Abnormal brain activation on functional MRI in cognitively asymptomatic HIV patients

Functional Imaging in Stroke Recovery

Assessing neurobiology of brain systems can provide information not available from anatomic or behavioral assessment. Such information may be of value in understanding, defining, and prescribing potential therapeutic interventions that target restorative brain events after stroke. A number of methods have been used to study stroke recovery, each with its relative merits and limitations. Several studies suggest that greater injury is associated with reduced laterality of brain activity. This might be in relation to changes in interhemispheric inhibition and is a phenomenon that is likely useful for functional gains in some patients. Many other features of brain activity change in the months after a stroke, including the site and size of activation in relevant brain network nodes. While there is incomplete agreement regarding which features of altered brain activity predict and parallel better behavioral outcome, studies converge on the conclusion that best outcome is achieved by activating the brain in a pattern that most resembles the normal state.

Neural mechanisms of working memory in ecstasy (MDMA) users who continue or discontinue ecstasy and amphetamine use: evidence from an 18-month longitudinal functional magnetic resonance imaging study

BACKGROUND

Working memory processing in ecstasy (3,4-methylenedioxymethamphetamine) users is associated with neural alterations as measured by functional magnetic resonance imaging. Here, we examined whether cortical activation patterns change after prolonged periods of continued use or abstinence from ecstasy and amphetamine.

METHODS

We used an n-back task and functional magnetic resonance imaging in 17 ecstasy users at baseline (t(1)) and after 18 months (t(2)). Based on the reported drug use at t(2) we separated subjects with continued ecstasy and amphetamine use from subjects reporting abstinence during the follow-up period (n = 9 and n = 8, respectively).

RESULTS

At baseline both groups had similar task performance and similar cortical activation patterns. Task performance remained unchanged in both groups. Furthermore, there were no detectable functional magnetic resonance imaging signal changes from t(1) to t(2) in the follow-up abstinent group. However, the continuing users showed a dose-dependent increased parietal activation for the 2-back task after the follow-up period.

CONCLUSIONS

Our data suggest that ecstasy use, particularly in high doses, is associated with greater parietal activation during working memory performance. An altered activation pattern might appear before changes in cognitive performance become apparent and, hence, may reflect an early stage of neuronal injury from the neurotoxic drug ecstasy.

[Correlation between clinical apparatus-based differential diagnosis and neuropathological diagnosis in patients with AIDS]

BACKGROUND

During the course of HIV infection, the majority of patients develop opportunistic cerebral neuro-manifestations. If conventional diagnostic tools are not sufficient, a stereotactic biopsy is often necessary.

PATIENTS AND METHODS

In order to evaluate the correctness of the clinical diagnosis of cerebral neuro-manifestations in HIV-infected patients, we compared the results of cerebral biopsy or autopsy with the previous clinical diagnosis. A total of 19 biopsies and 49 autopsies could be analyzed.

RESULTS

Except for HIV-associated encephalopathy, we detected a very high conformity between the clinical and the neuropathological diagnoses. We obtained the best sensitivity for progressive multifocal leukoencephalopathy (PML), whereas for cerebral toxoplasmosis the worst sensitivity and specificity was identified.

CONCLUSION

We conclude that the diagnosis of PML can be made on clinical grounds alone, whereas the diagnosis of cerebral toxoplasmosis and lymphoma often requires a biopsy, which should be performed early.

Antiretroviral Treatment Alters Relationship between Mcp-1 and Neurometabolites in HIV Patients

Objective

The relationships between neurometabolites and macrophage chemoattractant protein (MCP-1) in serum and cerebrospinal fluid (CSF) were evaluated in HIV patients before and after antiretroviral treatment. Design: Prior studies found higher CSF MCP-1 levels in patients with HIV-associated dementia compared to those in neuroasymptomatic. We hypothesized that CSF MCP-1 levels would correlate inversely to neuronal metabolites [including N-acetyl compounds, gluta-mate+glutamine, as assessed by principal component analyses (PCA)] and positively to glial metabolites (including myo-inositol and choline compounds).

Methods

Thirty-nine antiretroviral-naive HIV patients were evaluated prospectively with proton magnetic resonance spectroscopy (1H MRS), and serum and CSF MCP-1 measurements prior to highly active antiretroviral therapy (HAART); 31 of these patients completed follow-up studies after 3 months of HAART but only 24 had follow-up CSF studies.

Results

After HAART, brain metabolites and clinical signs showed no change despite improvements in systemic (CD4 counts, plasma viral load, MCP-1) and CSF (viral load and MCP-1) variables. CSF, but not serum, MCP-1 levels correlated inversely with the neuronal component (from PCA) prior to treatment ( r=-0.59, P=0.0008). Conversely, after 3 months of HAART, the glial component (from PCA) correlated positively with CSF MCP-1 levels ( r=0.70, P=0.0002; ANCOVA interaction for treatment status, P=0.003).

Conclusions

These findings suggest that higher CSF MCP-1 levels are associated with neuronal dysfunction in untreated patients. After 3 months of HAART, the decreased systemic factors (viral burden, systemically derived MCP-1) no longer associate with neuronal dysfunction, but subjects with the strongest glial response in the brain continue to produce the highest levels of MCP-1.

Cerebral reserve capacity: implications for alcohol and drug abuse

Cerebral reserve capacity (or functional reserve) refers to the brain's ability to maintain function when confronted by degenerative processes. Functional reserve can be estimated by several associated measures, including premorbid brain size, premorbid IQ, and level of education attained. There is accumulating evidence that the magnitude of reserve capacity is important in determining the onset and progression of the clinical manifestations of neurodegenerative brain diseases. Normal aging also whittles away at this cerebral reserve, and there may be a consequent unmasking of morbid effects that was not clinically evident when this compensatory reserve was sufficient. We review the evidence supporting this model for a number of degenerative brain processes, including Alzheimer's disease, presenile dementia, HIV dementia, aging, and chronic (multiyear) substance abuse. The concept of cerebral functional reserve has important implications for alcohol and drug abuse morbidity. First, given the high genetic contribution to substance abuse, there is an increased likelihood that the parents of substance abusers were substance abusers themselves. Substance abuse during pregnancy can inhibit brain growth, resulting in reduced brain size and reduced reserve capacity (and therefore less ability to compensate for loss of function later in life). Second, substance abuse is often coupled with poverty, and both substance abuse and poverty are associated with some of the same conditions that reduce brain growth. Finally, we comment on the most important public health implication of the cerebral reserve capacity model (vis-à-vis addiction).

Neural correlates of working memory in pure and polyvalent ecstasy (MDMA) users

Poor cognitive performance in ecstasy (3,4-methylenedioxymethamphetamine; MDMA) users has been related to the well-recognized neurotoxic effects of the drug upon central serotonergic and possibly also dopaminergic systems. However, concomitant use of other drugs has been a critical confound in most investigations. In this study we used an n-back task and fMRI to investigate working memory performance and related cerebral activation in eight, currently abstinent pure MDMA users and two matched groups of polyvalent MDMA users and non-users. Pure MDMA users presented lower activations than controls and/or polyvalent users, most notably in inferior temporal regions, the angular gyrus and the striate cortex, whereas polyvalent users did not differ from controls. Our results suggest that altered brain activation patterns during cognitive processing in ecstasy users may be mainly associated with prior MDMA use. Concomitant use of other drugs may modify this effect.

Autoimmune markers in HIV-associated dementia

The etiology of HIV-associated dementia (HAD) is still unknown although direct viral effects have not been supported. Although evidence supports a role for products of activated macrophages, other evidence suggested the possibility of associated autoimmune phenomena at least as a marker. In a blinded analysis, non-HIV-infected whole brain material was immunoblotted with samples of serum, and in certain cases cerebrospinal fluid (CSF), from HAD patients and controls. Distinct antibrain antibodies were detected in 11/12 of HIV+ HAD patients, 7/19 of HIV+ patients without HAD, and 0/11 HIV seronegative controls who were either healthy or had other neurologic diseases. Reactivity against control tissue was negative. Though the etiopathogenetic relation of these antibrain antibodies remains to be delineated, the data suggest that they may be a marker of HAD.