A rounded lesion in the right frontal lobe periventricular deep white matter has well-defined low signal intensity peripheral rim on T1 and T2 weighted images with an additional high signal intensity inner concentric rim (dual rim sign) on T2 weighted images. Centrally the lesion has a lobulated low T2 signal appearance.
The lesion only shows high diffusion-weighted signal peripherally, with heterogeneous values centrally. Ring enhancement with an irregular inner outline is noted on post-contrast images. MR spectroscopy shows an elevated lactate peak.
Moderate perilesional vasogenic edema, with mass effect left-sided midline shift are seen. No other additional lesions or abnormal meningeal enhancement is seen.
Conclusion: Solitary cerebral ring-enhancing lesion, which is likely of infective etiology (such as TB, fungal, or toxoplasmosis. Central T2 hypointensity compared to grey matter favors a tuberculoma, as this imaging feature is usually not seen in other causes. The possibility of focal neoplasm is less likely.