Gliomatosis cerebri is an infiltrative glial tumor growth pattern with involvement of at least three lobes of the brain and frequently bilateral. Interhemispheric spread of disease is achieved via the commissural fibers and interthalamic adhesion. The involved structures are diffusely enlarged causing regional mass effect with midline shift,  herniation or sulcal effacement. Gliomatosis cerebri typically does not demonstrate enhancement unless complicated by foci of higher grade malignant progression.  

Importantly, whereas gliomatosis was previously considered a distinct entity, since the 2016 update to the WHO classification of CNS tumors it is now merely thought of as a growth pattern.