The early symptoms of Parkinson's disease are divided into motor symptoms and non-motor symptoms. The onset of Parkinson's disease is relatively concealed and progresses gradually. The initial symptoms can be tremors, bradykinesia, or rigidity, occurring asymmetrically. It often starts in one upper limb and can initially appear in the lower limbs in a few cases, gradually extending to the limbs on the other side. Non-motor symptoms can occur at any stage of Parkinson's disease, including before motor symptoms arise, such as loss of smell, rapid eye movement sleep behavior disorder, constipation, and depression. These are often precursory symptoms of Parkinson’s disease, but such non-motor symptoms can also appear in other diseases, which can make them difficult to clearly distinguish.