What caused muhammad alis parkinsons?

Dementia pugilistica: Numerous brain injuries cause disruptions in the fragile circuits that govern brain function. When injuries occur deep within the brain, they may affect a part of the brain that regulates movements. The part of the brain most involved in suppressing Parkinsons movements is called the substantia nigra. Mr. Ali has had injuries that damaged this part of the brain, which leads to his tremor.