Inflammatory granulomas: evaluation with proton MRS

Intracranial inflammatory lesions consisting mainly of tuberculomas (n = 28), neurocysticercosis (NCC) (n = 10), and non-specific inflammatory granulomas (IG) (n = 22) were evaluated with proton MRS. Water-suppressed proton spectra were acquired from 60 patients using the STEAM sequence with an echo time of 135 ms and metabolite ratios determined from the spectra. Student's paired t-test and chi2-test were used to analyse the data. Statistically significant differences were observed for the following ratios between the three patient categories: NAA/ Cr (p < 0.0001), NAA/Cho (p = 0.001) and Cr/Cho (p = 0.02) for the non-specific IG and NCC, NAA/Cho (p = 0.03) for non-specific IG and tuberculoma, and NAA/Cr (p < 0.0001) for NCC and tuberculoma. While lipids were seen in 86% of the tuberculomas, they were observed in only 20% of the NCCs (chi2 = 6.81, p = 0.009), and 21% of the non-specific IGs (chi2 = 10.75, p = 0.0001). While the presence of lipid can be used for differentiating tuberculomas from both non-specific IG and NCC, the extremely low levels of metabolites together with a poor signal/noise ratio could itself act as a marker for NCC.