Early symptoms of Parkinson's disease may differ among cases, but they can include shaking in a limb or fingers, slower movements, improper balance, muscle rigidity, and difficulty speaking or writing, according to Mayo Clinic. Although early symptoms may go unnoticed, they often begin on one side of the body.
Parkinson's disease symptoms are caused by dying brain neurons, which decreases the production of dopamine, Mayo Clinic explains. Early tremors may start with simple movements, such as the forefinger rubbing against the thumb or a slight shake when the hand is relaxed. Slower movements may become more apparent over time, but it can start with shorter walking steps and foot-dragging. Movements that are typically unconscious, such as facial expressions or hand gestures, may start to decrease or take a conscious effort to control. Speech hesitation and slurring may also be early symptoms of Parkinson's.
As of 2015, it is unknown what exactly causes Parkinson's disease, but possible causes could be genetic or environmental, Mayo Clinic reports. Genetic mutations appear to play some role in Parkinson's, but researchers have only made specific family connections in rare cases. In rare cases, certain environmental toxins have been connected to Parkinson's. Research has focused on Lewy bodies, microscopic brain substances that appear common among Parkinson's patients, to gain a better understanding of how and why Parkinson's occurs.