Differentiating Cerebral Toxoplasmosis and Tumor Recurrence by Thallium-201 Single-Photon Emission Computerized Tomography in a 28-Year-Old Female with Astrocytoma

Abstract

Cerebral toxoplasmosis is an opportunistic infection that, by itself, is difficult to differentiate from cerebral neoplasms by conventional neuroimaging. It rarely occurs concurrently in patients with a primary brain tumor but when it does, it makes diagnosis and management more difficult. This is a case of a 28-year-old female, diagnosed with a right frontal pleomorphic xanthoastrocytoma with several recurrences, treated with surgery, radiation, and chemotherapy. Three years from diagnosis, the patient was readmitted for generalized body weakness, fever, and a decrease in sensorium. A repeat cranial magnetic resonance imaging showed multiple enhancing lesions in both cerebral hemispheres and in the posterior fossa. Serum toxoplasma IgM and IgG antibody titers were elevated. Single-photon emission computerized tomography (SPECT) with thallium-201 did not show increased tracer uptake in these lesions, favoring toxoplasmosis over tumor recurrence. The patient was treated with trimethoprim-sulfamethoxazole with significant improvement. This is a rare account of cerebral toxoplasmosis arising in the setting of astrocytoma. This is also the first case report to demonstrate the value of thallium-201 SPECT in differentiating central nervous system infection from tumor recurrence, which is pivotal in management. More studies exploring the use of thallium-201 SPECT in distinguishing central nervous system infections from glioma and other malignant tumors should be undertaken to maximize this imaging modality in neuro-oncology practice.