Effects of deep brain stimulation and verbal suggestions on pain in Parkinson's disease.

BACKGROUND AND OBJECTIVES: In Parkinson's disease (PD) patients, verbal suggestions have been shown to modulate motor and clinical outcomes in treatment with subthalamic deep brain stimulation (DBS). Furthermore, DBS may alleviate pain in PD. However, it is unknown if verbal suggestions influence DBS' effects on pain. METHODS: Twenty-four people with PD and DBS had stimulation downregulated (80-60 to 20%) and upregulated (from 20-60 to 80%) in a blinded manner on randomized test days: (1) with negative and positive suggestions of pain for down- and upregulation, respectively, and (2) with no suggestions to effect (control). Effects of DBS and verbal suggestions were assessed on ongoing and evoked pain (hypertonic saline injections) via 0-10 numerical rating scales along with motor symptoms, expectations, and blinding. RESULTS: Stimulation did not influence ongoing and evoked pain but influenced motor symptoms in the expected direction. Baseline and experimental pain measures showed no patterns in degree of pain. There was a trend toward negative suggestions increasing pain and positive suggestions decreasing pain. Results show significant differences in identical stimulation with negative vs positive suggestions (60% conditions AUC 38.75 vs 23.32, t(13) = 3.10, p < 0.001). Expectations to pain had small to moderate effects on evoked pain. Patients estimated stimulation level correctly within 10 points. CONCLUSION: Stimulation does not seem to influence ongoing and evoked pain, but verbal suggestions may influence pain levels. Patients appear to be unblinded to stimulation level which is an important consideration for future studies testing DBS in an attempted blind fashion.

Differentiated effects of deep brain stimulation and medication on somatosensory processing in Parkinson's disease.

OBJECTIVES: Deep brain stimulation (DBS) and dopaminergic medication effectively alleviate the motor symptoms in Parkinson's disease (PD) patients, but their effects on the sensory symptoms of PD are still not well understood. To explore early somatosensory processing in PD, we recorded magnetoencephalography (MEG) from thirteen DBS-treated PD patients and ten healthy controls during median nerve stimulation. METHODS: PD patients were measured during DBS-treated, untreated and dopaminergic-medicated states. We focused on early cortical somatosensory processing as indexed by N20m, induced gamma augmentation (31-45Hz and 55-100Hz) and induced beta suppression (13-30Hz). PD patients' motor symptoms were assessed by UPDRS-III. RESULTS: Using Bayesian statistics, we found positive evidence for differentiated effects of treatments on the induced gamma augmentation (31-45Hz) with highest gamma in the dopaminergic-medicated state and lowest in the DBS-treated and untreated states. In contrast, UPDRS-III scores showed beneficial effects of both DBS and dopaminergic medication on the patients' motor symptoms. Furthermore, treatments did not affect the amplitude of N20m. CONCLUSIONS: Our results suggest differentiated effects of DBS and dopaminergic medication on cortical somatosensory processing in PD patients despite consistent ameliorating effects of both treatments on PD motor symptoms. SIGNIFICANCE: The differentiated effect suggests differences in the effect mechanisms of the two treatments.

Gait and postural instability in Parkinson's disease treated with deep brain stimulation of the subthalamic nucleus.

In late stage Parkinson's disease (PD), medical treatment may not control the symptoms adequately, and the patient may become eligible for bilateral high frequency deep brain stimulation (DBS) in the subthalamic nucleus (STN). The effect of STN DBS on gait and postural instability is not always as predictable as the effect on clinical symptoms tremor, rigidity and bradykinesia. This may relate to the type of gait disorder or the stimulating electrode localization in the STN. We sought to evaluate the effect of STN DBS on gait performance during overground walking and gait initiation--assessed with 3D optokinetic movement analyses--and to compare the DBS effect with stimulation site localized on peri-operative MRI. The stimulation sites were grouped according to STN borders visualised on pre-operative MRI, and the active stimulation site was compared with clinical improvement and gait parameters. STN DBS is associated with improved movement amplitude while movement duration may be unaffected by both disease and stimulation. This may imply an improvement primarily on hypokinesia including gait hypokinesia.