gms | German Medical Science

Objective: The subthalamic nucleus(STN) is an effective target for deep brain stimulation(DBS) in Parkinson‘s disease. It is divided into the dorsolateral and the ventromedial part. Recently autocorrelogram analysis of single STN units showed a significant increase of oscillatory activity in the dorsolateral STN. The primary goal of this study was to analyze the optimal electrode contact position in relation to the anatomical and electro-physiological borders and isocenters of the STN. The secondary goal was to compare the discharge pattern of STN activity of the active contact with the most ventromedial inactive contact.

Methods: The borders of the STN activity were drawn by a marked amplitude increase in microelectrode recording in 21 PD patients. In 12 consecutive patients autocorrelograms of the action potentials were determined. The activity within the vicinity of the active contact (within 1,5 mm) was compared to the most ventromedial reference contact. The anatomical borders of the STN were assessed by T2 weighted magnetic resonance imaging. The localization of the clinically most effective contact was analyzed and the length and the centers of the anatomical and electrophysiological signal were compared.

Results: The mean anatomical length of the STN was 6,3 mm, whereas the mean length of electrophysiological activity was 3,8 mm. The center of the anatomical signal had a mean distance of 0,8 mm to the electrophysiological center. The active contact was dorsal to the anatomical center of the STN in 32 out of 42 electrodes and in 10 out of 42 electrodes ventral to the center. The active contact is found with a mean of 1,8 mm (electrophysiological) or 1,2 mm (anatomical) dorsal to the midline of the STN signal. None of the active contacts were found beyond the ventromedial border. A mean improvement of 45,4% on the motor UPDRS was found. In 67% oscillatory or bursty activity was found within the vicinity of the active contact. In 64% the ventromedial reference contact showed irregular activity.

Conclusions: The anatomical STN signal on T2 images is larger than the electrophysiological . However, the electrophysiological and anatomical center of the STN show no significant deviation using the described technique. There seems to be a positive correlation between the activity in the autocorrelogram and the final positioning of the active electrode contact. We can confirm that the optimal localisation of the finally stimulated contact is found within or dorsal to the dorsolateral STN.