The impact of HIV/AIDS on cognitive function is the topic of a paper appearing in STIs as early as 1989, where some degree of neurological impairment is observed in patients who otherwise appear ‘well’ (Carne & Harrison (STI)). Dementia may be rarely seen nowadays, but quality-of-life limiting cognitive impairment remains a serious issue for some HIV sufferers. Its impact on perinatally infected children has been reported (Chung & Herbert (STI)), while Levett & Wright (STI) discuss the management of elderly patients for whom HIV constitutes one among a number of potential causes of impaired cognitive function.
Curiously, the aetiology of this condition is not yet completely understood. Sandford & Collins in a yet to be published paper in Clinical Infectious Diseases report on a study investigating brain changes in 65 treated and untreated primary phase HIV-positive participants (<1 year) over the period from 2005 to 2011. Earlier studies have hypothesized that the neural damage occurs during the phase of primary infection. The researchers seek to establish this by using MRI to examine longitudinal trajectories of brain volume and cortical thickness, and to assess the impact of the introduction of cART. Of the 65 longitudinal participants, 34 had either recently begun cART (4) or did so in the course of the trial. Cross sectional data from a further 35 individuals – 16 chronically infected, 19 HIV negative – served as a control.
Participants with untreated primary infection showed reduction of brain volume at a median rate of 0.63% per year, and thinning of the cortex at median rate of 0.25mm per year. These rates need to be set against normal rates due to aging, which are 0.2% per year for brain volume and 0.01mm per year for cortical thinning. The researchers are inclined to attribute the higher rates seen in HIV positive participants in their study to inflammation, immune activation and suppression and blood brain barrier permeability. Without a longitudinal control group this cannot be established securely; but their results strongly suggest that, without cART, the levels of atrophy in participants would eventually have reached the levels seen in the chronically infected group. Fortunately, however, researchers also found that, with the introduction of cART, rates of deterioration returned to normal. There was even some slight cortical thickening in the front and temporal lobe with longer cART duration.
The results of this study offer a further argument in favour of the now standard – but once sometimes contested – policy of treating all HIV infected individuals with cART regardless of their CD4 count (Changes in the WHO Guidelines (STI/blog)). If disabling and potentially irrevocable changes take place in the primary phase of infection, but are interrupted by cART, then the promptest possible initiation becomes a matter of importance for the individual sufferer as well as for the potential victims of transmissions prevented by timely viral suppression.