Figure 1. Age at disease and myoclonus onset in patients with genetically identified progressive myoclonic epilepsies.

Gray segments of columns refer to the period before disease onset, yellow segments to the presentation of neurologic signs, and red segments to the presentation of myoclonus. The end of the columns defines the patients' ages at the time of the last observation. Columns representing EPM1 and EPM2 are based on mean values, whereas the other columns refer to individual patients. HD = Huntington disease; MERRF = myoclonic epilepsy with ragged-red fibers; NCL = neuronal ceroid lipofuscinosis; NPC = Niemann-Pick disease type C; SMA = spinal muscular atrophy.