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Published on: May 31, 2016
Effects of subthalamic nucleus stimulation on motor cortex excitability in Parkinson's disease
Valérie Fraix1, Pierre Pollak, Laurent Vercueil
1Department of Neurology, University Hospital of Grenoble and INSERM U836, Joseph Fourier University, 38000 Grenoble, France. Valerie.Fraix@ujf-grenoble.fr
Objective:
To study the effects of subthalamic nucleus (STN) stimulation on motor cortex excitability in Parkinson's disease (PD).
Methods:
Fifteen patients were evaluated under off-medication, OFF- and ON-STN conditions, using the UPDRS. We studied the effects of STN stimulation on motor cortex excitability under three conditions (OFF, ON with chronic therapeutic parameters, ON HighV with a voltage set 10% under permanent side effects threshold), using transcranial magnetic stimulation. We measured the central motor conduction time (CMCT), rest and active motor threshold (MT), F-wave persistence and amplitude, silent period (SP), intracortical inhibition and facilitation at 3, 5 and 15 ms interstimulus intervals (ISI).
Results:
The UPDRS motor score decreased from 44.4+/-14.0 under OFF, to 15.2+/-8.0 under ON-STN condition. The CMCT and MT did not change across STN conditions. The F-wave parameters were within normal range under STN stimulation. STN stimulation lengthened the SP and induced facilitation at 15 ms ISI compared to the OFF-STN condition.
Conclusion:
Therapeutic STN stimulation modulates cortical excitability in PD. High voltage STN stimulation could also act on spinal excitability.
Significance:
At the motor cortical level, STN stimulation may have a direct effect on intracortical interneurons, modifying the balance between excitation and inhibition.
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