Morilogium

From Memory Alpha, the free Star Trek reference

Morilogium is the final stage of the Ocampan lifespan, occurring mostly in an Ocampan's ninth and final year of life. Symptoms of the onset of morilogium are the rapid appearance of age, including wrinkles and graying hair, as well as a severe loss of memory.

In an alternate timeline on board the USS Voyager in the year 2378, Kes went through the morilogium and eventually lost over 99% of her memory engrams. (VOY: "Before and After")