Effects of Anesthesia Drugs on Neuronal Activity in the Basal Ganglia and Thalamus During Deep Brain Stimulation Electrode Implantation Surgery

Deep brain stimulation (DBS) of different brain nuclei is evolving as an essential component of the treatment for multiple brain disorders. The subthalamic nucleus (STN) and globus pallidus have been used to treat advanced Parkinson's disease for a long time. The ventral intermediate nucleus of the thalamus is an effective target for treating essential tremor patients. STN and the internal segment of the globus pallidus are useful targets for treating dystonia. Aside from movement disorders DBS has demonstrated efficacy in the treatment of other conditions such as chronic pain, obsessive compulsive disorder, depression and epilepsy. For these illnesses the specific brain region targeted depends upon the illness and the patient's characteristics. As the indications for DBS increase in number, so grows the number of patients that may be helped by this treatment. Increasing numbers of patients are undergoing these procedures for various maladies at our center and at other locations throughout the nation.

To achieve optimal clinical results and avoid side effects, the DBS electrode has to be implanted precisely within the targeted region. This was demonstrated elegantly for parkinsonian patients and the dorsolateral STN, but is likely to be the case for most DBS indications. To achieve this optimal electrode localization, many centers perform electrophysiological mapping of the target nuclei using microelectrode recording (MER). This way they can achieve precise localization of the electrode. During the mapping procedure, microelectrodes are passed through the target nuclei, and the electrical neuronal activity is observed and recorded. The surgical team can identify the precise location of the target nuclei and its borders according to the typical activity of its neurons.

Dexmedetomidine, propofol and remifentanyl are often used in awake neurosurgical procedures. Dexmedetomidine provides sedation and amnesia with minimal respiratory depression, and improves perioperative hemodynamic stability in neurosurgical patients. Propofol and remifentanil have a much shorter duration of action, and thus allow rapid titration. Both these agents allow reliable and safe sedation for awake craniotomies. However, the effects of any of these three agents on the electrical activity, and whether they will allow safe sedation during DBS electrode implantation at different targets and in different clinical conditions is unclear.

This study will compare the activity of neurons in several DBS targets before, during and after sedation with propofol, remifentanil and dexmedetomidine. The goal is to understand the effects of anesthetics on the neuronal activity in these targets, allowing the study team to choose the most appropriate sedation protocol to use during implantation of DBS electrodes in deep brain structures (bearing in mind that each structure may have a different optimal protocol).

The primary aim is to document the effects of commonly used anesthetic drugs on the neuronal activity during MER in different brain structures that are used as targets for DBS implantation.