Using a new MRI device, surgeons are able to perform deep brain stimulation therapy for Parkinson’s patients in half the time needed for conventional surgery. The device may make the procedure more widely available for patients with severe symptoms of Parkinson’s and similar diseases.
A trio of researchers led by Dr. Paul Larson from the University of California San Francisco Department of Neurosurgery yesterday presented updated results of software tests at the 79th Annual Scientific Meeting of the American Association of Neurological Surgeons in Denver.
The traditional surgical technique uses a metal frame that is temporarily bolted to the patient’s head to guide the electrodes into the brain, Larson told The Hub in an e-mail interview. Since the surgeon cannot see inside the brain, proper electrode placement requires recording the brain activity and evaluating the patient’s responses to stimulation; this requires that the patient be awake during surgery.
“The new system allows the surgery to take place entirely within a MRI scanner,” Larson said. “This allows the surgeon to see inside the brain, which eliminates the need to have the patient awake for the operation. It also eliminates the need for the metal frame, reduces penetration of the brain, and allows the surgeon to detect complications during the procedure such as bleeding or the electrode going into the wrong place.”
Doctors have used deep brain stimulation for more than a decade to improve mobility and reduce involuntary movements in patients with Parkinson’s disease. The treatment is similar to how a heart pacemaker controls abnormal heart rhythms. During the procedure a battery-operated brain stimulator electrode is implanted into deep movement-controlling structures of the brain, and overrides abnormal electrical patterns in those structures disrupting the signals causing involuntary movements.
Larson says the implanted device provides stable treatment for Parkinson's disease for a minimum of 7-8 years in most patients. After that, some people still have benefit but others may experience some decline in function. Deep brain stimulation does not cure Parkinson's or halt its progression it merely treats the symptoms. The MRI system developed by Larson, Dr. Philip Star, and MRI physicist Dr. Alastair Martin in collaboration with SurgiVision, a medical device company in Irvine, Calf. allows the surgeon to more accurately place the electrodes in much less time.
The system received FDA approval last summer. The new data presented at the neurological meeting involved software refinements of the system that gives the surgeon more control over probe placement. The software basically takes images from the MRI machine, performs an automatic recognition of all the hardware components and provides instructions to allow very accurate aiming of the hardware.
To obtain the data presented, the researchers performed 18 water phantom experiments to determine predictive accuracy of the software. Data from 16 experiments using a gelatin-filled skull phantom were performed to determine targeting accuracy of the aiming device and another 6 mock procedures in three cadaver heads were performed to compare performance and accuracy of the team’s first generation interventional MRI aiming device using Medtronic’s Nexframe MR with their second generation system using Surgivision’s ClearPoint.
Using the ClearPoint system, a physician sees and selects a neurological target, aims SurgiVision’s targeting device and watches via MRI as the surgical instrument is advanced to the target.
The results showed a significant improvement in probe placement accuracy on pitch and roll aiming and in the average placement error in X-Y translation aiming. In the mock surgeries in cadavers, the Nexframe MR system had an average radial error of 0.6 mm compared to an average radial error of 0.2 mm with the ClearPoint system. The average time of the procedure with the Nexframe system was 92 minutes compared to 88 minutes for the ClearPoint system.
“Conventional deep brain stimulation surgery is done with the patient awake and takes 6-8 hours in most cases,” Larson said. “The new device reduces the surgical time by half or even a third.”
The ClearPoint system is intended to be used as an integral part of procedures, such as biopsies and catheter and electrode insertions, which have traditionally been performed using stereotactic methods, and it is designed to allow those procedures to be performed in a hospital’s existing MRI suite.
By Michael O’Leary, contributing writer, Health Imaging Hub
