Multimodal Diagnostic Approach to Brain Abscess

A tertiary hospital based study comprising of a case series of 25 patients was carried out to evaluate various diagnostic modalities and arrive at a sensitive algorithm for diagnosis of brain abscess. Diagnostic efficacy of MRI scan, MR spectroscopy, PCR for tuberculosis & histological evaluation was assessed against a gold standard of Microbial diagnosis. The study group included 16 cases of pyogenic, 4 tubercular, 4 fungal and one actinomycotic abscess. Additionally, microvessel density and thickness of abscess wall was assessed by histo-morphometry. MRI was diagnostic in 92 % of the cases. MR spectroscopy revealed, lactate, lipids and amino acid metabolites all cases. Acetate and succinate indicated anaerobic etiology. Histological demonstration of microbes was possible in 6/16 cases of pyogenic abscesses, 3/4 cases of tubercular abscesses, in all 4/4 cases of fungal abscess and the 1/1 case had actinomycosis. M. tuberculosis was detected by PCR in all 4 cases of tubercular abscess. Morphometric analysis of the abscess wall showed prominent zone of inflammation in tubercular abscesses, which was significantly wider than in pyogenic abscesses (t=3.987, p= <0.001). This correlated well with the zone of enhancement inT1.weighted images in MR scans. Extent of microvessel proliferation in both groups was the same. Early diagnosis and accurate localization of brain abscess is possible by a combination of MRI & MR spectroscopy. Rapid diagnosis of tuberculous brain abscess can be achieved by PCR allowing initiation of therapy in the immediate postoperative period preventing fulminant infection.