Problems and symptoms that develop as consequences of the primary, or cardinal, symptoms of Parkinson’s disease. micro-graphia (small, cramped handwriting), for example, develops as a consequence of damage to fine motor control in the hands. Vision problems develop because Parkinson’s symptoms affect the muscles controlling movements of the eyes. constipation develops as a consequence of slowed muscle response in the gastrointestinal tract. Strictly speaking, all symptoms beyond the four cardinal symptoms resting tremor, bradykinesia, rigidity, and postural instability are considered secondary.
This does not mean they are less significant; in fact, secondary symptoms often are more frustrating to people with Parkinson’s because they are the symptoms that interfere with the small details of everyday living. Treating Parkinson’s disease’s cardinal symptoms also reduces or eliminates secondary symptoms, but treating secondary symptoms has little, if any, effect on cardinal symptoms. As Parkinson’s progresses, it becomes necessary to use adjunct therapies to treat secondary symptoms, mainly because anti-parkinson’s medications are no longer able to keep cardinal symptoms in check.