Influence of deep brain stimulation and levodopa on signs and symptoms in Parkinson's disease

Purpose: To examine sensory symptoms in Parkinson's disease (PD) and elucidate the effect of levodopa and deep brain stimulation of the subthalamic nucleus (STN-DBS) on sensory signs and symptoms.

Methods: 17 PD patients were included. All were asked for presence of sensory symptoms. Effect of levodopa and STN-DBS on sensory signs and symptoms was investigated with quantitative sensory testing (QST) six months after bilateral implantation of STN-electrodes. Additionally, in 12 of the patients presence of sensory symptoms prior and after STN-DBS was compared.

Results: Pain in PD was most frequently nociceptive. In about 30–40%, pain and sensory symptoms were associated with PD motor symptoms. In most of these cases, pain responded to levodopa. Intensity of pain was reduced post STN-DBS compared to pre STN-DBS. Levodopa had no influence on detection thresholds, whereas STN-DBS improved thermal detection thresholds. However, thermal and mechanical pain sensitivity was uninfluenced by levodopa or STN-DBS.

Conclusion: STN-DBS and levodopa might improve pain associated with PD motor symptoms, whereas pain sensitivity is not altered. Results suggest that a significant part of sensory symptoms including pain may be independent of a dopaminergic deficit and potentially of other primary origin, i.e. due to an abnormal somatosensory processing.