Differential diagnosis of intracranial lesions with high signal on T1 or low signal on T2-weighted MRI.

Magnetic resonance imaging (MRI) is the preferred technique for examining intracranial pathology in the non-acute setting in most cases. The aim of this review is to demonstrate the imaging appearances on unenhanced spin-echo MRI of lesions that show characteristic, unusual signal changes, which occur due to the presence of fat, cholesterol, paramagnetic substances, rapidly flowing fluids, air, cortical bone or calcification. The nature of the MRI signal, together with the anatomical location of the lesion should allow the provision of a narrow differential diagnosis, before the use of intravenous contrast medium or additional imaging sequences.