Frameless System for DBS
Undergoing any intracranial procedure is a stressful event for the patients and their family members and selecting a center where to undergo the surgery is a critical decision.
Our philosophy is to provide personalized support to ensure our patients’ comfort through the process. Having clear pre-surgical and post-surgical instructions and a detailed plan leading to the surgery can provide reassurance about the exact steps to come. To this end, our strategy is to perform extensive pre-operative planning to facilitate the surgery.
The surgical procedure for DBS revolves around the precise placement of the electrode in a pre-defined target. The steps used to ensure proper electrode implantation include: (1) pre-operative computer-assisted planning, (2) surgical guidance and (3) placement confirmation.
Pre-operative computer-assisted planning
In the weeks prior to the surgery, you will complete an MRI of the brain. This MRI is taken with thin slices to allow a precise reconstruction of the brain. We will be able to plan the entire trajectory of the electrodes using this scan. Special MRI sequences can also assist us in identifying our target. These images are imported into our planning software and once the trajectory (pathway) is defined, the software is able to show us detailed images along the path of the electrode. This step is critical to reduce the risks of the surgery by verifying that the electrode will not cross a region containing blood vessels.
Surgical Guidance
In order to place the electrode in a precise location, a guide is used during the deep brain simulation surgery. The traditional surgical guide for this procedure is the stereotactic frame. This device is fixated to your head and then guides the electrode along the preset trajectory by using mathematical coordinates (x, y, and z). After a CT scan on the same day, the frame is screwed into the operating room table, immobilizing your head for the duration of the procedure. The frames have been used for over 50 years and several studies have confirmed the accuracy of this system. The advantages of the frame-based approach include the versatility of the system and the minimal preparation time for the surgery. The disadvantages include the discomfort (weight of the frame and immobilization of the head) and longer surgical procedures.
In the last decade, new frameless technologies have emerged that can reduce patient’s discomfort. At Pacific Movement Disorders Center, we are offering DBS surgery using a frameless system called STarFix (FHC, Inc.). This system uses a laser sculpting technology to create a custom-made platform individualized for every patient. The personalized frameless system is created first by the placement of 4 fiducial anchors (screws) in the scalp under local anesthesia as an outpatient procedure. These anchors are 5mm (less than a quarter inch) in length and are left in place until the electrode placement, then removed after the procedure. A CT scan is done, which then is used to calculate the surgical pathway as well as the design of the STarFix platform.
Because the electrode guidance system directly interfaces with the platform, your head would not be immobilized on the operating table and you would not have to wear a large metallic stereotactic frame on the day of the surgery. There is no need for a CT scan on the day of the surgery for preoperative planning. The time in the operating room is reduced since the CT scan is acquired ahead of time and the planning is completed several days prior to the procedure. Several studies have confirmed the precision of the frameless system.
| Frame-based | Frameless |
|---|---|
| Frame is placed the day of surgery (shorter preparation time) | Fiducial placement 1 week prior |
| CT the day of surgery (in frame) | No bulky frame the day of surgery |
| Head is fixed to the table | Head remains mobile during the surgery |
| Standardized technology | Technology is customized to you |
| Higher rates of neck pain due to immobilization | Less neck pain |
| Longer surgery | Shorter surgery with maintained accuracy |
| May have longer recovery | May have easier recovery |
Placement Confirmation
A number of steps are employed to confirm that the electrode is accurately positioned at the target. In the operating room, we use microelectrode recording, which is a technique to look at the activity of individual neurons. Since neurons in different locations in the brain have specific activity pattern (i.e., firing frequency), this information can be used to verify that a specific target has been entered. Another important step in the operating room is to test the electrode. This is performed with the patient awake and the different settings are sequentially tested for benefits and side effects. Because of the intra-operative electrode testing, we typically recommend that the patient hold the morning dose of Parkinson’s disease or tremor medication so that symptoms can be obvious at the time of the surgery.
Finally, a CT scan is performed after the completion of the surgery. This scan serves two purposes: it verifies the absence of complications and it confirms the placement of the electrode in the intended target.
