T gondii IgG. Causes of false-negative results include recent infection and insensitive assays. Lumbar puncture may be contraindicated because of increased intracranial pressure. Lesions may enhance in a homogeneous or ring pattern with contrast. Imaging studies may be normal in diffuse toxoplasmosis. MRI is more sensitive than CT scan in detecting multiple lesions.
Single lesions favor the diagnosis of lymphoma over that of toxoplasmosis.
Diagnostic yield of stereotactic biopsies increases with the number of specimens obtained. A brain CT scan or MRI with and without contrast is indicated for all patients presenting with altered mental status, headaches, seizures, or focal neurological signs. MRI clearly is the superior technique but is not available universally. If imaging shows 1 or more focal mass lesions with impending herniation, an open biopsy with decompression is indicated. Treatment for lymphoma, toxoplasmosis, or other opportunistic infections and neoplasms is initiated, depending on biopsy results.