Analgesic Effects of Expectation and Deep Brain Stimulation in Patients With Parkinson's Disease

The study investigates analgesic effects of expectations and deep brain stimulation on chronic and evoked pain in patients with Parkinson's disease. The study includes patients with Parkinson's disease that are exposed to pain stimuli through injection of hypertonic saline. During pain induction and chronic pain evaluation deep brain stimulation treatment is regulated. Pain stimuli and regulation of deep brain stimulation are accompanied by verbal suggestions as to the analgesic effect of deep brain stimulation or no suggestions. During the test session patients evaluate their chronic and evoked pain and expectations. The study procedure is repeated on two separate test days to investigate pain during deep brain stimulation treatment with or without verbal suggestions. All participants will complete all study conditions with no suggestions and verbal suggestions, respectively.

A numerical rating scale from 0 (no pain) to 10 (worst pain) will be used to assess participants' subjective chronic and evoked pain in all study conditions.

Participants will be tested on two days. The numerical rating scale will be applied to assess chronic and evoked pain at baseline and in the five study conditions (after each deep brain stimulation regulation) on each day.

A numerical rating scale from 0 (no pain) to 10 (worst pain) will be used to assess participants' subjective expectations to chronic and evoked pain in all study conditions.

Participants will be tested on two days. The numerical rating scale will be applied to assess expectations to chronic and evoked pain at baseline and in the five study conditions (after each deep brain stimulation regulation) on each day.

Motor symptoms related to Parkinson's disease are assessed using the Unified Parkinson's Disease Rating Scale, part III in all study conditions.

Participants will be tested on two days. The Unified Parkinson's Disease Rating Scale will be used to evaluate motor symptoms at baseline and in the five study conditions (after each deep brain stimulation regulation) on each day.

Inclusion criteria: Diagnosis of PD (confirmed by a neurologist) Bilateral implanted DBS in the STN during the study or for a minimum of 6 months Exclusion criteria Other neurological or medical disorders (e.g. stroke, neuropathy, diabetes) or other disorders (e.g. musculoskeletal diseases) with expected influence on pain Dementia Untreated depression Patients unable to pause anti-parkinsonian medication Patients unable to cooperate Patients treated with painkillers except paracetamol and NSAID (except if pain and treatment is adequately stable as evaluated by a doctor)