noun
retrograde amnesia
Medical term for loss of memories from before a brain injury or disease onset.
事故の後、彼は逆向性健忘で過去数年の記憶を失った。
After the accident, he lost memories of the past few years due to retrograde amnesia.
Anterograde amnesia: inability to form new memories after the event, while 逆向性健忘 affects past memories.
Compound of 逆向 (reverse direction) + 性 (nature) + 健忘 (amnesia). A modern medical term likely calqued from English 'retrograde amnesia'.