gms | German Medical Science

Objective: Awake surgery is regarded as mandatory for optimal electrode implantation into the subthalamic nucleus (STN) for deep brain stimulation (DBS) in Parkinson's disease (PD). However, even in the awake state, clinical testing is limited by e.g. subjective rating, fluctuating/insufficient symptoms, carry-over effects, and limited patient compliance.

Methods: From 2005–2009, eleven PD patients (4 female, mean values for age 63.5, disease duration 17 yrs; Hoehn&Yahr 3; UPDRS III in OFF state 43) were operated under general anesthesia (GA). Intraoperative microrecordings and microstimulation were performed using 5 microelectrodes (Ben's Gun). Test stimulation (100 usec; 130 and 4 Hz) was performed after propofol and remifentanil levels were reduced with a focus on stimulation-induced limb movements as well as electromyography monitoring.

Results: The STN could be discerned by excessive bursts of long duration (> 10 spikes) interspersed with quiescent intervals, but not by means of an increase in background activity nor the usual irregular firing pattern observed in the awake state. The STN was traversed with 57 of 105 trajectories (average length 3.9 ± 1.6 mm; range, 1 – 6.5). Only 3 (of 21) electrodes were implanted along the medial trajectory. All other electrodes were implanted along the central (5) and anterior (13) tract, a pattern which did not differ from awake surgery. Postoperatively none of the patients displayed clinical signs for current spread (at least 4.0 V, 60 usec, 130 Hz) to the corticospinal tract. DBS resulted in improved non-axial motor symptoms, reduced levodopa-induced dyskinesias and motor fluctuations. Postoperative UPDRS III scores at follow-up (mean 2.8 yrs) had improved by 62% (mean score 14.6, n = 8; preoperative levodopa response with 41% improvement in UPDRS III). The levodopa equivalence dose was reduced by 59% (mean preoperative LEDD 1301 mg, n = 10). Only 3 of the 21 electrodes were stimulated in a bipolar mode which was felt to minimize dysarthria but this was not due to side effects from the internal capsule. Two patients developed a transient state of confusion after the operation. One patient developed a postoperative manic phase which was not due to ventral or medial electrode location.

Conclusions: STN surgery in GA can be performed in a safe and effective manner. Based on these retrospective, single-center, non-controlled, and non-randomized data, we have suggested GA when awake surgery bears a risk for the patient and it will be offered to anxious patients.