Large quantities of abnormally-branched brain glycogen are hypothesized to be accumulating in disorders such as Lafora disease and Adult Polyglucosan Body Disease (APBD). However, non-invasive tools for brain glycogen detection in vivo are lacking. In this work we have used natural abundance 13C MRS at 7T with NOE, to detect glycogen in both normal and APBD brain. Qualitative comparison of the respective glycogen C1 signals in these two cases indicates no dramatic increase of the detectable glycogen concentration in APBD. To our knowledge this is the first human cerebral glycogen detection via natural abundance 13C MRS.