Describe the features of a brain disease.?

What kind? I need more info to answer your question. How do you know it is a brain disease? In general, the brain is an organ just like your heart, lungs and liver. Things can go wrong in a number of ways: biochemically, electrically or structurally.
Noo vague. Need more details. What form of brain abnormality. Do you have a specific condition in mind?