During this time, many patients also develop peak-dose dyskinesia consisting of choreiform twisting, turning movements that occur when central dopamine levels are peaking. This marks an important milestone in the treatment of Parkinson's disease because it limits the amount of dopaminergic therapy that can be provided. At this point, higher doses of dopaminergic therapy are likely to increase peak-dose dyskinesia. Too much dopaminergic therapy exacerbates peak- dose dyskinesia and too little dopaminergic therapy fails to bring about sufficient benefit. Despite optimal titration, many patients eight or more years into symptomatic therapy suffer with troublesome or disabling motor fluctuations and dyskinesia.
Some patients develop dementia as the disease progresses.
As antiparkinsonian therapy can worsen confusion and hallucinations, the presence of cognitive dysfunction can also limit administration of medication to improve motor symptoms. By ten to twelve years into therapy, many patients have developed balance difficulty. This is another important milestone. True postural imbalance is not improved by any current antiparkinsonian therapy. Patients are then at risk for morbidity and mortality from falls.