Early Diagnostic Value of Contrast-Enhanced MRI in Distinguishing Toxoplasmic Encephalitis from CNS Lymphoma: A Case Report of AIDS with Seronegative Toxoplasmosis

Toxoplasmic encephalitis (TE) and primary central nervous system (CNS) lymphoma are the major differential diagnoses of ring-enhanced brain lesions in acquired immunodeficiency syndrome (AIDS). Biopsy may be difficult; thus, empirical anti-toxoplasma therapy is often initiated. We report an AIDS patient receiving chemotherapy for Kaposi's sarcoma who developed TE. Weekly gadolinium-enhanced magnetic resonance imaging (MRI) demonstrated diminishment of ring enhancement 7 days after treatment, preceding neurological improvement and lesion size reduction. This early radiological change, captured by rare weekly gadolinium-enhanced MRI, was useful for differentiating TE from lymphoma before neurological improvement.