Cerebral toxoplasmosis

  • Toxoplasma gondii – intracellular protozoan.  Infects humans via cat feces, ingestion of raw or undercooked meat, shellfish, unwashed fruits and vegetables
  • Healthy patients – asymptomatic, becomes latent in neuroparenchyma
  • Latent infection reactivated when immunocompromised, like HIV when CD4 count drops bellow 100 cells per cu.mm. 
  • Pyrimethamine-sulfadiazine and folic acid reduces size of lesions within a fortnight
Imaging
  • Ring-enhancing abscesses centered in basal ganglia, thalamus, along corticomedullary junction
  • Varying degrees of perilesional edema and mass effect
  • Nodular enhancement is seen, but sometimes absent in the immunocompromised
  • MRI: hypo on T1, hyper on T2/FLAIR. Target sign on T2 due to central hyper intensity (fluid), peripheral hypo (mural blood) and outer ring of bright perilesional edema 
Differential
  • Primary CNS lymphoma in immunocompromised: lymphomas show more diffusion restriction, much higher Thallium 201 SPECT and Fluorine 18 FDG uptake¬†
Read more

Camacho, Daniel LA, J. Keith Smith, and Mauricio Castillo. “Differentiation of toxoplasmosis and lymphoma in AIDS patients by using apparent diffusion coefficients.” American journal of neuroradiology 24.4 (2003): 633-637.

Chinn, R. J., et al. “Toxoplasmosis and primary central nervous system lymphoma in HIV infection: diagnosis with MR spectroscopy.” Radiology 197.3 (1995): 649-654.

Lee, Gregory Tse, Fernando Antelo, and Anton A. Mlikotic. “Cerebral toxoplasmosis.” Radiographics 29.4 (2009): 1200-1205.