The waterfall sign, also known as the cascade sign, is a radiological sign appreciated on MRI brain that is described in patients with neuro-Behçet disease involving the mesodiencephalic junction. The sign describes the involvement of the mesodiencephalic junction as seen on coronal T2/FLAIR sequences, whereby there is high signal that extends from the thalamus and/or internal capsule caudally to the ipsilateral midbrain. This region of high signal often has ill-defined margins and overall, has a shape which resembles a cascade or waterfall. This sign may help to distinguish neuro-Behçet from glioma.