Deep brain stimulation (DBS) is a regularly used way to relieve Parkinson's patients from uncontrolled movement or trembling. However, with the existing technology of placing DSB electrodes in the brain, mainly only top specialists are successful, as it works quite imprecisely. As a result, the application cannot often be used for every patient and waiting lists are created. Marc Janssens of TU Eindhoven therefore developed new instruments that allow brain surgeons with less experience with DBS to also place the electrode accurately in the right place in the brain. Janssens obtained his PhD on this subject yesterday.
In DBS, the surgeon places electrodes deep inside the brain, through small openings at the top of the skull. The electrodes are connected to a 'pacemaker' that delivers pulses, which can almost completely suppress uncontrolled limb movement and trembling. The treatment makes a normal life possible again for patients. Unfortunately, waiting times are long, De Telegraaf reported as recently as February, leading to Parliamentary questions. In the Netherlands, the waiting time can be up to two years, and this problem also exists in other countries.
Not changed since 1990s
In Parkinson's patients, the DBS electrodes usually have to exit into the nucleus subthalamicus, a crucial part of the brain that is only 8 by 4 millimetres in size. Most of it focuses on movements, but its edges control emotions and learning processes, among other things. Extremely precise placement is therefore essential. Current placement technology, which has essentially not changed since DBS was invented in the 1990s, is the bottleneck in this regard.
Error rate
Surgeons currently place DBS electrodes via a device clamped onto the patient's head that is actually too floppy for that precise task. But the biggest inaccuracy arises because there is no fixed reference point for electrode placement. Doctors first locate the target in the brain with an MRI scan, and then use a CT scan to record the position of the skull relative to the construct on the head, the stereotactic frame. Those two images are overlaid to see where the target is in relation to the frame. This creates a margin of error that can be several millimetres, which is hefty given the small size of the target, the nucleus subthalamicus.
Fixed reference point
Marc Janssens developed an entirely new technique that is much more accurate. Key in this is the adapter disc he developed, which gives the procedure a fixed reference point. This disc is placed on the back of the head with three surgical screws. This is much less uncomfortable and less painful than the stereotactic frame, which is clamped onto the head with four pins, through the skin. The disc contains a reference triangle that is clearly visible on the MRI scan.
Particularly compact and rigid
After the MRI scan, the patient moves to the new instrument Janssens designed and built for electrode placement. The adapter disc, which is still on the head, is clicked onto it, taking the patient's fixed reference point with it. His placement device is particularly compact and rigid, allowing much higher precision than with the classic placement arc. Combined with the fixed reference point, the procedure is expected to get an accuracy of a millimetre or less.
Now under anaesthesia
This allows brain surgeons who do not often perform this procedure to still perform successful procedures. An additional advantage is that patients basically do not need to be conscious anymore. In current practice, however, this is still necessary: the surgeon needs reactions from the patient to see if the electrodes are in the right place. So the patient has to experience the hours-long, unpleasant procedure from A to Z. With the new, high accuracy, feedback from the patient is no longer needed, allowing the patient to undergo the operation calmly under anaesthesia. All in all, this could significantly lower the threshold for DBS surgery, making this successful treatment available to more patients.
Craftsmanship
For mechanical instruments where high precision is crucial, high-tech robotic solutions are quickly thought of. What is special about Janssens' instruments is that there are no electronics involved; they are fully manually operated. This craftsmanship makes the instrument particularly reliable, light, compact and relatively inexpensive. The Eindhoven Medical Robotics company plans to further develop and market the instrument.
Source: TU Eindhoven.
Photo: Bart van Overbeeke
