Correctly, before orochimaru was reincarnated into Kimimaro's body, Kimimaro was already ill and his body could not be used. In fact, metempsychosis is a kind of enchantment endurance of orochimaru, which imprisons others in their own enchantment and devours their own bodies and souls. People who have surgery will have some mental residue, but it is no different from death. It took Sasuke Sarin's efforts to suppress the demarcation of orochimaru.