Presentation
Mild persistent throbbing headache for 6 weeks. Dizziness & numbness right half of the body 1 week. No fever, nausea, vomiting, or seizures.
Patient Data
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.
The patient went on to have a drainage.
Histopathology
Chronic granulomatous inflammation with caseating necrosis consistent with tuberculosis (tuberculoma). AFB and Grocott's special stains are negative.
TB PCR is positive for mycobacterium tuberculosis complex.
Status post right frontal craniotomy with excision of the right frontal lobe focal space-occupying lesion. Post-operative changes (focal hemorrhages and small air densities) are noted in the right frontal lobe. No gross interval change is seen in the right frontal lobe vasogenic edema, the mass effect over the frontal horn of the right lateral ventricle, and mild left-sided midline shift when compared with the prior MRI brain.
Case Discussion
Infections caused by somewhat atypical agents can result in lesions that don't look like typical pyogenic abscesses and can be mistaken for tumors. Low central T2 signal is a fairly good clue to the diagnosis of a tuberculoma.
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