John R. Hesselink Terry L. Jernigan William C. Heindel University of California School of Medicine at San Diego, and San Diego Department of Veterans Affairs Medical Center
Central nervous system (CNS) involvement has been reported in 30% to 73% of patients with acquired immunodeficiency syndrome (AIDS), with up to 87% of cases demonstrating CNS pathology at autopsy ( Belman, Ultmann, & Horoupian , 1985; Levy, Bredesen, & Rosenbloom, 1985). Many of the neurologic complications are opportunistic infections, such as toxoplasmosis, cryptocococcus, and progressive multifocal leukoencephalopathy (PML), or lymphoma. However, the most common pathogen of the neuraxis appears to be the HIV virus itself ( Shaw G. M., Harper M. E., Hahn B. H., Epstein L. G., Gajdusek D. C. , & Price R. W., 1985), which can produce an aseptic meningitis, a subacute white matter encephalitis, and a vacuolar myelopathy. Imaging studies in HIV-infected individuals have revealed brain atrophy (dilated cortical sulci and ventricles), parenchymal mass lesions secondary to opportunistic infection or lymphoma, diffuse white matter abnormality related to subacute encephalitis, and focal white matter lesions of uncertain etiology ( Jarvik, et al., 1988; Post, et al., 1985).
Because pathologic tissue is not easily obtained and not always available in clinical patients, it is important to develop imaging techniques and elucidate criteria for diagnosing HIV infection of the brain and its associated opportunistic infections and neoplastic diseases. Magnetic resonance (MR) imaging offers several advantages over previous in vivo methods for visualizing the human brain. No ionizing radiation is used. This permits multiple examinations over the course of an illness, without known risk to the patient. Moreover, images can be acquired in the axial, coronal, and sagittal planes with identical spatial resolution. This may be helpful when a particular brain structure (e.g., hippocampus, cerebellum) is difficult to resolve in one plane but relatively easy to delimit and