A Sexually Active 23-Year-Old With Seizures and Tongue Pain

Manuel Salinas, MD


October 05, 2021

Many other conditions may mimic CNS toxoplasmosis, such as chronic meningitis (especially from fungi or syphilis), cytomegalovirus encephalitis, herpes simplex encephalitis, HIV encephalitis, primary CNS lymphoma, progressive multifocal leukoencephalopathy, and malignancy (brain metastases). In patients with focal neurologic abnormalities, the presence of cerebrovascular disease (stroke) may need to be ruled out.[1.2]

Although serologic data are essential for confirmation, such tests are not solely diagnostic because the antibody is present in relatively high numbers in many populations. Rising serum immunoglobulin G titers are usually observed, and an immunoglobulin M antibody response is seen in cases of newly acquired toxoplasmosis. Antibody levels may be unexpectedly low in patients with AIDS, even in the presence of active disease. Isolation of T gondii from blood or body fluids or identification of tachyzoites in tissue sections or smears of body fluids (such as cerebrospinal fluid) signify acute infection. Polymerase chain reaction (PCR) amplification for the detection of T gondii DNA may also be used to clearly establish acute infection.[2]

Imaging is essential in the diagnosis of CNS toxoplasmosis. CT scans may reveal single or multiple bilateral, hypodense lesions with possible mass effect. In 70%-80% of cases, the lesions enhance in a homogeneous or ring pattern with contrast. Diffuse toxoplasmosis may appear on images as either normal or with findings suggestive of HIV encephalitis.

MRI is more sensitive in disclosing multiple lesions. When a single lesion is found in a patient with AIDS and clinical manifestations of CNS involvement, primary lymphoma is more likely, but this does not rule out toxoplasmosis. Multiple lesions may be incorrectly interpreted as multiple metastases in patients without a known history of HIV infection, so HIV and CNS toxoplasmosis must be considered in individuals with these findings and HIV risk factors.

Ultimately, single-photon emission computed tomography (SPECT) may be useful in differentiating lymphoma from toxoplasmosis. Whenever the diagnosis is uncertain, a brain biopsy is advocated. This option most often arises in the setting of a single mass lesion with negative serologic results and no response to empiric therapy.[1,2]


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