Weber’s syndrome in an HIV positive patient: Revisiting the concentric and eccentric target signs – Question paper

A case of cerebral toxoplasmosis: “Eccentric and concentric sign” in MRI

“…The "eccentric target sign" is seen on T1W post-contrast imaging as a ring-enhancing lesion with an eccentrically located enhancing mural nodule. It comprises three regions: the central eccentric enhancement region, the middle low signal region, and the outer ring/peripheral enhancement region 3 , 5 . Histologically, the central eccentric enhancement region represents inflamed small blood vessels, while the middle low signal region represents necrosis, and the outer ring enhancement area represents dense histiocytic response 3 , 4 , 5 .…”

“…It comprises three regions: the central eccentric enhancement region, the middle low signal region, and the outer ring/peripheral enhancement region 3 , 5 . Histologically, the central eccentric enhancement region represents inflamed small blood vessels, while the middle low signal region represents necrosis, and the outer ring enhancement area represents dense histiocytic response 3 , 4 , 5 . These two characteristic signs, the "eccentric target sign" and "concentric target sign," are highly suggestive of cerebral toxoplasmosis and are rarely displayed in the same lesion due to different pathological states 3 , 4 .…”