Serial imaging of a patient diagnosed with CLL. Cancer-directed therapy included >6 months of rituximab and idelalisib. (A) Initial magnetic resonance imaging performed 2 months after the onset of headaches and balance disturbance (gait instability and repeated falls) depicting the asymmetric atrophy of the left cerebellum, which was not present in imaging performed 7 months earlier (not depicted). Fluid-attenuated inversion recovery (FLAIR) signal abnormalities are not present elsewhere. (B) Imaging repeated 3 months later (1 month prior to death) showing the continued atrophy of the left cerebellum with new confluent areas of FLAIR signal throughout the left cerebellum and left cerebellar peduncle without enhancement. Again, no FLAIR signal abnormalities are seen in the cerebrum.