Central nervous system HIV-1 infection

Neurologic Complications of Human Immunodeficiency Virus

PURPOSE OF REVIEW

This article reviews the neurologic complications associated with human immunodeficiency virus (HIV) infection.

RECENT FINDINGS

Neurologic complications of HIV may be caused by direct virally mediated pathology, immune-mediated phenomena in response to viral infection, or opportunistic infections secondary to depletion of lymphocytes. These neurologic disorders may be influenced by the degree of immunosuppression (ie, CD4+ T-cell lymphocyte count) and stage of infection (early versus late), as well as use of antiretroviral therapy, and may manifest as a variety of central and peripheral neurologic syndromes, including the more commonly encountered HIV-associated cognitive disorders and length-dependent sensorimotor polyneuropathy, respectively. Immune dysregulation underlies the majority of these neurologic phenomena, as well as other HIV-associated conditions including immune reconstitution inflammatory syndrome (IRIS), CD8 lymphocytosis, and potentially the development of compartmentalized infection within the CSF, also referred to as CSF escape.

SUMMARY

This article reviews a spectrum of clinical syndromes and related neuropathologic states associated with HIV infection.

Highlighting the Role of Cognitive and Brain Reserve in the Substance use Disorder Field

BACKGROUND

Cognitive reserve (CR) refers to the ability of an individual to cope with brain pathology remaining free of cognitive symptoms. This protective factor has been related to compensatory and more efficient brain mechanisms involved in resisting brain damage. For its part, Brain reserve (BR) refers to individual differences in the structural properties of the brain which could also make us more resilient to suffer from neurodegenerative and mental diseases.

OBJECTIVE

This review summarizes how this construct, mainly mediated by educational level, occupational attainment, physical and mental activity, as well as successful social relationships, has gained scientific attention in the last years with regard to diseases, such as neurodegenerative diseases, stroke or traumatic brain injury. Nevertheless, although CR has been studied in a large number of disorders, few researches have addressed the role of this concept in drug addiction.

METHODS

We provide a selective overview of recent literature about the role of CR and BR in preventing substance use onset. Likewise, we will also discuss how variables involved in CR (healthy leisure, social support or job-related activities, among others) could be trained and included as complementary activities of substance use disorder treatments.

RESULTS

Evidence about this topic suggests a preventive role of CR and BR on drug use onset and when drug addiction is established, these factors led to less severe addiction-related problems, as well as better treatment outcomes.

CONCLUSION

CR and BR are variables not taken yet into account in drug addiction. However, they could give us a valuable information about people at risk, as well as patient's prognosis.

An Imaging-Based Approach to Spinal Cord Infection

Infections of the spinal cord, nerve roots, and surrounding meninges are uncommon, but highly significant given their potential for severe morbidity and even mortality. Prompt diagnosis can be lifesaving, as many spinal infections are treatable. Advances in imaging technology have now firmly established magnetic resonance imaging (MRI) as the gold standard for spinal cord imaging evaluation, enabling the depiction of infectious myelopathies with exquisite detail and contrast. In this article, we aim to provide an overview of MRI findings for spinal cord infections with special focus on imaging patterns of infection that are primarily confined to the spinal cord, spinal meninges, and spinal nerve roots. In this context, we describe and organize this review around 5 distinct patterns of transverse spinal abnormality that may be detected with MRI as follows: (1) extramedullary, (2) centromedullary, (3) eccentric, (4) frontal horn, and (5) irregular. We seek to classify the most common presentations for a wide variety of infectious agents within this image-based framework while realizing that significant overlap and variation exists, including some infections that remain occult with conventional imaging techniques.

HIV, opiates, and enteric neuron dysfunction

Human immune deficient virus (HIV) is an immunosuppressive virus that targets CD4(+) T-lymphocytes. HIV infections cause increased susceptibility to opportunistic infections and cancer. HIV infection can also alter central nervous system (CNS) function causing cognitive impairment. HIV does not infect neurons but it does infect astrocytes and microglia in the CNS. HIV can also infect enteric glia initiating an intestinal inflammatory response which causes enteric neural injury and gut dysfunction. Part of the inflammatory response is HIV induced production of proteins including, Transactivator of transcription (Tat) which contribute to neuronal injury after release from HIV infected glial cells. A risk factor for HIV infection is intravenous drug use with contaminated needles and chronic opiate use can exacerbate neural injury in the nervous system. While most research focuses on the actions of Tat and other HIV related proteins and opiates on the brain, recent data indicate that Tat can cause intestinal inflammation and disruption of enteric neuron function, including alteration of Na(+) channel activity and action potential generation. A paper published in this issue of Neurogastroenterology and Motility extends these findings by identifying an interaction between Tat and morphine on enteric neuron Na(+) channels and on intestinal motility in vivo using a Tat expressing transgenic mouse model. These new data show that Tat protein can enhance the inhibitory actions of morphine on action potential generation and propulsive motility. These findings are important to our understanding of how HIV causes diarrhea in infected patients and for the use of opioid drugs to treat HIV-induced diarrhea.

Viral diseases of the central nervous system

Virus-induced diseases of the central nervous system (CNS) represent a significant burden to human health worldwide. The complexity of these diseases is influenced by the sheer number of different neurotropic viruses, the diverse routes of CNS entry, viral tropism, and the immune system. Using a combination of human pathological data and experimental animal models, we have begun to uncover many of the mechanisms that viruses use to enter the CNS and cause disease. This review highlights a selection of neurotropic viruses that infect the CNS and explores the means by which they induce neurological diseases such as meningitis, encephalitis, and myelitis.