Bilateral dyskinesias induced by unilateral subthalamic nucleus deep brain stimulation: A case report

Subthalamic nucleus-deep brain stimulation (STN-DBS) is a well-established treatment for Parkinson's disease (PD). Contralateral dyskinesias are often observed during intraoperative testing and are considered predictors of the best postoperative effects on Parkinsonian's motor disability. Ipsilateral and bilateral dyskinesias are unusual and raise questions about the bilateral functional connectivity within basal nuclei circuitry in PD patients.

A 47-year-old right-handed male patient with advanced PD presented with freezing of gait, motor fluctuations, and disabling dyskinesias predominantly affecting the left side, despite optimized pharmacological treatment. He was subsequently selected for STN-DBS implantation. During the surgery, the proper, bipolar stimulation of the distal contact (contact 0, cathode; contact 1, anode) at 2 mA induced severe dyskinesia manifesting as chorea, starting in the right lower limb and extending bilaterally. The dyskinesias ceased when stimulation was interrupted. On the left STN, stimulation of the distal contact induced only contralateral lower limb dyskinesias.

This case report adds to the discussion on basal nuclei circuitry and its bilateral connections, enhancing our understanding of the physiological mechanisms underlying both the therapeutic and adverse effects of unilateral STN-DBS. It supports the hypothesis of abnormal bilateral connectivity in some PD patients, explaining bilateral dyskinesias and therapeutic implications.