Background on deep brain stimulation (DBS)
It’s hard to imagine the first surgical attempt over a century ago to cure an involuntary movement disorder. The surgeon sawed into the skull to remove a portion of it, then cut out the part of the brain thought to be responsible. Who was braver – the surgeon or the patient?
Those pioneers took us from open neurosurgery to modern deep brain stimulation (DBS) with implanted electrical wires. Most of the patients along the way had Parkinson’s disease (PD). In 2002 the FDA approved DBS to treat medication-resistant, tremor-dominant PD, and later to treat essential tremor (ET). Over 40,000 people with PD or ET have now had DBS.
The minimally invasive surgery has two parts: 1) placing a pacemaker-like battery pack in the chest to serve as a power source, and 2) drilling a small hole in the skull and (under image guidance) to implant wired electrodes into the target area of the brain. For this, the patient is awake so that stimulation tests can be given to confirm correct location. Once it is ascertained, the wires in the brain are connected to the battery pack in the chest, routing the connection through the neck. Patients usually spend a night in the hospital for monitoring.
When the device is activated and adjusted, the benefits of DBS in terms of controlling tremor are immediately evident. Whether used for one or both sides of the body, tremor is greatly reduced or in many cases completely gone. The effects are durability and adjustable as needed.
Risks of DBS
DBS is a major surgery that involves opening the skull, placing foreign objects in the brain and leaving them there. As with all brain surgery that invades skin, bone and brain, there are risks. The following points summarize the risks most often associated with DBS:
- During surgery, if placement of electrodes punctures a blood vessel, it can “lead to a stroke or stroke-like syndrome which may result in weakness, numbness, sensory loss, visual difficulties, or a host of other neurological problems.”1
- Infection is a risk at the time of surgery or later
- Sensations of numbness or tingling
- Speech, balance or gait problems
- Unwanted mood changes or worsening of preexisting cognitive difficulties
- Future stroke risk
- Need to revise placement of the leads due to migration of the wires
- Device failure or breaking a connecting wire (requires surgical replacement)
What stops people from choosing DBS
Hundreds of thousands of people could benefit from DBS, but only a minority of those who consider it decide to proceed. It’s not just their concern over the risks of side effects, since most of them are not very likely to occur. A powerful factor that deters them is psychological: they aren’t comfortable with the idea of having a hole drilled in their brain and wires implanted. Even though we don’t think about it very often, the brain is the source of our mind, and our mind is the source of “self”. Perhaps we each have a safety instinct to preserve who we are, making it hard to trust that “psychosurgery” will leave us as we were before. For many people, this may be their greatest fear.
MRgFUS as an alternative to DBS
Now there is a much simpler procedure for controlling tremors without breaking skin, drilling into the skull, and implanting wires. It is called MRI-guided Focused Ultrasound (MRgFUS). MRgFUS is an outpatient procedure done inside the MRI scanner. It uses focused beams of sound energy (ultrasound) to deaden the very small part of the thalamus that relays abnormal movement signals to the motor center of the brain. Interrupting these signals stops hand tremors, and the positive effect is immediate.
For ET patients with disabling tremors that do not respond to medication, or for those who do not wish to use medication, it is worthwhile to be evaluated by a neurologist or neurosurgeon to determine if they are qualified for MRgFUS. For PD patients, MRgFUS is currently in clinical trials. Learn more at clinicaltrials.gov.