Intra-axial

Intra-axial is a term that denotes lesions that are within the brain parenchyma, in contrast to extra-axial, which describes lesions outside the brain, and intraventricular, which denotes lesions within the ventricular system. Some authors include intraventricular lesions in the intra-axial group as most are lesions that arise from the brain parenchyma and grow exophytically into the ventricular system.