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Last Updated: March 27, 2020

Figure 1: Ill-defined regions of mass-like signal abnormality in the right corona radiata and parietal subcortical white matter. Notice the T1 iso- to slightly hypointense signal (top row left) with corresponding FLAIR hyperintensity (top row right). There is faint, DWI hyperintense mildly reduced diffusivity (middle row) associated with the aforementioned lesions corresponding to areas of peripheral mildly nodular enhancement (bottom row left). The right corona radiata lesion that closely approximates the ependyma of the right lateral ventricle has a characteristic “eccentric target sign” where there is an eccentric enhancing nodule within cavity (bottom row left). While not a specific sign, it can help narrow your differential. Additionally, there is faint hypointense signal on the SWI image (bottom row right) representing focal hemorrhage. This can be helpful to distinguish from non-treated lymphoma. If further differentiation is needed between toxoplasmosis and lymphoma, a thallium nuclear medicine scan can be helpful.