There are many causes of brain atrophy; whether it is hereditary depends on the specific disease causing it. Most diseases leading to brain atrophy are not hereditary. For instance, some patients suffer brain atrophy due to Alzheimer's disease, where the neurons die irreversibly. This disease is mostly sporadic and does not have a clear hereditary tendency. Of course, a few cases of Alzheimer's do have a family history and may have a genetic propensity. Additionally, brain atrophy can also occur due to intoxication, such as from alcohol, carbon monoxide, or other toxic substances, and these cases definitely are not hereditary. Some patients experience brain atrophy due to cerebral thrombosis, which also lacks a genetic predisposition.