. The alcohol group showed a lower total hippocampus volume, specifically in the left presubiculum, fimbria, and bilateral subiculum. Regression analysis assessing the influence of age and group showed that group was a more significant factor than age in most subfields. Our findings suggest that alcohol dependence alters hippocampal subfield volumes. Further longitudinal studies on the interaction of structural and neurocognitive changes would improve our understanding of brain structural changes resulting from long-term alcohol consumption.

Dissociated Accumbens and Hippocampal Structural Abnormalities across Obesity and Alcohol Dependence

BACKGROUND

Processing of food and drug rewards involves specific neurocircuitry, and emerging evidence implicates subcortical abnormalities, particularly the nucleus accumbens and hippocampus. We specifically hypothesized that these 2 established regions in addiction neurocircuitry are associated with distinctive in vivo structural abnormalities in obesity and alcohol dependence.

METHODS

To specifically investigate anatomically discrete volumetric changes associated with overconsumption of different rewards, we acquired T1 MRI data from 118 subjects in 3 groups comprising obesity (n=42), alcohol dependence (n=32), and healthy volunteer controls (n=44). To exploit novel methods of automated hippocampal subfield segmentation, we used Freesurfer software to generate volumetric data in subject groups for the hippocampal subiculum and its major striatal efferent target, the nucleus accumbens. Hypothesis-led, selective group difference comparisons were analyzed.

RESULTS

We found markedly greater accumbens volumes (P=.002) and relatively preserved hippocampal subfield volumes in obesity. Conversely, in alcohol dependence, we found preserved accumbens volumes but atrophy of specific ventral hippocampal subfields, the subiculum and presubiculum. Smaller global subcortical gray-matter volume was found in the alcohol dependence group only.

CONCLUSIONS

Reward neurocircuitry including the accumbens and ventral hippocampus may show key structural abnormalities in disorders involving processing of both food and drug rewards, although the foci of disruption may vary as a function of reward modality. Structural differences may subserve altered reward and motivational processes in obesity and alcohol dependence and represent a potential biomarker for therapeutic targeting in key public health disorders.

Structural and microstructral imaging of the brain in alcohol use disorders

Magnetic resonance imaging (MRI), by enabling rigorous in vivo study of the longitudinal, dynamic course of alcoholism through periods of drinking, sobriety, and relapse, has enabled characterization of the effects of chronic alcoholism on the brain in the human condition. Importantly, MRI has distinguished alcohol-related brain effects that are permanent versus those that are reversible with abstinence. In support of postmortem neuropathologic studies showing degeneration of white matter, MRI has shown a specific vulnerability of brain white matter to chronic alcohol exposure by demonstrating white-matter volume deficits, yet not leaving selective gray-matter structures unscathed. Diffusion tensor imaging (DTI), by permitting microstructural characterization of white matter, has extended MRI findings in alcoholics. This review focuses on MRI and DTI findings in common concomitants of alcoholism, including Wernicke's encephalopathy, Korsakoff's syndrome, hepatic encephalopathy, central pontine myelinolysis, alcoholic cerebellar degeneration, alcoholic dementia, and Marchiafava-Bignami disease as a framework for findings in so-called "uncomplicated alcoholism," and also covers findings in abstinence and relapse.

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.

Time-Course Analysis of Brain Regional Expression Network Responses to Chronic Intermittent Ethanol and Withdrawal: Implications for Mechanisms Underlying Excessive Ethanol Consumption

Long lasting abusive consumption, dependence, and withdrawal are characteristic features of alcohol use disorders (AUD). Mechanistically, persistent changes in gene expression are hypothesized to contribute to brain adaptations leading to ethanol toxicity and AUD. We employed repeated chronic intermittent ethanol (CIE) exposure by vapor chamber as a mouse model to simulate the cycles of ethanol exposure and withdrawal commonly seen with AUD. This model has been shown to induce progressive ethanol consumption in rodents. Brain CIE-responsive expression networks were identified by microarray analysis across five regions of the mesolimbic dopamine system and extended amygdala with tissue harvested from 0-hours to 7-days following CIE. Weighted Gene Correlated Network Analysis (WGCNA) was used to identify gene networks over-represented for CIE-induced temporal expression changes across brain regions. Differential gene expression analysis showed that long-lasting gene regulation occurred 7-days after the final cycle of ethanol exposure only in prefrontal cortex (PFC) and hippocampus. Across all brain regions, however, ethanol-responsive expression changes occurred mainly within the first 8-hours after removal from ethanol. Bioinformatics analysis showed that neuroinflammatory responses were seen across multiple brain regions at early time-points, whereas co-expression modules related to neuroplasticity, chromatin remodeling, and neurodevelopment were seen at later time-points and in specific brain regions (PFC or HPC). In PFC a module containing Bdnf was identified as highly CIE responsive in a biphasic manner, with peak changes at 0 hours and 5 days following CIE, suggesting a possible role in mechanisms underlying long-term molecular and behavioral response to CIE. Bioinformatics analysis of this network and several other modules identified Let-7 family microRNAs as potential regulators of gene expression changes induced by CIE. Our results suggest a complex temporal and regional pattern of widespread gene network responses involving neuroinflammatory and neuroplasticity related genes as contributing to physiological and behavioral responses to chronic ethanol.

Dendritic remodeling of hippocampal neurons is associated with altered NMDA receptor expression in alcohol dependent rats

Prolonged alcohol exposure has been previously shown to impair the structure and function of the hippocampus, although the underlying structural and biochemical alterations contributing to these deleterious effects are unclear. Also unclear is whether these changes persist into prolonged periods of abstinence. Previous work from our lab utilizing a clinically relevant rodent model of alcohol consumption demonstrated that alcohol dependence (induced by chronic intermittent ethanol vapor exposure or CIE) decreases proliferation and survival of neural stem cells in the hippocampal subgranular zone and hippocampal neurogenesis in the dentate gyrus, implicating this region of the cortex as particularly sensitive to the toxic effects of prolonged ethanol exposure. For this study, we investigated seven weeks of CIE-induced morphological changes (dendritic complexity and dendritic spine density) of dentate gyrus (DG) granule cell neurons, CA3, and CA1 pyramidal neurons and the associated alterations in biochemical markers of synaptic plasticity and toxicity (NMDA receptors and PSD-95) in the hippocampus in ethanol-experienced Wistar rats 3h (CIE) and 21days (protracted abstinence) after the last ethanol vapor exposure. CIE reduced dendritic arborization of DG neurons and this effect persisted into protracted abstinence. CIE enhanced dendritic arborization of pyramidal neurons and this effect did not persist into protracted abstinence. The architectural changes in dendrites did not correlate with alterations in dendritic spine density, however, they were associated with increases in the expression of pNR2B, total NR2B, and total NR2A immediately following CIE with expression levels returning to control levels in prolonged abstinence. Overall, these data provide the evidence that CIE produces profound changes in hippocampal structural plasticity and in molecular tools that maintain hippocampal structural plasticity, and these alterations may underlie cognitive dysfunction associated with alcohol dependence. In addition, the compensatory state concurrent with reduced plasticity during protracted abstinence could leave the hippocampus vulnerable to subsequent insult following chronic ethanol exposure.

Cognitive impairments in alcohol-dependent subjects

Chronic excessive alcohol consumption induces cognitive impairments mainly affecting executive functions, episodic memory, and visuospatial capacities related to multiple brain lesions. These cognitive impairments not only determine everyday management of these patients, but also impact on the efficacy of management and may compromise the abstinence prognosis. Maintenance of lasting abstinence is associated with cognitive recovery in these patients, but some impairments may persist and interfere with the good conduct and the efficacy of management. It therefore appears essential to clearly define neuropsychological management designed to identify and evaluate the type and severity of alcohol-related cognitive impairments. It is also essential to develop cognitive remediation therapy so that the patient can fully benefit from the management proposed in addiction medicine units.

Hippocampal volumes and cognitive functions in adult alcoholic patients with adolescent-onset

This study investigated hippocampal volumes and cognitive functions in adult alcoholic patients with adolescent- or late-onset alcohol use. Twenty-one male alcohol dependent inpatients and 13 healthy male controls were enrolled in this study. Cranial magnetic resonance imaging to measure hippocampal volumes and neuropsychological tests were performed in week 4 of abstinence in the patients and controls. The patients were divided into two subgroups (adolescent- and late-onset subgroups) according to the onset age of alcohol use. Alcoholic patients in general had significantly smaller right hippocampal volumes than the healthy controls. Patients' immediate memory, attention, acquisition and working memory subtest scores were inferior to those of the controls. The right hippocampus was significantly smaller in adult alcoholic patients with adolescent-onset use compared to the controls and the late-onset group. There was no significant correlation between neuropsychological test scores and hippocampal volumes. Our results suggest that hippocampal volume loss might be a feature of adolescent-onset alcoholic patients rather than of late-onset ones.

A [11C]Ro15 4513 PET study suggests that alcohol dependence in man is associated with reduced α5 benzodiazepine receptors in limbic regions

Preclinical evidence suggests the α5 subtype of the GABA-benzodiazepine receptor is involved in some of the actions of alcohol and in memory. The positron emission tomography (PET) tracer, [(11)C]Ro15 4513 shows relative selectivity in labelling the α5 subtype over the other GABA-benzodiazepine receptor subtypes in limbic regions of the brain. We used this tracer to investigate the distribution of α5 subtype availability in human alcohol dependence and its relationship to clinical variables. Abstinent (>6 weeks) alcohol-dependent men and healthy male controls underwent an [(11)C]Ro15 4513 PET scan. We report [(11)C]Ro15 4513 brain uptake for 8 alcohol-dependent men and 11 healthy controls. We found a significant reduction in [(11)C]Ro15 4513 binding in the nucleus accumbens, parahippocampal gyri, right hippocampus and amygdala in the alcohol-dependent compared with the healthy control group. Levels of [(11)C]Ro15 4513 binding in both hippocampi were significantly and positively associated with performance on a delayed verbal memory task in the alcohol-dependent but not the control group. We speculate that the reduced limbic [(11)C]Ro15 4513 binding seen here results from the effects of alcohol, though we cannot currently distinguish whether they are compensatory in nature or evidence of brain toxicity.

Alcohol withdrawal seizures

The topic of alcohol withdrawal syndrome (AWS), including delirium tremens and especially seizures, is reviewed. From mice and rat studies, it is known that both N-methyl-d-aspartate (NMDA) and gamma-aminobutyric acid (GABA) receptors are involved in AWS. During alcohol intoxication chronic adaptations of NMDA and GABA receptors occur, and during alcohol withdrawal a hyperexcitable state develops. In studies on humans, during intoxication the NMDA receptors are activated and mediate tonic inhibition. In withdrawal, a rebound activation of these receptors occurs. Both GABA-A and GABA-B receptors, especially the alpha2 subunit of GABA-A receptors, are also likely involved. Homocysteine increases with active drinking, and in withdrawal, excitotoxicity likely is induced by a further increase in homocysteine, viewed as a risk factor for AWS and also as a screening tool. The dopamine transporter gene is also associated with AWS. Characteristics involves changes in the ECG, especially an increase in QT interval, and EEG changes, including abnormal quantified EEG, at times periodic lateralized epileptiform discharges, and especially seizures, usually occurring 6-48h after the cessation of drinking. Therapy has emphasized benzodiazepines, mainly diazepam and lorazepam, but more standard antiepileptic drugs, like carbamazepine and topiramate, are also effective and safe.

Association of plasma total homocysteine levels with subclinical brain injury: cerebral volumes, white matter hyperintensity, and silent brain infarcts at volumetric magnetic resonance imaging in the Framingham Offspring Study

BACKGROUND

Elevated plasma total homocysteine (tHcy) levels have been associated with increased risk of dementia and stroke, but it is uncertain whether the mediating mechanisms are predominantly cellular, vascular, or both.

OBJECTIVE

To evaluate the relationship between tHcy levels and findings at brain magnetic resonance imaging (MRI) in a community-based sample.

DESIGN

Our sample comprised 1965 participants in the Framingham Offspring Study (1050 women; mean [SD] age, 62 [9] years) who were free of clinical stroke, dementia, or other neurologic disease affecting brain MRI and for whom at least 1 measurement of plasma tHcy level (1991-2001) and a brain MRI (1999-2002) were available. We used multivariate regression analysis to relate initial (1991-1995) and concurrent (1998-2001) plasma tHcy levels to total cerebral brain volume and lobar volumes as measures of neuronal loss and atrophy and to the presence or absence of silent brain infarcts and extensive white matter hyperintensity (log-white matter intensity > or =1 SD above the age-adjusted mean) as separate measures of vascular injury.

RESULTS

Mean total cerebral brain volume was 78%. At MRI, 218 participants had silent brain infarcts and 250 demonstrated extensive white matter hyperintensity. Participants with a plasma tHcy level in the highest age- (-0.37%, P = .01) or sex-specific (-0.48%, P < .001) quartile had smaller total cerebral brain volumes compared with participants with lower tHcy levels. Initial tHcy levels were associated with a higher prevalence of silent brain infarct (relative risk, 1.5; 95% confidence interval, 1.1-2.1; P = .02) and concurrent tHcy levels, with smaller frontal (-0.14%, P = .001) and temporal lobar (-0.10%, P = .04) volumes. Prevalence of extensive white matter hyperintensity did not differ according to initial or concurrent plasma tHcy levels (relative risk, both 1.0; 95% confidence interval, 0.7-1.4 and 0.8-1.4, respectively).

CONCLUSIONS

Higher plasma tHcy levels are associated with smaller brain volume and the presence of silent brain infarcts at MRI, even in healthy, middle-aged adults. Thus, both cellular and vascular mechanisms may underlie the association of plasma tHcy level with brain aging, as reflected by the effects on both subclinical and overt disease.

Chronic cigarette smoking modulates injury and short-term recovery of the medial temporal lobe in alcoholics

Memory function is largely mediated by the medial temporal lobe (MTL), and its compromise has been observed in alcohol dependence and chronic cigarette smoking. The effects of heavy alcohol consumption and chronic smoking on hippocampal volumes and MTL metabolites and their recovery during abstinence from alcohol have not been assessed. Male alcoholics in treatment (ALC) [13 smokers (sALC) and 11 non-smokers (nsALC)] underwent quantitative magnetic resonance imaging and short-echo proton magnetic resonance spectroscopic imaging at 1 week and 1 month of sobriety. Outcome measures were compared with 14 age-matched, non-smoking light-drinkers and were related to visuospatial learning and memory. Over 1 month of abstinence, N-acetyl-aspartate, a neuronal marker, and membrane-associated choline-containing metabolites normalized in the MTL of nsALC subjects, but remained low in the MTL of sALC subjects. Metabolite concentration changes in both groups were associated with improvements in visuospatial memory. Hippocampal volumes increased in both groups during abstinence, but increasing volumes correlated with visuospatial memory improvements only in nsALC subjects. In summary, chronic cigarette smoking in alcohol-dependent men appears to have adverse effects on MTL metabolite recovery during short-term sobriety. These data may also have implications for other conditions with established MTL involvement and significant smoking co-morbidity, such as schizophrenia-spectrum and mood disorders.

Genuine episodic memory deficits and executive dysfunctions in alcoholic subjects early in abstinence

BACKGROUND

Chronic alcoholism is known to impair episodic memory function, but the specific nature of this impairment is still unclear. Moreover, it has never been established whether episodic memory deficit in alcoholism is an intrinsic memory deficit or whether it has an executive origin. Thus, the objectives are to specify which episodic memory processes are impaired early in abstinence from alcohol and to determine whether they should be regarded as genuine memory deficits or rather as the indirect consequences of executive impairments.

METHODS

Forty recently detoxified alcoholic inpatients at alcohol entry treatment and 55 group-matched controls underwent a neuropsychological assessment of episodic memory and executive functions. The episodic memory evaluation consisted of 3 tasks complementing each other designed to measure the different episodic memory components (learning, storage, encoding and retrieval, contextual memory, and autonoetic consciousness) and 5 executive tasks testing capacities of organization, inhibition, flexibility, updating, and integration.

RESULTS

Compared with control subjects, alcoholic patients presented impaired learning abilities, encoding processes, retrieval processes, contextual memory and autonoetic consciousness. However, there was no difference between the 2 groups regarding the storage capacities assessed by the rate of forgetting. Concerning executive functions, alcoholic subjects displayed deficits in each executive task used. Nevertheless, stepwise regression analyses showed that only performances on fluency tasks were significantly predictive of some of the episodic memory disorders (learning abilities for 40%, encoding processes for 20%, temporal memory for 21%, and state of consciousness associated with memories for 26%) in the alcoholic group.

DISCUSSION

At alcohol treatment entry, alcoholic patients present genuine episodic memory deficits that cannot be regarded solely as the consequences of executive dysfunctions. These results are in accordance with neuroimaging findings showing hippocampal atrophy. Moreover, given the involvement of episodic memory and executive functions in alcohol treatment, these data could have clinical implications.

Hippocampus volume loss due to chronic heavy drinking

OBJECTIVE

No clear consensus exists regarding the effect of sustained, heavy drinking on hippocampal volume. Our prior work hypothesized significantly lowered total hippocampus volumes in heavy chronically drinking alcohol-dependent (AD) subjects compared with light-drinking nondependent control subjects matched for age and gender.

METHOD

Using a series of applicable exclusion criteria culled from previous published studies, we measured hippocampal volumes from MRI scan data acquired on a 3T scanner and subjected those data to automated volume analysis blind to the drinking history.

RESULTS

Comparison with AD test (n=8) and non-AD control (n=8) subjects found significant lessening in total (p=0.020) and left (p=0.010) hippocampal volumes with a near-significant difference on the right (p=0.051). Linear regression demonstrated that neither total brain volume nor intracranial volume affected the hippocampus measures.

CONCLUSIONS

These data support the view that heavy drinking exerts a unique and selectively injurious effect on the hippocampus. Further study in larger samples must verify this in a search for possible mechanisms of injury.

Alcohol and adult neurogenesis: Roles in neurodegeneration and recovery in chronic alcoholism

The concept of "structural plasticity" has emerged as a potential mechanism in neurodegenerative and psychiatric diseases such as drug abuse, depression, and dementia. Chronic alcoholism is a progressive neurodegenerative disease while the person continues to abuse alcohol, though clinical and imaging studies show that some recovery may occur with abstinence. The neural plasticity observed in chronic alcoholism coupled with conflicting reports on alcohol-induced hippocampal neuropathology make this disease ripe for reconsideration in terms of the phenomenon of adult neurogenesis. This review describes opposing neurogenic processes that occur with alcohol intoxication and abstinence following alcohol dependence and how these opposing events relate to neurodegeneration and recovery from chronic alcoholism.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Homocysteine as a neurotoxin in chronic alcoholism

There is evidence from in vitro and in vivo studies that homocysteine induces neuronal damage and cell loss by both excitotoxicity and different apoptotic processes. Clinical evidence suggest a strong relationship between higher plasma homocysteine levels and brain atrophy in healthy elderly subjects as well as in elderly at risk of and with Alzheimer's disease. Chronic alcoholism leads to elevated plasma homocysteine levels, as shown by clinical investigations and animal experiments. In addition, an association between brain atrophy and increased levels of homocysteine in chronic alcoholism was shown. This may have important implications for the pathogenesis of alcoholism-associated brain atrophy. Furthermore, taking into account that high plasma homocysteine levels are helpful in the prediction of alcohol withdrawal seizures, early anticonvulsive therapy could prevent this severe complication. Homocysteine plays a role in a shared biochemical cascade involving overstimulation of N-methyl-D-aspartate (NMDA) receptors, oxidative stress, activation of caspases, DNA damage, endoplasmic reticulum and mitochondrial dysfunction. These mechanisms are believed to be important in the pathogenesis of both excitotoxicity and apoptotic neurotoxicity. Prospective intervention studies may show whether the incidence of complications of alcohol withdrawal or alcoholism-associated disorders can be reduced by therapeutic measures with early lowering of elevated homocysteine levels (e.g. folate administration). The most important pathophysiological and pathobiochemical features of glutamatergic neurotransmission and of ethanol-induced hyperhomocysteinaemia are reviewed in relation to their excitotoxic and apoptotic potential.