The frequency and profile of neurology in black South African HIV infected (clade C) patients — A hospital-based prospective audit

Investigating latent syphilis in HIV treatment-experienced Ethiopians and response to therapy

Objectives

We investigated people with HIV (PWH) receiving combination antiretroviral therapy (cART) for latent syphilis infection prevalence, risk factors, treatment response, and neurosyphilis.

Methods

A prospective follow-up study was conducted on PWH and latent syphilis. The cases were randomly assigned to receive either benzathine penicillin G (BPG) or doxycycline (DOXY), and the posttreatment response was evaluated after 12 and 24 months. The traditional algorithm was used for serodiagnosis, and a semi-quantitative rapid plasma reagin (RPR) test monitored disease activity and treatment effectiveness.

Results

Of the 823 participants, 64.8% were women, and the mean age was 41.7±10 years. Thirty-one (3.8%) of the participants (22 males and nine females) had latent syphilis. The risk factors were male sex (aOR = 3.14), increasing age (aOR = 1.04 per year), and cART duration (aOR = 1.01 per month). Baseline RPR titers were: ≤1:4 in 19 (61.3%), between 1:8 and 1:32 in 10 (32.2%), and >1:32 in 2 (6.4%). None of the seven cerebrospinal fluid analyses supported a neurosyphilis diagnosis. In the 12^th month of treatment, 27 (87.1%) had adequate serological responses, three (9.7%) had serological nonresponse, and one (3.2%) had treatment failure. Syphilis treatment was repeated in the last four cases with the alternative drug. In terms of adequate serologic response, both therapies were comparable at the 12^th month, p = 0.37. All cases responded to treatment in the 24^th month.

Conclusion

In PWH receiving cART, latent syphilis occurred more in men than women, suggesting an investigation of sexual practices and the impact of antenatal syphilis screening. Syphilis disease activity reduces in the latent stage. Therefore, the routine cerebrospinal fluid analysis contributes little to the diagnosis of asymptomatic neurosyphilis and the treatment success of latent syphilis. DOXY is an alternative to BPG, and cART improves serologic response to latent syphilis treatment.

Seizure in HIV-infected patients: clinical presentation, cause and treatment outcome in Ethiopia-a retrospective study

BACKGROUND

The estimated number of adult patients living with HIV infection in Ethiopia in 2012 was approximately 800,000. Seizure occurs in 2 to 3% and 6.1% to 34.3% in patients with HIV infection and patients with neurological complications of HIV infection, respectively. Studies on HIV infection and seizure are rare in Ethiopia. The purpose of this study was to assess clinical presentation, cause and treatment outcome of patients with HIV infection presented with seizure.

METHODS

In this retrospective study, patients aged ≥ 13 years with HIV infection presented with seizure were included. Medical records were reviewed and demographic and clinical data were collected.

RESULTS

Records of 146 patients were analysed. Males were 55.5% and the mean age was 34 years. The diagnosis of HIV infection was made after current hospital admission in 69% of patients. Almost all patients (98.6%) had stage 4 HIV infection with very low CD4 count (mean = 77/mm³). In almost all patients seizure was a recent onset at current admission; either it started after admission (42.5%) or within 3 months prior to admission (52.5%). The types of seizures were: generalized tonic-clonic seizure [GTCS] (69.2%), focal motor with secondarily generalization [FMWSG] (19.9%) and simple focal motor (11%). The common causes of seizure were: cerebral toxoplasmosis (46%), tuberculous meningitis (35.6%) and cryptococcal meningitis (13.7%). Case-fatality was 53% and predictors of mortality were: seizure started after admission, change in mentation and comatose at initial evaluation.

CONCLUSIONS

Most patients had stage 4 HIV infection with very low CD4 count and a recent onset seizure which started within 3 months at initial evaluation. GTCS was the commonest seizure type and most causes of seizure were central nervous system opportunistic infections. The case-fatality was high and change in sensorium was an independent predictor of mortality. To prevent the high mortality and morbidity prevention of HIV infection, early diagnosis and treatment, improving diagnostic facilities and access to non-enzyme inducing antiepileptic drugs are recommended.

Neurological disorders in HIV in Africa: a review

BACKGROUND

Neurological disorders in HIV infection are a common cause of morbidity and mortality. The aim of this paper is to provide a narrative overview of up to date information concerning neurological disorders affecting HIV infected persons in Africa.

METHODS

Seminal research concerning neurological disorders among HIV-infected adults in sub-Saharan Africa from prior to 2000 was combined with an in-depth search of PubMed to identify literature published from 2000 to 2017. The following Mesh terms were used. "Nervous System Diseases" "HIV Infections" and "Africa South of the Sahara" and "Seizures" or "Spinal Cord Diseases" or "Peripheral Nervous System Diseases" or "AIDS Dementia Complex" or "Opportunistic Infections" or "Immune Reconstitution Inflammatory Syndrome" or "Stroke". Only those articles written in English were used. A total of 352 articles were identified, selected and reviewed and 180 were included in the study. These included case series, observational studies, interventional studies, guidelines and reviews with metanalyses. The author also included 15 publications on the subject covering the earlier phase of the HIV epidemic in Africa from 1987 to 1999 making a total of 195 references in the study. This was combined with extensive personal experience diagnosing and treating these neurological disorders.

RESULTS

Neurological disorders were common, typically occurring in WHO stages III/IV. These were in three main categories: those arising from opportunistic processes mostly infections, direct HIV infection and autoimmunity. The most common were those arising from direct HIV infection occurring in >50%. These included HIV-associated neurocognitive dysfunction (HAND), neuropathy and myelopathy. Opportunistic infections occurred in >20% and frequently had a 6-9-month mortality rate of 60-70%. The main causes were cryptococcus, tuberculosis, toxoplasmosis and acute bacterial meningitis. Concurrent systemic tuberculosis occurred in almost 50%.

CONCLUSION

Neurological disorders are common in HIV in Africa and the main CNS opportunistic infections result in high mortality rates. Strategies aimed at reducing their high burden, morbidity and mortality include early HIV diagnosis and anti-retroviral therapy (ART), screening and chemoprophylaxis of main opportunistic infections, improved clinical diagnosis and management and programme strengthening.

Neurological disorders in a consultant hospital in Northern Tanzania. A cohort study

OBJECTIVES

To determine the sociodemographic characteristics, clinical findings and outcome by HIV status in a series of adult patients presenting with neurological disorders (NDs) and admitted to a consultant hospital in Northern Tanzania.

METHODS

A cohort study took place over a 6-month period from Oct 2007 to March 2008 and included all adult patients with a neurological disorder admitted to the medical wards.

RESULTS

A total of 1790 patients were admitted during this period, of whom 337 (18.8%) were diagnosed with a neurological disorder and formed the study group. Of these 337, 69 (20.5%) were HIV-positive. Among the 69 HIV positives, 25% were previously known to be HIV seropositive of whom 82% were on antiretroviral (ARV) medication. Seropositive patients were more likely than seronegative patients to be younger, better educated, have a business occupation, present clinically with confusion, headache and aphasia and have meningitis/CNS infection or a space occupying lesion. Seropositive patients were more likely to present with a Glasgow Coma Score (GCS) of 9-12/15 (33.3% v 17.2%). Seropositive patients had a median CD4 T-lymphocyte count of 47cells/L and were more likely to be anaemic and have an elevated ESR. CT of the head was carried out on 132/337 (39%) patients. The overall findings were infarction 37%, hemorrhage 19%, tumors 15% and abscesses 9%. Brain abscess was more likely in seropositive patients and hemorrhage in seronegatives. The outcome at discharge for all patients was: death 27.6%, disability 54% and no disability 18.4% with death (39.1%) being more likely in seropositive patients. Patients presenting with coma (GCS <9/15) were more likely to die whilst those with stroke, para/quadriplegia and space occupying lesions (SOLs) were more likely to be discharged with disability. Case fatality rate was highest for tetanus 71.4%, meningitis 57.1%, cerebral malaria 42.9% and CNS infections 37.1%. Seropositive patients presenting with meningitis and other CNS infections were more likely to die than seronegatives.

CONCLUSION

This study reports NDs occurring in one fifth of adult medical admissions with stroke and infections as the leading causes. The prevalence of HIV infection in NDs was 20%. The HIV positive cohort was characterized by advanced immunosuppression, CNS infections and high mortality.

Neurosyphilis in Africa: A systematic review

Introduction

Neurological involvement is one of the most important clinical manifestations of syphilis and neurological disease occurs in both early and late syphilis. The impact of HIV co-infection on clinical neurosyphilis remains unclear. The highest prevalence of both syphilis and HIV is in Africa. Therefore it might be expected that neurosyphilis would be an important and not uncommon manifestation of syphilis in Africa and frequently occur in association with HIV co-infection; yet few data are available on neurosyphilis in Africa. The aim of this study is to review data on neurosyphilis in Africa since the onset of the HIV epidemic.

Methods

We searched the literature for references on neurosyphilis in Africa for studies published between the 1^st of January 1990 and 15^th February 2017. We included case reports, case series, and retrospective and prospective cohort and case-control studies. We did not limit inclusion based on the diagnostic criteria used for neurosyphilis. For retrospective and prospective cohorts, we calculated the proportion of study participants who were diagnosed with neurosyphilis according to the individual study criteria. Depending on the study, we assessed the proportion of patients with syphilis found to have neurosyphilis, and the proportion of patients with neurological syndromes who had neurosyphilis. Due to heterogeneity of data no formal pooling of the data or meta-analysis was undertaken.

Results

Amongst patients presenting with a neurological syndrome, three studies of patients with meningitis were identified; neurosyphilis was consistently reported to cause approximately 3% of all cases. Three studies on stroke reported mixed findings but were limited due to the small number of patients undergoing CSF examination, whilst neurosyphilis continued to be reported as a common cause of dementia in studies from North Africa. Ten studies reported on cases of neurosyphilis amongst patients known to have syphilis. Studies from both North and Southern Africa continue to report cases of late stage syphilis, including tabes dorsalis and neurosyphilis, in association with ocular disease.

Discussion

This is the first systematic review of the literature on neurosyphilis in Africa since the beginning of the HIV epidemic. Neurosyphilis continues to be reported as a manifestation of both early and late syphilis, but the methodological quality of the majority of the included studies was poor. Future well-designed prospective studies are needed to better delineate the incidence and clinical spectrum of neurosyphilis in Africa and to better define interactions with HIV in this setting.

Involvement of the central nervous system is an important manifestation of syphilis which may be more common in patients co-infected with HIV. As most cases of syphilis and HIV are seen in Africa it might be anticipated that neurosyphilis was common there. We reviewed all published material on neurosyphilis in Africa since 1990. There were few well designed studies of neurosyphilis. A small number of studies suggested that syphilis remains a cause of meningitis in Africa. Our data suggest that neuosyphilis remains an important disease in Africa but better prospective studies are needed to understand its epidemiology.

Acute EEG findings in HIV-infected Zambian adults with new-onset seizure

OBJECTIVE

To describe acute EEG findings in HIV-infected adults with new-onset seizure, assess baseline clinical characteristics associated with EEG abnormalities, and evaluate the relationship between EEG abnormalities and recurrent seizure.

METHODS

Eighty-one HIV-infected adults with new-onset seizure had EEG recordings during their index admission. Baseline characteristics assessed included HIV stage, seizure semiology, serum and CSF studies, neuroimaging, cognitive function based on the Zambian Mini-Mental State Examination and International HIV Dementia Scale, and psychiatric symptoms using the Shona Symptom Questionnaire. We evaluated the relationship between baseline characteristics and EEG abnormalities. Patients were followed for seizure recurrence, and the association between acute EEG abnormalities and seizure recurrence was assessed. Death was a secondary outcome.

RESULTS

Fifty-five patients had abnormal EEGs (68%): 18 (22%) had interictal spikes (12) or a recorded seizure (6). Among baseline clinical characteristics, more advanced HIV disease (p = 0.039) and any imaging abnormality (p = 0.027) were associated with abnormal EEGs. Cortical (p = 0.008) and white matter (p = 0.004) abnormalities were associated with slow posterior dominant rhythm. Patients were followed for a median of 303 days (interquartile range 103-560). Twenty-four (30%) died and 23 (28%) had recurrent seizures. EEG abnormalities were not associated with recurrent seizure. There was a nonsignificant association between seizures recorded during EEG and death (67% vs 26%, p = 0.051).

CONCLUSIONS

EEG abnormalities are common in this population, particularly in patients with imaging abnormalities and advanced HIV. Acute EEG abnormalities were not associated with recurrent seizure, but high mortality rates during follow-up limited this analysis.

The relationship between HIV and prevalence of disabilities in sub-Saharan Africa: systematic review (FA)

OBJECTIVE

To systematically review evidence on the prevalence and risk of disabilities among children and adults living with HIV in sub-Saharan Africa.

METHODS

Articles were identified from 1980 to June 2013 through searching seven electronic databases. Epidemiological studies conducted in sub-Saharan Africa that explored the association between HIV status and general disability or specific impairments, with or without an HIV-uninfected comparison group, were eligible for inclusion.

RESULTS

Of 12 867 records initially identified, 61 papers were deemed eligible for inclusion. The prevalence of disability was high across age groups, impairment types and study locations. Furthermore, 73% of studies using an HIV- comparator found significantly lower levels of functioning in people living with HIV (PLHIV). By disability type, the results were as follows: (i) for studies measuring physical impairments (n = 14), median prevalence of limitations in mobility and motor function among PLHIV was 25.0% (95% CI: 21.8-28.2%). Five of eight comparator studies found significantly reduced functioning among PLHIV; for arthritis, two of three studies which used an HIV- comparison group found significantly increased prevalence among PLHIV; (ii) for sensory impairment studies (n = 17), median prevalence of visual impairment was 11.2% (95%CI: 9.5-13.1%) and hearing impairment was 24.1% (95%CI: 19.2-29.0%) in PLHIV. Significantly increased prevalence among PLHIV was found in one of four (vision) and three of three studies (hearing) with comparators; (iii) for cognitive impairment in adults (n = 30), median prevalence for dementia was 25.3% (95% CI: 22.0-28.6%) and 40.9% (95% CI: 37.7-44.1%) for general cognitive impairment. Across all types of cognitive impairment, twelve of fourteen studies found a significant detrimental effect of HIV infection; (iv) for developmental delay in children with HIV (n = 20), median prevalence of motor delay was 67.7% (95% CI: 62.2-73.2%). All nine studies that included a comparator found a significant difference between PLHIV and controls; for cognitive development and global delay, a significant detrimental effect of HIV was found in five of six and one of two studies, respectively. In the nine cohort studies comparing vertically infected and uninfected children, eight showed a significant gap in development over time in children with HIV. Finally, fifteen of thirty-one (48%) studies found a statistically significant dose-response relationship between indicators of disease progression (CD4 or WHO stage) and disability.

CONCLUSIONS

HIV is widespread in sub-Saharan Africa and the evidence suggests that it is linked to disabilities, affecting a range of body structures and functions. More research is needed to better understand the implications of HIV-related disability for individuals, their families as well as those working in the fields of disability and HIV so that appropriate interventions can be developed.

Epidemiology of neurodegenerative diseases in sub-Saharan Africa: a systematic review

BACKGROUND

Sub-Saharan African (SSA) countries are experiencing rapid transitions with increased life expectancy. As a result the burden of age-related conditions such as neurodegenerative diseases might be increasing. We conducted a systematic review of published studies on common neurodegenerative diseases, and HIV-related neurocognitive impairment in SSA, in order to identify research gaps and inform prevention and control solutions.

METHODS

We searched MEDLINE via PubMed, 'Banque de Données de Santé Publique' and the database of the 'Institut d'Epidemiologie Neurologique et de Neurologie Tropicale' from inception to February 2013 for published original studies from SSA on neurodegenerative diseases and HIV-related neurocognitive impairment. Screening and data extraction were conducted by two investigators. Bibliographies and citations of eligible studies were investigated.

RESULTS

In all 144 publications reporting on dementia (n = 49 publications, mainly Alzheimer disease), Parkinsonism (PD, n = 20), HIV-related neurocognitive impairment (n = 47), Huntington disease (HD, n = 19), amyotrophic lateral sclerosis (ALS, n = 15), cerebellar degeneration (n = 4) and Lewy body dementia (n = 1). Of these studies, largely based on prevalent cases from retrospective data on urban populations, half originated from Nigeria and South Africa. The prevalence of dementia (Alzheimer disease) varied between <1% and 10.1% (0.7% and 5.6%) in population-based studies and from <1% to 47.8% in hospital-based studies. Incidence of dementia (Alzheimer disease) ranged from 8.7 to 21.8/1000/year (9.5 to 11.1), and major risk factors were advanced age and female sex. HIV-related neurocognitive impairment's prevalence (all from hospital-based studies) ranged from <1% to 80%. Population-based prevalence of PD and ALS varied from 10 to 235/100,000, and from 5 to 15/100,000 respectively while that for Huntington disease was 3.5/100,000. Equivalent figures for hospital based studies were the following: PD (0.41 to 7.2%), ALS (0.2 to 8.0/1000), and HD (0.2/100,000 to 46.0/100,000).

CONCLUSIONS

The body of literature on neurodegenerative disorders in SSA is large with regard to dementia and HIV-related neurocognitive disorders but limited for other neurodegenerative disorders. Shortcomings include few population-based studies, heterogeneous diagnostic criteria and uneven representation of countries on the continent. There are important knowledge gaps that need urgent action, in order to prepare the sub-continent for the anticipated local surge in neurodegenerative diseases.

Viral and cellular factors underlying neuropathogenesis in HIV associated neurocognitive disorders (HAND)

As the HIV-1 epidemic enters its fourth decade, HIV-1 associated neurological disorders (HAND) continue to be a major concern in the infected population, despite the widespread use of anti-retroviral therapy. Advancing age and increased life expectancy of the HIV-1 infected population have been shown to increase the risk of cognitive dysfunction. Over the past 10 years, there has been a significant progress in our understanding of the mechanisms and the risk factors involved in the development of HAND. Key events that lead up to neuronal damage in HIV-1 infected individuals can be categorized based on the interaction of HIV-1 with the various cell types, including but not limited to macrophages, brain endothelial cells, microglia, astrocytes and the neurons. This review attempts to decipher these interactions, beginning with HIV-1 infection of macrophages and ultimately resulting in the release of neurotoxic viral and host products. These include: interaction with endothelial cells, resulting in the impairment of the blood brain barrier; interaction with the astrocytes, leading to metabolic and neurotransmitter imbalance; interactions with resident immune cells in the brain, leading to release of toxic cytokines and chemokines. We also review the mechanisms underlying neuronal damage caused by the factors mentioned above. We have attempted to bring together recent findings in these areas to help appreciate the viral and host factors that bring about neurological dysfunction. In addition, we review host factors and viral genotypic differences that affect phenotypic pathological outcomes, as well as recent advances in treatment options to specifically address the neurotoxic mechanisms in play.

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.

Neurocognitive impairment in HIV-1-infected adults in Sub-Saharan Africa: a systematic review and meta-analysis

OBJECTIVE

To estimate the burden of HIV neurocognitive impairment (NCI) among adult patients on and off antiretroviral therapy (ART) in Sub-Saharan Africa.

METHODS

Estimates were derived from a random effects meta-analysis of prospective studies reporting HIV status, utilization of ART, and the presence of NCI determined using the International HIV Dementia Scale.

RESULTS

Sixteen studies with quality data from seven countries in Sub-Saharan Africa up to June 2012 were included. Among HIV patients, the frequency of NCI pre-ART was 42.37% (95% confidence interval (CI) 32.18-52.56%), and among those on ART for ≥6 months was 30.39% (95% CI 13.17-47.61%). Respective NCI estimates in studies from Uganda were 46.49% (95% CI 30.62-62.37%) and 28.50% (95% CI -1.31-58.30%). NCI was more common among patients with a concomitant psychiatric ailment. HIV-positive patients compared to HIV-negative controls were predisposed to NCI (odds ratio (OR) 6.49, 95% CI 1.68-25.08); the estimated unadjusted attributable risk of HIV infection leading to NCI was 85%. Meta-regression showed no associations between age, gender, CD4 cell counts, or years of education with NCI. Patients on ART were less likely to have NCI compared to HIV-infected pre-ART patients, with OR 0.36 (95% CI 0.19-0.69). In longitudinal studies with the same patients followed before and at ≥6 months after ART, the OR of NCI after ART compared to pre-ART was 0.23 (95% CI 0.14-0.37). The combined burden of NCI among pre-ART and on-ART patients in Sub-Saharan Africa was estimated at 8,121,910 (95% CI 5,772,140-10,471,680). No publication bias was observed, although residual confounding from differing environmental factors, stages of HIV infection, and viral clades might be a limitation.

CONCLUSIONS

HIV strongly predisposes to NCI leading to a huge burden in Sub-Saharan Africa, and scale-up of ART can substantially reduce it.

Non-traumatic myelopathy at the Chris Hani Baragwanath Hospital, South Africa--the influence of HIV

BACKGROUND

Non-traumatic myelopathy from developing regions has been described widely. In these regions infections, mainly tuberculosis, followed by acute transverse myelitis and neoplasms, dominate. These are also regions of high HIV prevalence. In developed regions, the most prominent reported spinal cord disease in HIV/AIDS is vacuolar myelopathy (VM). Other myelopathy causes in HIV/AIDS include opportunistic infections, neoplasms, vascular lesions and metabolic disease. In developing regions, opportunistic infections are more commonly encountered with VM occurring less frequently.

AIM

To determine the influence of HIV on the myelopathy spectrum in an HIV endemic region.

DESIGN

Prospective case series.

METHODS

Hundred unselected consecutive in-patients admitted with myelopathy were studied. Myelopathy aetiologies were established by collating information obtained from magnetic resonance imaging (MRI) scans, CSF and blood studies, CXR findings, non-neurological illness and response to treatment. Data were analysed in terms of two cohorts, HIV positive and HIV negative.

RESULTS

Approximately 50% of the patients presenting and admitted to our hospital with non-traumatic myelopathy are HIV positive. The HIV positive myelopathy patients were younger (20-40 years) and had infectious aetiologies. Tuberculosis was the most frequently identified cause of myelopathy. The majority of HIV-positive patients had advanced HIV infection. Anti-retroviral treatment did not influence myelopathy aetiologies. The HIV-negative patients were older and had neoplasms, followed by degenerative spondylosis as the main myelopathy causes.

CONCLUSION

HIV influences the non-traumatic myelopathy spectrum in regions with high HIV prevalence. Empiric treatment of HIV-myelopathy patients with anti-tuberculous medications where resources are severely limited has merit.

HIV-related neurocognitive impairment--a review

Neurocognitive impairments following central nervous system opportunistic infections and HIV-associated dementia (HAD) were common clinical features of HIV infection prior to anti-retroviral therapy. As HIV infection has evolved from an invariably fatal disease with a poor prognosis to a condition requiring long-term management, HIV-related neurocognitive disorders have been the subject of increasing research. This review will examine the recent changes in the understanding of the HIV-associated neurocognitive disorders (HAND) including the changing epidemiology, risk factors associated with its development, methods for screening for the disorders and evolving treatment options.

Host and viral factors influencing the pathogenesis of HIV-associated neurocognitive disorders

The human immunodeficiency virus (HIV) invades the central nervous system early in the course of infection and establishes a protected viral reservoir. However, neurocognitive consequences of HIV infection, known collectively as HIV-associated neurocognitive disorders (HAND), develop in only a small portion of infected patients. The precise mechanisms of pathogenesis involved in HIV-induced central nervous system injury are still not completely understood. In particular, most theories of HAND pathogenesis cannot account for either the selective vulnerability of specific neuronal populations to HIV-induced neurodegeneration or why only a subset of patients develop clinically detectable nervous system disease. Epidemiological and virological studies have identified a variety of host and viral factors that are associated with increased risk of developing HAND. Some host factors that predispose HIV-infected patients to HAND overlap with those associated with Alzheimer's disease (AD), suggesting the possibility that common pathogenic mechanisms may participate in both diseases. Here, we will review reports of host and viral factors associated with HAND and place these studies in the context of the data employed to support current theories regarding the molecular and cellular mechanisms that lead to HIV-induced neurodegeneration with additional focus on mechanisms common to AD pathogenesis.