Longitudinal multimodal imaging in mild to moderate Alzheimer disease: a pilot study with memantine

Extrasynaptic NMDA receptors in acute and chronic excitotoxicity: implications for preventive treatments of ischemic stroke and late-onset Alzheimer's disease

Stroke and late-onset Alzheimer's disease (AD) are risk factors for each other; the comorbidity of these brain disorders in aging individuals represents a significant challenge in basic research and clinical practice. The similarities and differences between stroke and AD in terms of pathogenesis and pathophysiology, however, have rarely been comparably reviewed. Here, we discuss the research background and recent progresses that are important and informative for the comorbidity of stroke and late-onset AD and related dementia (ADRD). Glutamatergic NMDA receptor (NMDAR) activity and NMDAR-mediated Ca²⁺ influx are essential for neuronal function and cell survival. An ischemic insult, however, can cause rapid increases in glutamate concentration and excessive activation of NMDARs, leading to swift Ca²⁺ overload in neuronal cells and acute excitotoxicity within hours and days. On the other hand, mild upregulation of NMDAR activity, commonly seen in AD animal models and patients, is not immediately cytotoxic. Sustained NMDAR hyperactivity and Ca²⁺ dysregulation lasting from months to years, nevertheless, can be pathogenic for slowly evolving events, i.e. degenerative excitotoxicity, in the development of AD/ADRD. Specifically, Ca²⁺ influx mediated by extrasynaptic NMDARs (eNMDARs) and a downstream pathway mediated by transient receptor potential cation channel subfamily M member (TRPM) are primarily responsible for excitotoxicity. On the other hand, the NMDAR subunit GluN3A plays a "gatekeeper" role in NMDAR activity and a neuroprotective role against both acute and chronic excitotoxicity. Thus, ischemic stroke and AD share an NMDAR- and Ca²⁺-mediated pathogenic mechanism that provides a common receptor target for preventive and possibly disease-modifying therapies. Memantine (MEM) preferentially blocks eNMDARs and was approved by the Federal Drug Administration (FDA) for symptomatic treatment of moderate-to-severe AD with variable efficacy. According to the pathogenic role of eNMDARs, it is conceivable that MEM and other eNMDAR antagonists should be administered much earlier, preferably during the presymptomatic phases of AD/ADRD. This anti-AD treatment could simultaneously serve as a preconditioning strategy against stroke that attacks ≥ 50% of AD patients. Future research on the regulation of NMDARs, enduring control of eNMDARs, Ca²⁺ homeostasis, and downstream events will provide a promising opportunity to understand and treat the comorbidity of AD/ADRD and stroke.

Virtual Therapy with the NMDA Antagonist Memantine in Hippocampal Models of Moderate to Severe Alzheimer’s Disease, in Silico Trials

The variability in clinical trial results on memantine treatment of Alzheimer’s disease remains incompletely explained. The aim of this in silico study is a virtual memantine therapy for Alzheimer’s disease that provides a different perspective on clinical trials; An in silico randomised trial using virtual hippocampi to treat moderate to severe Alzheimer’s disease with doses of memantine 3–30 µM compared to placebo. The primary endpoint was the number of impulses (spikes). Secondary endpoints included interspike interval and frequency; The number of virtual moderate-AD hippocampal spikes was significantly lower, at 1648.7 (95% CI, 1344.5–1952.9), versus those treated with the 3 µM dose, 2324.7 (95% CI, 2045.9–2603.5), and the 10 µM dose, 3607.0 (95% CI, 3137.6–4076.4). In contrast, the number of virtual spikes (spikes) of severe AD of the hippocampus was significantly lower, at 1461.8 (95% CI, 1196.2–1727.4), versus those treated with the 10 µM dose, at 2734.5 (95% CI, 2369.8–3099.2), and the 30 µM dose, at 3748.9 (95% CI, 3219.8–4278.0). The results of the analysis of secondary endpoints, interspike intervals and frequencies changed statistically significantly relative to the placebo; The results of the in silico study confirm that memantine monotherapy is effective in the treatment of moderate to severe Alzheimer’s disease, as assessed by various neuronal parameters.

Tracer-specific reference tissues selection improves detection of 18 F-FDG, 18 F-florbetapir, and 18 F-flortaucipir PET SUVR changes in Alzheimer's disease

This study sought to identify a reference tissue‐based quantification approach for improving the statistical power in detecting changes in brain glucose metabolism, amyloid, and tau deposition in Alzheimer's disease studies. A total of 794, 906, and 903 scans were included for ¹⁸F‐FDG, ¹⁸F‐florbetapir, and ¹⁸F‐flortaucipir, respectively. Positron emission tomography (PET) and T1‐weighted images of participants were collected from the Alzheimer's disease Neuroimaging Initiative database, followed by partial volume correction. The standardized uptake value ratios (SUVRs) calculated from the cerebellum gray matter, centrum semiovale, and pons were evaluated at both region of interest (ROI) and voxelwise levels. The statistical power of reference tissues in detecting longitudinal SUVR changes was assessed via paired t‐test. In cross‐sectional analysis, the impact of reference tissue‐based SUVR differences between cognitively normal and cognitively impaired groups was evaluated by effect sizes Cohen's d and two sample t‐test adjusted by age, sex, and education levels. The average ROI t values of pons were 86.62 and 38.40% higher than that of centrum semiovale and cerebellum gray matter in detecting glucose metabolism decreases, while the centrum semiovale reference tissue‐based SUVR provided higher t values for the detection of amyloid and tau deposition increases. The three reference tissues generated comparable d images for ¹⁸F‐FDG, ¹⁸F‐florbetapir, and ¹⁸F‐flortaucipir and comparable t maps for ¹⁸F‐florbetapir and ¹⁸F‐flortaucipir, but pons‐based t map showed superior performance in ¹⁸F‐FDG. In conclusion, the tracer‐specific reference tissue improved the detection of ¹⁸F‐FDG, ¹⁸F‐florbetapir, and ¹⁸F‐flortaucipir PET SUVR changes, which helps the early diagnosis, monitoring of disease progression, and therapeutic response in Alzheimer's disease.

Optimizing Use of Neuroimaging Tools in Evaluation of Prodromal Alzheimer's Disease and Related Disorders

Alzheimer's disease (AD) is the most common neurodegenerative disease and is characterized by preclinical, pre-dementia, and dementia phases. Progression of the disease leads to cognitive decline and is associated with loss of functional independence, personality changes, and behavioral disturbances. Current guidelines for AD diagnosis include the use of neuroimaging tools as biomarkers for identifying and monitoring pathological changes. Various imaging modalities, namely magnetic resonance imaging (MRI), fluorodeoxyglucose-positron emission tomography (FDG-PET) and PET with amyloid-beta tracers are available to facilitate early accurate diagnoses. Enhancing diagnosis in the early stages of the disease can allow for timely interventions that can delay progression of the disease. This paper will discuss the characteristic findings associated with each of the imaging tools for patients with AD, with a focus on FDG-PET due to its established accuracy in assisting with the differential diagnosis of dementia and discussion of other methods including MRI. Diagnostically-relevant features to aid clinicians in making a differential diagnosis will also be pointed out and multimodal imaging will be reviewed. We also discuss the role of quantification software in interpretation of brain imaging. Lastly, to guide evaluation of patients presenting with cognitive deficits, an algorithm for optimal integration of these imaging tools will be shared. Molecular imaging modalities used in dementia evaluations hold promise toward identifying AD-related pathology before symptoms are fully in evidence. The work describes state of the art functional and molecular imaging methods for AD. It will also overview a clinically applicable quantitative method for reproducible assessments of such scans in the early identification of AD.

Riluzole, a glutamate modulator, slows cerebral glucose metabolism decline in patients with Alzheimer's disease

Dysregulation of glutamatergic neural circuits has been implicated in a cycle of toxicity, believed among the neurobiological underpinning of Alzheimer's disease. Previously, we reported preclinical evidence that the glutamate modulator riluzole, which is FDA-approved for the treatment of amyotrophic lateral sclerosis, has potential benefits on cognition, structural and molecular markers of aging and Alzheimer's disease. The objective of this study was to evaluate in a pilot clinical trial, using neuroimaging biomarkers, the potential efficacy and safety of riluzole in patients with Alzheimer's disease as compared to placebo. A 6-month phase 2 double-blind, randomized, placebo-controlled study was conducted at two sites. Participants consisted of males and females, 50 to 95 years of age, with a clinical diagnosis of probable Alzheimer's disease, and Mini-Mental State Examination between 19 and 27. Ninety-four participants were screened, fifty subjects that met inclusion criteria were randomly assigned to receive 50 mg riluzole (n = 26) or placebo (n = 24) twice a day. Twenty-two riluzole-treated and 20 placebo participants completed the study. Primary endpoints were baseline to 6 months changes in a) cerebral glucose metabolism as measured with fluorodeoxyglucose-positron emission tomography in pre-specified regions of interest (hippocampus, posterior cingulate, precuneus, lateral temporal, inferior parietal, frontal) and b) changes in posterior cingulate levels of the neuronal viability marker N-acetylaspartate as measured with in vivo proton magnetic resonance spectroscopy. Secondary outcome measures were neuropsychological testing for correlation with neuroimaging biomarkers and in vivo measures of glutamate in posterior cingulate measured with magnetic resonance spectroscopy as a potential marker of target engagement. Measures of cerebral glucose metabolism, a well-established Alzheimer's disease biomarker and predictor of disease progression, declined significantly less in several pre-specified regions of interest with the most robust effect in posterior cingulate, and effects in precuneus, lateral temporal, right hippocampus and frontal cortex in riluzole-treated subjects in comparison to placebo group. No group effect was found in measures of N-acetylaspartate levels. A positive correlation was observed between cognitive measures and regional cerebral glucose metabolism. A group by visit interaction was observed in glutamate levels in posterior cingulate, potentially suggesting engagement of glutamatergic system by riluzole. In vivo glutamate levels positively correlated with cognitive performance. These findings support our main primary hypothesis that cerebral glucose metabolism would be better preserved in the riluzole treated group than in the placebo group and investigations in future larger and longer studies to test riluzole as a potential novel therapeutic intervention for Alzheimer's disease.

PET Neuroimaging of Alzheimer's Disease: Radiotracers and Their Utility in Clinical Research

Alzheimer's Disease (AD), the leading cause of senile dementia, is a progressive neurodegenerative disorder affecting millions of people worldwide and exerting tremendous socioeconomic burden on all societies. Although definitive diagnosis of AD is often made in the presence of clinical manifestations in late stages, it is now universally believed that AD is a continuum of disease commencing from the preclinical stage with typical neuropathological alterations appearing decades prior to its first symptom, to the prodromal stage with slight symptoms of amnesia (amnestic mild cognitive impairment, aMCI), and then to the terminal stage with extensive loss of basic cognitive functions, i.e., AD-dementia. Positron emission tomography (PET) radiotracers have been developed in a search to meet the increasing clinical need of early detection and treatment monitoring for AD, with reference to the pathophysiological targets in Alzheimer's brain. These include the pathological aggregations of misfolded proteins such as β-amyloid (Aβ) plagues and neurofibrillary tangles (NFTs), impaired neurotransmitter system, neuroinflammation, as well as deficient synaptic vesicles and glucose utilization. In this article we survey the various PET radiotracers available for AD imaging and discuss their clinical applications especially in terms of early detection and cognitive relevance.

Memantine for dementia

BACKGROUND

Memantine is a moderate affinity uncompetitive antagonist of glutamate NMDA receptors. It is licensed for use in moderate and severe Alzheimer's disease (AD); in the USA, it is also widely used off-label for mild AD.

OBJECTIVES

To determine efficacy and safety of memantine for people with dementia. To assess whether memantine adds benefit for people already taking cholinesterase inhibitors (ChEIs).

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's register of trials (http://www.medicine.ox.ac.uk/alois/) up to 25 March 2018. We examined clinical trials registries, press releases and posters of memantine manufacturers; and the web sites of the FDA, EMEA and NICE. We contacted authors and companies for missing information.

SELECTION CRITERIA

Double-blind, parallel group, placebo-controlled, randomised trials of memantine in people with dementia.

DATA COLLECTION AND ANALYSIS

We pooled and analysed data from four clinical domains across different aetiologies and severities of dementia and for AD with agitation. We assessed the impact of study duration, severity and concomitant use of ChEIs. Consequently, we restricted analyses to the licensed dose (20 mg/day or 28 mg extended release) and data at six to seven months duration of follow-up, and analysed separately results for mild and moderate-to-severe AD.We transformed results for efficacy outcomes into the difference in points on particular outcome scales.

MAIN RESULTS

Across all types of dementia, data were available from almost 10,000 participants in 44 included trials, most of which were at low or unclear risk of bias. For nearly half the studies, relevant data were obtained from unpublished sources. The majority of trials (29 in 7885 participants) were conducted in people with AD.1. Moderate-to-severe AD (with or without concomitant ChEIs). High-certainty evidence from up to 14 studies in around 3700 participants consistently shows a small clinical benefit for memantine versus placebo: clinical global rating (CGR): 0.21 CIBIC+ points (95% confidence interval (CI) 0.14 to 0.30); cognitive function (CF): 3.11 Severe Impairment Battery (SIB) points (95% CI 2.42 to 3.92); performance on activities of daily living (ADL): 1.09 ADL19 points (95% CI 0.62 to 1.64); and behaviour and mood (BM): 1.84 Neuropsychiatric Inventory (NPI) points (95% CI 1.05 to 2.76). There may be no difference in the number of people discontinuing memantine compared to placebo: risk ratio (RR) 0.93 (95% CI 0.83 to 1.04) corresponding to 13 fewer people per 1000 (95% CI 31 fewer to 7 more). Although there is moderate-certainty evidence that fewer people taking memantine experience agitation as an adverse event: RR 0.81 (95% CI 0.66 to 0.99) (25 fewer people per 1000, 95% CI 1 to 44 fewer), there is also moderate-certainty evidence, from three additional studies, suggesting that memantine is not beneficial as a treatment for agitation (e.g. Cohen Mansfield Agitation Inventory: clinical benefit of 0.50 CMAI points, 95% CI -3.71 to 4.71) .The presence of concomitant ChEI does not impact on the difference between memantine and placebo, with the possible exceptions of the BM outcome (larger effect in people taking ChEIs) and the CF outcome (smaller effect).2. Mild AD (Mini Mental State Examination (MMSE) 20 to 23): mainly moderate-certainty evidence based on post-hoc subgroups from up to four studies in around 600 participants suggests there is probably no difference between memantine and placebo for CF: 0.21 ADAS-Cog points (95% CI -0.95 to 1.38); performance on ADL: -0.07 ADL 23 points (95% CI -1.80 to 1.66); and BM: -0.29 NPI points (95% CI -2.16 to 1.58). There is less certainty in the CGR evidence, which also suggests there may be no difference: 0.09 CIBIC+ points (95% CI -0.12 to 0.30). Memantine (compared with placebo) may increase the numbers of people discontinuing treatment because of adverse events (RR 2.12, 95% CI 1.03 to 4.39).3. Mild-to-moderate vascular dementia. Moderate- and low-certainty evidence from two studies in around 750 participants indicates there is probably a small clinical benefit for CF: 2.15 ADAS-Cog points (95% CI 1.05 to 3.25); there may be a small clinical benefit for BM: 0.47 NOSGER disturbing behaviour points (95% CI 0.07 to 0.87); there is probably no difference in CGR: 0.03 CIBIC+ points (95% CI -0.28 to 0.34); and there may be no difference in ADL: 0.11 NOSGER II self-care subscale points (95% CI -0.35 to 0.54) or in the numbers of people discontinuing treatment: RR 1.05 (95% CI 0.83 to 1.34).There is limited, mainly low- or very low-certainty efficacy evidence for other types of dementia (Parkinson's disease and dementia Lewy bodies (for which CGR may show a small clinical benefit; four studies in 319 people); frontotemporal dementia (two studies in 133 people); and AIDS-related Dementia Complex (one study in 140 people)).There is high-certainty evidence showing no difference between memantine and placebo in the proportion experiencing at least one adverse event: RR 1.03 (95% CI 1.00 to 1.06); the RR does not differ between aetiologies or severities of dementia. Combining available data from all trials, there is moderate-certainty evidence that memantine is 1.6 times more likely than placebo to result in dizziness (6.1% versus 3.9%), low-certainty evidence of a 1.3-fold increased risk of headache (5.5% versus 4.3%), but high-certainty evidence of no difference in falls.

AUTHORS' CONCLUSIONS

We found important differences in the efficacy of memantine in mild AD compared to that in moderate-to-severe AD. There is a small clinical benefit of memantine in people with moderate-to-severe AD, which occurs irrespective of whether they are also taking a ChEI, but no benefit in people with mild AD.Clinical heterogeneity in AD makes it unlikely that any single drug will have a large effect size, and means that the optimal drug treatment may involve multiple drugs, each having an effect size that may be less than the minimum clinically important difference.A definitive long-duration trial in mild AD is needed to establish whether starting memantine earlier would be beneficial over the long term and safe: at present the evidence is against this, despite it being common practice. A long-duration trial in moderate-to-severe AD is needed to establish whether the benefit persists beyond six months.

Memantine for Alzheimer's Disease: An Updated Systematic Review and Meta-analysis

BACKGROUND

The clinical benefit of memantine for Alzheimer's disease (AD) remains inconclusive.

OBJECTIVE

We performed an updated systematic review and meta-analysis of the efficacy/safety of memantine in AD.

METHODS

We included randomized trials of memantine for AD patients. Cognitive function scores (CF), behavioral disturbances scores (BD), and all-cause discontinuation were used as primary measures. Effect size based on a random-effects model was evaluated in the meta-analyses.

RESULTS

Thirty studies (n = 7,567; memantine versus placebo: N = 11, n = 3,298; memantine + cholinesterase inhibitors (M+ChEIs) versus ChEIs: N = 17, n = 4,175) were identified. Memantine showed a significant improvement in CF [standardized mean difference (SMD) = -0.24, 95% confidence intervals (95% CIs) = -0.34, -0.15, p < 0.00001, I2 = 35% ] and BD (SMD = -0.16, 95% CIs = -0.29, -0.04, p = 0.01, I2 = 52%) compared with placebo. In the sensitivity analysis including only patients with moderate-severe AD, memantine was superior to the placebo in reducing BD without considerable heterogeneity (SMD = -0.20, 95% CIs = -0.34, -0.07, p = 0.003, I2 = 36%). Compared with ChEIs, M+ChEIs showed a greater reduction in BD (SMD = -0.20, 95% CIs = -0.36, -0.03, p = 0.02, I2 = 77%) and a trend of CF improvement (SMD = -0.11, 95% CIs = -0.22, 0.01, p = 0.06, I2 = 56%). However, in the sensitivity analysis of double-blind, placebo-controlled studies only, M+ChEIs showed a significant reduction in BD compared with ChEIs without considerable heterogeneity (SMD = -0.11, 95% CIs = -0.21, -0.01, p = 0.04, I2 = 40%). When performing the sensitivity analysis of donepezil studies only, M+ChEIs was superior to ChEIs in improving CF without considerable heterogeneity (SMD = -0.18, 95% CIs = -0.31, -0.05, p = 0.006, I2 = 49%). No differences were detected in all-cause discontinuation between the groups.

CONCLUSIONS

The meta-analyses suggest the credible efficacy and safety of memantine in treating AD when used alone or in combination with ChEIs.

Memantine improves semantic memory in patients with amnestic mild cognitive impairment: A single-photon emission computed tomography study

Objective This study was performed to assess the efficacy of memantine in patients with amnestic mild cognitive impairment (aMCI). Methods Thirty healthy controls and 45 patients diagnosed with aMCI based on the Petersen criteria were classified into 3 groups. Group 1 comprised patients who received a single memantine dose following examination (n = 25), Group 2 comprised patients who did not receive memantine treatment following examination (n = 20), and Group 3 comprised healthy age-matched volunteers (n = 30). Neuropsychological testing was performed, and the response to memantine was examined at baseline and at 12, 24, and 48 weeks. Single-photon emission computed tomography was performed at baseline and at 48 weeks in patients who received memantine treatment. Results Memantine treatment significantly improved the symptoms of aMCI according to the Wechsler Adult Intelligence Scale-Revised vocabulary subtest, backward digit span, and Blessed Dementia Rating Scale, all of which were recorded for the duration of the study. Conclusion These data indicate that patients with aMCI receiving memantine develop an improved semantic memory compared with no treatment. Further studies including larger patient cohorts are necessary to validate these findings.

PET Imaging for Early Detection of Alzheimer's Disease: From Pathologic to Physiologic Biomarkers

This article describes the application of various PET imaging agents in the investigation and diagnosis of Alzheimer's disease (AD), including radiotracers for pathologic biomarkers of AD such as β-amyloid deposits and tau protein aggregates, and the neuroinflammation biomarker 18 kDa translocator protein, as well as physiologic biomarkers, such as cholinergic receptors, glucose metabolism, and the synaptic density biomarker synaptic vesicle glycoprotein 2A. Potential of these biomarkers for early AD diagnosis is also assessed.

A Two-Year Treatment of Amnestic Mild Cognitive Impairment using a Compound Chinese Medicine: A Placebo Controlled Randomized Trial

We aimed to investigate the long-term therapeutic effects of a compound Chinese medicine, the Bushen capsule, on cognition and brain connectivity in patients with amnestic mild cognitive impairment (aMCI). Thus, sixty aMCI participants were recruited to this 24-month study and were randomly divided into treatment (30 with a Bushen capsule) and placebo (30 with a placebo capsule) groups. Neuropsychological tests with MMSE and episodic memory as the primary outcomes and resting-state functional magnetic resonance imaging (fMRI) were analyzed before and after the treatment over 24 month period. In contrast to the placebo group, the drug group presented improved or stable general cognitive function, memory, language and executive function especially the primary outcomes MMSE and episodic memory with Bushen capsule treatment. FMRI results showed increased connectivity in the right precuneus and the global connectivity indexed with goodness of fit (GOF) of the default mode network (DMN) in the drug group and decreased GOF in the placebo group. More importantly, we found the GOF change was positively correlated with changes in MMSE and memory scores after 24 months in the drug group. Over 24 months, treatment with the compound Chinese medicine Bushen capsule can improve multiple domains of cognition and increase the functional local (right precuneus) and global connectivity within the DMN, which are associated with better performance.

Brain maturation in neonatal rodents is impeded by sevoflurane anesthesia

BACKGROUND

A wealth of data shows neuronal demise after general anesthesia in the very young rodent brain. Herein, the authors apply proton magnetic resonance spectroscopy (1HMRS), testing the hypothesis that neurotoxic exposure during peak synaptogenesis can be tracked via changes in neuronal metabolites.

METHODS

1HMRS spectra were acquired in the brain (thalamus) of neonatal rat pups 24 and 48 h after sevoflurane exposure on postnatal day (PND) 7 and 15 and in unexposed, sham controls. A repeated measure ANOVA was performed to examine whether changes in metabolites were different between exposed and unexposed groups. Sevoflurane-induced neurotoxicity on PND7 was confirmed by immunohistochemistry.

RESULTS

In unexposed PND7 pups (N = 21), concentration of N-acetylaspartate (NAA; [NAA]) increased by 16% from PND8 to PND9, whereas in exposed PND7 pups (N = 19), [NAA] did not change and concentration of glycerophosphorylcholine and phosphorylcholine ([GPC + PCh]) decreased by 25%. In PND15 rats, [NAA] increased from PND16 to PND17 for both the exposed (N = 14) and the unexposed (N = 16) groups. Two-way ANOVA for PND7 pups demonstrated that changes over time observed in [NAA] (P = 0.031) and [GPC + PCh] (P = 0.024) were different between those two groups.

CONCLUSIONS

The authors demonstrated that normal [NAA] increase from PND8 to PND9 was impeded in sevoflurane-exposed rats when exposed at PND7; however, not impeded when exposed on PND15. Furthermore, the authors showed that noninvasive 1HMRS is sufficiently sensitive to detect subtle differences in developmental time trajectory of [NAA]. This is potentially clinically relevant because 1HMRS can be applied across species and may be useful in providing evidence of neurotoxicity in the human neonatal brain.

Protection against Brain Atrophy by Anti-dementia Medication in Mild Cognitive Impairment and Alzheimer's Disease: Meta-Analysis of Longitudinal Randomized Placebo-Controlled Trials

BACKGROUND

There has not been conclusive evidence for prevention of brain atrophy by anti-dementia drugs in mild cognitive impairment and Alzheimer's Disease.

METHODS

Relevant studies were identified through searches of PubMed, databases of the Cochrane Library, and PsycINFO citations up to 16 May, 2015. Only double-blind, randomized, placebo-controlled clinical trials of anti-dementia drugs in patients with mild cognitive impairment or Alzheimer's Disease were included. Primary outcomes were annualized percent change of total brain volume (%TBV/y), annualized percent change of hippocampal volume (%HV/y), and annualized percent change of ventricular volume (%VV/y) measured by magnetic resonance imaging. Standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated for relevant outcomes.

RESULTS

Seven randomized, placebo-controlled clinical trials (n=1708) were found to meet the inclusion criteria, including 4 mild cognitive impairment studies (n=1327) and 3 Alzheimer's Disease studies (n=381) [3 donepezil studies (2 mild cognitive impairment studies and 1 Alzheimer's Disease study), 1 galantaime study for mild cognitive impairment, 2 mementine studies for Alzheimer's Disease, and 1 rivastigmine study for mild cognitive impairment]. Pooled anti-dementia drugs showed superior protective outcomes compared with placebo regarding %TBV/y (SMD=-0.21, 95%CI=-0.37 to -0.04, P=.01, N=4, n=624) and %VV/y (SMD=-0.79, 95%CI=-1.40 to -0.19, P=.01, N=3, n=851). However, %HV/y failed to show difference between both groups. Among anti-dementia drugs, donepezil showed significantly greater protective effects than placebo regarding %TBV/y (SMD=-0.43, 95%CI=-0.74 to -0.12, P=.007, N=1, n=164) and %VV/y (SMD=-0.51, 95%CI=-0.73 to -0.29, P<.00001, N=2, n=338). Rivastigmine was also superior to placebo regarding %VV/y (SMD=-1.33, 95%CI=-1.52 to -1.14, P<.00001).

CONCLUSIONS

The results favored the hypothesis that anti-dementia drugs may prevent brain atrophy in patients with mild cognitive impairment and Alzheimer's Disease.

Efficacy and adverse effects of memantine treatment for Alzheimer's disease from randomized controlled trials

The role of memantine as a treatment for Alzheimer's disease (AD) has been controversial. In clinical trials, a high dropout rate and numerous adverse events associated with memantine have been observed. However, given the relative scarcity of effective treatments for AD it would seem prudent to re-examine existing evidence to determine whether or not memantine should be used. Eight databases were utilized for randomized controlled trials that were published prior to December 31, 2013 and were according with the inclusion criteria. Trial methods, clinical characteristics, outcomes, and adverse events were extracted and analyzed with Review Manager 5.2. We obtained 2293 studies and determined that 13 of those studies met the inclusion criteria. Memantine therapy showed significant benefits to cognition, mental state, activities of daily life, the clinician's global impression in term with MMSE, SIB, NPI, ADCS-ADL19, CIBIC-Plus, respectively. Memantine therapy did not significantly increase the incidence of total adverse events, serious adverse events, death but it did increase the risk for somnolence.

Memantine monotherapy for Alzheimer's disease: a systematic review and meta-analysis

BACKGROUND

We performed an updated meta-analysis of randomized placebo-controlled trials testing memantine monotherapy for patients with Alzheimer's disease (AD).

METHODS

The meta-analysis included randomized controlled trials of memantine monotherapy for AD, omitting those in which patients were also administered a cholinesterase inhibitor. Cognitive function, activities of daily living, behavioral disturbances, global function, stage of dementia, drug discontinuation rate, and individual side effects were compared between memantine monotherapy and placebo groups. The primary outcomes were cognitive function and behavioral disturbances; the others were secondary outcomes.

RESULTS

Nine studies including 2433 patients that met the study's inclusion criteria were identified. Memantine monotherapy significantly improved cognitive function [standardized mean difference (SMD)=-0.27, 95% confidence interval (CI)=-0.39 to -0.14, p=0.0001], behavioral disturbances (SMD=-0.12, 95% CI=-0.22 to -0.01, p=0.03), activities of daily living (SMD=-0.09, 95% CI=-0.19 to -0.00, p=0.05), global function assessment (SMD=-0.18, 95% CI=-0.27 to -0.09, p=0.0001), and stage of dementia (SMD=-0.23, 95% CI=-0.33 to -0.12, p=0.0001) scores. Memantine was superior to placebo in terms of discontinuation because of inefficacy [risk ratio (RR)=0.36, 95% CI=0.17¬ to 0.74, p=0.006, number needed to harm (NNH)=non significant]. Moreover, memantine was associated with less agitation compared with placebo (RR=0.68, 95% CI=0.49 to 0.94, p=0.02, NNH=non significant). There were no significant differences in the rate of discontinuation because of all causes, all adverse events, and individual side effects other than agitation between the memantine monotherapy and placebo groups.

CONCLUSIONS

Memantine monotherapy improved cognition, behavior, activities of daily living, global function, and stage of dementia and was well-tolerated by AD patients. However, the effect size in terms of efficacy outcomes was small and thus there is limited evidence of clinical benefit.

The effects of combine treatment of memantine and donepezil on Alzheimer's disease patients and its relationship with cerebral blood flow in the prefrontal area

BACKGROUND

In this study, we evaluated the effect on cognitive function of memantine, behavioral and psychological symptoms of dementia, and the care burden, in patients with moderate-to-severe Alzheimer's disease (AD). Furthermore, with near-infrared spectroscopy (NIRS), we examined the association between effect of memantine and brain blood flow.

METHODS

We evaluated the effect of memantine administration from baseline on Clinical Global Impression-Improvement scale, mini mental state examination (MMSE), Clock Drawing Test (CDT), Neuropsychiatric Inventory (NPI), Japanese version of the Zarit Burden Interview (J-ZBI) and NIRS in two groups, donepezil administration memantine combination group (combination group, n = 19) donepezil administration memantine non-administration group (control group, n = 18) were assessed at weeks 0, 4, 12, and 24.

RESULTS

Significant difference was found between the combination group and the control group in the score variation of Clinical Global Impression-Improvement scale, MMSE, CDT, NPI, and J-ZBI. In the NIRS measurements, trend oxyhemoglobin reduced suppression was observed in some channels centered on the superior frontal gyrus. A significant correlation was observed in the scores of MMSE, CDT, NPI, and J-ZBI. In addition, a significant positive correlation was also observed between the number of words in NIRS and scores of MMSE and CDT.

CONCLUSIONS

In this study, by administering memantine in AD patients that inhibit the reduction of cerebral blood flow in the prefrontal area and improve clinical symptoms overall cognitive function, behavioral and psychological symptoms of dementia, thereby reducing the care burden of caregivers was suggested.

Neuroimaging and genetic risk for Alzheimer's disease and addiction-related degenerative brain disorders

Neuroimaging offers a powerful means to assess the trajectory of brain degeneration in a variety of disorders, including Alzheimer's disease (AD). Here we describe how multi-modal imaging can be used to study the changing brain during the different stages of AD. We integrate findings from a range of studies using magnetic resonance imaging (MRI), positron emission tomography (PET), functional MRI (fMRI) and diffusion weighted imaging (DWI). Neuroimaging reveals how risk genes for degenerative disorders affect the brain, including several recently discovered genetic variants that may disrupt brain connectivity. We review some recent neuroimaging studies of genetic polymorphisms associated with increased risk for late-onset Alzheimer's disease (LOAD). Some genetic variants that increase risk for drug addiction may overlap with those associated with degenerative brain disorders. These common associations offer new insight into mechanisms underlying neurodegeneration and addictive behaviors, and may offer new leads for treating them before severe and irreversible neurological symptoms appear.

Evaluation of symptomatic drug effects in Alzheimer's disease: strategies for prediction of efficacy in humans

In chronic diseases such as Alzheimer's disease (AD), the arsenal of biomarkers available to determine the effectiveness of symptomatic treatment is very limited. Interpretation of the results provided in literature is cumbersome and it becomes difficult to predict their standardization to a larger patient population. Indeed, cognitive assessment alone does not appear to have sufficient predictive value of drug efficacy in early clinical development of AD treatment. In recent years, research has contributed to the emergence of new tools to assess brain activity relying on innovative technologies of imaging and electrophysiology. However, the relevance of the use of these newer markers in treatment response assessment is waiting for validation. This review shows how the early clinical assessment of symptomatic drugs could benefit from the inclusion of suitable pharmacodynamic markers. This review also emphasizes the importance of re-evaluating a step-by-step strategy in drug development.

Effects of memantine on clinical ratings, fluorodeoxyglucose positron emission tomography measurements, and cerebrospinal fluid assays in patients with moderate to severe Alzheimer dementia: a 24-week, randomized, clinical trial

Most experts consider that memantine has a symptomatic treatment, but clinical trials have not yet provided compelling evidence to support a disease-modifying effect. We investigate the effects of memantine on clinical ratings; fluorodeoxyglucose positron emission tomography (FDG-PET) measurements, which can monitor disease-modifying effect; and cerebrospinal fluid (CSF) assays in patients with moderate to severe probable Alzheimer disease (AD) dementia. Twenty-two patients completed a 24-week, double-blind, placebo-controlled, randomized clinical trial of memantine, titrated up to 10 mg twice per day using the Severe Impairment Battery, AD Assessment Scale-Cognitive subscale, Mini-Mental State Examination, FDG-PET measurements of the regional cerebral metabolic rate for glucose (CMRgl), and CSF amyloid β (Aβ) and tau assays. An automated brain mapping algorithm and predefined regions of interest were each used to analyze treatment-related regional CMRgl effects. In comparison with the placebo group, the memantine treatment group had significantly less cognitive decline on the Severe Impairment Battery and significantly less CMRgl declines in regions preferentially affected by AD. There were no significant treatment effects on CSF Aβ₁₋₄₂, CSF Aβ₁₋₄₀, total tau, or phosphor-tau levels or ratios. This relatively small and brief randomized clinical trial suggests an association between memantine's clinical benefit and its effects on FDG-PET measurements in AD-affected brain regions. Larger and longer studies are needed to confirm these findings, extend them to earlier clinical and preclinical stages of AD, and help determine the extent to which FDG-PET should be qualified for use as a reasonably likely surrogate end point in the evaluation of putative AD-modifying treatments.

Clinical effects of electroconvulsive therapy in severe depression and concomitant changes in cerebral glucose metabolism--an exploratory study

OBJECTIVE

Electroconvulsive therapy (ECT) is an effective mode of treatment--especially for severe depression and for depression refractory to pharmacotherapy, nevertheless the mode of action of ECT is far from being fully understood. This study assessed the effects of a series of ECT in depressive subjects on cerebral glucose metabolism measured by FDG-PET scans pre- and post-therapy in thus far the largest group of 12 patients.

METHODS

Our analysis included careful repeated evaluation of clinical changes in mood and behaviour by standardised questionnaires, which allowed testing for a potential correlation between clinical and cerebral metabolic changes. PET scanning was done within a predefined time window and we used predefined ROIs with counts normalized to the pons activity.

RESULTS

We observed few changes in cerebral glucose metabolism over time. There was a marginal increase in the left temporal and a trend for a decrease in left frontobasal areas subsequent to treatment in our sample. FDG uptake patterns remained remarkably stable in all the other predefined ROIs pre- and post-treatment. There were no significant correlations between changes in relative metabolic rates and changes in depression scores and parameters derived from neurocognitive testing.

CONCLUSIONS

Our study thus cannot support the view that FDG-PET can assess the functional brain changes that are likely to occur subsequent to ECT in such a scenario, but this may be related to limited sensitivity given the sample size. Future studies thus might wish to challenge this notion in larger patient samples to clarify this issue.

N-methyl D-aspartate (NMDA) receptor antagonists and memantine treatment for Alzheimer's disease, vascular dementia and Parkinson's disease

Memantine, a partial antagonist of N-methyl-D-aspartate receptor (NMDAR), approved for moderate to severe Alzheimer's disease (AD) treatment within the U.S. and Europe under brand name Namenda (Forest), Axura and Akatinol (Merz), and Ebixa and Abixa (Lundbeck), may have potential in alleviating additional neurological conditions, such as vascular dementia (VD) and Parkinson's disease (PD). In various animal models, memantine has been reported to be a neuroprotective agent that positively impacts both neurodegenerative and vascular processes. While excessive levels of glutamate result in neurotoxicity, in part through the over-activation of NMDARs, memantine-as a partial NMDAR antagonist, blocks the NMDA glutamate receptors to normalize the glutamatergic system and ameliorate cognitive and memory deficits. The key to memantine's therapeutic action lies in its uncompetitive binding to the NMDAR through which low affinity and rapid off-rate kinetics of memantine at the level of the NMDAR-channel preserves the physiological function of the receptor, underpinning memantine's tolerability and low adverse event profile. As the biochemical pathways evoked by NMDAR antagonism also play a role in PD and since no other drug is sufficiently effective to substitute for the first-line treatment of L-dopa despite its side effects, memantine may be useful in PD treatment with possibly fewer side effects. In spite of the relative modest nature of its adverse effects, memantine has been shown to provide only a moderate decrease in clinical deterioration in AD and VD, and hence efforts are being undertaken in the design of new and more potent memantine-based drugs to hopefully provide greater efficacy.

Longitudinal magnetization transfer imaging in mild to severe Alzheimer disease

BACKGROUND AND PURPOSE

MTI has been proposed as a sensitive technique for studying microstructural brain tissue changes in patients with AD, but the course of these changes over time is largely unknown. We therefore used a placebo-controlled study of memantine to follow the evolution of tissue damage in AD by means of MTR measurements and investigated how MTR changes were related to brain atrophy and cognition.

MATERIALS AND METHODS

Twenty-eight patients (76.5 ± 5.8 years) with mild to moderate AD underwent MTI, brain volume measurements, and cognitive testing at baseline and after 6 and 12 months. Nineteen healthy individuals (73.3 ± 3.2 years) served as controls. MTI was performed with a 2-minute protocol that was optimized for an enhanced MT effect and reduced motion sensitivity. Global and regional MTR measurements served as correlations with brain volumes and the MMSE score.

RESULTS

AD patients had significantly lower global MTR values than controls, and showed a consistent and significant MTR reduction in all regions investigated over a period of 12 months. These MTR changes were paralleled by a brain tissue loss of 2.2% per year. Associations between MTR and cognition were found for the hippocampus, putamen, and thalamus, and were more pronounced in the left hemisphere.

CONCLUSIONS

MTI in AD allows the assessment of ongoing global and regional brain damage independent of atrophy, and therefore appears to be a valuable marker for disease-related tissue changes.

Effect of memantine on resting state default mode network activity in Alzheimer's disease

BACKGROUND

Memantine is an approved symptomatic treatment for moderate to severe Alzheimer's disease that reduces the excitotoxic effects of hyperactive glutamatergic transmission. However, the exact mechanism of the effect of memantine in Alzheimer's disease patients is poorly understood. Importantly, the default mode network (DMN), which plays a key role in attention, is hypoactive in Alzheimer's disease and is under glutamatergic control.

OBJECTIVE

To assess the effect of memantine on the activity of the DMN in moderate to severe Alzheimer's disease.

METHODS

Functional magnetic resonance imaging (MRI) data from 15 patients with moderate to severe Alzheimer's disease, seven treated with memantine (mean ± SD age 77 ± 8 years, mean ± SD Mini-Mental State Examination [MMSE] score 16 ± 5) and eight with placebo (mean ± SD age 76 ± 6 years, mean ± SD MMSE score 13 ± 1), were acquired at baseline (T0) and after 6 months of treatment (T6). Resting state components were extracted after spatial normalization in individual patients with independent component analysis. The consistency of the components was assessed using ICASSO and the DMN was recognized through spatial correlation with a pre-defined template. Voxel-based statistical analyses were performed to study the change in DMN activity from T0 to T6 in the two groups.

RESULTS

At T0, the two groups showed similar DMN activity except in the precuneus and cuneus, where the patients who started treatment with memantine had slightly greater activity (p < 0.05 corrected for familywise error [FWE]). The prospective comparison between T0 and T6 in the treated patients showed increased DMN activation mapping in the precuneus (p < 0.05, FWE corrected), while the prospective comparison in the untreated patients did not show significant changes. The treatment × time interaction term was significant at p < 0.05, FWE corrected.

CONCLUSIONS

The results suggest a positive effect of memantine treatment in patients with moderate to severe Alzheimer's disease, resulting in an increased resting DMN activity in the precuneus region over 6 months. Future studies confirming the present findings are required to further demonstrate the beneficial effects of memantine on the DMN in Alzheimer's disease.

Magnetic resonance imaging and neuropsychological results from a trial of memantine in Alzheimer's disease

BACKGROUND

This study was designed to assess changes in brain volume and cognitive abilities in memantine-treated patients with Alzheimer's disease (AD) by using an exploratory, single-arm, delayed-start design.

METHODS

Cholinesterase inhibitor-treated patients with AD (N = 47; Mini-Mental State Examination score range: 15-23) were enrolled in an observational lead-in period (weeks: 1-24), followed by an open-label period of add-on memantine treatment (weeks: 25-48). The patients underwent magnetic resonance imaging at weeks 0 (baseline), 24 (immediately before memantine initiation), and 48 (endpoint), and a battery of neuropsychological tests at weeks 0, 24, 28, 36, and 48. The primary outcome measure was the annualized rate of change (%) in total brain volume (TBV) between the two study periods. Data were analyzed using paired t-tests.

RESULTS

There were no statistically significant differences in the rates of change in TBV, ventricular volume, or left hippocampal volume between the study periods; however, the memantine treatment period was associated with a significantly slower right hippocampal atrophy (-5.5% ± 12.0% vs -10.8% ± 7.2%; P = .038). Memantine treatment was also associated with superior performances on the Boston Naming Test (P = .034) and the Trail Making Test, Part B (P = .001), but also with a higher number of errors (i.e., repetitions and intrusions) on the California Verbal Learning Test. Memantine was found to be safe and well tolerated.

CONCLUSIONS

In this study, no difference in the rates of TBV change between the two periods was observed; however, memantine treatment was found to be associated with slowing of right hippocampal atrophy, and with improvement on one test of executive functioning as well as a test of confrontation naming ability. Trials using structural magnetic resonance imaging and a delayed-start design may be a feasible option for the assessment of treatments for AD.

Memantine: a treatment for Alzheimer’s disease with a new formulation

In nearly 20 years, aside from cholinesterase inhibitors, memantine is the only drug approved for the treatment of Alzheimer’s disease (AD). Memantine is an uncompetitive N-methyl-D-aspartate receptor antagonist that blocks pathological glutamate activity while permitting normal physiological function, thus preventing glutamate-induced excitotoxicity. Three Phase III pivotal trials demonstrated memantine’s efficacy in treating moderate-to-severe AD, which led to its initial approval by the EMA in 2002 and US FDA in 2003. The recommended target dose is 10 mg twice daily. The US FDA recently approved an extended-release (ER) formulation of memantine for once-daily 28-mg dosing. Memantine ER was evaluated in a 24-week placebo-controlled trial of patients with moderate-to-severe AD, which found significant benefits for cognition, global assessment, behavior and caregiver burden, but not function. The most common adverse events were headache, dizziness, diarrhea, hypertension, anxiety and influenza. Overall, memantine in all formulations has a favorable safety/tolerability profile and is safe to use with cholinesterase inhibitors. Memantine ER has yet to be evaluated against conventionally dosed immediate-release memantine.

Using MRI neuroimaging methods to detect treatment responses in Alzheimer’s disease

SUMMARY The rapid development of neuroimaging outcome measures for monitoring treatment effects and disease progression in neurological disorders presents both opportunities and hazards. An overview of functional MRI studies of regional brain activation using cognitive activation and resting state paradigms in mild cognitive impairment and Alzheimer’s disease indicates that this method can detect group treatment responses in the absence of overt behavioral change, as well as the kinetic and dynamic effects of the available symptomatic treatment compounds. Structural and spectroscopic MRI methods offer the prospect of objective and clinically meaningful assessment of progressive neuropathological changes and their modification through intervention. Including imaging parameters adequately powers small group studies of drug effects with additional advantages for more robust patient characterization and staging. These techniques should play an increasingly important role at an earlier stage of treatment evaluation, but the need for expert implementation and analysis means that clinical applications in individual cases are still in development.

Change in hippocampal volume on magnetic resonance imaging and cognitive decline among older depressed and nondepressed subjects in the neurocognitive outcomes of depression in the elderly study

INTRODUCTION

previous studies have linked hippocampal volume change and cognitive decline in older adults with dementia. The authors examined hippocampal volume change and cognitive change in older nondemented adults with and without major depression.

METHODS

the sample consisted of 90 depressed individuals and 72 healthy, nondepressed individuals aged 60 years and older who completed at least 2 years of follow-up data. All patients underwent periodic clinical evaluation by a geriatric psychiatrist as well as baseline and 2-year magnetic resonance imaging.

RESULTS

over 2 years, the depressed group showed a greater reduction in left hippocampal volume (normalized for total cerebral volume) compared with the nondepressed group (mean difference = 0.013 ± 0.0059, t = 2.18, df = 160, p <0.0305). The difference remained significant after controlling for age, sex, and baseline normalized left hippocampal volume. The authors also found that hippocampal change from baseline to 2 years was associated with subsequent change in Mini-Mental State Examination score from 2 years to 2½ years (left t = 2.81, df = 66, p = 0.0066; right t = 2.40, df = 66, p = 0.0193) among the depressed group.

CONCLUSIONS

these findings add to the literature linking hippocampal volume loss and late-life depression. Depressed patients with hippocampal volume loss are at greater risk of cognitive decline.

Effect of memantine treatment on regional cortical metabolism in Alzheimer's disease

OBJECTIVES

Cortical systems involved in the response to medication treatment for Alzheimer's disease (AD) are poorly understood. Preclinical studies have demonstrated the effect of memantine on neuroreceptors and cell physiology, although the impact of treatment on cortical activity in vivo is not known.

DESIGN

F-fluorodeoxyglucose positron emission tomography (PET) imaging and clinical assessment before and after open-label memantine treatment.

PARTICIPANTS/SETTING

Seventeen outpatients with probable AD on stable cholinesterase inhibitor medication.

INTERVENTION

Memantine up to 10 mg twice daily for 10 weeks.

MEASUREMENTS

Voxel-based analyses of change in cortical metabolic activity; Mattis Dementia Rating Scale (DRS), and Neurobehavioral Rating Scale (NRS).

RESULTS

: Mean age was 81 years; mean Mini-Mental State Examination score was 19.4. Compared with baseline, metabolic activity was significantly higher after 10 weeks memantine treatment in two cortical regions bilaterally: the inferior temporal gyrus (BA 20) and the angular gyrus/supramarginal gyrus (BA 39, 40). There was no significant relationship between change in DRS score and change in cortical metabolism, although change in NRS score was associated with the extent of metabolic change in the right parietal and temporal cortex.

CONCLUSION

Metabolic activity in bilateral inferior parietal and temporal cortex increases during 10 weeks of memantine treatment in patients with AD. PET imaging can reveal functional effects of medications on neural activity and may help to define critical mechanisms involved in drug treatment.

Quantitative evaluation of Alzheimer's disease

Alzheimer's disease (AD) can be definitively diagnosed only by histopathologic examination of brain tissue; the identification and differential diagnosis of AD is especially challenging in its early stages. Neuroimaging is playing an increasingly relevant role in the identification and quantification of AD in vivo, especially in the preclinical stages, when therapeutic intervention could be more effective. Neuroimaging enables quantification of brain volume loss (structural imaging), detection of early cerebral dysfunction (functional imaging), probing into the finest cerebral structures (microstructural imaging), and investigation of amyloid plaque and neurofibrillary tangle build-up (amyloid imaging). Throughout the years, several imaging tools have been developed, ranging from simple visual rating scales to sophisticated computerized algorithms. As recently revised criteria for AD require quantitative evaluation of biomarkers mostly based on imaging, this paper provides an overview of the main neuroimaging tools which might be used presently or in the future in routine clinical practice for AD diagnosis.

Comparison of eight methods for the estimation of the image-derived input function in dynamic [(18)F]-FDG PET human brain studies

The aim of this study was to compare eight methods for the estimation of the image-derived input function (IDIF) in [(18)F]-FDG positron emission tomography (PET) dynamic brain studies. The methods were tested on two digital phantoms and on four healthy volunteers. Image-derived input functions obtained with each method were compared with the reference input functions, that is, the activity in the carotid labels of the phantoms and arterial blood samples for the volunteers, in terms of visual inspection, areas under the curve, cerebral metabolic rates of glucose (CMRglc), and individual rate constants. Blood-sample-free methods provided less reliable results as compared with those obtained using the methods that require the use of blood samples. For some of the blood-sample-free methods, CMRglc estimations considerably improved when the IDIF was calibrated with a single blood sample. Only one of the methods tested in this study, and only in phantom studies, allowed a reliable calculation of the individual rate constants. For the estimation of CMRglc values using an IDIF in [(18)F]-FDG PET brain studies, a reliable absolute blood-sample-free procedure is not available yet.

Memantine versus donepezil in mild to moderate Alzheimer's disease: a randomized trial with magnetic resonance spectroscopy

BACKGROUND AND PURPOSE

To compare memantine with the most prescribed cholinesterase inhibitor (donepezil) from a clinical viewpoint when administered in early phases of Alzheimer disease (AD), and to find out whether memantine may produce changes in brain metabolite concentrations in comparison with donepezil.

METHODS

In this comparative rater-blinded parallel group randomized trial we recruited a consecutive sample of patients with probable mild to moderate AD. At baseline we carried out neuropsychological assessment with mini-mental, Clinical Dementia Rating Scale (CDR), Blessed Dementia Rating Scale, Alzheimer's Disease Assessment Scale, cognitive part (ADAS-cog), neuropsychiatric inventory (NPI), and disability assessment for dementia (DAD), as well as (1)H magnetic resonance spectroscopy (MRS) in several areas of the brain. Patients were randomized to receive either donepezil or memantine for 6 months. After this elapse of time we repeated the same procedures and observed the changes in clinical scales (ADAS-cog, NPI, DAD), as well as the changes in metabolite levels in every area of exploration (temporal, pre-frontal, posterior cingulated (PCG), and occipital), especially those of N-acetyl-aspartate (NAA) which is regarded as a surrogate marker of neuronal density.

RESULTS

A total of sixty-three patients completed the trial. We did not see significant differences in clinical scales and metabolite levels between those on donepezil (n = 32) and those on memantine (n = 31). In general, more patients worsened than improved on either of the drugs. The changes in the NAA/creatine ratio in the PCG correlated significantly with the changes in the ADAS-cog (P = 0.004).

CONCLUSIONS

Donepezil and memantine have similar modest clinical and spectroscopic effect on mild to moderate AD. MRS could be useful to monitor progression of the disease.

Magnetic resonance imaging and prediction of outcome in patients with major depressive disorder

Whether magnetic resonance imaging studies can provide useful information to clinicians who treat people with major depressive disorder remains to be established. There are, however, several recent findings that suggest that likelihood of response may be predicted by imaging findings. For example, morphometric studies have examined whether hippocampus volume is associated with clinically meaningful outcomes such as response to treatment. In general, patients who remit have larger pretreatment hippocampus volumes bilaterally compared with those who do not remit. There are similar preliminary findings for the anterior cingulate cortex. There are also a number of functional imaging studies that have identified different activity patterns in those who are likely to respond to treatment compared with those who are not. Using positron emission tomography, investigators have reported different patterns of response to treatment in those treated with medication compared with those treated with psychotherapy. Some of the potential barriers to the routine use of imaging in psychiatric practice are reviewed briefly.