Can positive or negative suggestions change pain during deep brain stimulation for Parkinson’s disease?

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Previous research has shown that verbal suggestions can modulate motor and clinical outcomes in people with Parkinson’s disease (PD) receiving subthalamic deep brain stimulation (DBS). DBS may also alleviate pain in PD, but whether verbal suggestions influence its effects on pain was unknown.

This experimental study included 24 people with PD and DBS. On randomized test days, stimulation was downregulated (80–60 to 20%) and upregulated (from 20–60 to 80%) in a blinded manner. One condition paired downregulation with negative suggestions about pain and upregulation with positive suggestions about pain; the control condition provided no suggestions about effects. Researchers assessed ongoing pain and pain evoked by hypertonic saline injections using 0–10 numerical rating scales. They also assessed motor symptoms, expectations, and blinding.

Stimulation did not influence ongoing or evoked pain, but it influenced motor symptoms in the expected direction. Baseline and experimental pain measures showed no patterns in the degree of pain. There was a trend toward negative suggestions increasing pain and positive suggestions decreasing pain. At identical 60% stimulation, negative versus positive suggestions produced significantly different pain results: area under the curve (AUC) 38.75 versus 23.32, t (13) = 3.10, p < 0.001. Expectations about pain had small to moderate effects on evoked pain.

Patients estimated their stimulation level correctly within 10 points. The authors concluded that stimulation does not seem to influence ongoing or evoked pain, but verbal suggestions may influence pain levels. Patients appeared not to be blinded to stimulation level, an important consideration for future studies attempting to test DBS under blinded conditions.