Hi Sir, My Father Is 54 Years Old Now And

Hi sir, my father is 54 years old now and was diagnosed with brain TB in Nov 2019 and is in undergoing treatment since then. He also suffered left side ischemic stroke which earlier gave him problem with speech, memory, cognitive skills and even moving and balancing. Most of his skills are restored as of now, he is able to talk, think, form new memories and move on his own now. The treatment is almost finished too but we recently had an MRI which stated diffuse Cerebral atrophy. Is this normal according to his age or should I be concerned. The doctor said it's okay.