Prevalence, associated factors, mood and cognitive outcomes of traumatic brain injury in later life: the health in men study (HIMS)

Associations Between Traumatic Brain Injury and Cognitive Decline Among Older Male Veterans: A Twin Study

BACKGROUND AND OBJECTIVES

Traumatic brain injuries (TBIs) are associated with increased risk of dementia, but whether lifetime TBI influences cognitive trajectories in later life is less clear. Cognitive interventions after TBI may improve cognitive trajectories and delay dementia. Because twins share many genes and environmental factors, we capitalize on the twin study design to examine the association between lifetime TBI and cognitive decline.

METHODS

Participants were members of the National Academy of Sciences-National Research Council's Twin Registry of male veterans of World War II with self or proxy-reported history of TBI and with up to 4 observations over 12 years of the modified Telephone Interview for Cognitive Status (TICS-m). We used linear random-effects mixed models to analyze the association between TBI and TICS-m in the full sample and among co-twins discordant for TBI. Additional TBI predictor variables included number of TBIs, severity (loss of consciousness [LOC]), and age of first TBI (age <25 vs 25+ years [older age TBI]). Models were adjusted for age (centered at 70 years), age-squared, education, wave, twin pair, lifestyle behaviors, and medical conditions.

RESULTS

Of 8,662 participants, 25% reported TBI. History of any TBI (β = -0.56, 95% CI -0.73 to -0.39), TBI with LOC (β = -0.51, 95% CI -0.71 to -0.31), and older age TBI (β = -0.66, 95% CI -0.90 to -0.42) were associated with lower TICS-m scores at 70 years. TBI with LOC (β = -0.03, 95% CI -0.05 to -0.001), more than one TBI (β = -0.05, 95% CI -0.09 to -0.002,), and older age TBI (β = -0.06, 95% CI -0.09 to -0.03) were associated with faster cognitive decline. Among monozygotic pairs discordant for TBI (589 pairs), history of any TBI (β = -0.55, 95% CI -0.91 to -0.19) and older age TBI (β = -0.74, 95% CI -1.22 to -0.26) were associated with lower TICS-m scores at 70 years. Those with more than one TBI (β = -0.13, 95% CI -0.23 to -0.03) and older age TBI (β = -0.07, 95% CI -0.13 to -0.002) showed greater cognitive decline compared with their co-twin without TBI.

DISCUSSION

These findings support an association of the effect of TBI on cognitive score and the rapidity of cognitive decline in later life. The results in monozygotic pairs, who share all genes and many exposures, particularly in early life, provide additional evidence of a causal relationship between TBI and poorer late-life cognitive outcomes.

Executive functioning in early and middle age adult patients operated for epidural hematoma: A comparative study

Epidural Hematoma (EDH) is a common condition of traumatic brain injury. It has a good prognosis if prompt surgical intervention is conducted. There is a dearth of studies on neuropsychological assessment of executive functioning exclusively in post-operative EDH patients. Moreover, age as a variable in determining executive functions in patients post-head injury, has been studied mostly in the older adults. This cross-sectional case-control study assessed Executive Functions (EF) in 62 post-surgery patients with EDH and compared 57 healthy controls (HC) using standardized assessment tools of sustained attention, speed, working memory, fluency, set-shifting, perseveration, planning, and response inhibition. Further, executive functions in two phases of adulthood, viz. Early Adulthood (20-39 years) and Middle Adulthood (40-60 years) were compared in the EDH group (E-EDH and M-EDH) and HC (E-HC and M-HC). A two-way Analysis of Variance (ANOVA) and correlational analysis was conducted. Results showed a trend where the M-EDH group performed significantly poorer on executive function tests (viz a viz., time taken, errors, and correct responses), followed by E-EDH, M-HC, and E-HC. The main effect of age was found significant on Digit Symbol, Color Trail 1, N-Back 2, Animal Naming, and Stroop Effect (p < 0.01 level) while N-Back 1, WCST-PE, and Tower of London (p < 0.05 level). The findings have significant clinical and therapeutic implications. In addition, it gives guidance regarding planning specific neuropsychological tests and rehabilitation targeting specific areas of executive functions decline due to age in EDH post-surgery patients.

The Impact of Age and Severity on Dementia After Traumatic Brain Injury: A Comparison Study

BACKGROUND

Growing evidence associates traumatic brain injury (TBI) with increased risk of dementia, but few studies have evaluated associations in patients younger than 55 yr using non-TBI orthopedic trauma (NTOT) patients as controls to investigate the influence of age and TBI severity, and to identify predictors of dementia after trauma.

OBJECTIVE

To investigate the relationship between TBI and dementia in an institutional group.

METHODS

Retrospective cohort study (2000-2018) of TBI patients aged 45 to 100 yr vs NTOT controls. Primary outcome was dementia after TBI (followed ≤10 yr). Cox proportional hazards models were used to assess risk of dementia; logistic regression models assessed predictors of dementia.

RESULTS

Among 24 846 patients, TBI patients developed dementia (7.5% vs 4.6%) at a younger age (78.6 vs 82.7 yr) and demonstrated higher 10-yr mortality than controls (27% vs 14%; P < .001). Mild TBI patients had higher incidence of dementia (9%) than moderate/severe TBI (5.4%), with lower 10-yr mortality (20% vs 31%; P < .001). Risk of dementia was significant in all mild TBI age groups, even 45 to 54 yr (hazard ratio 4.1, 95% CI 2.7-7.8). A total of 10-yr cumulative incidence was higher in mild TBI (14.4%) than moderate/severe TBI (11.3%) and controls (6.8%) (P < .001). Predictors of dementia include TBI, sex, age, hypertension, hyperlipidemia, stroke, depression, anxiety, and Injury Severity Score.

CONCLUSION

Mild and moderate/severe TBI patients experienced higher incidence of dementia, even in the youngest group (45-54 yr old), than NTOT controls. All TBI patients, especially middle-aged adults with minor injury who are more likely to be overlooked, should be monitored for dementia.

Conditioned Contextual Freezing is A Neurobehavioral Biomarker of Axonal Injury Indicated by Reduced Fractional Anisotropy in A Mouse Model of Blast-Induced Mild Traumatic Brain Injury

Mild traumatic brain injury (TBI) is an important public health problem generated by closed head injury. This study is focused on the impact of blast-induced mild TBI on auditory trace and delay fear conditioning, models of declarative and non-declarative memory, respectively, and the correlation of conditioned freezing and fractional anisotropy, a measure of axonal state. A supersonic helium pressure wave was generated by a shock tube to blast 8-week-old male mice on Day 1 for 1.4 msec with an incident pressure of 16 psi, corresponding to a reflected pressure of 56.9 psi at the mouse head. On Day 3, the mice were subjected to auditory trace- or delay-fear conditioning. On Day 4, contextual freezing in the trained context, and precue and cued freezing in a novel context were determined. After cardiac perfusion on Day 5, ex vivo images were obtained with diffusion tensor imaging at 14.1 Tesla. We observed that delay fear conditioning prevented or reversed the decrease in fractional anisotropy in both the medial and lateral corpus callosum suggesting axonal stabilization of potentially behavioral therapeutic significance. Moderately strong and statistically significant Pearson correlations were found between fractional anisotropy and contextual freezing in the medial and lateral corpus callosum of blasted and sham-blasted delay- or trace-fear conditioned mice. Thus, contextual freezing is a neurobehavioral biomarker for axonal injury in mild TBI and is a reliable and high-throughput behavioral assay for the evaluation of potential therapeutics to treat mild TBI.

[Mental disorders after acquired CNS damage]

Mental disorders are a frequent consequence of acquired central nervous damage. If not recognized and treated early, they have a negative impact on the course of neurological rehabilitation. This article deals with the diagnosis and treatment of mental disorders after acquired damage to the central nervous system.

Differences in Health-Related Quality of Life after Traumatic Brain Injury between Varying Patient Groups: Sensitivity of a Disease-Specific (QOLIBRI) and a Generic (SF-36) Instrument

Factors associated with health-related quality of life (HRQOL) in patients after traumatic brain injury (TBI) include severity of initial injury, different grades of trauma recovery, sociodemographic status, and psychological characteristics. Yet, sensitivity of HRQOL instruments to such effects is often underexplored. Thus, we aimed to compare the capacity of the disease-specific QOLIBRI (Quality of Life after Brain Injury) and the generic Medical Outcomes Study (MOS) 36-Item Short-Form Health Survey(SF-36) to detect significant differences in HRQOL between patients. Patients (n = 795) completed HRQOL, sociodemographic, clinical, psychological, and health status questionnaires. Univariate (Wilcoxon-Mann-Whitney) and multi-variate (Wei-Lachin) non-parametric analyses were conducted using the Wilcoxon-Mann-Whitney approach to compare the sensitivity of the QOLIBRI and the SF-36. For both instruments, HRQOL was particularly influenced by patients' reliance on others, depression, anxiety, and recovery status, whereas smaller effects were found for living arrangements and participation in leisure activities. Both HRQOL instruments were sensitive to group differences, but the QOLIBRI was able to detect a greater number of and finer differences between specific patient groups, which is particularly important in clinical and therapeutic contexts. This finding is likely explained by the QOLIBRI's greater specificity to disease-specific aspects of consequences of TBI. This head-to-head HRQOL instrument comparison resulted in a recommendation for the use of the QOLIBRI when detailed insight in the subjective consequences and impact of TBI on patients is required.

Initial Biphasic Fractional Anisotropy Response to Blast-Induced Mild Traumatic Brain Injury in a Mouse Model

Introduction

Blast-induced mild traumatic brain injury was generated in a mouse model using a shock tube to investigate recovery and axonal injury from single blast.

Methods

A supersonic helium wave hit the head of anesthetized male young adult mice with a reflected pressure of 69 psi for 0.2 ms on Day 1. Subsequently, the mice were cardioperfused on Days 2, 5, or 12. The isolated brains were subjected to diffusion tensor imaging. Reduced fractional anisotropy (FA) indicated axonal injury.

Results

After single blast, FA showed a biphasic response in the corpus callosum with decrease on Days 2 and 12 and increase on Day 5.

Conclusions

Blast-induced mild traumatic brain injury in a mouse model follows a biphasic FA response within 12 days after a single blast similar to that reported for human subjects.

The Relationship between living alone, sense of belonging, and depressive symptoms among older men: the moderating role of sexual orientation

Objectives: Living alone is a risk factor for depressive symptoms among older men, and is likely to occur due to belongingness needs being unmet. It is proposed the living alone-sense of belonging and living alone-depressive symptoms relations are stronger for gay men than heterosexual men, due to different family circumstances. This research tested a moderated mediation model, specifically whether the relationship between living alone and depressive symptoms is mediated by sense of belonging, and whether the living alone-sense of belonging and living alone-depressive symptoms relationships are moderated by sexual orientation.Method: A community sample of 169 Australian gay men aged 65 to 93 years and 187 Australian heterosexual men aged 65 to 94 years completed the Psychological subscale of the Sense of Belonging Instrument and the Center for Epidemiologic Studies Depression Scale.Results: Results supported the simple mediation model, with living alone being associated directly and indirectly with depressive symptoms via sense of belonging. The conditional indirect effect of living alone on depressive symptoms via sense of belonging was not significant, and therefore the moderated mediation model was not supported.Conclusion: Results imply that older men who live alone are at increased risk of depressive symptoms directly and indirectly via lower levels of sense of belonging.

Cinnamic acid rescues behavioral deficits in a mouse model of traumatic brain injury by targeting miR-455-3p/HDAC2

AIMS

Traumatic brain injury (TBI) not only induces physiological disabilities but also leads to cognitive impairment. However, no effective therapeutic approach for TBI-related memory decline exists. In this study, we treated TBI mice with cinnamic acid (CNA) to detect whether CNA is able to rescue the memory deficits induced by TBI and to explore the potential mechanisms.

MAIN METHODS

Mice were divided into the following groups: the sham group, the TBI group, the TBI + CNA group and the CNA group. Basic physiological parameters, neurological severity score and brain water content were analyzed. The Morris water maze and inhibitory avoidance step-down task were used to determine learning and memory. Golgi staining was used to measure alterations in dendritic spines. Western blot analysis and a commercial kit were used to detect the content and activity of HDAC2. qPCR was used to detect the relative level of miR-455.

KEY FINDINGS

CNA did not affect physiological function but effectively restored neurological function and brain edema. CNA alleviated the memory impairments induced by TBI in both the Morris water maze and step-down task. CNA also recovered abnormalities in the synapses of TBI mice by suppressing the activity of HDAC2. Furthermore, CNA did not alter HDAC mRNA because it promoted the expression of miR-455-3p, a miRNA that regulates HDAC2 at the posttranscriptional level.

SIGNIFICANCE

The application of CNA effectively treats TBI-induced memory deficits by increasing miR-455-3p and by inhibiting HDAC2.

Older men with bipolar disorder diagnosed in early and later life: Physical health morbidity and general hospital service use

BACKGROUND

Bipolar disorder (BD) has been associated with greater health morbidity burden, but it is unclear if this association is affected by age at the time of diagnosis and how this might impact on the use of general hospital services.

METHODS

Cross-sectional study investigating the prevalence of common medical morbidities among participants with early (EOBD) and late onset diagnosis of BD (LOBD - age at diagnosis ≥ 60 years) derived from a community-representative sample of 37,183 men aged 65-85 years. Cohort study over a follow up period of up to 17.7 years investigating the hazard of general hospital use among older men associated with EOBD and LOBD taking into account age and prevalent medical morbidities.

RESULTS

250 older men had a recorded diagnosis of BD, 75 of whom had LOBD. Diabetes, stroke and diseases of the respiratory and digestive systems were more frequent in men with than without BD. There were no differences in the distribution of medical morbidities between men with EOBD and LOBD. The adjusted hazard ratio (HR) of contact with general hospital services was significantly higher among men with EOBD (HR = 1.33; 95%CI = 1.14, 1.54) and LOBD (HR = 1.27, 95%CI = 1.06, 1.51) compared with older men without BD. Older men with EOBD had the highest number of contacts with general hospital services during follow up, although men with EOBD and LOBD did not differ in the number of contacts due to episodes of mania or depression. The medical reasons for contact with general hospital services of men with EOBD and LOBD overlapped but were not identical.

CONCLUSIONS

Older men with BD experience greater health morbidity than men without BD. Older men with BD access hospital services for the management of physical morbidities earlier and more frequently than men without BD. Age at the time of diagnosis of BD has limited impact on the risk of contact with general medical services, although subtle differences in the physical morbidity of men with EOBD and LOBD warrant further investigation.

Prevalence and correlates of traumatic brain injury (TBI) in older adults: results from the Well-being of the Singapore Elderly (WiSE) study

BACKGROUND

Older adults are among the most susceptible to sustain traumatic brain injury (TBI). The study aimed to determine the (1) prevalence of TBI among older adults in Singapore, and (2) socio-demographic, lifestyle, and clinical correlates of TBI.

METHODS

Data were extracted from the cross-sectional, Well-being of the Singapore Elderly (WiSE) study. The study included 2,565 participants aged 60 years and above (Mean = 72.75, SD = 9.54). Information on TBI, socio-demographic, and lifestyle factors were collected using participant self-report and verified with the informant report where necessary. Disability was measured using the World Health Organization - Disability Assessment Schedule 2.0 (WHO-DAS 2.0). Data were analyzed using logistic regression analysis.

RESULTS

The prevalence of TBI was 3.6%. Being female (vs. male) was found to be associated with decreased odds of having TBI. Having completed secondary education or lower (vs. tertiary education) was found to be associated with increased odds of having TBI. A history of fainting and diabetes were associated with the presence of TBI. Those with TBI were associated with higher disability scores on the WHO-DAS 2.0 than those without TBI.

CONCLUSIONS

The current study provides information on the prevalence and associated factors of TBI in the older adult population in Singapore. Since TBI was associated with older adults with diabetes, they must be cautioned about fall risk. Also, given the association with disability, older adults with TBI are likely to require support and rehabilitative care to ensure good quality of life.

Pumping the Brakes: Neurotrophic Factors for the Prevention of Cognitive Impairment and Dementia after Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of disability and death worldwide, affecting as many as 54,000,000-60,000,000 people annually. TBI is associated with significant impairments in brain function, impacting cognitive, emotional, behavioral, and physical functioning. Although much previous research has focused on the impairment immediately following injury, TBI may have much longer-lasting consequences, including neuropsychiatric disorders and cognitive impairment. TBI, even mild brain injury, has also been recognized as a significant risk factor for the later development of dementia and Alzheimer's disease. Although the link between TBI and dementia is currently unknown, several proposed mechanisms have been put forward, including alterations in glucose metabolism, excitotoxicity, calcium influx, mitochondrial dysfunction, oxidative stress, and neuroinflammation. A treatment for the devastating long-term consequences of TBI is desperately needed. Unfortunately, however, no such treatment is currently available, making this a major area of unmet medical need. Increasing the level of neurotrophic factor expression in key brain areas may be one potential therapeutic strategy. Of the neurotrophic factors, granulocyte-colony stimulating factor (G-CSF) may be particularly effective for preventing the emergence of long-term complications of TBI, including dementia, because of its ability to reduce apoptosis, stimulate neurogenesis, and increase neuroplasticity.

Correlation between Motor Cortex Excitability Changes and Cognitive Impairment in Vascular Depression: Pathophysiological Insights from a Longitudinal TMS Study

Background. Transcranial magnetic stimulation (TMS) highlighted functional changes in dementia, whereas there are few data in patients with vascular cognitive impairment-no dementia (VCI-ND). Similarly, little is known about the neurophysiological impact of vascular depression (VD) on deterioration of cognitive functions. We test whether depression might affect not only cognition but also specific cortical circuits in subcortical vascular disease. Methods. Sixteen VCI-ND and 11 VD patients, age-matched with 15 controls, underwent a clinical-cognitive, neuroimaging, and TMS assessment. After approximately two years, all participants were prospectively reevaluated. Results. At baseline, a significant more pronounced intracortical facilitation (ICF) was found in VCI-ND patients. Reevaluation revealed an increase of the global excitability in both VCI-ND and VD subjects. At follow-up, the ICF of VCI-ND becomes similar to the other groups. Only VD patients showed cognitive deterioration. Conclusions. Unlike VD, the hyperfacilitation found at baseline in VCI-ND patients suggests enhanced glutamatergic neurotransmission that might contribute to the preservation of cognitive functioning. The hyperexcitability observed at follow-up in both groups of patients also indicates functional changes in glutamatergic neurotransmission. The mechanisms enhancing the risk of dementia in VD might be related either to subcortical vascular lesions or to the lack of compensatory functional cortical changes.

Cognitive deficits develop 1month after diffuse brain injury and are exaggerated by microglia-associated reactivity to peripheral immune challenge

Traumatic brain injury (TBI) elicits immediate neuroinflammatory events that contribute to acute cognitive, motor, and affective disturbance. Despite resolution of these acute complications, significant neuropsychiatric and cognitive issues can develop and progress after TBI. We and others have provided novel evidence that these complications are potentiated by repeated injuries, immune challenges and stressors. A key component to this may be increased sensitization or priming of glia after TBI. Therefore, our objectives were to determine the degree to which cognitive deterioration occurred after diffuse TBI (moderate midline fluid percussion injury) and ascertain if glial reactivity induced by an acute immune challenge potentiated cognitive decline 30 days post injury (dpi). In post-recovery assessments, hippocampal-dependent learning and memory recall were normal 7 dpi, but anterograde learning was impaired by 30 dpi. Examination of mRNA and morphological profiles of glia 30 dpi indicated a low but persistent level of inflammation with elevated expression of GFAP and IL-1β in astrocytes and MHCII and IL-1β in microglia. Moreover, an acute immune challenge 30 dpi robustly interrupted memory consolidation specifically in TBI mice. These deficits were associated with exaggerated microglia-mediated inflammation with amplified (IL-1β, CCL2, TNFα) and prolonged (TNFα) cytokine/chemokine expression, and a marked reactive morphological profile of microglia in the CA3 of the hippocampus. Collectively, these data indicate that microglia remain sensitized 30 dpi after moderate TBI and a secondary inflammatory challenge elicits robust microglial reactivity that augments cognitive decline.

STATEMENT OF SIGNIFICANCE

Traumatic brain injury (TBI) is a major risk factor in development of neuropsychiatric problems long after injury, negatively affecting quality of life. Mounting evidence indicates that inflammatory processes worsen with time after a brain injury and are likely mediated by glia. Here, we show that primed microglia and astrocytes developed in mice 1 month following moderate diffuse TBI, coinciding with cognitive deficits that were not initially evident after injury. Additionally, TBI-induced glial priming may adversely affect the ability of glia to appropriately respond to immune challenges, which occur regularly across the lifespan. Indeed, we show that an acute immune challenge augmented microglial reactivity and cognitive deficits. This idea may provide new avenues of clinical assessments and treatments following TBI.

Traumatic brain injury and age at onset of cognitive impairment in older adults

There is a deficiency of knowledge regarding how traumatic brain injury (TBI) is associated with age at onset (AAO) of cognitive impairment in older adults. Participants with a TBI history were identified from the Alzheimer's disease neuroimaging initiative (ADNI 1/GO/2) medical history database. Using an analysis of covariance (ANCOVA) model, the AAO was compared between those with and without TBI, and potential confounding factors were controlled. The AAO was also compared between those with mild TBI (mTBI) and moderate or severe TBI (sTBI). Lastly, the effects of mTBI were analyzed on the AAO of participants with clinical diagnoses of either mild cognitive impairment (MCI) or Alzheimer's disease (AD). The AAO for a TBI group was 68.2 ± 1.1 years [95 % confidence interval (CI) 66.2-70.3, n = 62], which was significantly earlier than the AAO for the non-TBI group of 70.9 ± 0.2 years (95 % CI 70.5-71.4, n = 1197) (p = 0.013). Participants with mTBI history showed an AAO of 68.5 ± 1.1 years (n = 56), which was significantly earlier than the AAO for the non-TBI group (p = 0.032). Participants with both MCI and mTBI showed an AAO of 66.5 ± 1.3 years (95 % CI 63.9-69.1, n = 45), compared to 70.6 ± 0.3 years for the non-TBI MCI group (95 % CI 70.1-71.1, n = 935) (p = 0.016). As a conclusion, a history of TBI may accelerate the AAO of cognitive impairment by two or more years. These results were consistent with reports of TBI as a significant risk factor for cognitive decline in older adults, and TBI is associated with an earlier AAO found in patients with MCI or AD.

Assessment of Health-Related Quality of Life after TBI: Comparison of a Disease-Specific (QOLIBRI) with a Generic (SF-36) Instrument

Psychosocial, emotional, and physical problems can emerge after traumatic brain injury (TBI), potentially impacting health-related quality of life (HRQoL). Until now, however, neither the discriminatory power of disease-specific (QOLIBRI) and generic (SF-36) HRQoL nor their correlates have been compared in detail. These aspects as well as some psychometric item characteristics were studied in a sample of 795 TBI survivors. The Shannon H (') index absolute informativity, as an indicator of an instrument's power to differentiate between individuals within a specific group or health state, was investigated. Psychometric performance of the two instruments was predominantly good, generally higher, and more homogenous for the QOLIBRI than for the SF-36 subscales. Notably, the SF-36 "Role Physical," "Role Emotional," and "Social Functioning" subscales showed less satisfactory discriminatory power than all other dimensions or the sum scores of both instruments. The absolute informativity of disease-specific as well as generic HRQoL instruments concerning the different groups defined by different correlates differed significantly. When the focus is on how a certain subscale or sum score differentiates between individuals in one specific dimension/health state, the QOLIBRI can be recommended as the preferable instrument.

Correlation between Motor Cortex Excitability Changes and Cognitive Impairment in Vascular Depression: Pathophysiological Insights from a Longitudinal TMS Study

Background. Transcranial magnetic stimulation (TMS) highlighted functional changes in dementia, whereas there are few data in patients with vascular cognitive impairment-no dementia (VCI-ND). Similarly, little is known about the neurophysiological impact of vascular depression (VD) on deterioration of cognitive functions. We test whether depression might affect not only cognition but also specific cortical circuits in subcortical vascular disease. Methods. Sixteen VCI-ND and 11 VD patients, age-matched with 15 controls, underwent a clinical-cognitive, neuroimaging, and TMS assessment. After approximately two years, all participants were prospectively reevaluated. Results. At baseline, a significant more pronounced intracortical facilitation (ICF) was found in VCI-ND patients. Reevaluation revealed an increase of the global excitability in both VCI-ND and VD subjects. At follow-up, the ICF of VCI-ND becomes similar to the other groups. Only VD patients showed cognitive deterioration. Conclusions. Unlike VD, the hyperfacilitation found at baseline in VCI-ND patients suggests enhanced glutamatergic neurotransmission that might contribute to the preservation of cognitive functioning. The hyperexcitability observed at follow-up in both groups of patients also indicates functional changes in glutamatergic neurotransmission. The mechanisms enhancing the risk of dementia in VD might be related either to subcortical vascular lesions or to the lack of compensatory functional cortical changes.