Magnetic resonance imaging features of solitary inflammatory brain masses

Brain lesions in inflammatory diseases may present as solitary masses, prompting a biopsy. We present neuroimaging and histologic findings in five patients with solitary, inflammatory, demyelinating mass lesions located in the supratentorial white matter and gray-white junction. The patients presented with seizures, focal neurologic signs, and neuroimaging findings that indicated the possibility of a neoplasm. Computed tomography (CT) revealed enhancing, single hypodense lesions associated with mild or no mass effect. On MRI, the lesions were hypointense on T1-weighted images and hyperintense on T2-weighted images. Variable patterns of enhancement were noted on CT and MRI, including homogeneous/patchy (n = 3) and ring/nodular (n = 1) enhancement. There was no evidence of calcification or hemorrhage. Biopsies revealed a leukoencephalitis and demyelination, with varying degrees of demyelination among the cases. The syndrome, relating to a solitary lesion, was corticosteroid-sensitive, and it ultimately stabilized. Extensive longitudinal evaluations failed to reveal multiple sclerosis, infection, or neoplasm. Solitary inflammatory lesions add to the differential diagnosis of large, supratentorial, solitary space-occupying lesions noted on CT and MRI scans.