Brain correlates of memory dysfunction in alcoholic Korsakoff's syndrome

Identifying, Assessing, and Treating Korsakoff Syndrome Patients: Updated Perspectives

ABSTRACT

Objectives consist of updating published reports on the recognition, assessment, and care of patients with Wernicke-Korsakoff syndrome (WKS). Methods included defining relevant terms, describing core clinical phenomena, conducting meaningful reviews for latter-day WKS publications, and selecting instructive case examples. Findings covered epidemiology, precipitants, neuroimaging studies, alternate learning strategies in WKS, adjunctive treatments, and promising research. In conclusion, patients, their family members, clinicians, and public health experts should benefit from this updated knowledge. Countries with substantial alcohol consumption should consider emulating Holland in designating WKS research centers, founding regional clinical facilities, and funding multidisciplinary expert teams.

Temporal Cognitive and Brain Changes in Korsakoff Syndrome

OBJECTIVE

To investigate cognitive and brain changes in patients with Korsakoff syndrome (KS) over months and up to 10 years after the diagnosis.

METHODS

Two groups of 8 patients with KS underwent neuropsychological, motor, and neuroimaging investigations, including structural MRI and ¹⁸F-fluorodeoxyglucose-PET. The KS^C group, recruited at Caen University Hospital, was examined early after the KS diagnosis (KS^C-T1) and 1 year later (KS^C-T2). The KS^R group, recruited at nursing home at Roubaix, was evaluated 10 years after the diagnosis. Longitudinal comparisons in KS^C explored short-term changes, while cross-sectional comparisons between KS^C-T1 and KS^R informed about long-term changes.

RESULTS

No cognitive, motor, or brain deterioration occurred over time in patients with KS. There was no clear improvement either, with only modest recovery in the frontocerebellar circuit. Compared to the norms, KS^C-T1 had severe episodic memory impairments, ataxia, and some executive dysfunctions. They also presented widespread atrophy and hypometabolism as well as cerebellar hypermetabolism compared to 44 healthy matched controls. Episodic memory remained significantly impaired in KS^C-T2 and KS^R. Contrary to KS^C at T1 and T2, KS^R had preserved inhibition abilities. Atrophy was similar but less extended in KS^C-T2 and even more limited in KS^R. At all times, the thalamus, hypothalamus, and fornix remained severely atrophied. Hypometabolism was still widespread in KS^C-T2 and KS^R, notably affecting the diencephalon. Cerebellar metabolism decreased over time and normalized in KS^R, whereas motor dysfunction persisted.

CONCLUSION

In KS, structural and metabolic alterations of the Papez circuit persisted over time, in accordance with the irreversible nature of amnesia. There was neither significant recovery as observed in patients with alcohol use disorder nor progressive decline as in neurodegenerative diseases.

The thalamic midline nucleus reuniens: potential relevance for schizophrenia and epilepsy

Anatomical, electrophysiological and behavioral studies in rodents have shown that the thalamic midline nucleus reuniens (RE) is a crucial link in the communication between hippocampal formation (HIP, i.e., CA1, subiculum) and medial prefrontal cortex (mPFC), important structures for cognitive and executive functions. A common feature in neurodevelopmental and neurodegenerative brain diseases is a dysfunctional connectivity/communication between HIP and mPFC, and disturbances in the cognitive domain. Therefore, it is assumed that aberrant functioning of RE may contribute to behavioral/cognitive impairments in brain diseases characterized by cortico-thalamo-hippocampal circuit dysfunctions. In the human brain the connections of RE are largely unknown. Yet, recent studies have found important similarities in the functional connectivity of HIP-mPFC-RE in humans and rodents, making cautious extrapolating experimental findings from animal models to humans justifiable. The focus of this review is on a potential involvement of RE in schizophrenia and epilepsy.

The nucleus reuniens of the thalamus sits at the nexus of a hippocampus and medial prefrontal cortex circuit enabling memory and behavior

The nucleus reuniens of the thalamus (RE) is a key component of an extensive network of hippocampal and cortical structures and is a fundamental substrate for cognition. A common misconception is that RE is a simple relay structure. Instead, a better conceptualization is that RE is a critical component of a canonical higher-order cortico-thalamo-cortical circuit that supports communication between the medial prefrontal cortex (mPFC) and the hippocampus (HC). RE dysfunction is implicated in several clinical disorders including, but not limited to Alzheimer's disease, schizophrenia, and epilepsy. Here, we review key anatomical and physiological features of the RE based primarily on studies in rodents. We present a conceptual model of RE circuitry within the mPFC-RE-HC system and speculate on the computations RE enables. We review the rapidly growing literature demonstrating that RE is critical to, and its neurons represent, aspects of behavioral tasks that place demands on memory focusing on its role in navigation, spatial working memory, the temporal organization of memory, and executive functions.

Volumetric Reductions of Subcortical Structures and Their Localizations in Alcohol-Dependent Patients

Changes in brain morphometry have been extensively reported in various studies examining the effects of chronic alcohol use in alcohol-dependent patients. Such studies were able to confirm the association between chronic alcohol use and volumetric reductions in subcortical structures using FSL (FMRIB software library). However, each study that utilized FSL had different sets of subcortical structures that showed significant volumetric reduction. First, we aimed to investigate the reproducibility of using FSL to assess volumetric differences of subcortical structures between alcohol-dependent patients and control subjects. Second, we aimed to use Vertex analysis, a less utilized program, to visually inspect 3D meshes of subcortical structures and observe significant shape abnormalities that occurred in each subcortical structure. Vertex analysis results from the hippocampus and thalamus were overlaid on top of their respective subregional atlases to further pinpoint the subregional locations where shape abnormalities occurred. We analyzed the volumes of 14 subcortical structures (bilateral thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala, nucleus accumbens) in 21 alcohol-dependent subjects and 21 healthy controls using images acquired with 3T MRI. The images were run through various programs found in FSL, such as SIENAX, FIRST, and Vertex analysis. We found that in alcohol-dependent patients, the bilateral thalamus (left: p < 0.01, right: p = 0.01), bilateral putamen (left: p = 0.02, right: p < 0.01), right globus pallidus (p < 0.01), bilateral hippocampus (left: p = 0.05, right: p = 0.03) and bilateral nucleus accumbens (left: p = 0.05, right: p = 0.03) were significantly reduced compared to the corresponding subcortical structures of healthy controls. With vertex analysis, we observed surface reductions of the following hippocampal subfields: Presubiculum, hippocampal tail, hippocampal molecular layer, hippocampal fissure, fimbria, and CA3. We reproduced the assessment made in previous studies that reductions in subcortical volume were negatively associated with alcohol dependence by using the FMRIB Software Library. In addition, we identified the subfields of the thalamus and hippocampus that showed volumetric reduction.

Association of the alcohol dehydrogenase gene polymorphism rs1789891 with gray matter brain volume, alcohol consumption, alcohol craving and relapse risk

Alcohol metabolizing enzymes, such as the alcohol dehydrogenases and the aldehyde dehydrogenases, regulate the levels of acetaldehyde in the blood and play an important role in the development and maintenance of alcohol addiction. Recent genome-wide systematic searches found associations between a single nucleotide polymorphism (rs1789891, risk allele: A, protective allele: C) in the alcohol dehydrogenase gene cluster and the risk of alcohol dependence. The current study investigated the effect of this single nucleotide polymorphism on alcohol consumption, craving for alcohol, relapse risk and brain gray matter volume. Alcohol-dependent patients (n = 74) and controls (n = 43) were screened, genotyped and underwent magnetic resonance imaging scanning, and relapse data were collected during 3 months following the experiment. Alcohol-dependent A allele carriers reported increased alcohol craving and higher alcohol consumption compared with the group of alcohol-dependent individuals homozygous for the C allele, which displayed craving values similar to the control group. Further, follow-up data indicated that A allele carriers relapsed earlier to heavy drinking compared with individuals with two C alleles. Analyses of gray matter volume indicated a significant genotype difference in the patient group: individuals with two C alleles had reduced gray matter volume in the left and right superior, middle and inferior temporal gyri. Findings of the current study further support the relevance of genetic variants in alcohol metabolizing enzymes to addictive behavior, brain tissue volume and relapse risk. Genotype-dependent differences in acetaldehyde formation, implicated by earlier studies, might be the biological substrate of the genotype differences.

The thalamus as a relay station and gatekeeper: relevance to brain disorders

Here, we provide a review of behavioural, cognitive, and neural studies of the thalamus, including its role in attention, consciousness, sleep, and motor processes. We further discuss neuropsychological and brain disorders associated with thalamus function, including Parkinson’s disease, Alzheimer’s disease, Korsakoff’s syndrome, and sleep disorders. Importantly, we highlight how thalamus-related processes and disorders can be explained by the role of the thalamus as a relay station.

Integrity of white matter microstructure in alcoholics with and without Korsakoff's syndrome

Alcohol dependence results in two different clinical forms: "uncomplicated" alcoholism (UA) and Korsakoff's syndrome (KS). Certain brain networks are especially affected in UA and KS: the frontocerebellar circuit (FCC) and the Papez circuit (PC). Our aims were (1) to describe the profile of white matter (WM) microstructure in FCC and PC in the two clinical forms, (2) to identify those UA patients at risk of developing KS using their WM microstructural integrity as a biomarker. Tract-based spatial statistics and nonparametric voxel-based permutation tests were used to compare diffusion tensor imaging (DTI) data in 7 KS, 20 UA, and 14 healthy controls. The two patient groups were also pooled together and compared to controls. k-means classifications were then performed on mean fractional anisotropy values of significant clusters across all subjects for two fiber tracts from the FCC (the middle cerebellar peduncle and superior cerebellar peduncle) and two tracts from the PC (fornix and cingulum). We found graded effects of WM microstructural abnormalities in the PC of UA and KS. UA patients classified at risk of developing KS using fiber tracts of the PC from DTI data also had the lowest scores of episodic memory. That finding suggests that WM microstructure could be used as a biomarker for early detection of UA patients at risk of developing KS.

Sensitive biomarkers of alcoholism's effect on brain macrostructure: similarities and differences between France and the United States

Alcohol consumption patterns and recognition of health outcomes related to hazardous drinking vary widely internationally, raising the question whether these national differences are reflected in brain damage observed in alcoholism. This retrospective analysis assessed variability of alcoholism's effects on brain cerebrospinal fluid (CSF) and white matter volumes between France and the United States (U.S.). MRI data from two French sites (Caen and Orsay) and a U.S. laboratory (SRI/Stanford University) were acquired on 1.5T imaging systems in 287 controls, 165 uncomplicated alcoholics (ALC), and 26 alcoholics with Korsakoff's Syndrome (KS). All data were analyzed at the U.S. site using atlas-based parcellation. Results revealed graded CSF volume enlargement from ALC to KS and white matter volume deficits in KS only. In ALC from France but not the U.S., CSF and white matter volumes correlated with lifetime alcohol consumption, alcoholism duration, and length of sobriety. MRI highlighted CSF volume enlargement in both ALC and KS, serving as a basis for an ex vacuo process to explain correlated gray matter shrinkage. By contrast, MRI provided a sensitive in vivo biomarker of white matter volume shrinkage in KS only, suggesting a specific process sensitive to mechanisms contributing to Wernicke's encephalopathy, the precursor of KS. Identified structural brain abnormalities may provide biomarkers underlying alcoholism's heterogeneity in and among nations and suggest a substrate of gray matter tissue shrinkage. Proposed are hypotheses for national differences in interpreting whether the severity of sequelae observe a graded phenomenon or a continuum from uncomplicated alcoholism to alcoholism complicated by KS.

Impact of alcohol consumption in healthy adults: a magnetic resonance imaging investigation

The impact of alcohol on brain morphology was studied in a large group of cognitively intact people whose consumption of alcohol was below the threshold for abuse. Participants were 367 healthy subjects, aged 18 years or older, who underwent magnetic resonance imaging (MRI) for reasons other than cognitive impairment. MRI analyses were carried out using SPM8 software on the MATLAB 7.9 platform. Gray matter (GM) and white matter (WM) volumes were normalized for intracranial volume. Participants were interviewed about their lifetime consumption of alcohol, nicotine and other available illicit substances. Direct WM and GM comparisons between alcohol users and non-users did not detect significant differences. Differences also did not emerge from multiple regression analyses or in the subgroup aged 65 or older. Based on this study's findings, we cannot infer a detrimental effect of alcohol on the brain of normal adults. These data may be considered to provide reference information for clinical studies.

Neural Correlate of Anterograde Amnesia in Wernicke-Korsakoff Syndrome

The neural correlate of anterograde amnesia in Wernicke-Korsakoff syndrome (WKS) is still debated. While the capacity to learn new information has been associated with integrity of the medial temporal lobe (MTL), previous studies indicated that the WKS is associated with diencephalic lesions, mainly in the mammillary bodies and anterior or dorsomedial thalamic nuclei. The present study tested the hypothesis that amnesia in WKS is associated with a disrupted neural circuit between diencephalic and hippocampal structures. High-density evoked potentials were recorded in four severely amnesic patients with chronic WKS, in five patients with chronic alcoholism without WKS, and in ten age matched controls. Participants performed a continuous recognition task of pictures previously shown to induce a left medial temporal lobe dependent positive potential between 250 and 350 ms. In addition, the integrity of the fornix was assessed using diffusion tensor imaging (DTI). WKS, but not alcoholic patients without WKS, showed absence of the early, left MTL dependent positive potential following immediate picture repetitions. DTI indicated disruption of the fornix, which connects diencephalic and hippocampal structures. The findings support an interpretation of anterograde amnesia in WKS as a consequence of a disconnection between diencephalic and MTL structures with deficient contribution of the MTL to rapid consolidation.

Neuropathology of Chronic Alcohol Abuse

Alcohol abuse and dependence are serious public health problems worldwide, resulting in significant morbidity, mortality, and legal implications. Therefore, sudden unexpected, suspicious, or violent death in alcohol consuming persons are frequently seen in the forensic setting. Alcohol-induced brain damage is predominantly caused by nutritional deficiencies and repeated withdrawal syndrome. Brain lesions associated with heavy alcohol consumption include brain atrophy, hepatic encephalopathy, and central pontine myelinolysis. In addition, the dementing conditions Wernicke-Korsakoff syndrome, acquired hepatocerebral degeneration, Marchiafava-Bignami disease, and pellagrous encephalopathy are closely associated with chronic alcohol consumption. In neuroradiological and autopsy studies, cerebral and cerebellar atrophy has been demonstrated in alcoholics. There is a regional selectivity, with the frontal lobes being particularly affected. Moreover, a disproportionate loss of cerebral white matter relative to cerebral cortex suggests that a major neurotoxic effect of chronic alcohol consumption predominantly affects the white matter.

Applicability of the Rivermead Behavioural Memory Test - Third Edition (RBMT-3) in Korsakoff's syndrome and chronic alcoholics

PURPOSE

To examine the applicability of the newly developed Rivermead Behavioural Memory Test - Third Edition (RBMT-3) as an ecologically-valid memory test in patients with alcohol-related cognitive disorders.

PATIENTS AND METHODS

An authorized Dutch translation of the RBMT-3 was developed, equivalent to the UK version, and administered to a total of 151 participants - 49 patients with amnesia due to alcoholic Korsakoff's syndrome, 49 patients with cognitive impairment and a history of chronic alcoholism, not fulfilling the Korsakoff criteria, and 53 healthy controls. Between-group comparisons were made at subtest level, and the test's diagnostic accuracy was determined.

RESULTS

Korsakoff patients performed worse than controls on all RBMT-3 subtests (all P-values < 0.0005). The alcoholism group performed worse than controls on most (all P-values < 0.02), but not all RBMT-3 subtests. Largest effects were found between the Korsakoff patients and the controls after delayed testing. The RBMT-3 had good sensitivity and adequate specificity.

CONCLUSION

The RBMT-3 is a valid test battery to demonstrate everyday memory deficits in Korsakoff patients and non-Korsakoff patients with alcohol abuse disorder. Korsakoff patients showed an impaired performance on subtests relying on orientation, contextual memory and delayed testing. Our findings provide valuable information for treatment planning and adjustment in patients with alcohol-related cognitive impairments.

A voxel-based morphometry study comparing problem gamblers, alcohol abusers, and healthy controls

BACKGROUND

Alcohol use disorders (AUDs) are associated with smaller grey matter volumes in cortical and subcortical brain regions which are related to cognitive impairments often found in these disorders. Similar cognitive impairments have been found in patients suffering from problem gambling behaviour. However, in contrast to AUDs, gambling behaviour does not entail brain exposure to toxic agents. Although there are many clinical, neuropsychological, and neurobiological similarities between PG and substance use disorders it has not yet been established whether pathological gambling, similar to alcohol use disorders, is associated with abnormal regional grey matter volumes.

METHODS

With whole-brain voxel-based morphometry we compared a group of 40 treatment seeking problem gamblers, 36 subjects with an alcohol use disorder, and 54 healthy controls to evaluate potential group differences in regional grey matter volumes, corrected for age, IQ, smoking status, and total intracranial volume (TIV).

RESULTS

Significantly smaller grey matter volumes in left superior frontal cortex, left precentral cortex, right insula, right putamen, left thalamus, bilateral superior parietal cortex and right supramarginal cortex were present in subjects with an alcohol use disorder compared to healthy controls and problem gamblers. No significant grey matter volume differences were present between problem gamblers and healthy controls.

CONCLUSION

In conclusion, we replicated previous findings of smaller grey matter volumes in subjects with an alcohol use disorder and found no significant morphological brain abnormalities in problem gamblers.

Function and dysfunction of prefrontal brain circuitry in alcoholic Korsakoff's syndrome

The signature symptom of alcohol-induced persisting amnestic disorder, more commonly referred to as alcoholic Korsakoff's syndrome (KS), is anterograde amnesia, or memory loss for recent events, and until the mid 20th Century, the putative brain damage was considered to be in diencephalic and medial temporal lobe structures. Overall intelligence, as measured by standardized IQ tests, usually remains intact. Preservation of IQ occurs because memories formed before the onset of prolonged heavy drinking--the types of information and abilities tapped by intelligence tests--remain relatively well preserved compared with memories recently acquired. However, clinical and experimental evidence has shown that neurobehavioral dysfunction in alcoholic patients with KS does include nonmnemonic abilities, and further brain damage involves extensive frontal and limbic circuitries. Among the abnormalities are confabulation, disruption of elements of executive functioning and cognitive control, and emotional impairments. Here, we discuss the relationship between neurobehavioral impairments in KS and alcoholism-related brain damage. More specifically, we examine the role of damage to prefrontal brain systems in the neuropsychological profile of alcoholic KS.

Anterograde episodic memory in Korsakoff syndrome

A profound anterograde memory deficit for information, regardless of the nature of the material, is the hallmark of Korsakoff syndrome, an amnesic condition resulting from severe thiamine (vitamin B1) deficiency. Since the late nineteenth century when the Russian physician, S. S. Korsakoff, initially described this syndrome associated with "polyneuropathy," the observed global amnesia has been a primary focus of neuroscience and neuropsychology. In this review we highlight the historical studies that examined anterograde episodic memory processes in KS, present a timeline and evidence supporting the myriad theories proffered to account for this memory dysfunction, and summarize what is known about the neuroanatomical correlates and neural systems presumed affected in KS. Rigorous study of KS amnesia and associated memory disorders of other etiologies provide evidence for distinct mnemonic component processes and neural networks imperative for normal declarative and nondeclarative memory abilities and for mnemonic processes spared in KS, from whence emerged the appreciation that memory is not a unitary function. Debate continues regarding the qualitative and quantitative differences between KS and other amnesias and what brain regions and neural pathways are necessary and sufficient to produce KS amnesia.

Neuroimaging of Wernicke's encephalopathy and Korsakoff's syndrome

There is considerable evidence that neuroimaging findings can improve the early diagnosis of Wernicke's encephalopathy (WE) in clinical settings. The most distinctive neuroimaging finding of acute WE are cytotoxic edema and vasogenic edema, which are represented by bilateral symmetric hyperintensity alterations on T2-weighted MR images in the periphery of the third ventricle, periaqueductal area, mammillary bodies and midbrain tectal plate. An initial bout of WE can result in Korsakoff's syndrome (KS), but repeated bouts in conjunction with its typical comorbidity, chronic alcoholism, can result in signs of tissue degeneration in vulnerable brain regions. Chronic abnormalities identified with neuroimaging enable examination of brain damage in living patients with KS and have expanded the understanding of the neuropsychological deficits resulting from thiamine deficiency, alcohol neurotoxicity, and their comorbidity. Brain structure and functional studies indicate that the interactions involving the thalamus, mammillary bodies, hippocampus, frontal lobes, and cerebellum are crucial for memory formation and executive functions, and the interruption of these circuits by WE and chronic alcoholism can contribute substantially to the neuropsychological deficits in KS.

Context memory in Korsakoff's syndrome

Memory for contextual information and target-context integration are crucial for successful episodic memory formation and are impaired in patients with Korsakoff's syndrome. In this paper we review the evidence for the notion that a context memory deficit makes an important contribution to the amnesia in these patients. First, we focus on anterograde memory for contextual (spatial and temporal) information. Next, the use of contextual cues in memory retrieval is examined and their role in retrograde amnesia and confabulation. Evidence on the role of contextual cues and associations in working memory is discussed in relation to the underlying neurocognitive mechanisms and their dissociation from long-term encoding. Finally, we focus on implicit learning of contextual information in Korsakoff patients. It can be concluded that Korsakoff patients are impaired in the explicit processing of contextual information and in target-context binding, both in long-term (retrograde and anterograde) memory and in working memory. These results extend the context memory deficit hypothesis. In contrast, implicit contextual learning is relatively preserved in these patients. These findings are discussed in relation to evidence of dysfunction of the extended diencephalic-hippocampal memory circuit in Korsakoff's syndrome.

Remote memory function and dysfunction in Korsakoff's syndrome

Korsakoff's syndrome (KS) is a pervasive disorder of memory characterized by both anterograde and retrograde amnesia. Although retrograde memory impairment in KS has been less frequently studied, the status of remote memory in KS has been tested across a number of different tasks that measure knowledge of public information (e.g., famous faces/news events), general semantic information (e.g., vocabulary words), personal semantic information (e.g., facts about oneself), and autobiographical events (e.g., events from one's personal past). In each of these domains, Korsakoff patients demonstrate remote memory impairments that can extend back many years or decades. In addition, a majority of studies report that the extensive remote memory impairment in KS is temporally graded, with relative preservation of memories from childhood and early adulthood. The current paper reviews published experimental studies of remote memory in KS, with particular attention paid to (a) the selectivity of the deficit with respect to the age of the memory and (b) the relationship of memory impairment to underlying neuropathology. We discuss the significance of the reported pattern and extent of remote memory impairment with respect to theories about the nature of the underlying cognitive deficits in KS.

Facilitation of memory by contextual cues in patients with diencephalic or medial temporal lobe dysfunction

Item-context binding is crucial for successful episodic memory formation, and binding deficits have been suggested to underlie episodic-memory deficits. Here, our research investigated the facilitation of cued recall and recognition memory by contextual cues in 20 patients with Korsakoff's amnesia, 20 unilateral medial-temporal lobectomy (MTL) patients and 36 healthy controls. In a computerized task participants had to learn 40 nouns that were randomly combined with a photograph of an everyday scene. Korsakoff patients showed a general memory deficit in both the cued recall and the recognition condition. A less severe memory impairment was found in the patients with medial-temporal lobectomy. Contextual cues facilitated cued recall to an equal extent in unilateral temporal lobectomy patients and healthy controls. However, no facilitation was observed in Korsakoff patients, suggesting an impairment in item-context binding during cued recall tasks. In contrast to the presumed exclusive dependency of recognition memory on item information, all groups equally profited from the contextual cues in recognition tasks. Our findings show that unilateral lesions as with MTL result in normal binding of context and item information, while bilateral dysfunction of the hippocampal-diencephalic system results in impaired context and item binding.

Alliance for aging research AD biomarkers work group: structural MRI

Biomarkers of Alzheimer's disease (AD) are increasingly important. All modern AD therapeutic trials employ AD biomarkers in some capacity. In addition, AD biomarkers are an essential component of recently updated diagnostic criteria for AD from the National Institute on Aging--Alzheimer's Association. Biomarkers serve as proxies for specific pathophysiological features of disease. The 5 most well established AD biomarkers include both brain imaging and cerebrospinal fluid (CSF) measures--cerebrospinal fluid Abeta and tau, amyloid positron emission tomography (PET), fluorodeoxyglucose (FDG) positron emission tomography, and structural magnetic resonance imaging (MRI). This article reviews evidence supporting the position that MRI is a biomarker of neurodegenerative atrophy. Topics covered include methods of extracting quantitative and semiquantitative information from structural MRI; imaging-autopsy correlation; and evidence supporting diagnostic and prognostic value of MRI measures. Finally, the place of MRI in a hypothetical model of temporal ordering of AD biomarkers is reviewed.

Perspective taking in Korsakoff's syndrome: the role of executive functioning and task complexity

Oosterman JM, de Goede M, Wester AJ, van Zandvoort MJE, Kessels RPC. Perspective taking in Korsakoff's syndrome: the role of executive functioning and task complexity.

Objective: The ability to make inferences about knowledge, thoughts and feelings of others, i.e. perspective taking, is a key element of social cognition. Clinical observations indicate that Korsakoff patients may have impairments in social cognition, but studies are scarce. Also, executive dysfunction is present in Korsakoff patients, which may hamper perspective taking directly.

Methods: Twenty-three patients with Korsakoff's syndrome and 15 healthy matched controls were examined on a story comprehension task, in which inferences had to be made that either relied on perspective taking or not. The effects of task complexity were taken into account and executive function was assessed using an extensive neuropsychological test battery.

Results: The performance of Korsakoff patients declined with increasing complexity, but the pattern of decline for perspective-taking and non-perspective-taking stories was similar compared to that of the control group. Furthermore, the performance decline with increasing task complexity was directly related to the overall decline in executive functioning.

Conclusion: Executive dysfunction, not deficits in perspective taking per se, appears to underlie difficulties in story comprehension in patients with Korsakoff's syndrome.

The interaction of working memory performance and episodic memory formation in patients with Korsakoff's amnesia

Both neuroimaging work and studies investigating amnesic patients have shown involvement of the medial temporal lobe during working memory tasks, especially when multiple items or features have to be associated. However, so far no study has examined the relationship between working memory and subsequent episodic memory in patients using similar tasks. In this study, we compared patients with amnesia due to Korsakoff's syndrome (n=19) with healthy controls (n=18) on an associative working memory task followed by an unexpected subsequent episodic memory task. The computerized working memory task required participants to maintain two pairs of faces and houses for either short (3s) or long (6s) delays. Approximately 5 minutes after completion of the working memory task, an unexpected subsequent recognition task with a two-alternative forced choice paradigm was administered. By directly comparing working memory and subsequent episodic memory, we were able to examine long-term encoding processes that may take place after longer delays. As expected, patients performed at chance level on the episodic memory task. Interestingly, patients also showed significantly impaired working memory performance (p<.01), even at short delays. Longer delays did not result in better subsequent memory, indicating that they do not facilitate long-term encoding processes. Our results are discussed in relation to Baddeley's working memory model as the episodic buffer is assumed to be a short-term store for maintaining bound representations. In light of these results, the long-standing view that working memory and long-term memory are strictly dissociated may need to be revisited.

A case of probable korsakoff's syndrome: a syndrome of frontal lobe and diencephalic structural pathogenesis and a comparison with medial temporal lobe dementias

Korsakoff's Syndrome is an amnestic disorder that involves both anterograde and retrograde amnesia. Traditionally associated with longstanding alcohol misuse, thiamine deficiency has been long posited in its pathogenesis, as has dienecephalic lesions. Yet, through this case report, we highlight similarities (and differences) with medial temporal lobe memory disorders and the role of frontal lobe dysfunction in its retrograde amnesia.

Morphological and glucose metabolism abnormalities in alcoholic Korsakoff's syndrome: group comparisons and individual analyses

BACKGROUND

Gray matter volume studies have been limited to few brain regions of interest, and white matter and glucose metabolism have received limited research attention in Korsakoff's syndrome (KS). Because of the lack of brain biomarkers, KS was found to be underdiagnosed in postmortem studies.

METHODOLOGY/PRINCIPAL FINDINGS

Nine consecutively selected patients with KS and 22 matched controls underwent both structural magnetic resonance imaging and (18)F-fluorodeoxyglucose positron emission tomography examinations. Using a whole-brain analysis, the between-group comparisons of gray matter and white matter density and relative glucose uptake between patients with KS and controls showed the involvement of both the frontocerebellar and the Papez circuits, including morphological abnormalities in their nodes and connection tracts and probably resulting hypometabolism. The direct comparison of the regional distribution and degree of gray matter hypodensity and hypometabolism within the KS group indicated very consistent gray matter distribution of both abnormalities, with a single area of significant difference in the middle cingulate cortex showing greater hypometabolism than hypodensity. Finally, the analysis of the variability in the individual patterns of brain abnormalities within our sample of KS patients revealed that the middle cingulate cortex was the only brain region showing significant GM hypodensity and hypometabolism in each of our 9 KS patients.

CONCLUSIONS/SIGNIFICANCE

These results indicate widespread brain abnormalities in KS including both gray and white matter damage mainly involving two brain networks, namely, the fronto-cerebellar circuit and the Papez circuit. Furthermore, our findings suggest that the middle cingulate cortex may play a key role in the pathophysiology of KS and could be considered as a potential in vivo brain biomarker.

Neuroimaging of the Wernicke-Korsakoff syndrome

AIM

Presented is the neuroradiological signature of acute Wernicke's encephalopathy (WE), derived from different types of magnetic resonance imaging (MRI) sequences. WE results from thiamine depletion, and its most typical antecedent is chronic alcohol dependence. Brain regions observed with in vivo MRI affected in acute WE include the mammillary bodies, periaqueductal and periventricular gray matter, collicular bodies and thalamus. These affected areas are usually edematous and are best visualized and quantified with MRI sequences that highlight such tissue. Following the acute WE phase and resolution of edema and inflammation of affected brain tissue, WE, if not adequately treated with thiamine repletion, can herald Korsakoff's syndrome (KS), with its symptomatic hallmark of global amnesia, that is, the inability to commit newly encountered (episodic) information to memory for later recall or recognition.

METHODS

Neuropathology of KS detectable with MRI has a different neuroradiological signature from the acute stage and can be observed as tissue shrinkage or atrophy of selective brain structures, including the mammillary bodies and thalamus and ventricular expansion, probably indicative of atrophy of surrounding gray matter nuclei. Quantification of these and additional gray matter structures known to underlie global amnesia reveal substantial bilateral volume deficits in the hippocampus, in addition to the mammillary bodies and thalamus, and modest deficits in the medial septum/diagonal band of Broca. The infratentorium is also affected, exhibiting volume deficits in cerebellar hemispheres, anterior superior vermis and pons, contributing to ataxia of gait and stance.

RESULTS

Consideration of WKS structural brain changes in the context of the neuropathology of non-WKS alcoholism revealed a graded pattern of volume deficits, from mild in non-WKS alcoholics to moderate or severe in WKS, in the mammillary bodies, hippocampus, thalamus, cerebellum and pons. The development and resolution of brain structures affected in acute, chronic and treated WE was verified in longitudinal MRI study of rats that modeled of the interaction of extensive alcohol consumption and thiamine depletion and repletion.

CONCLUSIONS

Thus, neuroradiological examination with MRI is valuable in the diagnosis of acute WE and enables in vivo tracking of the progression of the brain pathology of WE from the acute pathological phase to resolution with thiamine treatment or to progression to KS without treatment. Further, in vivo MRI facilitates translational studies to model antecedent conditions contributing to the development, sequelae and treatment of WE.

How do Korsakoff patients learn new concepts?

The goal of the present investigation was to assess semantic learning in Korsakoff patients (KS), compared with uncomplicated alcoholics (AL) and control subjects (CS), taking the nature of the information to-be-learned and the episodic memory profiles of the three groups into account. Ten new complex concepts, each illustrated by a photo and composed of a label, a category and three features, were taught to 13 KS, 23 AL and 45 CS. When examined independently of the main experimental task, the two patients' groups presented episodic memory, working memory and executive impairments but episodic memory was more severely impaired in KS. Both AL and KS exhibited label learning deficits but KS were more severely impaired than AL. The episodic memory results were the main factor accounting for label learning performance when the three groups were pooled together. When examined within each group, the correlation was significant in CS and AL but not in KS. Only KS exhibited impaired category and feature learning results. Episodic memory did not account for category and feature learning performance. New label learning may be equivalent to that of proper names, requiring the involvement of episodic memory notably to arbitrarily associate a meaningless word with a specific identity. However, when episodic memory is severely impaired like in KS, an alternative neocortical learning route, bypassing episodic memory, may be invoked. Category and feature seem to be acquired independently of episodic memory. The specific impairment in category and feature learning in KS may therefore reflect a genuine deficit of semantic memory in Korsakoff's syndrome.

Mammillothalamic functional connectivity and memory function in Wernicke's encephalopathy

There is still debate over the neural mechanisms underlying pathogenic and even recovery processes of Wernicke's encephalopathy. Therefore, we attempted to validate the usefulness of resting-state functional connectivity analysis in assessing memory function and its neural correlation with the mammillothalamic tract in patients recovering from Wernicke's encephalopathy. Seven chronic alcoholics recovering from Wernicke's encephalopathy, 14 alcoholic comparisons without Wernicke's encephalopathy, and 14 healthy comparisons underwent functional connectivity MRI scans, as well as verbal and non-verbal memory tests after at least a 1 month abstinence from alcohol. Resting-state functional connectivity strength between the anterior thalamus and the mammillary bodies was investigated by calculating temporal correlations in magnetic resonance signal levels between the two regions during a 5-min passive viewing task. The mean values of the functional connectivity strength between the left anterior thalamus and the ipsilateral mammillary body differed significantly between Wernicke's encephalopathy patients and healthy comparisons (P = 0.014). This connectivity strength in alcoholic comparisons fell between those of the former two groups, with a significant difference from that of healthy comparisons (P = 0.038). In addition, the strength of this left-sided functional connectivity significantly correlated with delayed verbal recall scores (r = 0.771, P = 0.042) and verbal recognition score (r = 0.825, P = 0.022) in patients with Wernicke's encephalopathy. Our findings indicate that memory function in patients recovering from Wernicke's encephalopathy parallels the level of the mammillothalamic functional connectivity; this supports the usefulness of resting-state functional connectivity analysis as a practical alternative to pathological examination of the mammillothalamic tract in living patients with Wernicke's encephalopathy.

Spared unconscious influences of spatial memory in diencephalic amnesia

Spatial memory is crucial to our daily lives and in part strongly depends on automatic, implicit memory processes. This study investigates the neurocognitive basis of conscious and unconscious influences of object–location memory in amnesic patients with Korsakoff’s syndrome (N = 23) and healthy controls (N = 18) using a process-dissociation procedure in a computerized spatial memory task. As expected, the patients performed substantially worse on the conscious memory measures but showed even slightly stronger effects of unconscious influences than the controls. Moreover, a delayed test administered after 1 week revealed a strong decline in conscious influences in the patients, while unconscious influences were not affected. The presented results suggest that conscious and unconscious influences of spatial memory can be clearly dissociated in Korsakoff’s syndrome.

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.

Acute Korsakoff-like amnestic syndrome resulting from left thalamic infarction following a right hippocampal hemorrhage

Korsakoff-like amnestic syndromes have been rarely described following structural lesions of the central nervous system. In this report, we describe a case of acute Korsakoff-like syndrome resulting from the combination of a left anteromedian thalamic infarct and a right hippocampal hemorrhage. We also review the literature relevant to the neuropathology and pathophysiology of Korsakoff syndrome and anterograde amnesia.

Memory performance in multiple sclerosis patients correlates with central brain atrophy

OBJECTIVE

To assess whole brain and central brain atrophy as well as their differential relation to memory, cognitive performance, fatigue, depression and quality of life in patients with relapsing-remitting multiple sclerosis (RRMS).

METHODS

A 3D flow compensated gradient recalled T1-weighted MRI was acquired in 45 RRMS patients. An automated analysis tool was used to calculate brain parenchymal fraction (BPF) and ventricular brain fraction (VF). All patients were assessed with neuropsychological tests focusing on memory and self-rating scales for depression, fatigue and quality of life. Age corrected partial correlations between brain atrophy, motor performance, psychological scales and test scores were calculated.

RESULTS

BPF correlated moderately (0.3 < or = r < 0.5) with duration of symptoms and disease, the Expanded Disability Status Scale (EDSS), the upper extremity motor performance, and with mental aspects of quality of life. VF correlated moderately with EDSS, upper and lower extremity motor performance and memory functions. Neither BPF nor VF correlated with fatigue and depression. Results of several cognitive tests correlated moderately with depression and fatigue, the Paced Auditory Serial Addition Test (PASAT) showing the largest correlation.

CONCLUSIONS

Memory performance shows a correlation with relative ventricular size in RRMS patients, indicating the strategic location of the ventricle system along the structures of the limbic system and its vulnerability in MS. The PASAT and several other cognitive tests show moderate correlations with depression and fatigue, arguing for an inter relation between the cognitive functioning and the emotional state of patients. However, this relation is independent of measurable brain atrophy.

The contribution of familiarity to associative memory in amnesia

In Experiment 1, using the remember/know paradigm with control participants, we compared the contribution of recollection and familiarity to associative recognition for compound stimuli and for unrelated word pairs. It was demonstrated that familiarity makes a greater contribution to associative recognition of compound stimuli than to associative recognition of unrelated word pairs. In Experiment 2, we examined associative recognition memory in medial temporal lobe amnesics, diencephalic amnesics, and control participants for the stimuli employed in Experiment 1. Whereas associative recognition for compounds and unrelated words was nearly identical in control participants, associative recognition was higher for compounds than for unrelated word pairs in amnesic patients. This pattern was observed in the medial temporal amnesic group as well as in the diencephalic amnesic group. These results suggest that associative recognition in amnesia is enhanced to the extent that performance can be supported by study-induced familiarity for the studied pair.

Associations between alcohol intake and brain volumes in male and female moderate drinkers

BACKGROUND

Alcohol-dependent individuals have brain volume loss. Possibly, moderate drinkers who are not alcohol dependent have similar but less prominent brain damage. The authors investigated whether current or lifetime alcohol intake is related to volumes of total brain, cerebellum, ventricles, peripheral cerebrospinal fluid, and cerebral gray and white matter in moderate drinkers.

METHODS

The relation between current or lifetime alcohol intake and brain volumes of 47 male moderate drinkers (current alcohol intake 20 drinks per week, lifetime alcohol intake 240 kg) and 44 female moderate drinkers (current alcohol intake 15 drinks per week, lifetime alcohol intake 170 kg), all without a personal or family history of alcohol dependence, was determined using high-resolution magnetic resonance images, corrected for intracranial volume, age, and sex.

RESULTS

In males, mean lifetime alcohol intake was positively associated with cerebral white matter volume, particularly in the frontal region. In females, mean lifetime alcohol intake was not associated with brain volumes. Current alcohol intake was unrelated to brain volumes in either males or females.

CONCLUSIONS

Neither current nor lifetime alcohol intake is associated with decreases in brain volumes in male or female moderate drinkers. Because all participants had a negative personal and family history of alcohol dependence, the current results relatively purely concern the effects of moderate alcohol intake on brain volumes.

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.

Acute Korsakoff syndrome following mammillothalamic tract infarction

There are limited case reports of structural lesions causing Korsakoff syndrome. This report describes acute Korsakoff syndrome following localized, bilateral infarction of the mammillothalamic tracts (MTTs). Axial T2-weighted imaging revealed the lesions at the lateral wall level of the third ventricle and diffusion-weighted imaging confirmed that the left lesion was new and the right old. Korsakoff syndrome persisted 6 months after the onset. This case suggests that bilateral MTT dysfunction can lead to Korsakoff syndrome.

Korsakoff syndrome following chronic subdural hematoma

We describe a patient who developed Korsakoff syndrome following a spontaneous chronic subdural hematoma. The present case demonstrates persistence of both amnesia and confabulation long after recovery from the acute phase of spontaneous chronic subdural hematoma. There are few reports describing persistent amnesia with confabulation following brain damage. We considered that chronic subdural hematoma in the bilateral frontal and temporal lobes caused amnesia and confabulations, and these conditions persisted as a result of organic atrophic changes of both the frontal and temporal lobes due to long-term compression by chronic subdural hematoma.

Frontal lobe dysfunctions in Korsakoff's syndrome and chronic alcoholism: continuity or discontinuity?

The effect of long-term heavy alcohol consumption on brain functions is still under debate. The authors investigated a sample of 17 Korsakoff amnesics, 23 alcoholics without Korsakoff's syndrome, and 21 controls with peripheral nerve diseases, matched for intelligence and education. Executive functions were examined for word fluency, the modified Wisconsin Card Sorting Test, an alternate response task, and an "n-back" working memory task. Korsakoff amnesics, but not alcoholics, showed a marked memory impairment. They also scored lower in each of the executive tasks-the alcoholics only in the alternate response task. This task also correlated with the years of the alcohol dependency. First, the authors conclude that Korsakoff's syndrome is associated not only with a memory impairment but also with a global executive deficit. Second, the decline in the ability to alternate between different responses argues for a restricted neurotoxic effect of alcohol on some frontal lobe areas.

Medial temporal lobe atrophy predicts Alzheimer's disease in patients with minor cognitive impairment

OBJECTIVES

To investigate whether medial temporal lobe atrophy predicted outcome in patients with minor cognitive impairment and whether assessment of the medial temporal lobe could increase the predictive accuracy of age and delayed recall for outcome. Quantitative and qualitative methods of assessing the medial temporal lobe were also compared.

METHODS

Patients with minor cognitive impairment older than 50 years (n=31) were selected from a memory clinic and were followed up for on average 1.9 years. The medial temporal lobe was assessed in three different ways: volumetry of the hippocampus, volumetry of the parahippocampal gyrus, and qualitative rating of medial temporal lobe atrophy (MTA). Outcome measures were Alzheimer type dementia or cognitive decline at follow up. Delayed recall was tested with a verbal learning test.

RESULTS

Ten patients had experienced cognitive decline at follow up, of whom seven had probable Alzheimer type dementia. All medial temporal lobe measurements were associated with cognitive decline at follow up (p trend analysis between 0.001 (hippocampus) and 0.05 (parahippocampal gyrus)). Only the hippocampal volume and MTA score were associated with Alzheimer type dementia at follow up (p trend analysis respectively 0.003 and 0.01). All medial temporal lobe measurements increased the predictive accuracy of age and the delayed recall score for cognitive decline (p increase in predictive accuracy varied between <0.001 (hippocampus) and 0.02 (parahippocampal gyrus and MTA score)) and the hippocampal volume and the MTA score increased the predictive accuracy of age and the delayed recall score for Alzheimer type dementia (p= 0.02).

CONCLUSIONS

The ability to detect patients at high risk for Alzheimer type dementia among those with minor cognitive impairment increases when data on age and memory function are combined with measures of medial temporal lobe atrophy. Volumetry of the hippocampus is preferred, but qualitative rating of medial temporal lobe atrophy is a good alternative.

Verminderde vergrijzing en M. Korsakov; toeval of een voorbeeld van serendiptisme?

The clinical observation that patients with an alcohol amnestic disorder get grey hair at a higher age was investigated by comparing a group of Korsakov patients and patients with alcohol abuse with a reference sample from the literature. Korsakoff patients appeared to be significantly less grey than age-matched alcoholics and controls. Some putative etiological factors including the mechanism of apoptosis are discussed.

Automatic segmentation of the ventricular system from MR images of the human brain

An algorithm was developed that automatically segments the lateral and third ventricles from T1-weighted 3-D-FFE MR images of the human brain. The algorithm is based upon region-growing and mathematical morphology operators and starts from a coarse binary total brain segmentation, which is obtained from the 3-D-FFE image. Anatomical knowledge of the ventricular system has been incorporated into the method in order to find all constituting parts of the system, even if they are disconnected, and to avoid inclusion of nonventricle cerebrospinal fluid (CSF) regions. A test of the method on a synthetic MR brain image produced a segmentation overlap of 0.98 between the simulated ventricles ("model") and those defined by the algorithm. Further tests were performed on a large data set of 227 1.5 T MR brain images. The algorithm yielded useful results for 98% of the images. The automatic segmentations had intra-class correlation coefficients of 0.996 for the lateral ventricles and 0.86 for the third ventricle, with manually edited segmentations. Comparison of ventricular volumes of schizophrenia patients compared with those of healthy control subjects showed results in agreement with the literature.

Voxel-Based Mapping of Brain Hypometabolism in Permanent Amnesia with PET

In this study, we used voxel-based mapping methods to compare the resting cerebral metabolic rate of glucose (CMRglc) measured with PET in five patients with permanent amnesia (three with chronic Wernicke-Korsakoff and two with postanoxia syndrome) to that of nine healthy age-matched subjects. We assessed (i) a group pattern of relative hypometabolism; and (ii) the consistency of this group pattern, if any, in individual subjects, according to etiology. The results from the group analysis documented that permanent amnesia is associated with hypometabolism in the thalamus, posterior cingulate cortex, and mesial prefrontal cortex (near the anterior cingulate gyrus), bilaterally, as well as in the left supramarginal and middle temporal gyri. The individual analysis showed that this group pattern was found in essentially each patient, regardless of the cause of amnesia. Thus, permanent amnesia is subtended by dysfunction in structures belonging to Papez/limbic circuits as well as in left-hemisphere areas typically concerned with verbal functions, probably through a mechanism of thalamo-cortical disconnection and possibly involved in retrograde amnesia. The use of a voxel-based method allowed us to map a common network of synaptic dysfunction in a neuropsychological syndrome regardless of etiology. Our results indicate that this should be a powerful method in functional neuropsychology.