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THE NEUROLOGY OF HIV INFECTION

Since the onset of the AIDS pandemic in 1981, infection with the human immunodeficiency virus (HIV) has spread exponentially throughout the world with currently an estimated 40 million adults and children affected. Worldwide there are approximately 16 000 new infections per day. Every day 8000 HIV infected patients die. In the UK, there are currently about 50 000 individuals living with HIV/AIDS.

Since the introduction of highly active anti-retroviral therapy (HAART), in communities where this is available, HIV/AIDS has become a chronic disorder with dramatic reductions in mortality and morbidity both from the effects of HIV itself as well as from opportunistic infections and tumours.

In the UK, the clinician will encounter two broad groups of patients. The first group comprises individuals who have been infected with HIV for a number of years and are receiving HAART. This group is composed largely of homosexual men and those who acquired their infection in the UK. The second group consists of patients who present with opportunistic infections and tumours and who have late stage HIV infection. This is a situation that was previously encountered in the late 1980s and early 1990s. This cohort largely consists of men and women infected by heterosexual intercourse outside Europe.

HIV is neuro-invasive (with invasion occurring early in the course of the infection), neuro-virulent (causing a neuropathy, myopathy, myelopathy, and dementia), but it is not especially neurotrophic. The virus is rarely isolated from neurones either in the peripheral or central nervous system. Productive infection is usually found within the associated inflammatory infiltrate, predominantly macrophages.

Since all areas of the neuro-axis in an HIV infected individual may be affected by different aetiological agents, the clinical assessment of this group of patients may be more complex than assessment of the immune competent patient—the principle of “Ocam’s Razor” may not …