Continuous dopaminergic stimulation: is it the answer to the motor complications of levodopa?

Nigral Iron Deposition Is Associated With Levodopa-Induced Dyskinesia in Parkinson's Disease

Objective

To investigate iron deposition in the substantia nigra (SN) of Parkinson’s disease (PD) patients associated with levodopa-induced dyskinesia (LID).

Methods

Seventeen PD patients with LID, 17 PD patients without LID, and 16 healthy controls were recruited for this study. The mean QSM values of the whole, left, and right SN were compared among the three groups. A multivariate logistic regression model was constructed to determine the factors associated with increased risk of LID. The receiver operating characteristic curve of the QSM value of SN in discriminating PD with and without LID was evaluated.

Results

The mean QSM values of the whole and right SN in the PD with LID were higher than those in the PD without LID (^∗P = 0.03, ^∗P = 0.03). Multivariate logistic regression analysis revealed that the QSM value of whole, left, or right SN was a predictor of the development of LID (^∗P = 0.03, ^∗P = 0.04, and ^∗P = 0.04). The predictive accuracy of LID in adding the QSM value of the whole, left, and right SN to LID-related clinical risk factors was 70.6, 64.7, and 67.6%, respectively. The QSM cutoff values between PD with and without LID of the whole, left, and right SN were 148.3, 165.4, and 152.7 ppb, respectively.

Conclusion

This study provides the evidence of higher iron deposition in the SN of PD patients with LID than those without LID, suggesting that the QSM value of the SN may be a potential early diagnostic neuroimaging biomarker for LID.

Switching L-dopa Therapy from Pulsatile to Pulse Administration Reduces Motor Complications in Parkinson's Disease

OBJECTIVE

To evaluate the severity of wearing-off and dyskinesia in patients with complicated Parkinson disease (PD) after switching L-dopa oral therapy from a "pulsatile" administration, consisting in intermittent multiple daily small doses of the drug, to a "pulse" administration, consisting in standard oral doses given at specific interdose intervals.

METHODS

Thirty-four PD patients with motor complications were monitored twice with standardized waking day motor status evaluations using the Unified Parkinson Disease Rating Scale-Motor Examination (UPDRS-ME) and the Abnormal Involuntary Movement Scale (AIMS) after switching L-dopa administration modality from "pulsatile" to "pulse." To quantify predictable motor fluctuations, a Wearing Off Index was computed based on changes in treatment response magnitude.

RESULTS

On the whole, after switching from "pulsatile" to "pulse" administration, there was a reduction in number of L-dopa daily doses and an increase in the amount of the dosage of the single doses, AIMS maximum score decreased without increasing motor disability. More specifically, in predominant fluctuating patients, there was a significant reduction in UPDRS-ME average score as well as in Wearing Off Index. In predominant dyskinetic patients, there was a significant reduction in average and maximum AIMS scores with no changes in average and maximum UPDRS-ME scores.

CONCLUSIONS

Switching L-dopa therapy from "pulsatile" to "pulse" modality may reduce the severity of wearing-off and dyskinesia in complicated PD.