Unilateral subthalamic stimulation in the treatment of advanced Parkinson's disease

Introduction. The use of unilateral subthalamic stimulation (USTS) in the treatment of advanced Parkinson's disease can be effective and offer a series of advantages on comparing this technique with bilateral subthalamic stimulation (BSTS). Patients and methods. We studied 35 consecutive patients: 22 with BSTS and 13 with USTS (six left and seven right). The epidemiological features and the scores on the functional assessment scales -Hoehn and Yahr Schwab and England, and the Unified Parkinson's Disease Rating Scale (UPDRS) I to IV- were not significantly different in the two groups, except for the Hoehn and Yahr in off (USTS: 3.3 +/- 0.3; BSTS: 4.1 +/- 0.2; p = 0.004). Results. The overall percentages of improvement six months after surgery were UPDRS I: 12%; II: 21.6%; III-medication off/stimulator on: 30.6% (with respect to the baseline off state); III-on/on: 8.8% (with respect to the baseline on state); IV: 48.9%. Reduction in the levodopa equivalent dose: USTS: 26.3%; BSTS: 17%. These percentages of improvement were not significantly different in the two groups. If we consider the motor scale in medication-off and stimulator-on in the sixth month and we compare it with the same in the off state before surgery, the axial motor symptoms improved by 17.1% (USTS) and 25% (BSTS); in the extremities, USTS: 39.1% in the limbs contralateral to the implanted electrode, and 14.5% in the ipsilaterals; BSTS: right extremities, 32.6%; left extremities, 31.5%. No significant differences were found on comparing the electrical power consumed by the electrodes in the two groups of patients in the sixth month of treatment. Conclusions. USTS was effective in improving the axial symptoms. In our series, the reduction in medication following surgery was similar to that of the patients with BSTS.