"Asleep" Deep Brain Stimulation Surgery: A Critical Review of the Literature.

Objective: Although performing deep brain stimulation (DBS) with the patient under general anesthesia without microelectrode recording (MER) or intraoperative test stimulation (ITS) for movement disorders ("asleep" DBS) has become increasingly popular, its feasibility is based on the untested assumption that stereotactic accuracy correlates with positive clinical outcomes. To investigate outcomes after asleep DBS without MER or neurophysiological testing, we reviewed the medical literature on the topic.

Methods: We searched PubMed to identify all studies reporting clinical outcomes for patients who underwent DBS without MER or ITS for Parkinson disease (PD) or essential tremor (ET).

Results: We identified 9 studies with level 3b (n = 3) or level 4 evidence (n = 6). Eight PD studies (220 patients) reported asleep placement of 431 electrodes (341 subthalamic nucleus, 90 globus pallidus interna). Unified Parkinson Disease Rating Scale motor examination-III scores for 208 patients demonstrated significant improvement (40.2%-65%) at 6-12 months. The levodopa equivalent daily dose for 115 patients was significantly reduced (14%-49.3%) at 6-12 months in 103 patients. Two studies with a comparison cohort undergoing "awake" DBS with MER found no differences in postoperative Unified Parkinson Disease Rating Scale-III improvement or levodopa equivalent daily dose reduction. One study of asleep DBS for ET found no difference in functional outcomes between 17 patients undergoing asleep ventral intermediate nucleus DBS and 40 patients undergoing awake placement with ITS.

Conclusions: Initial evidence suggests that asleep DBS can be performed safely for PD and ET with good clinical outcomes. Long-term follow-up, larger cohorts, and double-armed studies are needed to validate these initial results.