Objective:

To describe a case of cerebral toxoplasmosis presenting with diffusion restriction on MRI, an atypical finding that mimics CNS lymphoma or pyogenic abscess.

Background:

Cerebral toxoplasmosis presents on MRI brain with contrast as ring-enhancing lesions with surrounding edema and no diffusion restriction, distinguishing it from primary CNS lymphoma and pyogenic abscess. However, in atypical cases, diffusion restriction has been reported due to high cellularity or viscous necrotic material. Previously reported cases have demonstrated restricted diffusion within lesion cores, peripheral “eccentric target” signs, and heterogeneous diffusion corresponding to areas of necrosis or high cellularity. Recognizing atypical imaging patterns is critical to avoid misdiagnosis and therapeutic delays.

Design/Methods:

We report the case of a patient with cerebral toxoplasmosis who underwent clinical evaluation, laboratory testing, and neuroimaging. The diagnosis was confirmed via immunoassay of serum Toxoplasma gondii IgG antibody and supported by improvement on imaging following treatment.

Results:

A 47-year-old male with hypertension presented with weakness and decreased sensation in the bilateral lower extremities and right upper extremity. Brain MRI with contrast revealed multifocal enhancing lesions in bilateral hemispheres, including a 3.9 cm left parietal lobe lesion with vasogenic edema, left lateral ventricle effacement, and 6 mm subfalcine herniation; these lesions demonstrated prominent diffusion restriction within core tissue. Labs were remarkable for positive HIV screen, CD4 count of 26 cells/UL, and toxoplasma IgG antibody of >400 IU/mL, for which six weeks of sulfamethoxazole-trimethoprim was started. Two weeks post-treatment, repeat MRI brain with contrast revealed decrease in size of the lesions and vasogenic edema.

Conclusions: