Objective: To compare the effectiveness of dopaminergic drugs on motor symptoms assessed by UPDRS- III in Parkinson’s disease patients pre and post deep brain stimulation of subthalamic nucleus.

Background: Subthalamic nucleus deep brain stimulation (STN DBS) has been used in advanced Parkinson’s disease (PD) since 1993. Many studies have reported significant improvement in the motor part of UPDRS,motor fluctuations, and dyskinesia after DBS.Some studies also have reported a loss of the levodopa response after the DBS surgery. 

Method: We have recruited 16 patients (M:F=10:6) who have undergone STN DBS at NIMHANS,Bangalore,India. Clinico-demographic details, Initial Disease severity (UPDRS-III), Levodopa Equivalent Dose (LEDD) pre-DBS, LEDD post DBS, Disease Severity Post-DBS was collected. Post-DBS, the UPDRS –III was obtained in four consecutive conditions within the same day in the following order: OFF -medications/ ON -stimulation (MED-OFF/ STIM-ON), OFF medications / OFF -stimulation (MED-OFF/ STIM-OFF), ON -medications/ OFF -stimulation (MED-ON/ STIM-OFF), and ON medications/ ON -stimulation (MED-ON/STIM-ON). OFF and ON stimulation conditions will be evaluated 60 and 30 minutes after turning off and on the stimulator, respectively.

Results: The mean age of the patients was 52.63 ± 10.00 years. The Pre DBS, UPDRS III motor score in OFF state was 52.00 ± 12.86 and ON state was 17.00 ± 8.21 suggesting a levodopa response of 67.3%. During Post DBS state, there was significant improvement in motor scores in DBS ON-Drug ON state (13.00 ± 7.45) as compared to DBS OFF-Drug OFF state (54.63 ± 12.24). But, during DBS OFF –Drug ON state, the UPDRS III motor score was 35.69 ± 17.42, suggesting a levodopa response of only 34.6%. Levodopa Equivalent Dose significantly reduced by 33.7% post DBS.

Conclusion: The most important finding of the current study is the significant reduction in levodopa responsiveness post STN DBS. In our study, there was reduction in levodopa response by 32.7% postoperatively. Although the exact mechanism of the decrease in levodopa response is not clear, this may be secondary to the gradual progression of the disease pathology in PD or reduced sensitivity of dopaminergic receptors secondary to reduction in the dose of dopaminergic medications after DBS, and changes in neuronal circuits due to chronic stimulation reflecting neuronal plasticity.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effectiveness-of-dopaminergic-drugs-on-motor-symptoms-in-parkinsons-disease-patients-with-deep-brain-stimulation-of-subthalamic-nucleus/