In seven cases of intracranial
tuberculomas showing different signal intensities on MRI (five characteristic and two nonspecific), detailed histopathological examination was performed to look for number of macrophages,
fibrosis,
gliosis, degree of inflammatory cellular infiltrate, and type of caseation. The
granulomas showing more macrophages,
fibrosis and
gliosis appeared hypointense on T2-weighted images.
Tuberculomas showing minimal macrophages, marked cellular infiltration, and minimal
fibrosis appeared hyperintense on T2-weighted images. Lesions showing similar signal intensity on T2-weighted images showed variation in the amount of macrophages, cellular infiltrates, maturity and
fibrosis.
Trace element estimation was done (
iron,
copper, and
magnesium) in two of these lesions appearing hypointense on T2 and two normal brain samples; these were significantly lower in
tuberculoma compared to normal brain tissue. Localised
proton spectroscopy was performed in two hypointense lesions which showed marked increase in peaks in the region of mobile
lipids (1.28 ppm) compared to normal brain parenchyma. It is concluded that the signal intensity of the lesions is dependent on the number of macrophages,
fibrosis and cellular infiltrates. In addition increased
lipid contents in the
tuberculoma also contribute to the hypointensity on T2-weighted images.