It could be much worse -- a brain transplantation, or more precisely a whole-body transplantation.

If someone wanted to prolong their life by transplanting their brain to a new young body, they would need to be very careful about not appearing too wise for their age. Younger than full age, and even their freedom to conduct mad science would be seriously limited. But when you get the body of a known child genius... suddenly everything has a natural explanation and all kinds of people are trying to help you!