Mapping the brain in younger and older asymptomatic HIV-1 men: Frontal volume changes in the absence of other cortical or diffusion tensor abnormalities

White matter measures are near normal in controlled HIV infection except in those with cognitive impairment and longer HIV duration

The objective of the current study was to quantify the degree of white matter (WM) abnormalities in chronic and virally suppressed HIV-infected (HIV+) persons while carefully taking into account demographic and disease factors. Diffusion tensor imaging (DTI) was conducted in 40 HIV- and 82 HIV+ men with comparable demographics and life style factors. The HIV+ sample was clinically stable with successful viral control. Diffusion was measured across 32 non-colinear directions with a b-value of 1000 s/mm²; fractional anisotropy (FA) and mean diffusivity (MD) maps were quantified with Itrack IDL. Using the ENIGMA DTI protocol, FA and MD values were extracted for each participant and in 11 skeleton regions of interest (SROI) from standard labels in the JHU ICBM-81 atlas covering major striato-frontal and parietal tracks. We found no major differences in FA and MD values across the 11 SROI between study groups. Within the HIV+ sample, we found that a higher CNS penetrating antiretroviral treatment, higher current CD4+ T cell count, and immune recovery from the nadir CD4+ T cell count were associated with increased FA and decreased MD (p < 0.05-0.006), while HIV duration, symptomatic, and asymptomatic cognitive impairment were associated with decreased FA and increased MD (p < 0.01-0.004). Stability of HIV treatment and antiretroviral CNS penetration efficiency in addition to current and historical immune recovery were related to higher FA and lower MD (p = 0.04-p < 0.01). In conclusion, WM DTI measures are near normal except for patients with neurocognitive impairment and longer HIV disease duration.

Longitudinal assessment of subcortical gray matter volume, cortical thickness, and white matter integrity in HIV-positive patients

PURPOSE

To longitudinally evaluate the cortical thickness and deep gray matter structures volume, measured from T1 three-dimensional (3D) Gradient echo-weighted imaging, and white matter integrity, assessed from diffusion tensor imaging (DTI) of HIV-positive patients.

MATERIALS AND METHODS

Twenty-one HIV-positive patients on stable highly active antiretroviral therapy (HAART) with CD4+ T lymphocytes count >200 cells/mL and viral load <50 copies/mL underwent two magnetic resonance imaging (MRI) scans with a median interval of 26.6 months. None of the patients had HIV-related dementia. T1 3D magnetization prepared rapid gradient echo-weighted imaging and DTI along 30 noncolinear directions were performed using a 1.5 Tesla MR scanner. FreeSurfer was used to perform cortical volumetric reconstruction and segmentation of deep gray matter structures. For tract-based spatial statistics analysis, a white matter skeleton was created, and a permutation-based inference with 5000 permutations, with a threshold of P < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The median, radial, and axial diffusivities were also projected onto the mean FA skeleton.

RESULTS

There were no significant differences in cortical thickness, deep gray matter structures volumes or diffusivity parameters between scans at the two time points (considering P < 0.05).

CONCLUSION

No longitudinal differences in cortical thickness, deep gray matter volumes, or white matter integrity were observed in an HIV-positive population on stable HAART, with undetectable viral load and high CD4+ T lymphocytes count. J. Magn. Reson. Imaging 2016;44:1262-1269.

Extracting patterns of morphometry distinguishing HIV associated neurodegeneration from mild cognitive impairment via group cardinality constrained classification

HIV-Associated Neurocognitive Disorder (HAND) is the most common constellation of cognitive dysfunctions in chronic HIV infected patients age 60 or older in the U.S. Only few published methods assist in distinguishing HAND from other forms of age-associated cognitive decline, such as Mild Cognitive Impairment (MCI). In this report, a data-driven, nonparameteric model to identify morphometric patterns separating HAND from MCI due to non-HIV conditions in this older age group was proposed. This model enhanced the potential for group separation by combining a smaller, longitudinal data set containing HAND samples with a larger, public data set including MCI cases. Using cross-validation, a linear model on healthy controls to harmonize the volumetric scores extracted from MRIs for demographic and acquisition differences between the two independent, disease-specific data sets was trained. Next, patterns distinguishing HAND from MCI via a group sparsity constrained logistic classifier were identified. Unlike existing approaches, our classifier directly solved the underlying minimization problem by decoupling the minimization of the logistic regression function from enforcing the group sparsity constraint. The extracted patterns consisted of eight regions that distinguished HAND from MCI on a significant level while being indifferent to differences in demographics and acquisition between the two sets. Individually selecting regions through conventional morphometric group analysis resulted in a larger number of regions that were less accurate. In conclusion, simultaneously analyzing all brain regions and time points for disease specific patterns contributed to distinguishing with high accuracy HAND-related impairment from cognitive impairment found in the HIV uninfected, MCI cohort. Hum Brain Mapp 37:4523-4538, 2016. © 2016 Wiley Periodicals, Inc.

Characteristics of Resting-State Functional Connectivity in HIV-Associated Neurocognitive Disorder

BACKGROUND

HIV-associated neurocognitive disorder (HAND) can occur in patients without prior AIDS defining illness and can be debilitating. This study aimed to evaluate the difference in the patterns of intrinsic brain activity between patients with or without HAND for deepening our understanding of HAND.

METHODS

We evaluated 24 HIV-infected individuals, 12 with previously diagnosed HAND and 12 previously diagnosed without HAND, and 11 seronegative individuals. These individuals then underwent repeat NP testing and a functional brain MRI scan. For functional MRI analysis, seed-based analysis with bilateral precuneus cortex seed was applied.

RESULTS

Among the 12 individuals with previously diagnosed HAND, 3 showed improvement of their neurocognitive function and 1 was excluded for worsening liver disease. Among the 12 patients who previously had normal neurocognitive function, 2 showed neurocognitive impairment. Overall, the HAND group, who had impaired cognitive function at the time of MRI scan, showed significant decrease of resting status functional connectivity between bilateral precuneus and prefrontal cortex (PFC) compared with nonHAND group, those who had normal neurocognitive function (Corrected P<0.05). The functional connectivity with the right inferior frontal operculum and right superior frontal gyrus was positively correlated with memory and learning ability.

CONCLUSIONS

This cross-sectional study found a significant difference in fMRI patterns between patients with and without HAND. Decreased functional connectivity between precuneus and PFC could be possible functional substrate for cognitive dysfunction in HIV patients, which should be characterized in a longitudinal study.

Effects of HIV and childhood trauma on brain morphometry and neurocognitive function

A wide spectrum of neurocognitive deficits characterises HIV infection in adults. HIV infection is additionally associated with morphological brain abnormalities affecting neural substrates that subserve neurocognitive function. Early life stress (ELS) also has a direct influence on brain morphology. However, the combined impact of ELS and HIV on brain structure and neurocognitive function has not been examined in an all-female sample with advanced HIV disease. The present study examined the effects of HIV and childhood trauma on brain morphometry and neurocognitive function. Structural data were acquired using a 3T Magnetom MRI scanner, and a battery of neurocognitive tests was administered to 124 women: HIV-positive with ELS (n = 32), HIV-positive without ELS (n = 30), HIV-negative with ELS (n = 31) and HIV-negative without ELS (n = 31). Results revealed significant group volumetric differences for right anterior cingulate cortex (ACC), bilateral hippocampi, corpus callosum, left and right caudate and left and right putamen. Mean regional volumes were lowest in HIV-positive women with ELS compared to all other groups. Although causality cannot be inferred, findings also suggest that alterations in the left frontal lobe, right ACC, left hippocampus, corpus callosum, left and right amygdala and left caudate may be associated with poorer neurocognitive performance in the domains of processing speed, attention/working memory, abstraction/executive functions, motor skills, learning and language/fluency with these effects more pronounced in women living with both HIV and childhood trauma. This study highlights the potential contributory role of childhood trauma to brain alterations and neurocognitive decline in HIV-infected individuals.

White matter structure alterations in HIV-1-infected men with sustained suppression of viraemia on treatment

OBJECTIVE

Cognitive impairment is highly prevalent in HIV-1-infected (HIV+) patients, despite adequate suppression of viral replication by combination antiretroviral therapy (cART). Cerebral white matter structure alterations are often associated with cognitive impairment and have commonly been reported in the natural course of HIV infection. However, the existence of these alterations in adequately treated HIV+ patients remains unknown, as well as its possible association with cognitive impairment.

DESIGN

We used diffusion tensor imaging (DTI) to investigate whether white matter structure alterations exist in HIV+ patients with sustained suppressed viral replication on cART, and if such alterations are related to HIV-associated cognitive deficits.

METHODS

We compared 100 aviraemic HIV+ men on cART with 70 HIV-uninfected, otherwise comparable men. Clinical and neuropsychological assessments were performed. From DTI data, white matter fractional anisotropy and mean diffusion were calculated. Subsequently, tract-based spatial statistics (TBSS) was performed, with and without masking out white matter lesions.

RESULTS

HIV+ patients showed diffuse white matter structure alterations as compared with HIV-uninfected controls, observed as widespread decreased fractional anisotropy and an increased mean diffusion. These white matter structure alterations were associated with the number of years spent with a CD4 cell count below 500 cells/μl, but not with HIV-associated cognitive deficits.

CONCLUSION

Cerebral white matter structure alterations are found in middle-aged HIV+ men with sustained suppression of viraemia on cART, and may result from periods with immune deficiency when viral toxicity and host-inflammatory responses were at their peak. These white matter structure alterations were not associated with the observed subtle HIV-associated cognitive deficits.

VIDEO ABSTRACT

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Gray and white matter alterations in early HIV-infected patients: Combined voxel-based morphometry and tract-based spatial statistics

PURPOSE

To investigate both the gray matter (GM) and whiter matter (WM) alterations in a homogeneous cohort of early HIV-infected patients by combining voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS).

MATERIALS AND METHODS

Twenty-six HIV and 26 control subjects enrolled in this study with 3D T1 and diffusion-tensor imaging acquired on a 3.0T Siemens scanner. Group differences in regional GM were assessed using VBM analysis, while differences in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and relative anisotropy (RD) of WM were evaluated using TBSS analysis. After that, interactions between GM changes and white matter alterations were investigated by using a correlation analysis.

RESULTS

The HIV-infected patients displayed decreased GM volume, mainly located in the bilateral frontal cortices, bilateral anterior cingulate cortex, and left supplementary motor area (P < 0.05, false discovery rate-corrected). Meanwhile, the patient group showed decreased FA in the genu of capsule callosum, body of capsule callosum, and bilateral anterior corona radiate (P < 0.05, family wise error [FEW]-corrected). Areas of increased MD, RD, and AD in HIV patients were more extensive and observed in most skeleton locations (P < 0.05, FEW-corrected). The interaction analysis in the patient group revealed that there were no significant correlations between GM changes and WM alterations (P > 0.05).

CONCLUSION

Our results indicate that structural brain alterations occurred early in HIV-infected patients. The current study may shed further light on the potential brain effects of HIV. J. Magn. Reson. Imaging 2016;43:1474-1483.

The impact of human immune deficiency virus and hepatitis C coinfection on white matter microstructural integrity

The purpose of the present study is to examine the integrity of white matter microstructure among individuals coinfected with HIV and HCV using diffusion tensor imaging (DTI). Twenty-five HIV+ patients, 21 HIV+/HCV+ patients, and 25 HIV- controls were included in this study. All HIV+ individuals were stable on combination antiretroviral therapy (cART; ≥3 months). All participants completed MRI and neuropsychological measures. Clinical variables including liver function, HIV-viral load, and CD4 count were collected from the patient groups. DTI metrics including mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) from five subregions of the corpus callosum were compared across groups. The HIV+/HCV+ group and HIV+ group were similar in terms of HIV clinical variables. None of the participants met criteria for cirrhosis or fibrosis. Within the anterior corpus callosum, significant differences were observed between both HIV+ groups compared to HIV- controls on DTI measures. HIV+ and HIV+/HCV+ groups had significantly lower FA values and higher MD and RD values compared to HIV- controls; however, no differences were present between the HIV+ and HIV+/HCV+ groups. Duration of HIV infection was significantly related to DTI metrics in total corpus callosum FA only, but not other markers of HIV disease burden or neurocognitive function. Both HIV+ and HIV+/HCV+ individuals had significant alterations in white matter integrity within the corpus callosum; however, there was no evidence for an additive effect of HCV coinfection. The association between DTI metrics and duration of HIV infection suggests that HIV may continue to negatively impact white matter integrity even in well-controlled disease.

Cognitive functioning, wellbeing and brain correlates in HIV-1 infected patients on long-term combination antiretroviral therapy

OBJECTIVE

The objective of the current study is to integrate results from extensive neuropsychological assessment, subjective wellbeing reports and structural neuroimaging findings in successfully treated HIV-infected patients in comparison with a HIV-negative control group.

DESIGN

A cross-sectional study.

METHODS

Neuropsychological functioning and self-reported wellbeing were assessed in a group of 102 virologically suppressed HIV-infected patients on combination antiretroviral therapy (cART) and 56 controls. Both groups underwent magnetic resonance (MR) examinations and grey matter, white matter and subcortical volumes were determined. Brain parenchymal fraction (BPF) was calculated as an estimated measure of global brain atrophy.

RESULTS

HIV-infected patients showed worse information processing speed (P = 0.01) and motor function (P = 0.03) than controls. Also, higher levels of anxiety and depressive symptoms, somatic and cognitive complaints, sleep problems and health distress were found, as well as lower levels of general health perceptions, social functioning and energy (P < 0.05). No differences in wellbeing reports were found between patients on regimens containing either efavirenz or nevirapine and patients on cART without these drugs (P > 0.05). Patients had a smaller BPF (P = 0.04) and thalamus (P = 0.05) than controls. A lower BPF was related to worse motor function and information processing speed in the patients. A smaller thalamus volume was related to lower motor function in the patient group and lower speed of information processing in the controls.

CONCLUSION

No profound deficits were found in the current study. The present results demonstrate that HIV has a minor impact on brain, cognition and wellbeing among HIV-infected patients who are otherwise healthy and maintained on a good control of cART.

Mapping abnormal subcortical brain morphometry in an elderly HIV+ cohort

Over 50% of HIV + individuals exhibit neurocognitive impairment and subcortical atrophy, but the profile of brain abnormalities associated with HIV is still poorly understood. Using surface-based shape analyses, we mapped the 3D profile of subcortical morphometry in 63 elderly HIV + participants and 31 uninfected controls. The thalamus, caudate, putamen, pallidum, hippocampus, amygdala, brainstem, accumbens, callosum and ventricles were segmented from high-resolution MRIs. To investigate shape-based morphometry, we analyzed the Jacobian determinant (JD) and radial distances (RD) defined on each region's surfaces. We also investigated effects of nadir CD4 + T-cell counts, viral load, time since diagnosis (TSD) and cognition on subcortical morphology. Lastly, we explored whether HIV + participants were distinguishable from unaffected controls in a machine learning context. All shape and volume features were included in a random forest (RF) model. The model was validated with 2-fold cross-validation. Volumes of HIV + participants' bilateral thalamus, left pallidum, left putamen and callosum were significantly reduced while ventricular spaces were enlarged. Significant shape variation was associated with HIV status, TSD and the Wechsler adult intelligence scale. HIV + people had diffuse atrophy, particularly in the caudate, putamen, hippocampus and thalamus. Unexpectedly, extended TSD was associated with increased thickness of the anterior right pallidum. In the classification of HIV + participants vs. controls, our RF model attained an area under the curve of 72%.

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We model subcortical morphometry of elderly HIV + participants.

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We explore classifying HIV status based on shape and volume of brain regions.

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Morphometry of brain regions was associated with infection status and duration.

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HIV status was classifiable with 72% accuracy in morphometry-based classifiers.

Prediction of brain atrophy using three drug scores in neuroasymptomatic HIV-infected patients with controlled viremia

Background

Despite potent antiretroviral therapy, HIV still causes brain damage. Better penetration into the CNS and efficient elimination of monocyte/macrophages reservoirs are two main characteristics of an antiretroviral drug that could prevent brain damage. The aim of our study was to assess efficacy of three antiretroviral drug scores to predict brain atrophy in HIV-infected patients.

Methods

A cross sectional study consisting of 56 HIV-infected patients with controlled viremia, who had no clinically evident neurocognitive impairment. All patients had MRI of the head. A typical T2 transversal slice was analyzed and ventricles–brain ratio (VBr) as an overall brain atrophy index was calculated. Three antiretroviral drug scores were used and correlated with VBr: 2008 and 2010 CNS penetration effectiveness scores (ΣCPE₂₀₀₈ and ΣCPE₂₀₁₀) and the recently established monocyte efficacy (ΣME) score. A p-value <0.05 was considered significant.

Results

ΣCPE₂₀₁₀ was significantly associated with VBr in both univariate (r = −0.285, p = 0.033) and multivariate (β = −0.299, p = 0.016) regression models, while ΣCPE₂₀₀₈ was not (r = −0.141, p = 0.300 and β = −0.156, p = 0.214). ΣME was associated with VBr in multivariate model only (r = −0.297, p = 0.111 and β = −0.406, p = 0.029). Age and reported duration of HIV infection were also significant predictors of overall brain atrophy in multivariate regression models.

Conclusions

Although based on similar type of research, ΣCPE₂₀₁₀ is a superior drug score compared to ΣCPE₂₀₀₈. ΣME is an efficient drug score in determining brain damage. Both ΣCPE₂₀₁₀ and ΣME scores should be taken into account in preventive strategies of brain atrophy and neurocognitive impairment in HIV-infected patients.

HIV-associated neurocognitive disorders: A review for NPs

This review discusses HIV-associated neurocognitive disorders. Practical screening methods are needed for the nurse practitioner to detect neurocognitive impairment in HIV-infected patients.

Compartmentalized intrathecal immunoglobulin synthesis during HIV infection - a model of chronic CNS inflammation?

HIV infects the central nervous system (CNS) during primary infection and persists in resident macrophages. CNS infection initiates a strong local immune response that fails to control the virus but is responsible for by-stander lesions involved in neurocognitive disorders. Although highly active anti-retroviral therapy now offers an almost complete control of CNS viral proliferation, low-grade CNS inflammation persists. This review focuses on HIV-induced intrathecal immunoglobulin (Ig) synthesis. Intrathecal Ig synthesis early occurs in more than three-quarters of patients in response to viral infection of the CNS and persists throughout the course of the disease. Viral antigens are targeted but this specific response accounts for <5% of the whole intrathecal synthesis. Although the nature and mechanisms leading to non-specific synthesis are unknown, this prominent proportion is comparable to that observed in various CNS viral infections. Cerebrospinal fluid-floating antibody-secreting cells account for a minority of the whole synthesis, which mainly takes place in perivascular inflammatory infiltrates of the CNS parenchyma. B-cell traffic and lineage across the blood-brain-barrier have not yet been described. We review common technical pitfalls and update the pending questions in the field. Moreover, since HIV infection is associated with an intrathecal chronic oligoclonal (and mostly non-specific) Ig synthesis and associates with low-grade axonal lesions, this could be an interesting model of the chronic intrathecal synthesis occurring during multiple sclerosis.

HIV effects on age-associated neurocognitive dysfunction: premature cognitive aging or neurodegenerative disease?

Marked improvements in survival and health outcome for people infected with HIV have occurred since the advent of combination antiretroviral therapy over a decade ago. Yet HIV-associated neurocognitive disorders continue to occur with an alarming prevalence. This may reflect the fact that infected people are now living longer with chronic infection. There is mounting evidence that HIV exacerbates age-associated cognitive decline. Many middle-aged HIV-infected people are experiencing cognitive decline similar that to that found among much older adults. An increased prevalence of vascular and metabolic comorbidities has also been observed and is greatest among older adults with HIV. Premature age-associated neurocognitive decline appears to be related to structural and functional brain changes on neuroimaging, and of particular concern is the fact that pathology indicative of neurodegenerative disease has been shown to occur in the brains of HIV-infected people. Yet notable differences also exist between the clinical presentation and brain disturbances occurring with HIV and those occurring in neurodegenerative conditions such as Alzheimer’s disease. HIV interacts with the aging brain to affect neurological structure and function. However, whether this interaction directly affects neurodegenerative processes, accelerates normal cognitive aging, or contributes to a worsening of other comorbidities that affect the brain in older adults remains an open question. Evidence for and against each of these possibilities is reviewed.

Reduced neural specificity in middle-aged HIV+ women in the absence of behavioral deficits

In the post combination antiretroviral therapy (cART) era, the prevalence of mild forms of HIV-associated neurocognitive disorders (HAND) in individuals with HIV-infection remains high. There is a pressing need to find biomarkers that can aid clinical assessment of HAND, especially in those with mild or no neurocognitive symptoms. Here we hypothesized that a reduction in neural specificity, or the specificity of neuronal tuning, could serve as a potential biomarker of asymptomatic HAND. To directly test this hypothesis, we applied two advanced fMRI techniques to examine the difference in neural specificity between middle-aged HIV+ women and age-matched negative controls, with a focus on the fusiform face area (FFA), a critical region in face processing. Face discrimination performance was assessed outside of the scanner. While the behavioral performance of face discrimination was comparable between the two groups, a reduced neural specificity in the FFA of HIV-positive women was revealed by a novel fMRI analysis technique, local regional heterogeneity analysis, or H_corr, as well as an established technique, fMRI-rapid adaptation. In contrast, conventional fMRI techniques were insensitive to these early changes. These results suggest that, prior to the onset of detectable behavioral deficits, significant neuronal dysfunctions are already present in HIV+ individuals, and these early neuronal dysfunctions can be detected and assessed via neural specificity, which, in combining with the novel H_corr technique, has a strong potential to serve as a biomarker of asymptomatic HAND and other neurodegenerative diseases.

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We investigate early neuronal dysfunctions in cognitively normal HIV+ women.

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Conventional fMRI technique reveals normal neural activity in the FFA of HIV+ women.

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fMRI-adaptation reveals a decrease in neural specificity in the FFA of HIV+ women.

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H_corr, a novel fMRI technique, confirms the fMRI-adaptation results

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H_corr-estimated neural specificity might serve as a biomarker of asymptomatic HAND

Cross-sectional study of unexplained white matter lesions in HIV positive individuals undergoing brain magnetic resonance imaging

White matter (WM) abnormalities are frequently seen on brain MRI of HIV positive (HIV+) patients. We aimed to determine the prevalence of unexplained WM abnormalities and their associations with HIV disease and cardiovascular risk factors. We conducted a retrospective, cross-sectional study of brain MRI of HIV+ patients conducted between 2004 and 2009 at our center. Clinical and laboratory data were compiled, and images were independently reviewed for WM lesions. Images were obtained from 254 patients: 70% male, 53% white, 40% black, mean age 42 years, median current CD4 count 240 cells/mm(3), and 41% not taking antiretroviral therapy (ART). Hyperintense WM lesions were present in 161 patients (63.4%): 89 scans (35.0%) showed diffuse WM signal abnormality (DWMSA), 61 (24.0%) were consistent with small vessel disease (SVD, graded by Fazekas' scale), and 37 (14.6%) showed large asymmetrical focal WM lesions. SVD changes were associated with age and cardiovascular risk factors, and while cerebral SVD may be related to HIV infection, the MRI findings were not associated with HIV-related factors. The only risk factor for DWMSA was black race, and no correlation with cardiovascular risk factors, CD4 count, or clinical presentation was identified. DWMSA are therefore of uncertain neurological significance in HIV+ patients and could represent more than one clinicopathological entity.

Neural dysregulation during a working memory task in human immunodeficiency virus-seropositive and hepatitis C coinfected individuals

Cognitive and functional neural correlates of human immunodeficiency virus (HIV) are only partially understood at present. Variability in neural response, which has been noted in the literature, may relate to clinical factors associated with HIV, including time since HIV diagnosis, CD4 count and nadir, HIV viral load, and comorbid infectious processes, especially hepatitis C. The present investigation evaluated working memory-related functional neural activation in 26 HIV+ participants, 28 demographically matched HIV-seronegative individuals, and 8 HIV+ individuals with hepatitis C coinfection. Analyses examined impact of HIV infection duration, CD4 count and nadir, HIV viral load, and hepatitis C serostatus. Results showed that HIV-seronegative participants had fastest reaction times, and during the working memory task, HIV+ participants with hepatitis C coinfection showed strongest bias toward commission errors; however, signal detection (i.e., overall task performance) was equivalent across groups. Functional magnetic resonance imaging (fMRI) results showed HIV-related greater activation to an easier vigilance task and HIV-related lower activation to a more difficult working memory task, consistent with reduced cognitive reserve. Hepatitis C coinfection related to diffuse neural dysregulation. Correlational analyses suggested relationships of increasingly severe disease with poorer functioning in brain regions linked to error monitoring and attention regulation.

HIV clades B and C are associated with reduced brain volumetrics

The human immunodeficiency virus (HIV) has multiple genetic clades with varying prevalence throughout the world. Both HIV clade C (HIV-C) and HIV clade B (HIV-B) can cause cognitive impairment, but it is unclear if these clades are characterized by similar patterns of brain dysfunction. We examined brain volumetrics and neuropsychological performance among highly active antiretroviral therapy (HAART)-naïve HIV-B and HIV-C participants. Thirty-four HAART-naïve HIV-infected (HIV+) participants [17 HIV-B (USA); 17 HIV-C (South Africa)] and 34 age- and education-matched HIV-uninfected (HIV−) participants were evaluated. All participants underwent similar laboratory, neuropsychological, and neuroimaging studies. Brain volume measures were assessed within the caudate, putamen, amygdala, thalamus, hippocampus, corpus callosum, and cortical (gray and white matter) structures. A linear model that included HIV status, region, and their interaction assessed the effects of the virus on brain volumetrics. HIV− and HIV+ individuals were similar in age. On laboratory examination, HIV-C participants had lower CD4 cell counts and higher plasma HIV viral loads than HIV-B individuals. In general, HIV+ participants performed significantly worse on neuropsychological measures of processing speed and memory and had significantly smaller relative volumetrics within the thalamus, hippocampus, corpus callosum, and cortical gray and white matter compared to the respective HIV− controls. Both HIV-B and HIV-C are associated with similar volumetric declines when compared to matched HIV− controls. HIV-B and HIV-C were associated with significant reductions in brain volumetrics and poorer neuropsychological performance; however, no specific effect of HIV clade subtype was evident. These findings suggest that HIV-B and HIV-C both detrimentally affect brain integrity.

HIV and aging: effects on the central nervous system

With the introduction of combination antiretroviral therapy, many human immunodeficiency virus-positive (HIV+) individuals are reaching advanced age. The proportion of people living with HIV older than 50 years already exceeds 50% in many communities, and is expected to reach this level nationally by 2015. HIV and aging are independently associated with neuropathological changes, but their concurrence may have a more deleterious effect on the central nervous system (CNS). Published data about neurocognitive and neuroimaging markers of HIV and aging are reviewed. Putative factors contributing to neurocognitive impairment and neuroimaging changes in the aging HIV+ brain, such as metabolic disturbances, cardiovascular risk factors, immune senescence, and neuroinflammation, are described. The possible relationship between HIV and some markers of Alzheimer's disease is presented. Current research findings emphasize multiple mechanisms related to HIV and combination antiretroviral therapy that compromise CNS structure and function with advancing age.

Role of neuroimaging in HIV-associated neurocognitive disorders

Human immunodeficiency virus (HIV) enters the brain soon after seroconversion and can cause HIV-associated neurocognitive disorders (HAND). Although the more severe and progressive forms of HAND are less prevalent due to combination antiretroviral therapy (cART), ∼ 40% of HIV-infected (HIV+) patients continue to have cognitive impairment. Some HIV+ individuals who have effective plasma HIV-1 RNA suppression with cART still develop HAND. It is often difficult to diagnose HAND in the outpatient setting as detailed neuropsychological performance testing is required. Additional biomarkers that are relatively easy to obtain and clinically relevant are needed for assessing HIV-associated neuropathologic changes. Recently developed noninvasive magnetic resonance imaging (MRI) techniques have great potential to serve as biomarkers. The authors review the application of some of these neuroimaging techniques, magnetic resonance spectroscopy (MRS), volumetric MRI, diffusion tensor imaging (DTI), functional MRI (fMRI), in HIV+ individuals. Each of the neuroimaging methods offers unique insight into mechanisms underlying neuroHIV, could monitor disease progression, and may assist in evaluating the efficacy of particular cART regimens. It is hoped that considerable progress will continue to occur such that some of these neuroimaging methods will be incorporated across multiple sites and included in future HAND guidelines.

Select neurocognitive impairment in HIV-infected women: associations with HIV viral load, hepatitis C virus, and depression, but not leukocyte telomere length

BACKGROUND

Through implementation of combination antiretroviral therapy (cART) remarkable gains have been achieved in the management of HIV infection; nonetheless, the neurocognitive consequences of infection remain a pivotal concern in the cART era. Research has often employed norm-referenced neuropsychological scores, derived from healthy populations (excluding many seronegative individuals at high risk for HIV infection), to characterize impairments in predominately male HIV-infected populations.

METHODS

Using matched-group methodology, we assessed 81 HIV-seropositive (HIV+) women with established neuropsychological measures validated for detection of HIV-related impairments, as well as additional detailed tests of executive function and decision-making from the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

On validated tests, the HIV+ women exhibited impairments that were limited to significantly slower information processing speed when compared with 45 HIV-seronegative (HIV-) women with very similar demographic backgrounds and illness comorbidities. Additionally, select executive impairments in shifting attention (i.e., reversal learning) and in decision-making quality were revealed in HIV+ participants. Modifiers of neurocognition in HIV-infected women included detectable HIV plasma viral load, active hepatitis C virus co-infection, and self-reported depression symptoms. In contrast, leukocyte telomere length (LTL), a marker of cellular aging, did not significantly differ between HIV+ and HIV- women, nor was LTL associated with overall neurocognition in the HIV+ group.

CONCLUSIONS

The findings suggest that well-managed HIV infection may entail a more circumscribed neurocognitive deficit pattern than that reported in many norm-referenced studies, and that common comorbidities make a secondary contribution to HIV-related neurocognitive impairments.

Mapping white matter integrity in elderly people with HIV

People with HIV are living longer as combination antiretroviral therapy (cART) becomes more widely available. However, even when plasma viral load is reduced to untraceable levels, chronic HIV infection is associated with neurological deficits and brain atrophy beyond that of normal aging. HIV is often marked by cortical and subcortical atrophy, but the integrity of the brain's white matter (WM) pathways also progressively declines. Few studies focus on older cohorts where normal aging may be compounded with HIV infection to influence deficit patterns. In this relatively large diffusion tensor imaging (DTI) study, we investigated abnormalities in WM fiber integrity in 56 HIV+ adults with access to cART (mean age: 63.9 ± 3.7 years), compared to 31 matched healthy controls (65.4 ± 2.2 years). Statistical 3D maps revealed the independent effects of HIV diagnosis and age on fractional anisotropy (FA) and diffusivity, but we did not find any evidence for an age by diagnosis interaction in our current sample. Compared to healthy controls, HIV patients showed pervasive FA decreases and diffusivity increases throughout WM. We also assessed neuropsychological (NP) summary z-score associations. In both patients and controls, fiber integrity measures were associated with NP summary scores. The greatest differences were detected in the corpus callosum and in the projection fibers of the corona radiata. These deficits are consistent with published NP deficits and cortical atrophy patterns in elderly people with HIV.

HIV-associated neurocognitive disease: case studies and suggestions for diagnosis and management in different patient subgroups

The incidence of HIV-associated dementia has decreased significantly with the introduction of combination antiretroviral therapy; however, milder or more subtle forms of neurocognitive disorders associated with HIV appear to remain common. There is a lack of consensus on when to screen and on which methods are most appropriate for identifying patients at risk of neurocognitive impairment. Multiple factors (demographic, social, genetic, psychological and medical) can play a role in its aetiology and progression, including potential central nervous system toxicity of antiviral therapy. It is important to identify these factors in order to apply relevant management strategies. In this review, we discuss a series of case studies that address some of the challenges presented by the diagnosis and management of HIV-associated neurocognitive impairment in different patient types.

Evaluation of emotion processing in HIV-infected patients and correlation with cognitive performance

BACKGROUND

Facial emotion recognition depends on cortical and subcortical networks. HIV infection of the central nervous system can damage these networks, leading to impaired facial emotion recognition.

METHODS

We performed a cross-sectional single cohort study consecutively enrolling HIV + subjects during routine outpatient visits. Age, gender and education-matched HIV-negative healthy individuals were also selected. Subjects were submitted to a Facial Emotion Recognition Test, which assesses the ability to recognize six basic emotions (disgust, anger, fear, happiness, surprise, sadness). The score for each emotion and a global score (obtained by summing scores for each emotion) were analyzed. General cognitive status of patients was also assessed.

RESULTS

A total of 49 HIV + and 20 HIV - subjects were enrolled. On the Facial Emotion Recognition Test, ANOVA revealed a significantly lower performance of HIV + subjects than healthy controls in recognizing fear. Moreover, fear facial emotion recognition was directly correlated with Immediate Recall of Rey Words. The lower the patients' neurocognitive performance the less accurate they were in recognizing happiness. AIDS-defining events were negatively related to the correct recognition of happiness.

CONCLUSIONS

Fear recognition deficit in HIV + patients might be related to the impaired function of neural networks in the frontostriatal system. AIDS events, including non-neurological ones, may have a negative effect on this system. Inclusion of an emotion recognition test in the neuropsychological test battery could help clinicians during the long term management of HIV-infected patients, to better understand the cognitive mechanisms involved in the reduction of emotion recognition ability and the impact of this impairment on daily life.

White matter fiber compromise contributes differentially to attention and emotion processing impairment in alcoholism, HIV-infection, and their comorbidity

Alcoholism (ALC) and HIV-1 infection (HIV) each affects emotional and attentional processes and integrity of brain white matter fibers likely contributing to functional compromise. The highly prevalent ALC+HIV comorbidity may exacerbate compromise. We used diffusion tensor imaging (DTI) and an emotional Stroop Match-to-Sample task in 19 ALC, 16 HIV, 15 ALC+HIV, and 15 control participants to investigate whether disruption of fiber system integrity accounts for compromised attentional and emotional processing. The task required matching a cue color to that of an emotional word with faces appearing between the color cue and the Stroop word in half of the trials. Nonmatched cue-word color pairs assessed selective attention, and face-word pairs assessed emotion. Relative to controls, DTI-based fiber tracking revealed lower inferior longitudinal fasciculus (ilf) integrity in HIV and ALC+HIV and lower uncinate fasciculus (uf) integrity in all three patient groups. Controls exhibited Stroop effects to positive face-word emotion, and greater interference was related to greater callosal, cingulum and ilf integrity. By contrast, HIV showed greater interference from negative Stroop words during color-nonmatch trials, correlating with greater uf compromise. For face trials, ALC and ALC+HIV showed greater Stroop-word interference, correlating with lower cingulate and callosal integrity. Thus, in HIV, conflict resolution was diminished when challenging conditions usurped resources needed to manage interference from negative emotion and to disengage attention from wrongly cued colors (nonmatch). In ALC and ALC+HIV, poorer callosal integrity was related to enhanced emotional interference suggesting curtailed interhemispheric exchange needed between preferentially right-hemispheric emotion and left-hemispheric Stroop-word functions.

Regional brain structural dysmorphology in human immunodeficiency virus infection: effects of acquired immune deficiency syndrome, alcoholism, and age

BACKGROUND

Human immunodeficiency virus (HIV) infection and alcoholism each carries liability for disruption of brain structure and function integrity. Despite considerable prevalence of HIV-alcoholism comorbidity, few studies examined the potentially heightened burden of disease comorbidity.

METHODS

Participants were 342 men and women: 110 alcoholics, 59 with HIV infection, 65 with HIV infection and alcoholism, and 108 healthy control subjects. This design enabled examination of independent and combined effects of HIV infection and alcoholism along with other factors (acquired immune deficiency syndrome [AIDS]-defining events, hepatitis C infection, age) on regional brain volumes derived from T1-weighted magnetic resonance images.

RESULTS

Brain volumes, expressed as Z scores corrected for intracranial volume and age, were measured in 20 tissue and 5 ventricular and sulcal regions. The most profound and consistent volume deficits occurred with alcohol use disorders, notable in the cortical mantle, insular and anterior cingulate cortices, thalamus, corpus callosum, and frontal sulci. The HIV-only group had smaller thalamic and larger frontal sulcal volumes than control subjects. HIV disease-related factors associated with greater volume abnormalities included CD4 cell count nadir, clinical staging, history of AIDS-defining events, infection age, and current age. Longer sobriety and less lifetime alcohol consumption were predictive of attenuated brain volume abnormalities in both alcohol groups.

CONCLUSIONS

Having HIV infection with alcoholism and AIDS had an especially poor outcome on brain structures. That longer periods of sobriety and less lifetime alcohol consumption were predictive of attenuated brain volume abnormalities encourages the inclusion of alcohol recovery efforts in HIV/AIDS therapeutic settings.

The effects of HIV and combination antiretroviral therapy on white matter integrity

OBJECTIVE

HIV preferentially affects white matter in the brain. Although combination antiretroviral therapy (cART) reduces HIV viral load within the brain, continued inflammation can persist. We investigated the effect of HIV and cART on white matter integrity.

DESIGN

We used diffusion tensor imaging (DTI) to examine the effects of HIV and cART on white matter integrity within the corpus callosum and centrum semiovale (CSO).

METHODS

Neuropsychological testing and DTI measures (fractional anisotropy, mean diffusivity, axial diffusivity, radial diffusivity) were obtained from 21 HIV-uninfected controls, 21 HIV-infected patients naive to cART (HIV+/cART-), and 21 HIV+ patients receiving stable cART (HIV+/cART+). A subset of the HIV+/cART- individuals (n=10) was assessed before and 6 months after receiving medications. Differences among the cross-sectional groups were assessed using an analysis of variance, whereas paired t-tests evaluated longitudinal changes.

RESULTS

HIV+/cART- participants had significantly lower mean diffusivity, axial diffusivity, and radial diffusivity for the corpus callosum and CSO compared to HIV- controls and HIV+/cART+ individuals. No significant difference existed between HIV- controls and HIV+/cART+ patients. cART initiation significantly improved mean diffusivity, radial diffusivity, and axial diffusivity, but not fractional anisotropy, in the corpus callosum and CSO in some HIV-infected patients.

CONCLUSION

Observed decreases in DTI parameters between HIV+/cART+ and HIV+/cART- individuals could reflect the presence of inflammatory cells or cytotoxic edema in HIV+/cART- patients. Initiating cART could lead to a reduction in neuro-inflammation and improvement in DTI measures. Future DTI studies may be useful for evaluating the efficacy higher brain penetrating cART regimens.

Effects of HIV and early life stress on amygdala morphometry and neurocognitive function

Both HIV infection and high levels of early life stress (ELS) have been related to abnormalities in frontal-subcortical structures, yet the combined effects of HIV and ELS on brain structure and function have not been previously investigated. In this study we assessed 49 non-demented HIV-seropositive (HIV+) and 47 age-matched HIV-seronegative healthy control (HC) adults. Levels of ELS exposure were quantified and used to define four HIV-ELS groups: HC Low-ELS (N = 20); HC High-ELS (N = 27); HIV+ Low-ELS (N = 24); HIV+ High-ELS (N = 25). An automated segmentation tool measured volumes of brain structures known to show HIV-related or ELS-related effects; a brief neurocognitive battery was administered. A significant HIV-ELS interaction was observed for amygdala volumes, which was driven by enlargements in HIV+ High-ELS participants. The HIV+ High-ELS group also demonstrated significant reductions in psychomotor/processing speed compared with HC Low-ELS. Regression analyses in the HIV+ group revealed that amygdala enlargements were associated with higher ELS, lower nadir CD4 counts, and reduced psychomotor/processing speed. Our results suggest that HIV infection and high ELS interact to increase amygdala volume, which is associated with neurocognitive dysfunction in HIV+ patients. These findings highlight the lasting neuropathological influence of ELS and suggest that high ELS may be a significant risk factor for neurocognitive impairment in HIV-infected individuals.

Neuroimaging studies of the aging HIV-1-infected brain

Highly active antiretroviral therapy (HAART) has increased life expectancy among HIV-infected individuals, and by 2015, at least half of all HIV-infected individuals will be over 50 years of age. Neurodegenerative processes associated with aging may be facilitated by HIV-1 infection, resulting in premature brain aging. This review will highlight brain abnormalities in HIV patients in the setting of aging, focusing on recent neuroimaging studies of the structural, physiological, functional and neurochemical changes. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy studies performed during the pre-HAART era or on antiretroviral-naive subjects suggest an accelerated aging process, while those on HAART-treated subjects suggest premature brain atrophy. Diffusion tensor imaging studies yielded conflicting findings on the relationship between HIV and age in neuroasymptomatic individuals. Functional MRI studies found evidence of premature or accelerated aging processes in the brains of HIV subjects. Lastly, many age-related illnesses such as diabetes, stroke, and depression, as well as comorbid substance abuse, may further exacerbate the aging process in the HIV-infected brain, leading to premature or accelerated age-related brain changes. Given the different pathologic or physiologic changes in the brain assessed by the different neuroimaging techniques, using a multimodal approach in longitudinal follow-up studies is recommended for future studies.

Early microstructural white matter changes in patients with HIV: a diffusion tensor imaging study

BACKGROUND

Previous studies have reported white matter (WM) brain alterations in asymptomatic patients with human immunodeficiency virus (HIV).

METHODS

We compared diffusion tensor imaging (DTI) derived WM fractional anisotropy (FA) between HIV-patients with and without mild macroscopic brain lesions determined using standard magnetic resonance imaging (MRI). We furthermore investigated whether WM alterations co-occurred with neurocognitive deficits and depression. We performed structural MRI and DTI for 19 patients and 19 age-matched healthy controls. Regionally-specific WM integrity was investigated using voxel-based statistics of whole-brain FA maps and region-of-interest analysis. Each patient underwent laboratory and neuropsychological tests.

RESULTS

Structural MRI revealed no lesions in twelve (HIV-MRN) and unspecific mild macrostructural lesions in seven patients (HIV-MRL). Both analyses revealed widespread FA-alterations in all patients. Patients with HIV-MRL had FA-alterations primarily adjacent to the observed lesions and, whilst reduced in extent, patients with HIV-MRN also exhibited FA-alterations in similar regions. Patients with evidence of depression showed FA-increase in the ventral tegmental area, pallidum and nucleus accumbens in both hemispheres, and patients with evidence of HIV-associated neurocognitive disorder showed widespread FA-reduction.

CONCLUSION

These results show that patients with HIV-MRN have evidence of FA-alterations in similar regions that are lesioned in HIV-MRL patients, suggesting common neuropathological processes. Furthermore, they suggest a biological rather than a reactive origin of depression in HIV-patients.

Regional cerebral blood flow and FDG uptake in asymptomatic HIV-1 men

Despite advances in the treatment of patients with human immunodeficiency virus (HIV), HIV-associated neurocognitive disorder occurs in 15-50% of HIV-infected individuals, and may become more apparent as ageing advances. In the present study we investigated regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of glucose uptake (rCMRglc) in medically and psychiatrically stable HIV-1-infected participants in two age-groups. Positron emission tomography (PET) and magnetic resonance imaging (MRI)-based arterial spin labeling (ASL) were used to measure rCMRglc and rCBF, respectively, in 35 HIV-infected participants and 37 HIV-negative matched controls. All participants were currently asymptomatic with undetectable HIV-1 viral loads, without medical or psychiatric comorbidity, alcohol or substance misuse, stable on medication for at least 6 months before enrolment in the study. We found significant age effects on both ASL and PET with reduced rCBF and rCMRglc in related frontal brain regions, and consistent, although small, reductions in rCBF and rCMRglc in the anterior cingulate cortex (ACC) in HIV, a finding of potential clinical significance. There was no significant interaction between HIV status and the ageing process, and no significant HIV-related changes elsewhere in the brain on PET or ASL. This is the first paper to combine evidence from ASL and PET method in HIV participants. These finding provide evidence of crossvalidity between the two techniques, both in ageing and a clinical condition (HIV).

Frontal callosal disconnection syndromes

The interhemispheric connections of the cortical areas of the human brain are distributed within the corpus callosum according to a topographic order which is being studied in detail by novel imaging techniques. Total section of the corpus callosum is followed by a variety of interhemispheric disconnection symptoms each of which can be attributed to the interruption of fibers in a specific callosal sector. Disconnection symptoms deriving from posterior callosal sections, disconnecting parietal, temporal and occipital lobes across the midline, are more apparent than those following anterior callosal sections disconnecting the frontal lobes. In spite of the massive bulk of the frontal callosal connections in man, ascertained consequences of their interruption are limited to disorders of motor control, with particular regard to bimanual coordination. Technical advances in brain imaging and the design of appropriate tests are expected to reveal so far undetected deficits in the domain of executive and higher cognitive functions, resulting from callosal disconnection of the prefrontal cortices.