Cover legend: Spongy myelin degeneration is the hallmark of Canavan disease, which is caused by the accumulation of N-acetylaspartate. This image shows a section from the cerebellum of an aspartoacylase-deficient mouse (an animal model for Canavan disease) exhibiting widespread vacuolation throughout the white matter. For more information, see the article by Maier et al. (pages 14501–14516).