Isso soa como a história de Greg Egan " Razões para ser alegre ", exceto o protagonista de que era um menino.
Um breve resumo da Wikipedia:
A boy discovers he has a serious brain tumour, which was causing him to be amazingly happy. With it removed, he becomes despondent, and undergoes a new and extensive treatment eventually, with a form of brain network, to try to get back to a more useful life many years later.