The goal of this feature is to assist the busy physician with a short but diagnostically challenging case, allowing the physician to neurologically reason the answer. Readers will be challenged to arrive at the correct diagnosis for the case from a small dataset, including case narratives and imaging. Readers will see a short clinical synopsis and relevant images and laboratory information, permitting them to exercise their diagnostic skills. The correct diagnostic answer will not simply be the thought of the physician author but will, in all cases, be a definitive diagnosis with confirmation by genetic, laboratory, or biopsy or autopsy pathological information. The feature will be published online, allowing the physician to take the challenge and then have immediate access to the answer, the actual diagnosis, and an accompanying brief discussion of how it was reasonable to come to that diagnosis from the case synopsis. In the online version, the physician will be able to see, as in prior online quizzes, which answers colleagues favored. In the print version, the answer and discussion will be available toward the end of the pages in the same journal issue.