Korsakoff's syndrome, cognition and clonidine

Pharmacological enhancing agents targeting cognition in patients with alcohol-induced neurocognitive disorders: A systematic review

Debilitating neurocognitive deficits are seen in alcohol use disorders (AUD) and Wernicke-Korsakoff's syndrome (WKS). These shared characteristics suggest a spectrum of alcohol-induced neurocognitive disorders (AIND). Cognitive pharmacological enhancing agents (CPEA) have been examined in the treatment of other psychiatric disorders, but little is known about the effects of these agents on AINDs. Our aim was to synthesize the evidence for the effectiveness of CPEAs on AINDs. Databases were searched for controlled trials examining CPEAs on AUD, WKS, and alcohol-related dementia (ARD). Eligible studies were included in a qualitative synthesis and a quality assessment was conducted. The search identified 23 studies (4 ≤ ns ≤ 98). Evidence suggests that modafinil may improve executive functions in AUD and ARD, but this effect may only be present in patients with severe deficits. The studies were rated as having a moderate risk of bias. Despite the promising effects of modafinil, small samples and inconsistent evidence deem the results preliminary. More research is warranted examining the effects of transdiagnostic CPEAs on deficits across AINDs.

A systematic review of treatments for alcohol-related cognitive impairment: lessons from the past and gaps for future interventions

Alcohol-related cognitive impairment (ARCI) is highly prevalent among patients with alcohol dependence. Although it negatively influences treatment outcome, this condition is underdiagnosed and undertreated. The aim of this systematic review is to investigate the existing evidence regarding both cognitive and pharmacological interventions for ARCI. We systematically reviewed PubMed, Scopus and Science direct databases up to May 2019 and followed the PRISMA guidelines. The quality of the studies was assessed using the Jadad Scale. Twenty-six studies were eligible for inclusion (14 referring to neuropsychological interventions and 12 to pharmacological treatments). Among neuropsychological interventions, computerised treatments, errorless learning and component method showed positive effects on working memory, memory measures and general cognitive function. On the other hand, thiamine, memantine and methylphenidate improved working memory, long-term memory and general cognitive function. Nevertheless, these studies have several limitations, such as small sample size, lack of replication of the results or low specificity of the interventions. Therefore, no gold-standard intervention can yet be recommended for clinical practice, and further research based on promising strategies (e.g. digital interventions, thiamine) is required.

The effect of alpha-2 adrenergic agonists on memory and cognitive flexibility

BACKGROUND

The noradrenergic system modulates cognitive flexibility for insight-based problem solving in studies using beta-adrenergic antagonists, which block noradrenergic neurotransmission postsynaptically. However, it is not known whether alpha2-adrenergic agonists, that decrease noradrenergic neurotransmission by presynaptic inhibition, have the same effect.

OBJECTIVES

Therefore, we wished to test whether alpha2-adrenergic agonists would have a similar effect on cognitive flexibility.

METHODS

Eighteen normal adults were tested on cognitive flexibility, problem solving, verbal and spatial memory tasks after receiving clonidine (0.1 mg), an alpha2-agonist, placebo, or ephedrine (25 mg), a noradrenergic stimulant.

RESULTS

Three-way analysis of variance revealed no significant drug effect on cognitive flexibility or problem solving. There was also no significant effect of clonidine on memory.

CONCLUSIONS

Therefore, alpha2-agonists do not influence cognitive flexibility in the same manner as beta-antagonists. Better performance on memory with clonidine might be expected based on primate studies demonstrating benefits in working memory using clonidine. This benefit was not observed for the commonly used clinical memory tasks in our study. This may have implications for why clonidine has not demonstrated efficacy for cognitive disorders such as Alzheimer disease, despite its known benefit for working memory in animal models.

Preventive effect of kami-untan-to on performance in the forced swimming test in thiamine-deficient mice: Relationship to functions of catecholaminergic neurons

The kampo (Japanese herbal) medicine "kami-untan-to" (KUT) has been used for a long time in the treatment of neuropsychiatric disorders. We have recently reported that mice put on a thiamine-deficient (TD) diet exhibit a depressive behavior and impairment in avoidance learning after 20 days, and that this impairment was reversed by the chronic administration of KUT. In the present study, we investigated the effect of KUT on the depressive behavior observed in TD mice by using the forced swimming test. Our results show that oral administration of KUT from the 1st day of TD feeding prevented the increased duration of immobility in TD mice. Administration of KUT from the 10th day of TD feeding also had a beneficial effect on depressive behavior. To examine the relationship between the potential effects of KUT on monoaminergic neuronal functions and the depressive behavior observed in TD mice, we measured the immunohistochemical distribution of tyrosine hydroxylase (TH) in the brain using microphotometry. The fluorescence intensity of TH decreased in the limbic cortex and brainstem in TD mice compared with pair-fed mice as the control group, while KUT treatment protected against these decreases. These results suggest that KUT treatment may prevent a sign of depressive behavior, the animal immobility time, induced by TD feeding through a mechanism that involves the decrease of TH in some brain areas of TD mice.

Influence of reboxetine on salivary MHPG concentration and cognitive symptoms among patients with alcohol-related Korsakoff's syndrome

This study is based on the hypothesis of a paraventricular cerebral noradrenaline deficit in alcoholic Korsakoff's syndrome. In a randomized open study the effects of a 4-week treatment with the selective noradrenaline reuptake inhibitor reboxetine on (1) the salivary concentration of the noradrenaline metabolite MHPG and (2) changes in cognitive performance measured by the Mini Mental Status Test were examined. The study group consisted of 105 patients diagnosed with alcohol-related Korsakoff's syndrome (ICD-10: F10.6). Korsakoff's patients showed a reduced concentration of salivary MHPG compared to healthy controls; this reduction did not correlate with the results of the Mini Mental Status Test. An increase in salivary MHPG was found together with an improvement in the Mini Mental Status Test both in the verum group treated with reboxetine and in the control group upon completion of the 4-week study. However, a subgroup with a shorter duration of disease (<1 year) was found to profit significantly from reboxetine treatment, as shown by improvements in cognitive performance.

Neuropsychiatric effects of cardiovascular drug therapy

Various cardiovascular drugs have been shown to have neuropsychiatric effects that can be harmful or therapeutically beneficial to patients. As an example, both sedation and mental depression have been described in patients receiving centrally acting antihypertensive drugs and beta-adrenergic blockers, related to their antiadrenergic actions. In contrast, because of these antiadrenergic actions, agents like clonidine have been used to treat opiate, alcohol, and nicotine withdrawal, while beta blockers have been used to treat symptoms of performance anxiety, migraine, and psychocardiac disorders. Some antiarrhythmic drugs have been associated with delirium, and digitalis toxicity has been shown to cause hallucinations, mania, euphoria, and depression. The calcium-channel blocker verapamil has been used as an adjunctive treatment in patients with bipolar disorders. Since neuropsychiatric symptoms are seen in patients with cardiovascular disease, clinicians should be aware of the possible relationship between these symptoms and concurrent cardiovascular drug therapy.

Therapeutic effects of an acetylcholinesterase inhibitor (donepezil) on memory in Wernicke-Korsakoff's disease

Wernicke-Korsakoff's disease (WKD) is cognitively an amnestic state resulting from strategic lesions in the limbic system subserving the episodic memory network and resulting from thiamine deficiency. Neurochemical deficits have been implicated in the pathophysiology of amnesia based on the pathologic observations that various brainstem and basal forebrain nuclei are also affected. Previous treatment attempts with serotoninergic, noradrenergic, and cholinergic drugs have given controversial results. The objective of this study was to assess the effects of a cholinesterase inhibitor, donepezil, on memory, attention, and executive functions in patients with nonalcoholic WKD. Seven patients who developed WKD after a hunger strike were included in this single, blind, placebo-controlled, one-way, crossover study. The patients were administered donepezil during the first 30 days, and were administered placebo during the following 30 days. Neuropsychological tests to evaluate verbal and visual memory, and attention and executive function were performed on days 0, 31, and 61. All patients completed both phases of the study. There were no statistically significant differences between the three evaluations, except for a difference between active treatment and the placebo phase during recall of the Rey-Osterrieth complex figure, which was in favor of the placebo phase. There were no significant changes in favor of the active treatment. Cholinergic treatment with the cholinesterase inhibitor donepezil does not seem to provide marked beneficial effects in patients with WKD in this small, descriptive study. This may be because pathways mediating channel and state-dependent functions are impaired in this disease, and enhancement of state-dependent cholinergic transmission may not be sufficient. Subtle benefits, however, cannot be excluded because of the small sample size and the relatively short duration of the treatment.

The Korsakoff syndrome

BACKGROUND

Investigations of the Korsakoff syndrome by researchers from different disciplines have proliferated in recent years, making it apposite to review the various findings.

METHOD

This review is based on the author's knowledge of reports in the major clinical and neuropsychological journals, supplemented by Medline searches to update particular subtopics.

RESULTS

The Korsakoff syndrome is defined as a disproportionate impairment in memory, relative to other aspects of cognitive function, resulting from a nutritional (thiamine) depletion. The initial manifestations of the disorder are variable, and a persistent memory impairment can result from a non-alcoholic aetiology, although this seems to happen much less commonly than in the past - presumably because of generally higher standards of nutrition. Although there is agreement on the underlying neuropathology, the critical lesion sites for memory disorder have been debated. Recent evidence suggests that the circuit involving the mammillary bodies, the mammillo-thalamic tract and the anterior thalamus, rather than the medial dorsal nucleus of the thalamus, is particularly critical in the formation of new memories. The relationship of these deficits to thiamine depletion remains a topic of current investigation, as does the purported role of neurotransmitter depletions in the cholinergic, glutamate/GABA and catecholamine and serotonergic systems. Neuro-imaging studies have confirmed autopsy findings of more widespread structural and metabolic abnormalities, particularly involving the frontal lobes.

CONCLUSIONS

The relationship of these neuropathological, neurochemical, and metabolic abnormalities to cognitive functioning, with particular reference to specific aspects of memory processing, has been considered in some detail. Whereas structural and/or neurochemical abnormalities within the limbic/diencephalic circuits account for anterograde amnesia, some other factor, such as frontal lobe dysfunction, must underlie the severe retrograde memory loss which is characteristically found in this syndrome.

Effects of fluvoxamine treatment on cognitive functioning in the alcoholic Korsakoff syndrome

Eight patients suffering from the alcoholic Korsakoff syndrome (AKS) were entered in a double-blind cross-over trial of fluvoxamine 200 mg per day for 4 weeks versus matched placebo for 4 weeks. At the end of each phase, patients were assessed using a detailed neuropsychological test battery. Verbal fluency performance was significantly impaired following fluvoxamine treatment. No significant differences emerged on any of the other cognitive test measures when fluvoxamine was compared with placebo. However, two of the patients developed a major depressive episode while receiving fluvoxamine.

Pharmacological manipulations of the alpha 2-noradrenergic system. Effects on cognition

Electrophysiological and neurosurgical lesion studies with experimental animals have implicated the ascending dorsal noradrenergic bundle of the locus coeruleus system in cognitive process such as memory, learning and selective attention. However, it has also been suggested that noradrenaline (norepinephrine) is crucial in certain cognitive functions associated with the frontal lobes, particularly the prevention of distractibility by irrelevant stimuli. The alpha 2-receptors of the prefrontal cortex appear to be of particular importance in this respect. Studies with humans and experimental primates provide substantial support for this view. The aged primate brain is prone to degeneration of the locus coeruleus, as well as profound catecholamine depletion in the prefrontal cortex, and so is ideal for psychopharmacological investigation of the role of noradrenaline in frontal lobe function. Elderly monkeys show deficits in performance of the delayed response task, which can be reversed directly by both the mixed alpha 1/alpha 2-agonist clonidine, the more specific alpha 2-agonist guanfacine and also, indirectly, by the alpha 2-antagonist yohimbine. It is suggested that these results can be explained by an attenuation of the distracting properties of irrelevant stimuli following stimulation of noradrenergic activity. Conversely, distractibility is magnified whenever noradrenergic activity is reduced. This is supported by similar findings in psychopharmacological studies of healthy humans. The exception to this is when the locus coeruleus is likely to be firing, e.g. in times of stress or when novel stimuli are encountered. Clonidine attenuates locus coeruleus firing on such occasions, and so counteracts any beneficial (or deleterious) effects of stress on task performance. alpha 2-Adrenoceptor agents have little therapeutic value in patients with dementia of the Alzheimer's type. However, they may have some clinical use in patients who have a cognitive symptomatology similar to that of patients who have received neurosurgical excisions to the frontal lobes, e.g. deficits in working memory, executive function or focused attention, with relative sparing of episodic short term memory. Patients with Korsakoff's disease, attention deficit disorder or schizophrenia may benefit from treatment with alpha 2-agents. In particular, idazoxan has putative therapeutic effects in patients with a neurodegenerative disorder, namely dementia of frontal type.

Memory impairment in schizophrenia--a comparison with that observed in the Alcoholic Korsakoff syndrome

Until very recently, memory impairment was not considered to be a central feature of schizophrenia, except in chronic, deteriorated patients. In this study of a heterogeneous sample of 40 patients with DSM-III-R schizophrenia, episodic memory impairment was found to be prevalent, and in some cases, severe. The degree of memory impairment was not attributable to neuroleptic or anticholinergic medication, or to poor motivation or cooperation. These results, therefore, replicate those reported by McKenna et al. (1990) and Tamlyn et al. (1992), who suggested that the pattern of memory impairment in schizophrenia may conform in important respects to that of the classic amnesic syndrome. However, in a direct comparison of the schizophrenic sample with 18 patients suffering from the Alcoholic Korsakoff Syndrome (AKS), both quantitative and qualitative differences were found to exist between the two groups of patients. In particular, the level of long-term episodic memory impairment was found in the AKS sample to be far greater than that in the schizophrenic group. An interesting possible double-dissociation emerged between the two groups; although demonstrating superior episodic memory functioning, the schizophrenic sample were found to perform significantly more poorly than the AKS sample on a test of semantic memory.

Clonidine infusion increases uptake of 99mTc-Exametazime in anterior cingulate cortex in Korsakoff's psychosis

The effects upon regional brain function of infusing either saline or clonidine (1.5 microgram/kg) has been examined in 18 patients with alcoholic Korsakoff's psychosis using 99mTc-hexamethylpropyleneamineoxime (99mTc-HMPAO or 99mTc-Exametazime) and Single Photon Emission Tomography (SPET or SPECT). The hypothesis tested was that frontal lobe function would be increased by adrenoceptor stimulation. This was confirmed by an increase in the uptake of 99mTc-Exametazime into anterior cingulate regions of the frontal lobes. Patients were scanned before and after saline or clonidine infusion during performance of a verbal fluency task. There was a significantly increased performance of verbal fluency in patients given clonidine. This effect was variable and could not be unequivocably distinguished from increases in performance in the saline treated group. Nevertheless, the increase in neuropsychological performance was also correlated with increased function in left dorsolateral frontal cortex within the clonidine treated group. An exploratory examination of other brain areas suggested that relative increases in posterior cingulate cortex and changes in the symmetry of function within the thalamus may also be produced by acute infusion of clonidine in Korsakoff patients. The findings support the idea that adrenergic mechanisms may modulate cognitive performance by actions on attentional systems within the brain. These appear to be located primarily within limbic cortex. It is, of course, notable that this can occur in patients with profound and disabling amnesia.