Spect and Transcranial Doppler Sonography for the Assessment of Cerebral Perfusion in Intravenous Drug Users with AIDS Encephalopathy

Abstract

Infection with human immunodeficiency virus type 1 (HIV-1) can lead to a variety of central nervous system (CNS) manifestations [5]. AIDS encephalopathy (AE), considered as a primary HIV-1-induced CNS affection, has been recognized as the most common cause of neurological dysfunction [12]. The diagnosis of AE is mainly based on neuropsychiatric features. Computerized tomography (CT), magnetic resonance imaging (MRI), and cerebrospinal fluid analysis are useful for ruling out other manifestations and for supporting the diagnosis of AE. More sensitively than CT and MRI, functional imaging methods like positron emission tomography (PET) and single photon emission computed tomography (SPECT) show pathological changes even in early stages of the disease [3,6,10,11,13,15]. The pathogenesis of AE has not been clearly defined. Besides mechanisms like neuropathological changes following infection of monocytes/macrophages and related microglia, alterations of regional cerebral blood flow (rCBF) can be considered as an additional pathogenetic factor. This suggestion is supported by a series of recent findings:

• microvascular changes of small brain vessels [2,8,14];

• microscopically noted cerebral infarcts [4,8];

• presence of HIV-1 antigens in brain endothelial cells [16];

• perivascular localization and occasional vasculitic appearance of HIV-1-related ultifocal giant cell encephalitis [1];

• interference of HIV-1 envelope proteins with physiological regulation mechanisms of rCBF [9];

• previous SPECT studies demonstrating focal or multifocal reduction of rCBF in almost all of the patients with AE [3,6,10,11,15].