Clinical Presentation

Most opportunistic CNS infections and neoplasms are associated with headache, fever, meningismus, altered level of consciousness or focal neurologic deficit. The presence of one or more of these symptoms should alert the medical care provider to the possibility of CNS disease. Clinical and radiologic features of a CNS lesion may distinguish between the various opportunistic infections and neoplasms (Table 36.1).

Reactivation of previously acquired infection is responsible for the majority of opportunistic CNS infections and neoplasms. In the USA, 10-40% of people with AIDS are latently infected with Toxoplasma gondii, as determined by presence of serum anti-toxoplasma immunoglobulin G (IgG) antibodies. In France, the seroprevalence of anti-toxo IgG in people with AIDS is 80%. One-third of people with serum anti-toxo IgG antibodies will develop TE. The absence of serum anti-toxo IgG or IgM antibodies does not exclude the diagnosis of TE, as 22% of people with biopsy-confirmed TE do not have IgG antibodies and immunoglobulin M (IgM) antibodies are rarely present [5]. The incidence of TE is reduced in people who take TMP/SMX or dapsone/pyrimethamine as prophylaxis against pneumocystis carinii pneumonia (PCP).

Cryptococcus neoformans is a ubiquitous yeast that causes meningitis in 7% of people with AIDS living in the USA and 30% of those living in Africa. Cryptococcal polysaccharide capsular antigen (CrAg) is detectable in 99% of serum samples and 91% of CSF samples of people with cryptococcal meningitis [6]. Thus, a negative serum CrAg virtually excludes the diagnosis of cryptococcal meningitis.

Reactivation of latent Epstein-Barr virus (EBV) infection is associated with PCNSL and can be detected by polymerase chain reaction (PCR) assay in CSF of up to 100% of patients with PCNSL [7]. Reactivation of latent JacobCreutzfeldt (JC) virus infection is associated with PML and can be detected in the CSF of 92%

of patients with PML [8]. The majority of people in the USA have serum antibodies against EBV and JC. Presence of antibodies against either EBV or JC in the serum is not associated with increased incidence of PCNSL or PML.

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