To determine whether PC death is a shared feature of motor neuron diseases, we investigated the cerebellum of milder Smn2B/- SMA mice as well as SOD1-G93A and Ighmbp2NMD-2J mice as models of familial ALS and SMA with respiratory distress type 1 (SMARD1), respectively. Here, SOD1 is linked to proximal spinal muscular atrophy.