Complex sentence: He was in a mental hospital for over a year, and in July 1946 underwent a leucotomy (lobotomy), at the height of the procedure's popularity, after which he made a strong recovery and was able to resume teaching.
Split into simpler sentences: He was in a mental hospital for over a year, and in July 1946 underwent a leucotomy (lobotomy). He subsequently made a strong recovery and was able to resume teaching.