ABSTRACT
OBJECTIVE: Directional leads are used for deep brain stimulation (DBS). Two of the four contacts of the leads are divided into three parts, enabling controlled stimulation in a circumferential direction. The direction of adverse effects evoked by DBS in the subthalamic nucleus (STN) and stimulation strategies using directional leads were evaluated. METHODS: Directional leads were implanted into the bilateral STN of six parkinsonian patients (1 man, 5 women; mean age 66.2 years). The contact centers were located within the upper border of the STN, and the locations were identified electrically using microrecordings. Adverse effects were evaluated with electrical stimulation (30 μs, 130 Hz, limit 11 mA) using the directional part of each lead after surgery, and the final stimulation direction was investigated. Unified Parkinson's disease rating scale (UPDRS) scores were evaluated before and after DBS. RESULTS: Fifty-six motor and four sensory symptoms were evoked by stimulation; no adverse effect was evoked in 14 contacts. Motor and sensory symptoms were evoked by stimulation in the anterolateral direction and medial to posterolateral direction, respectively. Stimulation in the posteromedial direction produced adverse effects less frequently. The most frequently used contacts were located above the STN (63%), followed by the upper part of the STN (32%). The mean UPDRS part III and dyskinesia scores decreased after DBS from 30.2 ± 11.7 to 7.2 ± 2.9 and 3.3 ± 2.4 to 0.5 ± 0.8, respectively. CONCLUSION: The incidence of adverse effects was low for the posteromedial stimulation of the STN. Placing the directional part of the lead above the STN may facilitate the control of dyskinesia.