Clinicians Need Localized Proton MRS of the Brain in the Management of HIV-Related Encephaiopathies

The neurological complications of AIDS (neuro AIDS) represent the principal cause of disability and death in HIV-patients (Gray et al., 1993; McArthur, et al., 1993). Several types of lesions affect the brain tissue: direct infection of the nervous tissue by HIV, opportunistic infections (such as toxoplasmosis, cytomegalovirus encephalitis, tuberculosis, progressive rnultifocal encephalopathy....), and lymphomas. The AIDS-related dementia complex (ADC) affects about 60% of patients in the late stage of AIDS. ADC is characterized by the occurrence of sub-cortical dementia with cognitive, behavioral, and motor decline, psychomotor slowing and apathy. ADC is related to the presence of a diffuse encephalopathy leading to a cortical and sub-cortical atrophy, as well as diffuse white-matter lesions. There is a distinct advantage in diagnosing as early as possible the neurological complications (e.g. encephalopathy) of AIDS, since early treatment can improve significantly the quality of life in patients by slowing down or even stopping the neurological and psychological degradation. Neuroimaging techniques, and mainly magnetic resonance imaging (MRI), constitute so far the best diagnostic tools of neuro-AIDS (Kent et al., 1993; Mundinger et al., 1992). In addition, localized magnetic resonance spectroscopy (MRS) of the brain provides a non-invasive exploration of intracerebral metabolism in vivo, and can be performed following a standard MRI examination [for a review see Vion-Dury et al. (1994)]. Several key molecules of brain metabolism can be detected, including N-acetyl-aspartic acid which is thought to be a neuronal marker, choline-containing molecules (involved in phospholipid metabolism), glutamate, glutamine, inositol, phosphocreatine and creatine, and lactate. Recently, significant modifications in the concentration of brain metabolites detected by phosphorus and proton MRS have been described in patients with ADC (Bottomley et al., 1992; Deicken et al., 1991; Menon et al., 1992; Chong et al., 1993; Meyerhoff et al., 1993; Confort-Gouny et al., 1993). In a preliminary study, we have observed that even, if MR images are normal (without atrophy, focal or diffuse lesions) or if the patients are neuroasymptomatic, the values of metabolic parameters measured by MRS are often modified (Vion-Dury et al., 1994).