Although acquired immune deficiency syndrome is not typically considered a brain disorder, the human immunodeficiency virus (HIV) that cripples immune cells also damages neurons; about 40 percent of patients show neurological impairments ranging from balance problems to dementia.
Reporting in the Oct. 10-14 online edition of the Proceedings of the National Academy of Sciences, neurology professor Paul Thompson and colleagues at the University of California, Los Angeles, have shown brain tissue loss corresponding to these symptoms. Using three-dimensional "maps" generated from magnetic resonance imaging (MRI) scans, the researchers studied the cortex-the brain's outer covering-at a level of detail not possible with conventional MRI.
Areas of the cortex involved with motor coordination, language, and planning and reasoning were thinner than normal by as much as 15 percent. Patients taking antiviral "cocktails" showed as much tissue loss as those who were not, indicating that current therapies, while protecting the immune system, are powerless against the neurological phase of the disease.
Thompson explains that most drugs cannot follow the virus into the brain, making the brain "a reservoir where HIV can multiply and attack cells unchecked." Ironically the drugs, in extending life expectancy by 20 to 30 years, help patients live long enough to develop cognitive impairment.
"Newer drugs are aimed at protecting the brain as well," says Thompson. "Our mapping technique may be helpful in clinical trials that measure their success."