[Diagnosis of diffuse encephalopathies in adults with HIV infection. I].

The diagnostic approach of focal central nervous system lesions in AIDS patients is now well established. In contrast, it is extremely difficult to determine the cause of diffuse encephalopathies, occurring frequently at the terminal stage of AIDS. Imaging is usually non specific and laboratory investigations are seldom contributive. In most cases, the aetiological diagnosis is provided by post mortem examination. In this first part of the study the authors deal with viral encephalitides which represent a classical and frequent cause of diffuse encephalopathy in AIDS. HIV encephalitis usually causes a progressive brain disease resulting in severe dementia; imaging may show diffuse leucoencephalopathy and/or cortico-subcortical atrophy. CMV encephalitis is often asymptomatic, discovered at autopsy; however, this diagnosis should be considered in patients with an encephalopathy of rapid onset, discrete signs of meningitis, symptoms of myelo-radiculitis, or a systemic CMV infection. Varicella-zoster virus encephalitis is not uncommon and may occur in the absence of characteristic rash. Infections by herpes simplex and measles viruses are exceptional.