| Study || N || Toxo || Crypto || Primary CNS Lymphoma || PML || TB || Bacterial|
| Lucas et al., 1993 (Abidjan) || 247 || 15% || 3% || 1% || 1% || 8% || 5%|
| Lanjewar et al., 1998 (India) || 85 || 13% || 8% || — || — || 12% || —|
| Kibayashi et al., 1999 (Tanzania) || 10 || — || 10% || — || — || 10% || 10%|
| Rana et al., 2000 (Kenya) || 75 || 3% || 5% || 1% || — || 11% || 5%|
| Rosemberg et al., 1986 (RJ, Brazil) || 22 || 18% || 14% || 9% || 1% || — || —|
| Michalany et al., 1987 (SP, Brazil) || 15 || 40% || 27% || 7% || — || 1% || 1%|
| Chimelli et al., 1992 (RJ, Brazil) || 252 || 34% || 14% || 4% || || 1% || 2%|
| Wainstein et al., 1992 (PA, Brazil) || 138 || 21% || 12% || 2% || — || 1% || 1%|
| Cury et al., 2003 (SP, Brazil) || 92 || 10% || 3% || — || — || 1% || 5%|
| Eza et al., 2006 (Lima, Peru) || 16 || 13% || 6% || — || — || — || —|
In most of the pathologic studies from developing countries, “you can see the low proportion of cases of primary CNS lymphoma and… the relatively high percentage of CNS tuberculosis (TB) and bacterial infections [while in] studies from South America (most of them from Brazil) there is a predominance of toxoplasmosis and cryptococcosis and a few cases of primary CNS lymphoma.
In contrast, few studies from South America reported much CNS TB or bacterial infections,” said Dr Vidal, although a couple of recent studies in Brazil since the introduction of ART are now reporting more CNS TB.
Meanwhile, in India, according to Dr Manisha Ghate, Assistant Director of the National AIDS Research Institute in Pune, autopsy studies show a high rate of CNS lesions (79%, 38% of which were due to opportunistic infections). In cross-sectional studies from Southern and Western India, Cryptococcal meningitis, CNS TB meningitis and toxoplasmosis are also the most common opportunistic infections seen in people with HIV.
Finally, preliminary results from the inpatient substudy of the Asia Pacific NeuroAIDS Consortium Study (APNAC), conducted at eight sites throughout the region and presented by Dr Edwina Wright of the Alfred Hospital in Melbourne Australia, diagnosed a high rate (43%) of neurological disorders among 160 people with HIV who checked into one of the study sites.
These patients had very advanced disease (median CD4 cell count of 18 in 51 tested) and about a third were already on ART. Nonetheless, the most common diagnoses were cryptococcal meningitis (29%), cerebral toxoplasmosis (28%), TB meningitis (14%), seizures (7%), aseptic/bacterial meningitis (6%) and the remainder were strokes, spinal TB, tuberculomas and other conditions.
Prof. Hakim and other presenters later in the meeting highlighted the importance of strokes in the young (between 15 to 45 years of age) though the causes of stroke could vary by region. Investigations in Africa, suggest that in the context of HIV, most of these strokes appear to be linked to infective conditions such as cryptococcol disease or TB.
In one of these Indian studies that Dr Ghate described, a high number of strokes were attributed directly to HIV. Meanwhile, studies in the developed world suggest that HIV infection itself may cause subclinical atherosclerosis that increases the risk of stroke and cerebrovascular disease.
But the incidence of some infections also can vary greatly from one country to the next even within the same region. “People talk about the developing world or of Sub-Saharan Africa as if it were homogenous. Far from it,” said Prof. Hakim. For example, he noted that toxoplasmosis is a major problem in India, Asia and Brazil, and even nearby in South Africa.
But, “interestingly, in our own environment in Zimbabwe we’ve specifically looked for it and we’ve seen exceedingly few cases,” he said. “What is interesting is that some 40 or 50 years ago, there were surveys that were done by veterinarians and medical laboratory scientists in Zimbabwe, and the serological tests at that time showed that the prevalence of serological positive sera from both animals and patients was up to 30%, but currently we seem to see a lot less and I would really value any discussion on that.”
According to Dr Rezza, some factors probably do have a real effect upon the patterns of CNS disease such as differences in the circulation of specific infectious agents like Chagas disease and HTLV-1 and 2 that are common in South America but not elsewhere. Indeed, Dr Vidal and speakers from Brazil highlighted the growing importance of these emerging diseases in their region. Major epidemic coinfections such as hepatitis C virus — which data now suggest can also affect the brain — and malaria could also have an impact on neurologic disorders in people coinfected with HIV.
The case of malaria may provide one possible explanation for the low rates of toxoplasmosis seen in some of the malarial countries in Africa, since several of the drugs in widespread use to treat or prevent malaria, such as cotrimoxazole and Fansidar can also prevent toxoplasmosis.
The risk of CNS disorders could also differ according to whether a country’s HIV epidemic is generalised or limited to certain vulnerable groups. For example, Dr Rezza shared data from the Italian National AIDS Registry that suggested injection drug users (IDUs) were 50% more likely to present with HIV encephalopathy than non-IDUs. Interestingly, in some of the cross-sectional studies in India, where most of the early transmission of HIV in India was through injection drug use, there are very high rates of peripheral neuropathy, cranial neuropathies and stroke attributed to HIV — which suggests a greater likelihood of neurological problems among this population.