Objective: To evaluate the clinical effect (motor, non-motor and cognitive) of a three-month switch from constant-voltage (CV) to constant-current (CC) stimulation in Parkinson’s disease (PD) patients with subthalamic (STN) deep brain stimulation (DBS).

Background: STN DBS was based on a CV mode of stimulation, the new devices allow CC stimulation. In a CV stimulation, the amount of current delivered to the target varies according to impedance changes. In a CC stimulation, the voltage is automatically adjusted according to impedance changes and the amount of current delivered remains stable over time. The clinical relevance of CC stimulation is matter of debate. Some evidence suggest that the CC stimulation may theoretically maximize clinical benefit and limit side effects of DBS by maintaining stable the volume of tissue activated. We performed a prospective study to compare the clinical effect of CV and CC stimulations.

Methods: PD patients implanted with electrodes model 3389 (Medtronic Inc.) allowing either CV or CC stimulation were recruited. They had a good response to DBS, stable clinical control of motor symptoms and no cognitive impairment. After baseline assessment, the patients were switched from CV to CC stimulation for three months. No changes of stimulation setting or baseline dopaminergic therapy were allowed. The evaluation included the assessment of motor (UPDRS-III), non-motor (NMSS), cognitive (Stroop Test, Trial Making test, n-back test, divided attention test and Go/noGo test) and quality of life (PDQ-8) features, A within subjects comparison was performed and significance level was set at 0.05.

Results: 20 PD patients were included. Age was 57.3 years, disease duration 13.7 years, age at surgery 53.7 years and levodopa equivalent daily dose 490.9 mg. Two patients dropped out as they increased dopaminergic replacement therapy upon advice of their local doctor. After three months of CC stimulation the patients showed a better performance in the Go/noGo test in term of number of correct items (p= .041) and number of errors (p= .024); no other differences were found between CV and CC stimulations.

Conclusions: The findings show that the clinical effect of CC stimulation is comparable to CV stimulation in PD patients with chronic STN DBS stimulation. CC stimulation may improve cognitive abilities related to STN functioning. Further studies needed to ascertain this hypothesis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/constant-current-stimulation-in-parkinsons-disease-patients/