2. Huntington’s Disease
This disorder is inherited and kills off brain cells, progressing from somewhat mild behavioral issues into full-blown problems such as difficulty walking and the inability to speak.
Neuropathology-Web.org explains that the fatal condition usually shows up in middle age, but some people can get it before the age of 20 (or much later in life). The source notes that certain areas of the brain of Huntington’s patients are affected by atrophy, “which are obvious on MRI in advanced cases”. Changes to the brain can be detected by medical imaging long before any symptoms of the disease show up, it adds.