THE RELATIONSHIP BETWEEN HIV AND THE CENTRAL NERVOUS SYSTEM

EFFECTS OF HIV ON THE CENTRAL NERVOUS SYSTEM: DEFINING THE ISSUES

A group of organic nervous system disorders may complicate the course of HIV infection and may result directly from HIV infection. HIV-associated conditions affecting both the central nervous system (CNS) and peripheral nervous system (PNS) are common and result in considerable morbidity and mortality. They can be classified in a number of ways. Many can be considered secondary complications of HIV infection, resulting from opportunistic infections or systemic organ dysfunction that follows from immune deficiency induced by HIV infection. Among the major CNS complications of AIDS are cerebral toxoplasmosis, primary CNS lymphoma (an opportunistic neoplasm associated with Blymphocyte infection by Epstein-Barr virus), cryptococcal meningitis, and progressive multifocal leukoencephalopathy (PML) caused by the JC virus (for reviews, see Brew et al., 1988; Johnson, 1994; Koppel, 1992; Price, 1994; Price and Worley, 1994; Snider et al., 1983).

Other conditions likely relate more directly to HIV infection itself, rather than to an additional opportunistic infection or systemic organ dysfunction. These can be considered primary nervous system complications of HIV. While their pathogenesis is not yet clearly understood, they are thought to be sequelae of interactions among HIV, the immune system, and various components of the nervous system. These include some unusual disorders complicating the early phases of HIV infection as well as common conditions occurring later. In the earliest phase of infection, a number of syndromes have been described, including mild meningitis with headache. However, while these syndromes are usually absent or mild, it is likely that in the course of spreading throughout the lymphatic system, HIV also reaches the brain at this time within infected lymphocytes, but without causing any clinical symptoms or signs.

Later in the course of systemic HIV infection, patients may develop so-called ''aseptic" meningitis that presumably is caused by HIV infection of the membranes surrounding the brain. They also may experience a peripheral neuropathy causing pain in the feet. However, of particular relevance to the issues of this report, HIV-infected persons also are susceptible late in the course of



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