Deep Brain Stimulation (DBS) Sedation

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.

The secondary aims is to Identifying effective sedation regimens for the different DBS
targets; (2) Documenting the time course of the different drug's effect on the neuronal
activity. Having this information will allow planning and performing sedation during the
procedure prior to the MER without affecting the quality of the MER. This may prove useful in
cases where no sedation regimen is completely devoid of effect on the MER; (3) Creating a
database that includes the neuronal activity changes at multiple brain regions under the
effect of different sedation drugs to enable further study of the effects of anesthetics on
brain regions and the mechanisms underlying loss of consciousness.

Inclusion Criteria:

- All patients scheduled to undergo DBS electrode implantation surgery with MER that
agree to participate in the experiment and sign an informed consent are candidates to
participate in the study, unless one of the exclusion criteria is met

Exclusion Criteria:

1. Known or suspected obstructive sleep apnea.

2. Suspected difficult intubation.

3. Pregnancy (pregnancy test is standard care for women of childbearing age)

4. Under 18 years of age or over 85 years of age

5. Cognitive disability impairing understanding the experiment or signing the informed
consent form.